Initialize module and dependencies

vendor/golang.org/x/tools/go/ssa/TODO

@@ -0,0 +1,16 @@
+-*- text -*-
+
+SSA Generics to-do list
+===========================
+
+DOCUMENTATION:
+- Read me for internals
+
+TYPE PARAMETERIZED GENERIC FUNCTIONS:
+- sanity.go updates.
+- Check source functions going to generics.
+- Tests, tests, tests...
+
+USAGE:
+- Back fill users for handling ssa.InstantiateGenerics being off.
+

vendor/golang.org/x/tools/go/ssa/block.go

@@ -0,0 +1,113 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import "fmt"
+
+// This file implements the BasicBlock type.
+
+// addEdge adds a control-flow graph edge from from to to.
+func addEdge(from, to *BasicBlock) {
+	from.Succs = append(from.Succs, to)
+	to.Preds = append(to.Preds, from)
+}
+
+// Parent returns the function that contains block b.
+func (b *BasicBlock) Parent() *Function { return b.parent }
+
+// String returns a human-readable label of this block.
+// It is not guaranteed unique within the function.
+func (b *BasicBlock) String() string {
+	return fmt.Sprintf("%d", b.Index)
+}
+
+// emit appends an instruction to the current basic block.
+// If the instruction defines a Value, it is returned.
+func (b *BasicBlock) emit(i Instruction) Value {
+	i.setBlock(b)
+	b.Instrs = append(b.Instrs, i)
+	v, _ := i.(Value)
+	return v
+}
+
+// predIndex returns the i such that b.Preds[i] == c or panics if
+// there is none.
+func (b *BasicBlock) predIndex(c *BasicBlock) int {
+	for i, pred := range b.Preds {
+		if pred == c {
+			return i
+		}
+	}
+	panic(fmt.Sprintf("no edge %s -> %s", c, b))
+}
+
+// hasPhi returns true if b.Instrs contains φ-nodes.
+func (b *BasicBlock) hasPhi() bool {
+	_, ok := b.Instrs[0].(*Phi)
+	return ok
+}
+
+// phis returns the prefix of b.Instrs containing all the block's φ-nodes.
+func (b *BasicBlock) phis() []Instruction {
+	for i, instr := range b.Instrs {
+		if _, ok := instr.(*Phi); !ok {
+			return b.Instrs[:i]
+		}
+	}
+	return nil // unreachable in well-formed blocks
+}
+
+// replacePred replaces all occurrences of p in b's predecessor list with q.
+// Ordinarily there should be at most one.
+func (b *BasicBlock) replacePred(p, q *BasicBlock) {
+	for i, pred := range b.Preds {
+		if pred == p {
+			b.Preds[i] = q
+		}
+	}
+}
+
+// replaceSucc replaces all occurrences of p in b's successor list with q.
+// Ordinarily there should be at most one.
+func (b *BasicBlock) replaceSucc(p, q *BasicBlock) {
+	for i, succ := range b.Succs {
+		if succ == p {
+			b.Succs[i] = q
+		}
+	}
+}
+
+// removePred removes all occurrences of p in b's
+// predecessor list and φ-nodes.
+// Ordinarily there should be at most one.
+func (b *BasicBlock) removePred(p *BasicBlock) {
+	phis := b.phis()
+
+	// We must preserve edge order for φ-nodes.
+	j := 0
+	for i, pred := range b.Preds {
+		if pred != p {
+			b.Preds[j] = b.Preds[i]
+			// Strike out φ-edge too.
+			for _, instr := range phis {
+				phi := instr.(*Phi)
+				phi.Edges[j] = phi.Edges[i]
+			}
+			j++
+		}
+	}
+	// Nil out b.Preds[j:] and φ-edges[j:] to aid GC.
+	for i := j; i < len(b.Preds); i++ {
+		b.Preds[i] = nil
+		for _, instr := range phis {
+			instr.(*Phi).Edges[i] = nil
+		}
+	}
+	b.Preds = b.Preds[:j]
+	for _, instr := range phis {
+		phi := instr.(*Phi)
+		phi.Edges = phi.Edges[:j]
+	}
+}

vendor/golang.org/x/tools/go/ssa/blockopt.go

@@ -0,0 +1,183 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// Simple block optimizations to simplify the control flow graph.
+
+// TODO(adonovan): opt: instead of creating several "unreachable" blocks
+// per function in the Builder, reuse a single one (e.g. at Blocks[1])
+// to reduce garbage.
+
+import (
+	"fmt"
+	"os"
+)
+
+// If true, perform sanity checking and show progress at each
+// successive iteration of optimizeBlocks.  Very verbose.
+const debugBlockOpt = false
+
+// markReachable sets Index=-1 for all blocks reachable from b.
+func markReachable(b *BasicBlock) {
+	b.Index = -1
+	for _, succ := range b.Succs {
+		if succ.Index == 0 {
+			markReachable(succ)
+		}
+	}
+}
+
+// deleteUnreachableBlocks marks all reachable blocks of f and
+// eliminates (nils) all others, including possibly cyclic subgraphs.
+func deleteUnreachableBlocks(f *Function) {
+	const white, black = 0, -1
+	// We borrow b.Index temporarily as the mark bit.
+	for _, b := range f.Blocks {
+		b.Index = white
+	}
+	markReachable(f.Blocks[0])
+	if f.Recover != nil {
+		markReachable(f.Recover)
+	}
+	for i, b := range f.Blocks {
+		if b.Index == white {
+			for _, c := range b.Succs {
+				if c.Index == black {
+					c.removePred(b) // delete white->black edge
+				}
+			}
+			if debugBlockOpt {
+				fmt.Fprintln(os.Stderr, "unreachable", b)
+			}
+			f.Blocks[i] = nil // delete b
+		}
+	}
+	f.removeNilBlocks()
+}
+
+// jumpThreading attempts to apply simple jump-threading to block b,
+// in which a->b->c become a->c if b is just a Jump.
+// The result is true if the optimization was applied.
+func jumpThreading(f *Function, b *BasicBlock) bool {
+	if b.Index == 0 {
+		return false // don't apply to entry block
+	}
+	if b.Instrs == nil {
+		return false
+	}
+	if _, ok := b.Instrs[0].(*Jump); !ok {
+		return false // not just a jump
+	}
+	c := b.Succs[0]
+	if c == b {
+		return false // don't apply to degenerate jump-to-self.
+	}
+	if c.hasPhi() {
+		return false // not sound without more effort
+	}
+	for j, a := range b.Preds {
+		a.replaceSucc(b, c)
+
+		// If a now has two edges to c, replace its degenerate If by Jump.
+		if len(a.Succs) == 2 && a.Succs[0] == c && a.Succs[1] == c {
+			jump := new(Jump)
+			jump.setBlock(a)
+			a.Instrs[len(a.Instrs)-1] = jump
+			a.Succs = a.Succs[:1]
+			c.removePred(b)
+		} else {
+			if j == 0 {
+				c.replacePred(b, a)
+			} else {
+				c.Preds = append(c.Preds, a)
+			}
+		}
+
+		if debugBlockOpt {
+			fmt.Fprintln(os.Stderr, "jumpThreading", a, b, c)
+		}
+	}
+	f.Blocks[b.Index] = nil // delete b
+	return true
+}
+
+// fuseBlocks attempts to apply the block fusion optimization to block
+// a, in which a->b becomes ab if len(a.Succs)==len(b.Preds)==1.
+// The result is true if the optimization was applied.
+func fuseBlocks(f *Function, a *BasicBlock) bool {
+	if len(a.Succs) != 1 {
+		return false
+	}
+	b := a.Succs[0]
+	if len(b.Preds) != 1 {
+		return false
+	}
+
+	// Degenerate &&/|| ops may result in a straight-line CFG
+	// containing φ-nodes. (Ideally we'd replace such them with
+	// their sole operand but that requires Referrers, built later.)
+	if b.hasPhi() {
+		return false // not sound without further effort
+	}
+
+	// Eliminate jump at end of A, then copy all of B across.
+	a.Instrs = append(a.Instrs[:len(a.Instrs)-1], b.Instrs...)
+	for _, instr := range b.Instrs {
+		instr.setBlock(a)
+	}
+
+	// A inherits B's successors
+	a.Succs = append(a.succs2[:0], b.Succs...)
+
+	// Fix up Preds links of all successors of B.
+	for _, c := range b.Succs {
+		c.replacePred(b, a)
+	}
+
+	if debugBlockOpt {
+		fmt.Fprintln(os.Stderr, "fuseBlocks", a, b)
+	}
+
+	f.Blocks[b.Index] = nil // delete b
+	return true
+}
+
+// optimizeBlocks() performs some simple block optimizations on a
+// completed function: dead block elimination, block fusion, jump
+// threading.
+func optimizeBlocks(f *Function) {
+	deleteUnreachableBlocks(f)
+
+	// Loop until no further progress.
+	changed := true
+	for changed {
+		changed = false
+
+		if debugBlockOpt {
+			f.WriteTo(os.Stderr)
+			mustSanityCheck(f, nil)
+		}
+
+		for _, b := range f.Blocks {
+			// f.Blocks will temporarily contain nils to indicate
+			// deleted blocks; we remove them at the end.
+			if b == nil {
+				continue
+			}
+
+			// Fuse blocks.  b->c becomes bc.
+			if fuseBlocks(f, b) {
+				changed = true
+			}
+
+			// a->b->c becomes a->c if b contains only a Jump.
+			if jumpThreading(f, b) {
+				changed = true
+				continue // (b was disconnected)
+			}
+		}
+	}
+	f.removeNilBlocks()
+}

vendor/golang.org/x/tools/go/ssa/const.go

@@ -0,0 +1,193 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines the Const SSA value type.
+
+import (
+	"fmt"
+	"go/constant"
+	"go/token"
+	"go/types"
+	"strconv"
+
+	"golang.org/x/tools/internal/typeparams"
+	"golang.org/x/tools/internal/typesinternal"
+)
+
+// NewConst returns a new constant of the specified value and type.
+// val must be valid according to the specification of Const.Value.
+func NewConst(val constant.Value, typ types.Type) *Const {
+	if val == nil {
+		switch soleTypeKind(typ) {
+		case types.IsBoolean:
+			val = constant.MakeBool(false)
+		case types.IsInteger:
+			val = constant.MakeInt64(0)
+		case types.IsString:
+			val = constant.MakeString("")
+		}
+	}
+	return &Const{typ, val}
+}
+
+// soleTypeKind returns a BasicInfo for which constant.Value can
+// represent all zero values for the types in the type set.
+//
+//	types.IsBoolean for false is a representative.
+//	types.IsInteger for 0
+//	types.IsString for ""
+//	0 otherwise.
+func soleTypeKind(typ types.Type) types.BasicInfo {
+	// State records the set of possible zero values (false, 0, "").
+	// Candidates (perhaps all) are eliminated during the type-set
+	// iteration, which executes at least once.
+	state := types.IsBoolean | types.IsInteger | types.IsString
+	underIs(typ, func(ut types.Type) bool {
+		var c types.BasicInfo
+		if t, ok := ut.(*types.Basic); ok {
+			c = t.Info()
+		}
+		if c&types.IsNumeric != 0 { // int/float/complex
+			c = types.IsInteger
+		}
+		state = state & c
+		return state != 0
+	})
+	return state
+}
+
+// intConst returns an 'int' constant that evaluates to i.
+// (i is an int64 in case the host is narrower than the target.)
+func intConst(i int64) *Const {
+	return NewConst(constant.MakeInt64(i), tInt)
+}
+
+// stringConst returns a 'string' constant that evaluates to s.
+func stringConst(s string) *Const {
+	return NewConst(constant.MakeString(s), tString)
+}
+
+// zeroConst returns a new "zero" constant of the specified type.
+func zeroConst(t types.Type) *Const {
+	return NewConst(nil, t)
+}
+
+func (c *Const) RelString(from *types.Package) string {
+	var s string
+	if c.Value == nil {
+		s, _ = typesinternal.ZeroString(c.typ, types.RelativeTo(from))
+	} else if c.Value.Kind() == constant.String {
+		s = constant.StringVal(c.Value)
+		const max = 20
+		// TODO(adonovan): don't cut a rune in half.
+		if len(s) > max {
+			s = s[:max-3] + "..." // abbreviate
+		}
+		s = strconv.Quote(s)
+	} else {
+		s = c.Value.String()
+	}
+	return s + ":" + relType(c.Type(), from)
+}
+
+func (c *Const) Name() string {
+	return c.RelString(nil)
+}
+
+func (c *Const) String() string {
+	return c.Name()
+}
+
+func (c *Const) Type() types.Type {
+	return c.typ
+}
+
+func (c *Const) Referrers() *[]Instruction {
+	return nil
+}
+
+func (c *Const) Parent() *Function { return nil }
+
+func (c *Const) Pos() token.Pos {
+	return token.NoPos
+}
+
+// IsNil returns true if this constant is a nil value of
+// a nillable reference type (pointer, slice, channel, map, or function),
+// a basic interface type, or
+// a type parameter all of whose possible instantiations are themselves nillable.
+func (c *Const) IsNil() bool {
+	return c.Value == nil && nillable(c.typ)
+}
+
+// nillable reports whether *new(T) == nil is legal for type T.
+func nillable(t types.Type) bool {
+	if typeparams.IsTypeParam(t) {
+		return underIs(t, func(u types.Type) bool {
+			// empty type set (u==nil) => any underlying types => not nillable
+			return u != nil && nillable(u)
+		})
+	}
+	switch t.Underlying().(type) {
+	case *types.Pointer, *types.Slice, *types.Chan, *types.Map, *types.Signature:
+		return true
+	case *types.Interface:
+		return true // basic interface.
+	default:
+		return false
+	}
+}
+
+// TODO(adonovan): move everything below into golang.org/x/tools/go/ssa/interp.
+
+// Int64 returns the numeric value of this constant truncated to fit
+// a signed 64-bit integer.
+func (c *Const) Int64() int64 {
+	switch x := constant.ToInt(c.Value); x.Kind() {
+	case constant.Int:
+		if i, ok := constant.Int64Val(x); ok {
+			return i
+		}
+		return 0
+	case constant.Float:
+		f, _ := constant.Float64Val(x)
+		return int64(f)
+	}
+	panic(fmt.Sprintf("unexpected constant value: %T", c.Value))
+}
+
+// Uint64 returns the numeric value of this constant truncated to fit
+// an unsigned 64-bit integer.
+func (c *Const) Uint64() uint64 {
+	switch x := constant.ToInt(c.Value); x.Kind() {
+	case constant.Int:
+		if u, ok := constant.Uint64Val(x); ok {
+			return u
+		}
+		return 0
+	case constant.Float:
+		f, _ := constant.Float64Val(x)
+		return uint64(f)
+	}
+	panic(fmt.Sprintf("unexpected constant value: %T", c.Value))
+}
+
+// Float64 returns the numeric value of this constant truncated to fit
+// a float64.
+func (c *Const) Float64() float64 {
+	x := constant.ToFloat(c.Value) // (c.Value == nil) => x.Kind() == Unknown
+	f, _ := constant.Float64Val(x)
+	return f
+}
+
+// Complex128 returns the complex value of this constant truncated to
+// fit a complex128.
+func (c *Const) Complex128() complex128 {
+	x := constant.ToComplex(c.Value) // (c.Value == nil) => x.Kind() == Unknown
+	re, _ := constant.Float64Val(constant.Real(x))
+	im, _ := constant.Float64Val(constant.Imag(x))
+	return complex(re, im)
+}

vendor/golang.org/x/tools/go/ssa/create.go

@@ -0,0 +1,325 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file implements the CREATE phase of SSA construction.
+// See builder.go for explanation.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"os"
+	"sync"
+
+	"golang.org/x/tools/internal/versions"
+)
+
+// NewProgram returns a new SSA Program.
+//
+// mode controls diagnostics and checking during SSA construction.
+//
+// To construct an SSA program:
+//
+//   - Call NewProgram to create an empty Program.
+//   - Call CreatePackage providing typed syntax for each package
+//     you want to build, and call it with types but not
+//     syntax for each of those package's direct dependencies.
+//   - Call [Package.Build] on each syntax package you wish to build,
+//     or [Program.Build] to build all of them.
+//
+// See the Example tests for simple examples.
+func NewProgram(fset *token.FileSet, mode BuilderMode) *Program {
+	return &Program{
+		Fset:     fset,
+		imported: make(map[string]*Package),
+		packages: make(map[*types.Package]*Package),
+		mode:     mode,
+		canon:    newCanonizer(),
+		ctxt:     types.NewContext(),
+	}
+}
+
+// memberFromObject populates package pkg with a member for the
+// typechecker object obj.
+//
+// For objects from Go source code, syntax is the associated syntax
+// tree (for funcs and vars only) and goversion defines the
+// appropriate interpretation; they will be used during the build
+// phase.
+func memberFromObject(pkg *Package, obj types.Object, syntax ast.Node, goversion string) {
+	name := obj.Name()
+	switch obj := obj.(type) {
+	case *types.Builtin:
+		if pkg.Pkg != types.Unsafe {
+			panic("unexpected builtin object: " + obj.String())
+		}
+
+	case *types.TypeName:
+		if name != "_" {
+			pkg.Members[name] = &Type{
+				object: obj,
+				pkg:    pkg,
+			}
+		}
+
+	case *types.Const:
+		c := &NamedConst{
+			object: obj,
+			Value:  NewConst(obj.Val(), obj.Type()),
+			pkg:    pkg,
+		}
+		pkg.objects[obj] = c
+		if name != "_" {
+			pkg.Members[name] = c
+		}
+
+	case *types.Var:
+		g := &Global{
+			Pkg:    pkg,
+			name:   name,
+			object: obj,
+			typ:    types.NewPointer(obj.Type()), // address
+			pos:    obj.Pos(),
+		}
+		pkg.objects[obj] = g
+		if name != "_" {
+			pkg.Members[name] = g
+		}
+
+	case *types.Func:
+		sig := obj.Type().(*types.Signature)
+		if sig.Recv() == nil && name == "init" {
+			pkg.ninit++
+			name = fmt.Sprintf("init#%d", pkg.ninit)
+		}
+		fn := createFunction(pkg.Prog, obj, name, syntax, pkg.info, goversion)
+		fn.Pkg = pkg
+		pkg.created = append(pkg.created, fn)
+		pkg.objects[obj] = fn
+		if name != "_" && sig.Recv() == nil {
+			pkg.Members[name] = fn // package-level function
+		}
+
+	default: // (incl. *types.Package)
+		panic("unexpected Object type: " + obj.String())
+	}
+}
+
+// createFunction creates a function or method. It supports both
+// CreatePackage (with or without syntax) and the on-demand creation
+// of methods in non-created packages based on their types.Func.
+func createFunction(prog *Program, obj *types.Func, name string, syntax ast.Node, info *types.Info, goversion string) *Function {
+	sig := obj.Type().(*types.Signature)
+
+	// Collect type parameters.
+	var tparams *types.TypeParamList
+	if rtparams := sig.RecvTypeParams(); rtparams.Len() > 0 {
+		tparams = rtparams // method of generic type
+	} else if sigparams := sig.TypeParams(); sigparams.Len() > 0 {
+		tparams = sigparams // generic function
+	}
+
+	/* declared function/method (from syntax or export data) */
+	fn := &Function{
+		name:       name,
+		object:     obj,
+		Signature:  sig,
+		build:      (*builder).buildFromSyntax,
+		syntax:     syntax,
+		info:       info,
+		goversion:  goversion,
+		pos:        obj.Pos(),
+		Pkg:        nil, // may be set by caller
+		Prog:       prog,
+		typeparams: tparams,
+	}
+	if fn.syntax == nil {
+		fn.Synthetic = "from type information"
+		fn.build = (*builder).buildParamsOnly
+	}
+	if tparams.Len() > 0 {
+		fn.generic = new(generic)
+	}
+	return fn
+}
+
+// membersFromDecl populates package pkg with members for each
+// typechecker object (var, func, const or type) associated with the
+// specified decl.
+func membersFromDecl(pkg *Package, decl ast.Decl, goversion string) {
+	switch decl := decl.(type) {
+	case *ast.GenDecl: // import, const, type or var
+		switch decl.Tok {
+		case token.CONST:
+			for _, spec := range decl.Specs {
+				for _, id := range spec.(*ast.ValueSpec).Names {
+					memberFromObject(pkg, pkg.info.Defs[id], nil, "")
+				}
+			}
+
+		case token.VAR:
+			for _, spec := range decl.Specs {
+				for _, rhs := range spec.(*ast.ValueSpec).Values {
+					pkg.initVersion[rhs] = goversion
+				}
+				for _, id := range spec.(*ast.ValueSpec).Names {
+					memberFromObject(pkg, pkg.info.Defs[id], spec, goversion)
+				}
+			}
+
+		case token.TYPE:
+			for _, spec := range decl.Specs {
+				id := spec.(*ast.TypeSpec).Name
+				memberFromObject(pkg, pkg.info.Defs[id], nil, "")
+			}
+		}
+
+	case *ast.FuncDecl:
+		id := decl.Name
+		memberFromObject(pkg, pkg.info.Defs[id], decl, goversion)
+	}
+}
+
+// CreatePackage creates and returns an SSA Package from the
+// specified type-checked, error-free file ASTs, and populates its
+// Members mapping.
+//
+// importable determines whether this package should be returned by a
+// subsequent call to ImportedPackage(pkg.Path()).
+//
+// The real work of building SSA form for each function is not done
+// until a subsequent call to Package.Build.
+func (prog *Program) CreatePackage(pkg *types.Package, files []*ast.File, info *types.Info, importable bool) *Package {
+	if pkg == nil {
+		panic("nil pkg") // otherwise pkg.Scope below returns types.Universe!
+	}
+	p := &Package{
+		Prog:    prog,
+		Members: make(map[string]Member),
+		objects: make(map[types.Object]Member),
+		Pkg:     pkg,
+		syntax:  info != nil,
+		// transient values (cleared after Package.Build)
+		info:        info,
+		files:       files,
+		initVersion: make(map[ast.Expr]string),
+	}
+
+	/* synthesized package initializer */
+	p.init = &Function{
+		name:      "init",
+		Signature: new(types.Signature),
+		Synthetic: "package initializer",
+		Pkg:       p,
+		Prog:      prog,
+		build:     (*builder).buildPackageInit,
+		info:      p.info,
+		goversion: "", // See Package.build for details.
+	}
+	p.Members[p.init.name] = p.init
+	p.created = append(p.created, p.init)
+
+	// Allocate all package members: vars, funcs, consts and types.
+	if len(files) > 0 {
+		// Go source package.
+		for _, file := range files {
+			goversion := versions.Lang(versions.FileVersion(p.info, file))
+			for _, decl := range file.Decls {
+				membersFromDecl(p, decl, goversion)
+			}
+		}
+	} else {
+		// GC-compiled binary package (or "unsafe")
+		// No code.
+		// No position information.
+		scope := p.Pkg.Scope()
+		for _, name := range scope.Names() {
+			obj := scope.Lookup(name)
+			memberFromObject(p, obj, nil, "")
+			if obj, ok := obj.(*types.TypeName); ok {
+				// No Unalias: aliases should not duplicate methods.
+				if named, ok := obj.Type().(*types.Named); ok {
+					for i, n := 0, named.NumMethods(); i < n; i++ {
+						memberFromObject(p, named.Method(i), nil, "")
+					}
+				}
+			}
+		}
+	}
+
+	if prog.mode&BareInits == 0 {
+		// Add initializer guard variable.
+		initguard := &Global{
+			Pkg:  p,
+			name: "init$guard",
+			typ:  types.NewPointer(tBool),
+		}
+		p.Members[initguard.Name()] = initguard
+	}
+
+	if prog.mode&GlobalDebug != 0 {
+		p.SetDebugMode(true)
+	}
+
+	if prog.mode&PrintPackages != 0 {
+		printMu.Lock()
+		p.WriteTo(os.Stdout)
+		printMu.Unlock()
+	}
+
+	if importable {
+		prog.imported[p.Pkg.Path()] = p
+	}
+	prog.packages[p.Pkg] = p
+
+	return p
+}
+
+// printMu serializes printing of Packages/Functions to stdout.
+var printMu sync.Mutex
+
+// AllPackages returns a new slice containing all packages created by
+// prog.CreatePackage in unspecified order.
+func (prog *Program) AllPackages() []*Package {
+	pkgs := make([]*Package, 0, len(prog.packages))
+	for _, pkg := range prog.packages {
+		pkgs = append(pkgs, pkg)
+	}
+	return pkgs
+}
+
+// ImportedPackage returns the importable Package whose PkgPath
+// is path, or nil if no such Package has been created.
+//
+// A parameter to CreatePackage determines whether a package should be
+// considered importable. For example, no import declaration can resolve
+// to the ad-hoc main package created by 'go build foo.go'.
+//
+// TODO(adonovan): rethink this function and the "importable" concept;
+// most packages are importable. This function assumes that all
+// types.Package.Path values are unique within the ssa.Program, which is
+// false---yet this function remains very convenient.
+// Clients should use (*Program).Package instead where possible.
+// SSA doesn't really need a string-keyed map of packages.
+//
+// Furthermore, the graph of packages may contain multiple variants
+// (e.g. "p" vs "p as compiled for q.test"), and each has a different
+// view of its dependencies.
+func (prog *Program) ImportedPackage(path string) *Package {
+	return prog.imported[path]
+}
+
+// SetNoReturn sets the predicate used when building the ssa.Program
+// prog that reports whether a given function cannot return.
+// This may be used to prune spurious control flow edges
+// after (e.g.) log.Fatal, improving the precision of analyses.
+//
+// A typical implementation is the [ctrlflow.CFGs.NoReturn] method from
+// [golang.org/x/tools/go/analysis/passes/ctrlflow].
+func (prog *Program) SetNoReturn(noReturn func(*types.Func) bool) {
+	prog.noReturn = noReturn
+}

vendor/golang.org/x/tools/go/ssa/doc.go

@@ -0,0 +1,122 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package ssa defines a representation of the elements of Go programs
+// (packages, types, functions, variables and constants) using a
+// static single-assignment (SSA) form intermediate representation
+// (IR) for the bodies of functions.
+//
+// For an introduction to SSA form, see
+// http://en.wikipedia.org/wiki/Static_single_assignment_form.
+// This page provides a broader reading list:
+// http://www.dcs.gla.ac.uk/~jsinger/ssa.html.
+//
+// The level of abstraction of the SSA form is intentionally close to
+// the source language to facilitate construction of source analysis
+// tools.  It is not intended for machine code generation.
+//
+// All looping, branching and switching constructs are replaced with
+// unstructured control flow.  Higher-level control flow constructs
+// such as multi-way branch can be reconstructed as needed; see
+// [golang.org/x/tools/go/ssa/ssautil.Switches] for an example.
+//
+// The simplest way to create the SSA representation of a package is
+// to load typed syntax trees using [golang.org/x/tools/go/packages], then
+// invoke the [golang.org/x/tools/go/ssa/ssautil.Packages] helper function.
+// (See the package-level Examples named LoadPackages and LoadWholeProgram.)
+// The resulting [ssa.Program] contains all the packages and their
+// members, but SSA code is not created for function bodies until a
+// subsequent call to [Package.Build] or [Program.Build].
+//
+// The builder initially builds a naive SSA form in which all local
+// variables are addresses of stack locations with explicit loads and
+// stores.  Registerisation of eligible locals and φ-node insertion
+// using dominance and dataflow are then performed as a second pass
+// called "lifting" to improve the accuracy and performance of
+// subsequent analyses; this pass can be skipped by setting the
+// NaiveForm builder flag.
+//
+// The primary interfaces of this package are:
+//
+//   - [Member]: a named member of a Go package.
+//   - [Value]: an expression that yields a value.
+//   - [Instruction]: a statement that consumes values and performs computation.
+//   - [Node]: a [Value] or [Instruction] (emphasizing its membership in the SSA value graph)
+//
+// A computation that yields a result implements both the [Value] and
+// [Instruction] interfaces.  The following table shows for each
+// concrete type which of these interfaces it implements.
+//
+//	                   Value?          Instruction?      Member?
+//	*Alloc                ✔               ✔
+//	*BinOp                ✔               ✔
+//	*Builtin              ✔
+//	*Call                 ✔               ✔
+//	*ChangeInterface      ✔               ✔
+//	*ChangeType           ✔               ✔
+//	*Const                ✔
+//	*Convert              ✔               ✔
+//	*DebugRef                             ✔
+//	*Defer                                ✔
+//	*Extract              ✔               ✔
+//	*Field                ✔               ✔
+//	*FieldAddr            ✔               ✔
+//	*FreeVar              ✔
+//	*Function             ✔                               ✔ (func)
+//	*Global               ✔                               ✔ (var)
+//	*Go                                   ✔
+//	*If                                   ✔
+//	*Index                ✔               ✔
+//	*IndexAddr            ✔               ✔
+//	*Jump                                 ✔
+//	*Lookup               ✔               ✔
+//	*MakeChan             ✔               ✔
+//	*MakeClosure          ✔               ✔
+//	*MakeInterface        ✔               ✔
+//	*MakeMap              ✔               ✔
+//	*MakeSlice            ✔               ✔
+//	*MapUpdate                            ✔
+//	*MultiConvert         ✔               ✔
+//	*NamedConst                                           ✔ (const)
+//	*Next                 ✔               ✔
+//	*Panic                                ✔
+//	*Parameter            ✔
+//	*Phi                  ✔               ✔
+//	*Range                ✔               ✔
+//	*Return                               ✔
+//	*RunDefers                            ✔
+//	*Select               ✔               ✔
+//	*Send                                 ✔
+//	*Slice                ✔               ✔
+//	*SliceToArrayPointer  ✔               ✔
+//	*Store                                ✔
+//	*Type                                                 ✔ (type)
+//	*TypeAssert           ✔               ✔
+//	*UnOp                 ✔               ✔
+//
+// Other key types in this package include: [Program], [Package], [Function]
+// and [BasicBlock].
+//
+// The program representation constructed by this package is fully
+// resolved internally, i.e. it does not rely on the names of Values,
+// Packages, Functions, Types or BasicBlocks for the correct
+// interpretation of the program.  Only the identities of objects and
+// the topology of the SSA and type graphs are semantically
+// significant.  (There is one exception: [types.Id] values, which identify field
+// and method names, contain strings.)  Avoidance of name-based
+// operations simplifies the implementation of subsequent passes and
+// can make them very efficient.  Many objects are nonetheless named
+// to aid in debugging, but it is not essential that the names be
+// either accurate or unambiguous.  The public API exposes a number of
+// name-based maps for client convenience.
+//
+// The [golang.org/x/tools/go/ssa/ssautil] package provides various
+// helper functions, for example to simplify loading a Go program into
+// SSA form.
+//
+// TODO(adonovan): write a how-to document for all the various cases
+// of trying to determine corresponding elements across the four
+// domains of source locations, ast.Nodes, types.Objects,
+// ssa.Values/Instructions.
+package ssa // import "golang.org/x/tools/go/ssa"

vendor/golang.org/x/tools/go/ssa/dom.go

@@ -0,0 +1,342 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines algorithms related to dominance.
+
+// Dominator tree construction ----------------------------------------
+//
+// We use the algorithm described in Lengauer & Tarjan. 1979.  A fast
+// algorithm for finding dominators in a flowgraph.
+// http://doi.acm.org/10.1145/357062.357071
+//
+// We also apply the optimizations to SLT described in Georgiadis et
+// al, Finding Dominators in Practice, JGAA 2006,
+// http://jgaa.info/accepted/2006/GeorgiadisTarjanWerneck2006.10.1.pdf
+// to avoid the need for buckets of size > 1.
+
+import (
+	"bytes"
+	"fmt"
+	"math/big"
+	"os"
+	"slices"
+	"sort"
+)
+
+// Idom returns the block that immediately dominates b:
+// its parent in the dominator tree, if any.
+// Neither the entry node (b.Index==0) nor recover node
+// (b==b.Parent().Recover()) have a parent.
+func (b *BasicBlock) Idom() *BasicBlock { return b.dom.idom }
+
+// Dominees returns the list of blocks that b immediately dominates:
+// its children in the dominator tree.
+func (b *BasicBlock) Dominees() []*BasicBlock { return b.dom.children }
+
+// Dominates reports whether b dominates c.
+func (b *BasicBlock) Dominates(c *BasicBlock) bool {
+	return b.dom.pre <= c.dom.pre && c.dom.post <= b.dom.post
+}
+
+// DomPreorder returns a new slice containing the blocks of f
+// in a preorder traversal of the dominator tree.
+func (f *Function) DomPreorder() []*BasicBlock {
+	slice := slices.Clone(f.Blocks)
+	sort.Slice(slice, func(i, j int) bool {
+		return slice[i].dom.pre < slice[j].dom.pre
+	})
+	return slice
+}
+
+// DomPostorder returns a new slice containing the blocks of f
+// in a postorder traversal of the dominator tree.
+// (This is not the same as a postdominance order.)
+func (f *Function) DomPostorder() []*BasicBlock {
+	slice := slices.Clone(f.Blocks)
+	sort.Slice(slice, func(i, j int) bool {
+		return slice[i].dom.post < slice[j].dom.post
+	})
+	return slice
+}
+
+// domInfo contains a BasicBlock's dominance information.
+type domInfo struct {
+	idom      *BasicBlock   // immediate dominator (parent in domtree)
+	children  []*BasicBlock // nodes immediately dominated by this one
+	pre, post int32         // pre- and post-order numbering within domtree
+}
+
+// ltState holds the working state for Lengauer-Tarjan algorithm
+// (during which domInfo.pre is repurposed for CFG DFS preorder number).
+type ltState struct {
+	// Each slice is indexed by b.Index.
+	sdom     []*BasicBlock // b's semidominator
+	parent   []*BasicBlock // b's parent in DFS traversal of CFG
+	ancestor []*BasicBlock // b's ancestor with least sdom
+}
+
+// dfs implements the depth-first search part of the LT algorithm.
+func (lt *ltState) dfs(v *BasicBlock, i int32, preorder []*BasicBlock) int32 {
+	preorder[i] = v
+	v.dom.pre = i // For now: DFS preorder of spanning tree of CFG
+	i++
+	lt.sdom[v.Index] = v
+	lt.link(nil, v)
+	for _, w := range v.Succs {
+		if lt.sdom[w.Index] == nil {
+			lt.parent[w.Index] = v
+			i = lt.dfs(w, i, preorder)
+		}
+	}
+	return i
+}
+
+// eval implements the EVAL part of the LT algorithm.
+func (lt *ltState) eval(v *BasicBlock) *BasicBlock {
+	// TODO(adonovan): opt: do path compression per simple LT.
+	u := v
+	for ; lt.ancestor[v.Index] != nil; v = lt.ancestor[v.Index] {
+		if lt.sdom[v.Index].dom.pre < lt.sdom[u.Index].dom.pre {
+			u = v
+		}
+	}
+	return u
+}
+
+// link implements the LINK part of the LT algorithm.
+func (lt *ltState) link(v, w *BasicBlock) {
+	lt.ancestor[w.Index] = v
+}
+
+// buildDomTree computes the dominator tree of f using the LT algorithm.
+// Precondition: all blocks are reachable (e.g. optimizeBlocks has been run).
+func buildDomTree(f *Function) {
+	// The step numbers refer to the original LT paper; the
+	// reordering is due to Georgiadis.
+
+	// Clear any previous domInfo.
+	for _, b := range f.Blocks {
+		b.dom = domInfo{}
+	}
+
+	n := len(f.Blocks)
+	// Allocate space for 5 contiguous [n]*BasicBlock arrays:
+	// sdom, parent, ancestor, preorder, buckets.
+	space := make([]*BasicBlock, 5*n)
+	lt := ltState{
+		sdom:     space[0:n],
+		parent:   space[n : 2*n],
+		ancestor: space[2*n : 3*n],
+	}
+
+	// Step 1.  Number vertices by depth-first preorder.
+	preorder := space[3*n : 4*n]
+	root := f.Blocks[0]
+	prenum := lt.dfs(root, 0, preorder)
+	recover := f.Recover
+	if recover != nil {
+		lt.dfs(recover, prenum, preorder)
+	}
+
+	buckets := space[4*n : 5*n]
+	copy(buckets, preorder)
+
+	// In reverse preorder...
+	for i := int32(n) - 1; i > 0; i-- {
+		w := preorder[i]
+
+		// Step 3. Implicitly define the immediate dominator of each node.
+		for v := buckets[i]; v != w; v = buckets[v.dom.pre] {
+			u := lt.eval(v)
+			if lt.sdom[u.Index].dom.pre < i {
+				v.dom.idom = u
+			} else {
+				v.dom.idom = w
+			}
+		}
+
+		// Step 2. Compute the semidominators of all nodes.
+		lt.sdom[w.Index] = lt.parent[w.Index]
+		for _, v := range w.Preds {
+			u := lt.eval(v)
+			if lt.sdom[u.Index].dom.pre < lt.sdom[w.Index].dom.pre {
+				lt.sdom[w.Index] = lt.sdom[u.Index]
+			}
+		}
+
+		lt.link(lt.parent[w.Index], w)
+
+		if lt.parent[w.Index] == lt.sdom[w.Index] {
+			w.dom.idom = lt.parent[w.Index]
+		} else {
+			buckets[i] = buckets[lt.sdom[w.Index].dom.pre]
+			buckets[lt.sdom[w.Index].dom.pre] = w
+		}
+	}
+
+	// The final 'Step 3' is now outside the loop.
+	for v := buckets[0]; v != root; v = buckets[v.dom.pre] {
+		v.dom.idom = root
+	}
+
+	// Step 4. Explicitly define the immediate dominator of each
+	// node, in preorder.
+	for _, w := range preorder[1:] {
+		if w == root || w == recover {
+			w.dom.idom = nil
+		} else {
+			if w.dom.idom != lt.sdom[w.Index] {
+				w.dom.idom = w.dom.idom.dom.idom
+			}
+			// Calculate Children relation as inverse of Idom.
+			w.dom.idom.dom.children = append(w.dom.idom.dom.children, w)
+		}
+	}
+
+	pre, post := numberDomTree(root, 0, 0)
+	if recover != nil {
+		numberDomTree(recover, pre, post)
+	}
+
+	// printDomTreeDot(os.Stderr, f)        // debugging
+	// printDomTreeText(os.Stderr, root, 0) // debugging
+
+	if f.Prog.mode&SanityCheckFunctions != 0 {
+		sanityCheckDomTree(f)
+	}
+}
+
+// numberDomTree sets the pre- and post-order numbers of a depth-first
+// traversal of the dominator tree rooted at v.  These are used to
+// answer dominance queries in constant time.
+func numberDomTree(v *BasicBlock, pre, post int32) (int32, int32) {
+	v.dom.pre = pre
+	pre++
+	for _, child := range v.dom.children {
+		pre, post = numberDomTree(child, pre, post)
+	}
+	v.dom.post = post
+	post++
+	return pre, post
+}
+
+// Testing utilities ----------------------------------------
+
+// sanityCheckDomTree checks the correctness of the dominator tree
+// computed by the LT algorithm by comparing against the dominance
+// relation computed by a naive Kildall-style forward dataflow
+// analysis (Algorithm 10.16 from the "Dragon" book).
+func sanityCheckDomTree(f *Function) {
+	n := len(f.Blocks)
+
+	// D[i] is the set of blocks that dominate f.Blocks[i],
+	// represented as a bit-set of block indices.
+	D := make([]big.Int, n)
+
+	one := big.NewInt(1)
+
+	// all is the set of all blocks; constant.
+	var all big.Int
+	all.Set(one).Lsh(&all, uint(n)).Sub(&all, one)
+
+	// Initialization.
+	for i, b := range f.Blocks {
+		if i == 0 || b == f.Recover {
+			// A root is dominated only by itself.
+			D[i].SetBit(&D[0], 0, 1)
+		} else {
+			// All other blocks are (initially) dominated
+			// by every block.
+			D[i].Set(&all)
+		}
+	}
+
+	// Iteration until fixed point.
+	for changed := true; changed; {
+		changed = false
+		for i, b := range f.Blocks {
+			if i == 0 || b == f.Recover {
+				continue
+			}
+			// Compute intersection across predecessors.
+			var x big.Int
+			x.Set(&all)
+			for _, pred := range b.Preds {
+				x.And(&x, &D[pred.Index])
+			}
+			x.SetBit(&x, i, 1) // a block always dominates itself.
+			if D[i].Cmp(&x) != 0 {
+				D[i].Set(&x)
+				changed = true
+			}
+		}
+	}
+
+	// Check the entire relation.  O(n^2).
+	// The Recover block (if any) must be treated specially so we skip it.
+	ok := true
+	for i := range n {
+		for j := range n {
+			b, c := f.Blocks[i], f.Blocks[j]
+			if c == f.Recover {
+				continue
+			}
+			actual := b.Dominates(c)
+			expected := D[j].Bit(i) == 1
+			if actual != expected {
+				fmt.Fprintf(os.Stderr, "dominates(%s, %s)==%t, want %t\n", b, c, actual, expected)
+				ok = false
+			}
+		}
+	}
+
+	preorder := f.DomPreorder()
+	for _, b := range f.Blocks {
+		if got := preorder[b.dom.pre]; got != b {
+			fmt.Fprintf(os.Stderr, "preorder[%d]==%s, want %s\n", b.dom.pre, got, b)
+			ok = false
+		}
+	}
+
+	if !ok {
+		panic("sanityCheckDomTree failed for " + f.String())
+	}
+
+}
+
+// Printing functions ----------------------------------------
+
+// printDomTreeText prints the dominator tree as text, using indentation.
+func printDomTreeText(buf *bytes.Buffer, v *BasicBlock, indent int) {
+	fmt.Fprintf(buf, "%*s%s\n", 4*indent, "", v)
+	for _, child := range v.dom.children {
+		printDomTreeText(buf, child, indent+1)
+	}
+}
+
+// printDomTreeDot prints the dominator tree of f in AT&T GraphViz
+// (.dot) format.
+// (unused; retained for debugging)
+func printDomTreeDot(buf *bytes.Buffer, f *Function) {
+	fmt.Fprintln(buf, "//", f)
+	fmt.Fprintln(buf, "digraph domtree {")
+	for i, b := range f.Blocks {
+		v := b.dom
+		fmt.Fprintf(buf, "\tn%d [label=\"%s (%d, %d)\",shape=\"rectangle\"];\n", v.pre, b, v.pre, v.post)
+		// TODO(adonovan): improve appearance of edges
+		// belonging to both dominator tree and CFG.
+
+		// Dominator tree edge.
+		if i != 0 {
+			fmt.Fprintf(buf, "\tn%d -> n%d [style=\"solid\",weight=100];\n", v.idom.dom.pre, v.pre)
+		}
+		// CFG edges.
+		for _, pred := range b.Preds {
+			fmt.Fprintf(buf, "\tn%d -> n%d [style=\"dotted\",weight=0];\n", pred.dom.pre, v.pre)
+		}
+	}
+	fmt.Fprintln(buf, "}")
+}

vendor/golang.org/x/tools/go/ssa/emit.go

@@ -0,0 +1,629 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// Helpers for emitting SSA instructions.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// emitAlloc emits to f a new Alloc instruction allocating a variable
+// of type typ.
+//
+// The caller must set Alloc.Heap=true (for a heap-allocated variable)
+// or add the Alloc to f.Locals (for a frame-allocated variable).
+//
+// During building, a variable in f.Locals may have its Heap flag
+// set when it is discovered that its address is taken.
+// These Allocs are removed from f.Locals at the end.
+//
+// The builder should generally call one of the emit{New,Local,LocalVar} wrappers instead.
+func emitAlloc(f *Function, typ types.Type, pos token.Pos, comment string) *Alloc {
+	v := &Alloc{Comment: comment}
+	v.setType(types.NewPointer(typ))
+	v.setPos(pos)
+	f.emit(v)
+	return v
+}
+
+// emitNew emits to f a new Alloc instruction heap-allocating a
+// variable of type typ. pos is the optional source location.
+func emitNew(f *Function, typ types.Type, pos token.Pos, comment string) *Alloc {
+	alloc := emitAlloc(f, typ, pos, comment)
+	alloc.Heap = true
+	return alloc
+}
+
+// emitLocal creates a local var for (t, pos, comment) and
+// emits an Alloc instruction for it.
+//
+// (Use this function or emitNew for synthetic variables;
+// for source-level variables in the same function, use emitLocalVar.)
+func emitLocal(f *Function, t types.Type, pos token.Pos, comment string) *Alloc {
+	local := emitAlloc(f, t, pos, comment)
+	f.Locals = append(f.Locals, local)
+	return local
+}
+
+// emitLocalVar creates a local var for v and emits an Alloc instruction for it.
+// Subsequent calls to f.lookup(v) return it.
+// It applies the appropriate generic instantiation to the type.
+func emitLocalVar(f *Function, v *types.Var) *Alloc {
+	alloc := emitLocal(f, f.typ(v.Type()), v.Pos(), v.Name())
+	f.vars[v] = alloc
+	return alloc
+}
+
+// emitLoad emits to f an instruction to load the address addr into a
+// new temporary, and returns the value so defined.
+func emitLoad(f *Function, addr Value) *UnOp {
+	v := &UnOp{Op: token.MUL, X: addr}
+	v.setType(typeparams.MustDeref(addr.Type()))
+	f.emit(v)
+	return v
+}
+
+// emitDebugRef emits to f a DebugRef pseudo-instruction associating
+// expression e with value v.
+func emitDebugRef(f *Function, e ast.Expr, v Value, isAddr bool) {
+	if !f.debugInfo() {
+		return // debugging not enabled
+	}
+	if v == nil || e == nil {
+		panic("nil")
+	}
+	var obj types.Object
+	e = ast.Unparen(e)
+	if id, ok := e.(*ast.Ident); ok {
+		if isBlankIdent(id) {
+			return
+		}
+		obj = f.objectOf(id)
+		switch obj.(type) {
+		case *types.Nil, *types.Const, *types.Builtin:
+			return
+		}
+	}
+	f.emit(&DebugRef{
+		X:      v,
+		Expr:   e,
+		IsAddr: isAddr,
+		object: obj,
+	})
+}
+
+// emitArith emits to f code to compute the binary operation op(x, y)
+// where op is an eager shift, logical or arithmetic operation.
+// (Use emitCompare() for comparisons and Builder.logicalBinop() for
+// non-eager operations.)
+func emitArith(f *Function, op token.Token, x, y Value, t types.Type, pos token.Pos) Value {
+	switch op {
+	case token.SHL, token.SHR:
+		x = emitConv(f, x, t)
+		// y may be signed or an 'untyped' constant.
+
+		// There is a runtime panic if y is signed and <0. Instead of inserting a check for y<0
+		// and converting to an unsigned value (like the compiler) leave y as is.
+
+		if isUntyped(y.Type().Underlying()) {
+			// Untyped conversion:
+			// Spec https://go.dev/ref/spec#Operators:
+			// The right operand in a shift expression must have integer type or be an untyped constant
+			// representable by a value of type uint.
+			y = emitConv(f, y, types.Typ[types.Uint])
+		}
+
+	case token.ADD, token.SUB, token.MUL, token.QUO, token.REM, token.AND, token.OR, token.XOR, token.AND_NOT:
+		x = emitConv(f, x, t)
+		y = emitConv(f, y, t)
+
+	default:
+		panic("illegal op in emitArith: " + op.String())
+
+	}
+	v := &BinOp{
+		Op: op,
+		X:  x,
+		Y:  y,
+	}
+	v.setPos(pos)
+	v.setType(t)
+	return f.emit(v)
+}
+
+// emitCompare emits to f code compute the boolean result of
+// comparison 'x op y'.
+func emitCompare(f *Function, op token.Token, x, y Value, pos token.Pos) Value {
+	xt := x.Type().Underlying()
+	yt := y.Type().Underlying()
+
+	// Special case to optimise a tagless SwitchStmt so that
+	// these are equivalent
+	//   switch { case e: ...}
+	//   switch true { case e: ... }
+	//   if e==true { ... }
+	// even in the case when e's type is an interface.
+	// TODO(adonovan): opt: generalise to x==true, false!=y, etc.
+	if x == vTrue && op == token.EQL {
+		if yt, ok := yt.(*types.Basic); ok && yt.Info()&types.IsBoolean != 0 {
+			return y
+		}
+	}
+
+	if types.Identical(xt, yt) {
+		// no conversion necessary
+	} else if isNonTypeParamInterface(x.Type()) {
+		y = emitConv(f, y, x.Type())
+	} else if isNonTypeParamInterface(y.Type()) {
+		x = emitConv(f, x, y.Type())
+	} else if _, ok := x.(*Const); ok {
+		x = emitConv(f, x, y.Type())
+	} else if _, ok := y.(*Const); ok {
+		y = emitConv(f, y, x.Type())
+	} else {
+		// other cases, e.g. channels.  No-op.
+	}
+
+	v := &BinOp{
+		Op: op,
+		X:  x,
+		Y:  y,
+	}
+	v.setPos(pos)
+	v.setType(tBool)
+	return f.emit(v)
+}
+
+// isValuePreserving returns true if a conversion from ut_src to
+// ut_dst is value-preserving, i.e. just a change of type.
+// Precondition: neither argument is a named or alias type.
+func isValuePreserving(ut_src, ut_dst types.Type) bool {
+	// Identical underlying types?
+	if types.IdenticalIgnoreTags(ut_dst, ut_src) {
+		return true
+	}
+
+	switch ut_dst.(type) {
+	case *types.Chan:
+		// Conversion between channel types?
+		_, ok := ut_src.(*types.Chan)
+		return ok
+
+	case *types.Pointer:
+		// Conversion between pointers with identical base types?
+		_, ok := ut_src.(*types.Pointer)
+		return ok
+	}
+	return false
+}
+
+// emitConv emits to f code to convert Value val to exactly type typ,
+// and returns the converted value.  Implicit conversions are required
+// by language assignability rules in assignments, parameter passing,
+// etc.
+func emitConv(f *Function, val Value, typ types.Type) Value {
+	t_src := val.Type()
+
+	// Identical types?  Conversion is a no-op.
+	if types.Identical(t_src, typ) {
+		return val
+	}
+	ut_dst := typ.Underlying()
+	ut_src := t_src.Underlying()
+
+	// Conversion to, or construction of a value of, an interface type?
+	if isNonTypeParamInterface(typ) {
+		// Interface name change?
+		if isValuePreserving(ut_src, ut_dst) {
+			c := &ChangeType{X: val}
+			c.setType(typ)
+			return f.emit(c)
+		}
+
+		// Assignment from one interface type to another?
+		if isNonTypeParamInterface(t_src) {
+			c := &ChangeInterface{X: val}
+			c.setType(typ)
+			return f.emit(c)
+		}
+
+		// Untyped nil constant?  Return interface-typed nil constant.
+		if ut_src == tUntypedNil {
+			return zeroConst(typ)
+		}
+
+		// Convert (non-nil) "untyped" literals to their default type.
+		if t, ok := ut_src.(*types.Basic); ok && t.Info()&types.IsUntyped != 0 {
+			val = emitConv(f, val, types.Default(ut_src))
+		}
+
+		// Record the types of operands to MakeInterface, if
+		// non-parameterized, as they are the set of runtime types.
+		t := val.Type()
+		if f.typeparams.Len() == 0 || !f.Prog.isParameterized(t) {
+			addMakeInterfaceType(f.Prog, t)
+		}
+
+		mi := &MakeInterface{X: val}
+		mi.setType(typ)
+		return f.emit(mi)
+	}
+
+	// conversionCase describes an instruction pattern that maybe emitted to
+	// model d <- s for d in dst_terms and s in src_terms.
+	// Multiple conversions can match the same pattern.
+	type conversionCase uint8
+	const (
+		changeType conversionCase = 1 << iota
+		sliceToArray
+		sliceToArrayPtr
+		sliceTo0Array
+		sliceTo0ArrayPtr
+		convert
+	)
+	// classify the conversion case of a source type us to a destination type ud.
+	// us and ud are underlying types (not *Named or *Alias)
+	classify := func(us, ud types.Type) conversionCase {
+		// Just a change of type, but not value or representation?
+		if isValuePreserving(us, ud) {
+			return changeType
+		}
+
+		// Conversion from slice to array or slice to array pointer?
+		if slice, ok := us.(*types.Slice); ok {
+			var arr *types.Array
+			var ptr bool
+			// Conversion from slice to array pointer?
+			switch d := ud.(type) {
+			case *types.Array:
+				arr = d
+			case *types.Pointer:
+				arr, _ = d.Elem().Underlying().(*types.Array)
+				ptr = true
+			}
+			if arr != nil && types.Identical(slice.Elem(), arr.Elem()) {
+				if arr.Len() == 0 {
+					if ptr {
+						return sliceTo0ArrayPtr
+					} else {
+						return sliceTo0Array
+					}
+				}
+				if ptr {
+					return sliceToArrayPtr
+				} else {
+					return sliceToArray
+				}
+			}
+		}
+
+		// The only remaining case in well-typed code is a representation-
+		// changing conversion of basic types (possibly with []byte/[]rune).
+		if !isBasic(us) && !isBasic(ud) {
+			panic(fmt.Sprintf("in %s: cannot convert term %s (%s [within %s]) to type %s [within %s]", f, val, val.Type(), us, typ, ud))
+		}
+		return convert
+	}
+
+	var classifications conversionCase
+	underIs(ut_src, func(us types.Type) bool {
+		return underIs(ut_dst, func(ud types.Type) bool {
+			if us != nil && ud != nil {
+				classifications |= classify(us, ud)
+			}
+			return classifications != 0
+		})
+	})
+	if classifications == 0 {
+		panic(fmt.Sprintf("in %s: cannot convert %s (%s) to %s", f, val, val.Type(), typ))
+	}
+
+	// Conversion of a compile-time constant value?
+	if c, ok := val.(*Const); ok {
+		// Conversion to a basic type?
+		if isBasic(ut_dst) {
+			// Conversion of a compile-time constant to
+			// another constant type results in a new
+			// constant of the destination type and
+			// (initially) the same abstract value.
+			// We don't truncate the value yet.
+			return NewConst(c.Value, typ)
+		}
+		// Can we always convert from zero value without panicking?
+		const mayPanic = sliceToArray | sliceToArrayPtr
+		if c.Value == nil && classifications&mayPanic == 0 {
+			return NewConst(nil, typ)
+		}
+
+		// We're converting from constant to non-constant type,
+		// e.g. string -> []byte/[]rune.
+	}
+
+	switch classifications {
+	case changeType: // representation-preserving change
+		c := &ChangeType{X: val}
+		c.setType(typ)
+		return f.emit(c)
+
+	case sliceToArrayPtr, sliceTo0ArrayPtr: // slice to array pointer
+		c := &SliceToArrayPointer{X: val}
+		c.setType(typ)
+		return f.emit(c)
+
+	case sliceToArray: // slice to arrays (not zero-length)
+		ptype := types.NewPointer(typ)
+		p := &SliceToArrayPointer{X: val}
+		p.setType(ptype)
+		x := f.emit(p)
+		unOp := &UnOp{Op: token.MUL, X: x}
+		unOp.setType(typ)
+		return f.emit(unOp)
+
+	case sliceTo0Array: // slice to zero-length arrays (constant)
+		return zeroConst(typ)
+
+	case convert: // representation-changing conversion
+		c := &Convert{X: val}
+		c.setType(typ)
+		return f.emit(c)
+
+	default: // The conversion represents a cross product.
+		c := &MultiConvert{X: val, from: t_src, to: typ}
+		c.setType(typ)
+		return f.emit(c)
+	}
+}
+
+// emitTypeCoercion emits to f code to coerce the type of a
+// Value v to exactly type typ, and returns the coerced value.
+//
+// Requires that coercing v.Typ() to typ is a value preserving change.
+//
+// Currently used only when v.Type() is a type instance of typ or vice versa.
+// A type v is a type instance of a type t if there exists a
+// type parameter substitution σ s.t. σ(v) == t. Example:
+//
+//	σ(func(T) T) == func(int) int for σ == [T ↦ int]
+//
+// This happens in instantiation wrappers for conversion
+// from an instantiation to a parameterized type (and vice versa)
+// with σ substituting f.typeparams by f.typeargs.
+func emitTypeCoercion(f *Function, v Value, typ types.Type) Value {
+	if types.Identical(v.Type(), typ) {
+		return v // no coercion needed
+	}
+	// TODO(taking): for instances should we record which side is the instance?
+	c := &ChangeType{
+		X: v,
+	}
+	c.setType(typ)
+	f.emit(c)
+	return c
+}
+
+// emitStore emits to f an instruction to store value val at location
+// addr, applying implicit conversions as required by assignability rules.
+func emitStore(f *Function, addr, val Value, pos token.Pos) *Store {
+	typ := typeparams.MustDeref(addr.Type())
+	s := &Store{
+		Addr: addr,
+		Val:  emitConv(f, val, typ),
+		pos:  pos,
+	}
+	f.emit(s)
+	return s
+}
+
+// emitJump emits to f a jump to target, and updates the control-flow graph.
+// Postcondition: f.currentBlock is nil.
+func emitJump(f *Function, target *BasicBlock) {
+	b := f.currentBlock
+	b.emit(new(Jump))
+	addEdge(b, target)
+	f.currentBlock = nil
+}
+
+// emitIf emits to f a conditional jump to tblock or fblock based on
+// cond, and updates the control-flow graph.
+// Postcondition: f.currentBlock is nil.
+func emitIf(f *Function, cond Value, tblock, fblock *BasicBlock) {
+	b := f.currentBlock
+	b.emit(&If{Cond: cond})
+	addEdge(b, tblock)
+	addEdge(b, fblock)
+	f.currentBlock = nil
+}
+
+// emitExtract emits to f an instruction to extract the index'th
+// component of tuple.  It returns the extracted value.
+func emitExtract(f *Function, tuple Value, index int) Value {
+	e := &Extract{Tuple: tuple, Index: index}
+	e.setType(tuple.Type().(*types.Tuple).At(index).Type())
+	return f.emit(e)
+}
+
+// emitTypeAssert emits to f a type assertion value := x.(t) and
+// returns the value.  x.Type() must be an interface.
+func emitTypeAssert(f *Function, x Value, t types.Type, pos token.Pos) Value {
+	a := &TypeAssert{X: x, AssertedType: t}
+	a.setPos(pos)
+	a.setType(t)
+	return f.emit(a)
+}
+
+// emitTypeTest emits to f a type test value,ok := x.(t) and returns
+// a (value, ok) tuple.  x.Type() must be an interface.
+func emitTypeTest(f *Function, x Value, t types.Type, pos token.Pos) Value {
+	a := &TypeAssert{
+		X:            x,
+		AssertedType: t,
+		CommaOk:      true,
+	}
+	a.setPos(pos)
+	a.setType(types.NewTuple(
+		newVar("value", t),
+		varOk,
+	))
+	return f.emit(a)
+}
+
+// emitTailCall emits to f a function call in tail position.  The
+// caller is responsible for all fields of 'call' except its type.
+// Intended for wrapper methods.
+// Precondition: f does/will not use deferred procedure calls.
+// Postcondition: f.currentBlock is nil.
+func emitTailCall(f *Function, call *Call) {
+	tresults := f.Signature.Results()
+	nr := tresults.Len()
+	if nr == 1 {
+		call.typ = tresults.At(0).Type()
+	} else {
+		call.typ = tresults
+	}
+	tuple := emitCall(f, call)
+	var ret Return
+	switch nr {
+	case 0:
+		// no-op
+	case 1:
+		ret.Results = []Value{tuple}
+	default:
+		for i := range nr {
+			v := emitExtract(f, tuple, i)
+			// TODO(adonovan): in principle, this is required:
+			//   v = emitConv(f, o.Type, f.Signature.Results[i].Type)
+			// but in practice emitTailCall is only used when
+			// the types exactly match.
+			ret.Results = append(ret.Results, v)
+		}
+	}
+	f.emit(&ret)
+	f.currentBlock = nil
+}
+
+// emitCall emits a call instruction. If the callee is "no return",
+// it also emits a panic to eliminate infeasible CFG edges.
+func emitCall(fn *Function, call *Call) Value {
+	res := fn.emit(call)
+
+	callee := call.Call.StaticCallee()
+	if callee != nil &&
+		callee.object != nil &&
+		fn.Prog.noReturn != nil &&
+		fn.Prog.noReturn(callee.object) {
+		// Call cannot return. Insert a panic after it.
+		fn.emit(&Panic{
+			X:   emitConv(fn, vNoReturn, tEface),
+			pos: call.Pos(),
+		})
+		fn.currentBlock = fn.newBasicBlock("unreachable.noreturn")
+	}
+
+	return res
+}
+
+// emitImplicitSelections emits to f code to apply the sequence of
+// implicit field selections specified by indices to base value v, and
+// returns the selected value.
+//
+// If v is the address of a struct, the result will be the address of
+// a field; if it is the value of a struct, the result will be the
+// value of a field.
+func emitImplicitSelections(f *Function, v Value, indices []int, pos token.Pos) Value {
+	for _, index := range indices {
+		if isPointerCore(v.Type()) {
+			fld := fieldOf(typeparams.MustDeref(v.Type()), index)
+			instr := &FieldAddr{
+				X:     v,
+				Field: index,
+			}
+			instr.setPos(pos)
+			instr.setType(types.NewPointer(fld.Type()))
+			v = f.emit(instr)
+			// Load the field's value iff indirectly embedded.
+			if isPointerCore(fld.Type()) {
+				v = emitLoad(f, v)
+			}
+		} else {
+			fld := fieldOf(v.Type(), index)
+			instr := &Field{
+				X:     v,
+				Field: index,
+			}
+			instr.setPos(pos)
+			instr.setType(fld.Type())
+			v = f.emit(instr)
+		}
+	}
+	return v
+}
+
+// emitFieldSelection emits to f code to select the index'th field of v.
+//
+// If wantAddr, the input must be a pointer-to-struct and the result
+// will be the field's address; otherwise the result will be the
+// field's value.
+// Ident id is used for position and debug info.
+func emitFieldSelection(f *Function, v Value, index int, wantAddr bool, id *ast.Ident) Value {
+	if isPointerCore(v.Type()) {
+		fld := fieldOf(typeparams.MustDeref(v.Type()), index)
+		instr := &FieldAddr{
+			X:     v,
+			Field: index,
+		}
+		instr.setPos(id.Pos())
+		instr.setType(types.NewPointer(fld.Type()))
+		v = f.emit(instr)
+		// Load the field's value iff we don't want its address.
+		if !wantAddr {
+			v = emitLoad(f, v)
+		}
+	} else {
+		fld := fieldOf(v.Type(), index)
+		instr := &Field{
+			X:     v,
+			Field: index,
+		}
+		instr.setPos(id.Pos())
+		instr.setType(fld.Type())
+		v = f.emit(instr)
+	}
+	emitDebugRef(f, id, v, wantAddr)
+	return v
+}
+
+// createRecoverBlock emits to f a block of code to return after a
+// recovered panic, and sets f.Recover to it.
+//
+// If f's result parameters are named, the code loads and returns
+// their current values, otherwise it returns the zero values of their
+// type.
+//
+// Idempotent.
+func createRecoverBlock(f *Function) {
+	if f.Recover != nil {
+		return // already created
+	}
+	saved := f.currentBlock
+
+	f.Recover = f.newBasicBlock("recover")
+	f.currentBlock = f.Recover
+
+	var results []Value
+	// Reload NRPs to form value tuple.
+	for _, nr := range f.results {
+		results = append(results, emitLoad(f, nr))
+	}
+
+	f.emit(&Return{Results: results})
+
+	f.currentBlock = saved
+}

vendor/golang.org/x/tools/go/ssa/func.go

@@ -0,0 +1,836 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file implements the Function type.
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"io"
+	"iter"
+	"os"
+	"strings"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Like ObjectOf, but panics instead of returning nil.
+// Only valid during f's create and build phases.
+func (f *Function) objectOf(id *ast.Ident) types.Object {
+	if o := f.info.ObjectOf(id); o != nil {
+		return o
+	}
+	panic(fmt.Sprintf("no types.Object for ast.Ident %s @ %s",
+		id.Name, f.Prog.Fset.Position(id.Pos())))
+}
+
+// Like TypeOf, but panics instead of returning nil.
+// Only valid during f's create and build phases.
+func (f *Function) typeOf(e ast.Expr) types.Type {
+	if T := f.info.TypeOf(e); T != nil {
+		return f.typ(T)
+	}
+	panic(fmt.Sprintf("no type for %T @ %s", e, f.Prog.Fset.Position(e.Pos())))
+}
+
+// typ is the locally instantiated type of T.
+// If f is not an instantiation, then f.typ(T)==T.
+func (f *Function) typ(T types.Type) types.Type {
+	return f.subst.typ(T)
+}
+
+// If id is an Instance, returns info.Instances[id].Type.
+// Otherwise returns f.typeOf(id).
+func (f *Function) instanceType(id *ast.Ident) types.Type {
+	if t, ok := f.info.Instances[id]; ok {
+		return t.Type
+	}
+	return f.typeOf(id)
+}
+
+// selection returns a *selection corresponding to f.info.Selections[selector]
+// with potential updates for type substitution.
+func (f *Function) selection(selector *ast.SelectorExpr) *selection {
+	sel := f.info.Selections[selector]
+	if sel == nil {
+		return nil
+	}
+
+	switch sel.Kind() {
+	case types.MethodExpr, types.MethodVal:
+		if recv := f.typ(sel.Recv()); recv != sel.Recv() {
+			// recv changed during type substitution.
+			pkg := f.declaredPackage().Pkg
+			obj, index, indirect := types.LookupFieldOrMethod(recv, true, pkg, sel.Obj().Name())
+
+			// sig replaces sel.Type(). See (types.Selection).Typ() for details.
+			sig := obj.Type().(*types.Signature)
+			sig = changeRecv(sig, newVar(sig.Recv().Name(), recv))
+			if sel.Kind() == types.MethodExpr {
+				sig = recvAsFirstArg(sig)
+			}
+			return &selection{
+				kind:     sel.Kind(),
+				recv:     recv,
+				typ:      sig,
+				obj:      obj,
+				index:    index,
+				indirect: indirect,
+			}
+		}
+	}
+	return toSelection(sel)
+}
+
+// Destinations associated with unlabelled for/switch/select stmts.
+// We push/pop one of these as we enter/leave each construct and for
+// each BranchStmt we scan for the innermost target of the right type.
+type targets struct {
+	tail         *targets // rest of stack
+	_break       *BasicBlock
+	_continue    *BasicBlock
+	_fallthrough *BasicBlock
+}
+
+// Destinations associated with a labelled block.
+// We populate these as labels are encountered in forward gotos or
+// labelled statements.
+// Forward gotos are resolved once it is known which statement they
+// are associated with inside the Function.
+type lblock struct {
+	label     *types.Label // Label targeted by the blocks.
+	resolved  bool         // _goto block encountered (back jump or resolved fwd jump)
+	_goto     *BasicBlock
+	_break    *BasicBlock
+	_continue *BasicBlock
+}
+
+// label returns the symbol denoted by a label identifier.
+//
+// label should be a non-blank identifier (label.Name != "_").
+func (f *Function) label(label *ast.Ident) *types.Label {
+	return f.objectOf(label).(*types.Label)
+}
+
+// lblockOf returns the branch target associated with the
+// specified label, creating it if needed.
+func (f *Function) lblockOf(label *types.Label) *lblock {
+	lb := f.lblocks[label]
+	if lb == nil {
+		lb = &lblock{
+			label: label,
+			_goto: f.newBasicBlock(label.Name()),
+		}
+		if f.lblocks == nil {
+			f.lblocks = make(map[*types.Label]*lblock)
+		}
+		f.lblocks[label] = lb
+	}
+	return lb
+}
+
+// labelledBlock searches f for the block of the specified label.
+//
+// If f is a yield function, it additionally searches ancestor Functions
+// corresponding to enclosing range-over-func statements within the
+// same source function, so the returned block may belong to a different Function.
+func labelledBlock(f *Function, label *types.Label, tok token.Token) *BasicBlock {
+	if lb := f.lblocks[label]; lb != nil {
+		var block *BasicBlock
+		switch tok {
+		case token.BREAK:
+			block = lb._break
+		case token.CONTINUE:
+			block = lb._continue
+		case token.GOTO:
+			block = lb._goto
+		}
+		if block != nil {
+			return block
+		}
+	}
+	// Search ancestors if this is a yield function.
+	if f.jump != nil {
+		return labelledBlock(f.parent, label, tok)
+	}
+	return nil
+}
+
+// targetedBlock looks for the nearest block in f.targets
+// (and f's ancestors) that matches tok's type, and returns
+// the block and function it was found in.
+func targetedBlock(f *Function, tok token.Token) *BasicBlock {
+	if f == nil {
+		return nil
+	}
+	for t := f.targets; t != nil; t = t.tail {
+		var block *BasicBlock
+		switch tok {
+		case token.BREAK:
+			block = t._break
+		case token.CONTINUE:
+			block = t._continue
+		case token.FALLTHROUGH:
+			block = t._fallthrough
+		}
+		if block != nil {
+			return block
+		}
+	}
+	// Search f's ancestors (in case f is a yield function).
+	return targetedBlock(f.parent, tok)
+}
+
+// instrs returns an iterator that returns each reachable instruction of the SSA function.
+func (f *Function) instrs() iter.Seq[Instruction] {
+	return func(yield func(i Instruction) bool) {
+		for _, block := range f.Blocks {
+			for _, instr := range block.Instrs {
+				if !yield(instr) {
+					return
+				}
+			}
+		}
+	}
+}
+
+// addResultVar adds a result for a variable v to f.results and v to f.returnVars.
+func (f *Function) addResultVar(v *types.Var) {
+	result := emitLocalVar(f, v)
+	f.results = append(f.results, result)
+	f.returnVars = append(f.returnVars, v)
+}
+
+// addParamVar adds a parameter to f.Params.
+func (f *Function) addParamVar(v *types.Var) *Parameter {
+	name := v.Name()
+	if name == "" {
+		name = fmt.Sprintf("arg%d", len(f.Params))
+	}
+	param := &Parameter{
+		name:   name,
+		object: v,
+		typ:    f.typ(v.Type()),
+		parent: f,
+	}
+	f.Params = append(f.Params, param)
+	return param
+}
+
+// addSpilledParam declares a parameter that is pre-spilled to the
+// stack; the function body will load/store the spilled location.
+// Subsequent lifting will eliminate spills where possible.
+func (f *Function) addSpilledParam(obj *types.Var) {
+	param := f.addParamVar(obj)
+	spill := emitLocalVar(f, obj)
+	f.emit(&Store{Addr: spill, Val: param})
+}
+
+// startBody initializes the function prior to generating SSA code for its body.
+// Precondition: f.Type() already set.
+func (f *Function) startBody() {
+	f.currentBlock = f.newBasicBlock("entry")
+	f.vars = make(map[*types.Var]Value) // needed for some synthetics, e.g. init
+}
+
+// createSyntacticParams populates f.Params and generates code (spills
+// and named result locals) for all the parameters declared in the
+// syntax.  In addition it populates the f.objects mapping.
+//
+// Preconditions:
+// f.startBody() was called. f.info != nil.
+// Postcondition:
+// len(f.Params) == len(f.Signature.Params) + (f.Signature.Recv() ? 1 : 0)
+func (f *Function) createSyntacticParams(recv *ast.FieldList, functype *ast.FuncType) {
+	// Receiver (at most one inner iteration).
+	if recv != nil {
+		for _, field := range recv.List {
+			for _, n := range field.Names {
+				f.addSpilledParam(identVar(f, n))
+			}
+			// Anonymous receiver?  No need to spill.
+			if field.Names == nil {
+				f.addParamVar(f.Signature.Recv())
+			}
+		}
+	}
+
+	// Parameters.
+	if functype.Params != nil {
+		n := len(f.Params) // 1 if has recv, 0 otherwise
+		for _, field := range functype.Params.List {
+			for _, n := range field.Names {
+				f.addSpilledParam(identVar(f, n))
+			}
+			// Anonymous parameter?  No need to spill.
+			if field.Names == nil {
+				f.addParamVar(f.Signature.Params().At(len(f.Params) - n))
+			}
+		}
+	}
+
+	// Results.
+	if functype.Results != nil {
+		for _, field := range functype.Results.List {
+			// Implicit "var" decl of locals for named results.
+			for _, n := range field.Names {
+				v := identVar(f, n)
+				f.addResultVar(v)
+			}
+			// Implicit "var" decl of local for an unnamed result.
+			if field.Names == nil {
+				v := f.Signature.Results().At(len(f.results))
+				f.addResultVar(v)
+			}
+		}
+	}
+}
+
+// createDeferStack initializes fn.deferstack to local variable
+// initialized to a ssa:deferstack() call.
+func (fn *Function) createDeferStack() {
+	// Each syntactic function makes a call to ssa:deferstack,
+	// which is spilled to a local. Unused ones are later removed.
+	fn.deferstack = newVar("defer$stack", tDeferStack)
+	call := &Call{Call: CallCommon{Value: vDeferStack}}
+	call.setType(tDeferStack)
+	deferstack := fn.emit(call)
+	spill := emitLocalVar(fn, fn.deferstack)
+	emitStore(fn, spill, deferstack, token.NoPos)
+}
+
+type setNumable interface {
+	setNum(int)
+}
+
+// numberRegisters assigns numbers to all SSA registers
+// (value-defining Instructions) in f, to aid debugging.
+// (Non-Instruction Values are named at construction.)
+func numberRegisters(f *Function) {
+	v := 0
+	for _, b := range f.Blocks {
+		for _, instr := range b.Instrs {
+			switch instr.(type) {
+			case Value:
+				instr.(setNumable).setNum(v)
+				v++
+			}
+		}
+	}
+}
+
+// buildReferrers populates the def/use information in all non-nil
+// Value.Referrers slice.
+// Precondition: all such slices are initially empty.
+func buildReferrers(f *Function) {
+	var rands []*Value
+	for _, b := range f.Blocks {
+		for _, instr := range b.Instrs {
+			rands = instr.Operands(rands[:0]) // recycle storage
+			for _, rand := range rands {
+				if r := *rand; r != nil {
+					if ref := r.Referrers(); ref != nil {
+						*ref = append(*ref, instr)
+					}
+				}
+			}
+		}
+	}
+}
+
+// finishBody() finalizes the contents of the function after SSA code generation of its body.
+//
+// The function is not done being built until done() is called.
+func (f *Function) finishBody() {
+	f.currentBlock = nil
+	f.lblocks = nil
+	f.returnVars = nil
+	f.jump = nil
+	f.source = nil
+	f.exits = nil
+
+	// Remove from f.Locals any Allocs that escape to the heap.
+	j := 0
+	for _, l := range f.Locals {
+		if !l.Heap {
+			f.Locals[j] = l
+			j++
+		}
+	}
+	// Nil out f.Locals[j:] to aid GC.
+	for i := j; i < len(f.Locals); i++ {
+		f.Locals[i] = nil
+	}
+	f.Locals = f.Locals[:j]
+
+	optimizeBlocks(f)
+
+	buildReferrers(f)
+
+	buildDomTree(f)
+
+	if f.Prog.mode&NaiveForm == 0 {
+		// For debugging pre-state of lifting pass:
+		// numberRegisters(f)
+		// f.WriteTo(os.Stderr)
+		lift(f)
+	}
+
+	// clear remaining builder state
+	f.results = nil    // (used by lifting)
+	f.deferstack = nil // (used by lifting)
+	f.vars = nil       // (used by lifting)
+
+	// clear out other function state (keep consistent with buildParamsOnly)
+	f.subst = nil
+
+	numberRegisters(f) // uses f.namedRegisters
+}
+
+// done marks the building of f's SSA body complete,
+// along with any nested functions, and optionally prints them.
+func (f *Function) done() {
+	assert(f.parent == nil, "done called on an anonymous function")
+
+	var visit func(*Function)
+	visit = func(f *Function) {
+		for _, anon := range f.AnonFuncs {
+			visit(anon) // anon is done building before f.
+		}
+
+		f.uniq = 0    // done with uniq
+		f.build = nil // function is built
+
+		if f.Prog.mode&PrintFunctions != 0 {
+			printMu.Lock()
+			f.WriteTo(os.Stdout)
+			printMu.Unlock()
+		}
+
+		if f.Prog.mode&SanityCheckFunctions != 0 {
+			mustSanityCheck(f, nil)
+		}
+	}
+	visit(f)
+}
+
+// removeNilBlocks eliminates nils from f.Blocks and updates each
+// BasicBlock.Index.  Use this after any pass that may delete blocks.
+func (f *Function) removeNilBlocks() {
+	j := 0
+	for _, b := range f.Blocks {
+		if b != nil {
+			b.Index = j
+			f.Blocks[j] = b
+			j++
+		}
+	}
+	// Nil out f.Blocks[j:] to aid GC.
+	for i := j; i < len(f.Blocks); i++ {
+		f.Blocks[i] = nil
+	}
+	f.Blocks = f.Blocks[:j]
+}
+
+// SetDebugMode sets the debug mode for package pkg.  If true, all its
+// functions will include full debug info.  This greatly increases the
+// size of the instruction stream, and causes Functions to depend upon
+// the ASTs, potentially keeping them live in memory for longer.
+func (pkg *Package) SetDebugMode(debug bool) {
+	pkg.debug = debug
+}
+
+// debugInfo reports whether debug info is wanted for this function.
+func (f *Function) debugInfo() bool {
+	// debug info for instantiations follows the debug info of their origin.
+	p := f.declaredPackage()
+	return p != nil && p.debug
+}
+
+// lookup returns the address of the named variable identified by obj
+// that is local to function f or one of its enclosing functions.
+// If escaping, the reference comes from a potentially escaping pointer
+// expression and the referent must be heap-allocated.
+// We assume the referent is a *Alloc or *Phi.
+// (The only Phis at this stage are those created directly by go1.22 "for" loops.)
+func (f *Function) lookup(obj *types.Var, escaping bool) Value {
+	if v, ok := f.vars[obj]; ok {
+		if escaping {
+			switch v := v.(type) {
+			case *Alloc:
+				v.Heap = true
+			case *Phi:
+				for _, edge := range v.Edges {
+					if alloc, ok := edge.(*Alloc); ok {
+						alloc.Heap = true
+					}
+				}
+			}
+		}
+		return v // function-local var (address)
+	}
+
+	// Definition must be in an enclosing function;
+	// plumb it through intervening closures.
+	if f.parent == nil {
+		panic("no ssa.Value for " + obj.String())
+	}
+	outer := f.parent.lookup(obj, true) // escaping
+	v := &FreeVar{
+		name:   obj.Name(),
+		typ:    outer.Type(),
+		pos:    outer.Pos(),
+		outer:  outer,
+		parent: f,
+	}
+	f.vars[obj] = v
+	f.FreeVars = append(f.FreeVars, v)
+	return v
+}
+
+// emit emits the specified instruction to function f.
+func (f *Function) emit(instr Instruction) Value {
+	return f.currentBlock.emit(instr)
+}
+
+// RelString returns the full name of this function, qualified by
+// package name, receiver type, etc.
+//
+// The specific formatting rules are not guaranteed and may change.
+//
+// Examples:
+//
+//	"math.IsNaN"                  // a package-level function
+//	"(*bytes.Buffer).Bytes"       // a declared method or a wrapper
+//	"(*bytes.Buffer).Bytes$thunk" // thunk (func wrapping method; receiver is param 0)
+//	"(*bytes.Buffer).Bytes$bound" // bound (func wrapping method; receiver supplied by closure)
+//	"main.main$1"                 // an anonymous function in main
+//	"main.init#1"                 // a declared init function
+//	"main.init"                   // the synthesized package initializer
+//
+// When these functions are referred to from within the same package
+// (i.e. from == f.Pkg.Object), they are rendered without the package path.
+// For example: "IsNaN", "(*Buffer).Bytes", etc.
+//
+// All non-synthetic functions have distinct package-qualified names.
+// (But two methods may have the same name "(T).f" if one is a synthetic
+// wrapper promoting a non-exported method "f" from another package; in
+// that case, the strings are equal but the identifiers "f" are distinct.)
+func (f *Function) RelString(from *types.Package) string {
+	// Anonymous?
+	if f.parent != nil {
+		// An anonymous function's Name() looks like "parentName$1",
+		// but its String() should include the type/package/etc.
+		parent := f.parent.RelString(from)
+		for i, anon := range f.parent.AnonFuncs {
+			if anon == f {
+				return fmt.Sprintf("%s$%d", parent, 1+i)
+			}
+		}
+
+		return f.name // should never happen
+	}
+
+	// Method (declared or wrapper)?
+	if recv := f.Signature.Recv(); recv != nil {
+		return f.relMethod(from, recv.Type())
+	}
+
+	// Thunk?
+	if f.method != nil {
+		return f.relMethod(from, f.method.recv)
+	}
+
+	// Bound?
+	if len(f.FreeVars) == 1 && strings.HasSuffix(f.name, "$bound") {
+		return f.relMethod(from, f.FreeVars[0].Type())
+	}
+
+	// Package-level function?
+	// Prefix with package name for cross-package references only.
+	if p := f.relPkg(); p != nil && p != from {
+		return fmt.Sprintf("%s.%s", p.Path(), f.name)
+	}
+
+	// Unknown.
+	return f.name
+}
+
+func (f *Function) relMethod(from *types.Package, recv types.Type) string {
+	return fmt.Sprintf("(%s).%s", relType(recv, from), f.name)
+}
+
+// writeSignature writes to buf the signature sig in declaration syntax.
+func writeSignature(buf *bytes.Buffer, from *types.Package, name string, sig *types.Signature) {
+	buf.WriteString("func ")
+	if recv := sig.Recv(); recv != nil {
+		buf.WriteString("(")
+		if name := recv.Name(); name != "" {
+			buf.WriteString(name)
+			buf.WriteString(" ")
+		}
+		types.WriteType(buf, recv.Type(), types.RelativeTo(from))
+		buf.WriteString(") ")
+	}
+	buf.WriteString(name)
+	types.WriteSignature(buf, sig, types.RelativeTo(from))
+}
+
+// declaredPackage returns the package fn is declared in or nil if the
+// function is not declared in a package.
+func (fn *Function) declaredPackage() *Package {
+	switch {
+	case fn.Pkg != nil:
+		return fn.Pkg // non-generic function  (does that follow??)
+	case fn.topLevelOrigin != nil:
+		return fn.topLevelOrigin.Pkg // instance of a named generic function
+	case fn.parent != nil:
+		return fn.parent.declaredPackage() // instance of an anonymous [generic] function
+	default:
+		return nil // function is not declared in a package, e.g. a wrapper.
+	}
+}
+
+// relPkg returns types.Package fn is printed in relationship to.
+func (fn *Function) relPkg() *types.Package {
+	if p := fn.declaredPackage(); p != nil {
+		return p.Pkg
+	}
+	return nil
+}
+
+var _ io.WriterTo = (*Function)(nil) // *Function implements io.Writer
+
+func (f *Function) WriteTo(w io.Writer) (int64, error) {
+	var buf bytes.Buffer
+	WriteFunction(&buf, f)
+	n, err := w.Write(buf.Bytes())
+	return int64(n), err
+}
+
+// WriteFunction writes to buf a human-readable "disassembly" of f.
+func WriteFunction(buf *bytes.Buffer, f *Function) {
+	fmt.Fprintf(buf, "# Name: %s\n", f.String())
+	if f.Pkg != nil {
+		fmt.Fprintf(buf, "# Package: %s\n", f.Pkg.Pkg.Path())
+	}
+	if syn := f.Synthetic; syn != "" {
+		fmt.Fprintln(buf, "# Synthetic:", syn)
+	}
+	if pos := f.Pos(); pos.IsValid() {
+		fmt.Fprintf(buf, "# Location: %s\n", f.Prog.Fset.Position(pos))
+	}
+
+	if f.parent != nil {
+		fmt.Fprintf(buf, "# Parent: %s\n", f.parent.Name())
+	}
+
+	if f.Recover != nil {
+		fmt.Fprintf(buf, "# Recover: %s\n", f.Recover)
+	}
+
+	from := f.relPkg()
+
+	if f.FreeVars != nil {
+		buf.WriteString("# Free variables:\n")
+		for i, fv := range f.FreeVars {
+			fmt.Fprintf(buf, "# % 3d:\t%s %s\n", i, fv.Name(), relType(fv.Type(), from))
+		}
+	}
+
+	if len(f.Locals) > 0 {
+		buf.WriteString("# Locals:\n")
+		for i, l := range f.Locals {
+			fmt.Fprintf(buf, "# % 3d:\t%s %s\n", i, l.Name(), relType(typeparams.MustDeref(l.Type()), from))
+		}
+	}
+	writeSignature(buf, from, f.Name(), f.Signature)
+	buf.WriteString(":\n")
+
+	if f.Blocks == nil {
+		buf.WriteString("\t(external)\n")
+	}
+
+	// NB. column calculations are confused by non-ASCII
+	// characters and assume 8-space tabs.
+	const punchcard = 80 // for old time's sake.
+	const tabwidth = 8
+	for _, b := range f.Blocks {
+		if b == nil {
+			// Corrupt CFG.
+			fmt.Fprintf(buf, ".nil:\n")
+			continue
+		}
+		n, _ := fmt.Fprintf(buf, "%d:", b.Index)
+		// (|predecessors|, |successors|, immediate dominator)
+		bmsg := fmt.Sprintf("%s P:%d S:%d", b.Comment, len(b.Preds), len(b.Succs))
+		if b.Idom() != nil {
+			bmsg = fmt.Sprintf("%s idom:%d", bmsg, b.Idom().Index)
+		}
+		fmt.Fprintf(buf, "%*s%s\n", punchcard-1-n-len(bmsg), "", bmsg)
+
+		if false { // CFG debugging
+			fmt.Fprintf(buf, "\t# CFG: %s --> %s --> %s\n", b.Preds, b, b.Succs)
+		}
+		for _, instr := range b.Instrs {
+			buf.WriteString("\t")
+			switch v := instr.(type) {
+			case Value:
+				l := punchcard - tabwidth
+				// Left-align the instruction.
+				if name := v.Name(); name != "" {
+					n, _ := fmt.Fprintf(buf, "%s = ", name)
+					l -= n
+				}
+				n, _ := buf.WriteString(instr.String())
+				l -= n
+				// Right-align the type if there's space.
+				if t := v.Type(); t != nil {
+					buf.WriteByte(' ')
+					ts := relType(t, from)
+					l -= len(ts) + len("  ") // (spaces before and after type)
+					if l > 0 {
+						fmt.Fprintf(buf, "%*s", l, "")
+					}
+					buf.WriteString(ts)
+				}
+			case nil:
+				// Be robust against bad transforms.
+				buf.WriteString("<deleted>")
+			default:
+				buf.WriteString(instr.String())
+			}
+			// -mode=S: show line numbers
+			if f.Prog.mode&LogSource != 0 {
+				if pos := instr.Pos(); pos.IsValid() {
+					fmt.Fprintf(buf, " L%d", f.Prog.Fset.Position(pos).Line)
+				}
+			}
+			buf.WriteString("\n")
+		}
+	}
+	fmt.Fprintf(buf, "\n")
+}
+
+// newBasicBlock adds to f a new basic block and returns it.  It does
+// not automatically become the current block for subsequent calls to emit.
+// comment is an optional string for more readable debugging output.
+func (f *Function) newBasicBlock(comment string) *BasicBlock {
+	b := &BasicBlock{
+		Index:   len(f.Blocks),
+		Comment: comment,
+		parent:  f,
+	}
+	b.Succs = b.succs2[:0]
+	f.Blocks = append(f.Blocks, b)
+	return b
+}
+
+// NewFunction returns a new synthetic Function instance belonging to
+// prog, with its name and signature fields set as specified.
+//
+// The caller is responsible for initializing the remaining fields of
+// the function object, e.g. Pkg, Params, Blocks.
+//
+// It is practically impossible for clients to construct well-formed
+// SSA functions/packages/programs directly, so we assume this is the
+// job of the Builder alone.  NewFunction exists to provide clients a
+// little flexibility.  For example, analysis tools may wish to
+// construct fake Functions for the root of the callgraph, a fake
+// "reflect" package, etc.
+//
+// TODO(adonovan): think harder about the API here.
+func (prog *Program) NewFunction(name string, sig *types.Signature, provenance string) *Function {
+	return &Function{Prog: prog, name: name, Signature: sig, Synthetic: provenance}
+}
+
+// Syntax returns the function's syntax (*ast.Func{Decl,Lit})
+// if it was produced from syntax or an *ast.RangeStmt if
+// it is a range-over-func yield function.
+func (f *Function) Syntax() ast.Node { return f.syntax }
+
+// identVar returns the variable defined by id.
+func identVar(fn *Function, id *ast.Ident) *types.Var {
+	return fn.info.Defs[id].(*types.Var)
+}
+
+// unique returns a unique positive int within the source tree of f.
+// The source tree of f includes all of f's ancestors by parent and all
+// of the AnonFuncs contained within these.
+func unique(f *Function) int64 {
+	f.uniq++
+	return f.uniq
+}
+
+// exit is a change of control flow going from a range-over-func
+// yield function to an ancestor function caused by a break, continue,
+// goto, or return statement.
+//
+// There are 3 types of exits:
+// * return from the source function (from ReturnStmt),
+// * jump to a block (from break and continue statements [labelled/unlabelled]),
+// * go to a label (from goto statements).
+//
+// As the builder does one pass over the ast, it is unclear whether
+// a forward goto statement will leave a range-over-func body.
+// The function being exited to is unresolved until the end
+// of building the range-over-func body.
+type exit struct {
+	id   int64     // unique value for exit within from and to
+	from *Function // the function the exit starts from
+	to   *Function // the function being exited to (nil if unresolved)
+	pos  token.Pos
+
+	block *BasicBlock  // basic block within to being jumped to.
+	label *types.Label // forward label being jumped to via goto.
+	// block == nil && label == nil => return
+}
+
+// storeVar emits to function f code to store a value v to a *types.Var x.
+func storeVar(f *Function, x *types.Var, v Value, pos token.Pos) {
+	emitStore(f, f.lookup(x, true), v, pos)
+}
+
+// labelExit creates a new exit to a yield fn to exit the function using a label.
+func labelExit(fn *Function, label *types.Label, pos token.Pos) *exit {
+	e := &exit{
+		id:    unique(fn),
+		from:  fn,
+		to:    nil,
+		pos:   pos,
+		label: label,
+	}
+	fn.exits = append(fn.exits, e)
+	return e
+}
+
+// blockExit creates a new exit to a yield fn that jumps to a basic block.
+func blockExit(fn *Function, block *BasicBlock, pos token.Pos) *exit {
+	e := &exit{
+		id:    unique(fn),
+		from:  fn,
+		to:    block.parent,
+		pos:   pos,
+		block: block,
+	}
+	fn.exits = append(fn.exits, e)
+	return e
+}
+
+// returnExit creates a new exit to a yield fn that returns the source function.
+func returnExit(fn *Function, pos token.Pos) *exit {
+	e := &exit{
+		id:   unique(fn),
+		from: fn,
+		to:   fn.source,
+		pos:  pos,
+	}
+	fn.exits = append(fn.exits, e)
+	return e
+}

vendor/golang.org/x/tools/go/ssa/instantiate.go

@@ -0,0 +1,127 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"fmt"
+	"go/types"
+	"slices"
+	"sync"
+)
+
+// A generic records information about a generic origin function,
+// including a cache of existing instantiations.
+type generic struct {
+	instancesMu sync.Mutex
+	instances   map[*typeList]*Function // canonical type arguments to an instance.
+}
+
+// instance returns a Function that is the instantiation of generic
+// origin function fn with the type arguments targs.
+//
+// Any created instance is added to cr.
+//
+// Acquires fn.generic.instancesMu.
+func (fn *Function) instance(targs []types.Type, b *builder) *Function {
+	key := fn.Prog.canon.List(targs)
+
+	gen := fn.generic
+
+	gen.instancesMu.Lock()
+	defer gen.instancesMu.Unlock()
+	inst, ok := gen.instances[key]
+	if !ok {
+		inst = createInstance(fn, targs)
+		inst.buildshared = b.shared()
+		b.enqueue(inst)
+
+		if gen.instances == nil {
+			gen.instances = make(map[*typeList]*Function)
+		}
+		gen.instances[key] = inst
+	} else {
+		b.waitForSharedFunction(inst)
+	}
+	return inst
+}
+
+// createInstance returns the instantiation of generic function fn using targs.
+//
+// Requires fn.generic.instancesMu.
+func createInstance(fn *Function, targs []types.Type) *Function {
+	prog := fn.Prog
+
+	// Compute signature.
+	var sig *types.Signature
+	var obj *types.Func
+	if recv := fn.Signature.Recv(); recv != nil {
+		// method
+		obj = prog.canon.instantiateMethod(fn.object, targs, prog.ctxt)
+		sig = obj.Type().(*types.Signature)
+	} else {
+		// function
+		instSig, err := types.Instantiate(prog.ctxt, fn.Signature, targs, false)
+		if err != nil {
+			panic(err)
+		}
+		instance, ok := instSig.(*types.Signature)
+		if !ok {
+			panic("Instantiate of a Signature returned a non-signature")
+		}
+		obj = fn.object // instantiation does not exist yet
+		sig = prog.canon.Type(instance).(*types.Signature)
+	}
+
+	// Choose strategy (instance or wrapper).
+	var (
+		synthetic string
+		subst     *subster
+		build     buildFunc
+	)
+	if prog.mode&InstantiateGenerics != 0 && !prog.isParameterized(targs...) {
+		synthetic = fmt.Sprintf("instance of %s", fn.Name())
+		if fn.syntax != nil {
+			subst = makeSubster(prog.ctxt, obj, fn.typeparams, targs)
+			build = (*builder).buildFromSyntax
+		} else {
+			build = (*builder).buildParamsOnly
+		}
+	} else {
+		synthetic = fmt.Sprintf("instantiation wrapper of %s", fn.Name())
+		build = (*builder).buildInstantiationWrapper
+	}
+
+	/* generic instance or instantiation wrapper */
+	return &Function{
+		name:           fmt.Sprintf("%s%s", fn.Name(), targs), // may not be unique
+		object:         obj,
+		Signature:      sig,
+		Synthetic:      synthetic,
+		syntax:         fn.syntax,    // \
+		info:           fn.info,      //  } empty for non-created packages
+		goversion:      fn.goversion, // /
+		build:          build,
+		topLevelOrigin: fn,
+		pos:            obj.Pos(),
+		Pkg:            nil,
+		Prog:           fn.Prog,
+		typeparams:     fn.typeparams, // share with origin
+		typeargs:       targs,
+		subst:          subst,
+	}
+}
+
+// isParameterized reports whether any of the specified types contains
+// a free type parameter. It is safe to call concurrently.
+func (prog *Program) isParameterized(ts ...types.Type) bool {
+	prog.hasParamsMu.Lock()
+	defer prog.hasParamsMu.Unlock()
+
+	// TODO(adonovan): profile. If this operation is expensive,
+	// handle the most common but shallow cases such as T, pkg.T,
+	// *T without consulting the cache under the lock.
+
+	return slices.ContainsFunc(ts, prog.hasParams.Has)
+}

vendor/golang.org/x/tools/go/ssa/lift.go

@@ -0,0 +1,671 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines the lifting pass which tries to "lift" Alloc
+// cells (new/local variables) into SSA registers, replacing loads
+// with the dominating stored value, eliminating loads and stores, and
+// inserting φ-nodes as needed.
+
+// Cited papers and resources:
+//
+// Ron Cytron et al. 1991. Efficiently computing SSA form...
+// http://doi.acm.org/10.1145/115372.115320
+//
+// Cooper, Harvey, Kennedy.  2001.  A Simple, Fast Dominance Algorithm.
+// Software Practice and Experience 2001, 4:1-10.
+// http://www.hipersoft.rice.edu/grads/publications/dom14.pdf
+//
+// Daniel Berlin, llvmdev mailing list, 2012.
+// http://lists.cs.uiuc.edu/pipermail/llvmdev/2012-January/046638.html
+// (Be sure to expand the whole thread.)
+
+// TODO(adonovan): opt: there are many optimizations worth evaluating, and
+// the conventional wisdom for SSA construction is that a simple
+// algorithm well engineered often beats those of better asymptotic
+// complexity on all but the most egregious inputs.
+//
+// Danny Berlin suggests that the Cooper et al. algorithm for
+// computing the dominance frontier is superior to Cytron et al.
+// Furthermore he recommends that rather than computing the DF for the
+// whole function then renaming all alloc cells, it may be cheaper to
+// compute the DF for each alloc cell separately and throw it away.
+//
+// Consider exploiting liveness information to avoid creating dead
+// φ-nodes which we then immediately remove.
+//
+// Also see many other "TODO: opt" suggestions in the code.
+
+import (
+	"fmt"
+	"go/token"
+	"math/big"
+	"os"
+	"slices"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// If true, show diagnostic information at each step of lifting.
+// Very verbose.
+const debugLifting = false
+
+// domFrontier maps each block to the set of blocks in its dominance
+// frontier.  The outer slice is conceptually a map keyed by
+// Block.Index.  The inner slice is conceptually a set, possibly
+// containing duplicates.
+//
+// TODO(adonovan): opt: measure impact of dups; consider a packed bit
+// representation, e.g. big.Int, and bitwise parallel operations for
+// the union step in the Children loop.
+//
+// domFrontier's methods mutate the slice's elements but not its
+// length, so their receivers needn't be pointers.
+type domFrontier [][]*BasicBlock
+
+func (df domFrontier) add(u, v *BasicBlock) {
+	p := &df[u.Index]
+	*p = append(*p, v)
+}
+
+// build builds the dominance frontier df for the dominator (sub)tree
+// rooted at u, using the Cytron et al. algorithm.
+//
+// TODO(adonovan): opt: consider Berlin approach, computing pruned SSA
+// by pruning the entire IDF computation, rather than merely pruning
+// the DF -> IDF step.
+func (df domFrontier) build(u *BasicBlock) {
+	// Encounter each node u in postorder of dom tree.
+	for _, child := range u.dom.children {
+		df.build(child)
+	}
+	for _, vb := range u.Succs {
+		if v := vb.dom; v.idom != u {
+			df.add(u, vb)
+		}
+	}
+	for _, w := range u.dom.children {
+		for _, vb := range df[w.Index] {
+			// TODO(adonovan): opt: use word-parallel bitwise union.
+			if v := vb.dom; v.idom != u {
+				df.add(u, vb)
+			}
+		}
+	}
+}
+
+func buildDomFrontier(fn *Function) domFrontier {
+	df := make(domFrontier, len(fn.Blocks))
+	df.build(fn.Blocks[0])
+	if fn.Recover != nil {
+		df.build(fn.Recover)
+	}
+	return df
+}
+
+func removeInstr(refs []Instruction, instr Instruction) []Instruction {
+	return slices.DeleteFunc(refs, func(i Instruction) bool { return i == instr })
+}
+
+// lift replaces local and new Allocs accessed only with
+// load/store by SSA registers, inserting φ-nodes where necessary.
+// The result is a program in classical pruned SSA form.
+//
+// Preconditions:
+// - fn has no dead blocks (blockopt has run).
+// - Def/use info (Operands and Referrers) is up-to-date.
+// - The dominator tree is up-to-date.
+func lift(fn *Function) {
+	// TODO(adonovan): opt: lots of little optimizations may be
+	// worthwhile here, especially if they cause us to avoid
+	// buildDomFrontier.  For example:
+	//
+	// - Alloc never loaded?  Eliminate.
+	// - Alloc never stored?  Replace all loads with a zero constant.
+	// - Alloc stored once?  Replace loads with dominating store;
+	//   don't forget that an Alloc is itself an effective store
+	//   of zero.
+	// - Alloc used only within a single block?
+	//   Use degenerate algorithm avoiding φ-nodes.
+	// - Consider synergy with scalar replacement of aggregates (SRA).
+	//   e.g. *(&x.f) where x is an Alloc.
+	//   Perhaps we'd get better results if we generated this as x.f
+	//   i.e. Field(x, .f) instead of Load(FieldIndex(x, .f)).
+	//   Unclear.
+	//
+	// But we will start with the simplest correct code.
+	df := buildDomFrontier(fn)
+
+	if debugLifting {
+		title := false
+		for i, blocks := range df {
+			if blocks != nil {
+				if !title {
+					fmt.Fprintf(os.Stderr, "Dominance frontier of %s:\n", fn)
+					title = true
+				}
+				fmt.Fprintf(os.Stderr, "\t%s: %s\n", fn.Blocks[i], blocks)
+			}
+		}
+	}
+
+	newPhis := make(newPhiMap)
+
+	// During this pass we will replace some BasicBlock.Instrs
+	// (allocs, loads and stores) with nil, keeping a count in
+	// BasicBlock.gaps.  At the end we will reset Instrs to the
+	// concatenation of all non-dead newPhis and non-nil Instrs
+	// for the block, reusing the original array if space permits.
+
+	// While we're here, we also eliminate 'rundefers'
+	// instructions and ssa:deferstack() in functions that contain no
+	// 'defer' instructions. For now, we also eliminate
+	// 's = ssa:deferstack()' calls if s doesn't escape, replacing s
+	// with nil in Defer{DeferStack: s}. This has the same meaning,
+	// but allows eliminating the intrinsic function `ssa:deferstack()`
+	// (unless it is needed due to range-over-func instances). This gives
+	// ssa users more time to support range-over-func.
+	usesDefer := false
+	deferstackAlloc, deferstackCall := deferstackPreamble(fn)
+	eliminateDeferStack := deferstackAlloc != nil && !deferstackAlloc.Heap
+
+	// A counter used to generate ~unique ids for Phi nodes, as an
+	// aid to debugging.  We use large numbers to make them highly
+	// visible.  All nodes are renumbered later.
+	fresh := 1000
+
+	// Determine which allocs we can lift and number them densely.
+	// The renaming phase uses this numbering for compact maps.
+	numAllocs := 0
+	for _, b := range fn.Blocks {
+		b.gaps = 0
+		b.rundefers = 0
+		for _, instr := range b.Instrs {
+			switch instr := instr.(type) {
+			case *Alloc:
+				index := -1
+				if liftAlloc(df, instr, newPhis, &fresh) {
+					index = numAllocs
+					numAllocs++
+				}
+				instr.index = index
+			case *Defer:
+				usesDefer = true
+				if eliminateDeferStack {
+					// Clear DeferStack and remove references to loads
+					if instr.DeferStack != nil {
+						if refs := instr.DeferStack.Referrers(); refs != nil {
+							*refs = removeInstr(*refs, instr)
+						}
+						instr.DeferStack = nil
+					}
+				}
+			case *RunDefers:
+				b.rundefers++
+			}
+		}
+	}
+
+	// renaming maps an alloc (keyed by index) to its replacement
+	// value.  Initially the renaming contains nil, signifying the
+	// zero constant of the appropriate type; we construct the
+	// Const lazily at most once on each path through the domtree.
+	// TODO(adonovan): opt: cache per-function not per subtree.
+	renaming := make([]Value, numAllocs)
+
+	// Renaming.
+	rename(fn.Blocks[0], renaming, newPhis)
+
+	// Eliminate dead φ-nodes.
+	removeDeadPhis(fn.Blocks, newPhis)
+
+	// Eliminate ssa:deferstack() call.
+	if eliminateDeferStack {
+		b := deferstackCall.block
+		for i, instr := range b.Instrs {
+			if instr == deferstackCall {
+				b.Instrs[i] = nil
+				b.gaps++
+				break
+			}
+		}
+	}
+
+	// Prepend remaining live φ-nodes to each block.
+	for _, b := range fn.Blocks {
+		nps := newPhis[b]
+		j := len(nps)
+
+		rundefersToKill := b.rundefers
+		if usesDefer {
+			rundefersToKill = 0
+		}
+
+		if j+b.gaps+rundefersToKill == 0 {
+			continue // fast path: no new phis or gaps
+		}
+
+		// Compact nps + non-nil Instrs into a new slice.
+		// TODO(adonovan): opt: compact in situ (rightwards)
+		// if Instrs has sufficient space or slack.
+		dst := make([]Instruction, len(b.Instrs)+j-b.gaps-rundefersToKill)
+		for i, np := range nps {
+			dst[i] = np.phi
+		}
+		for _, instr := range b.Instrs {
+			if instr == nil {
+				continue
+			}
+			if !usesDefer {
+				if _, ok := instr.(*RunDefers); ok {
+					continue
+				}
+			}
+			dst[j] = instr
+			j++
+		}
+		b.Instrs = dst
+	}
+
+	// Remove any fn.Locals that were lifted.
+	j := 0
+	for _, l := range fn.Locals {
+		if l.index < 0 {
+			fn.Locals[j] = l
+			j++
+		}
+	}
+	// Nil out fn.Locals[j:] to aid GC.
+	for i := j; i < len(fn.Locals); i++ {
+		fn.Locals[i] = nil
+	}
+	fn.Locals = fn.Locals[:j]
+}
+
+// removeDeadPhis removes φ-nodes not transitively needed by a
+// non-Phi, non-DebugRef instruction.
+func removeDeadPhis(blocks []*BasicBlock, newPhis newPhiMap) {
+	// First pass: find the set of "live" φ-nodes: those reachable
+	// from some non-Phi instruction.
+	//
+	// We compute reachability in reverse, starting from each φ,
+	// rather than forwards, starting from each live non-Phi
+	// instruction, because this way visits much less of the
+	// Value graph.
+	livePhis := make(map[*Phi]bool)
+	for _, npList := range newPhis {
+		for _, np := range npList {
+			phi := np.phi
+			if !livePhis[phi] && phiHasDirectReferrer(phi) {
+				markLivePhi(livePhis, phi)
+			}
+		}
+	}
+
+	// Existing φ-nodes due to && and || operators
+	// are all considered live (see Go issue 19622).
+	for _, b := range blocks {
+		for _, phi := range b.phis() {
+			markLivePhi(livePhis, phi.(*Phi))
+		}
+	}
+
+	// Second pass: eliminate unused phis from newPhis.
+	for block, npList := range newPhis {
+		j := 0
+		for _, np := range npList {
+			if livePhis[np.phi] {
+				npList[j] = np
+				j++
+			} else {
+				// discard it, first removing it from referrers
+				for _, val := range np.phi.Edges {
+					if refs := val.Referrers(); refs != nil {
+						*refs = removeInstr(*refs, np.phi)
+					}
+				}
+				np.phi.block = nil
+			}
+		}
+		newPhis[block] = npList[:j]
+	}
+}
+
+// markLivePhi marks phi, and all φ-nodes transitively reachable via
+// its Operands, live.
+func markLivePhi(livePhis map[*Phi]bool, phi *Phi) {
+	livePhis[phi] = true
+	for _, rand := range phi.Operands(nil) {
+		if q, ok := (*rand).(*Phi); ok {
+			if !livePhis[q] {
+				markLivePhi(livePhis, q)
+			}
+		}
+	}
+}
+
+// phiHasDirectReferrer reports whether phi is directly referred to by
+// a non-Phi instruction.  Such instructions are the
+// roots of the liveness traversal.
+func phiHasDirectReferrer(phi *Phi) bool {
+	for _, instr := range *phi.Referrers() {
+		if _, ok := instr.(*Phi); !ok {
+			return true
+		}
+	}
+	return false
+}
+
+type blockSet struct{ big.Int } // (inherit methods from Int)
+
+// add adds b to the set and returns true if the set changed.
+func (s *blockSet) add(b *BasicBlock) bool {
+	i := b.Index
+	if s.Bit(i) != 0 {
+		return false
+	}
+	s.SetBit(&s.Int, i, 1)
+	return true
+}
+
+// take removes an arbitrary element from a set s and
+// returns its index, or returns -1 if empty.
+func (s *blockSet) take() int {
+	l := s.BitLen()
+	for i := range l {
+		if s.Bit(i) == 1 {
+			s.SetBit(&s.Int, i, 0)
+			return i
+		}
+	}
+	return -1
+}
+
+// newPhi is a pair of a newly introduced φ-node and the lifted Alloc
+// it replaces.
+type newPhi struct {
+	phi   *Phi
+	alloc *Alloc
+}
+
+// newPhiMap records for each basic block, the set of newPhis that
+// must be prepended to the block.
+type newPhiMap map[*BasicBlock][]newPhi
+
+// liftAlloc determines whether alloc can be lifted into registers,
+// and if so, it populates newPhis with all the φ-nodes it may require
+// and returns true.
+//
+// fresh is a source of fresh ids for phi nodes.
+func liftAlloc(df domFrontier, alloc *Alloc, newPhis newPhiMap, fresh *int) bool {
+	// Don't lift result values in functions that defer
+	// calls that may recover from panic.
+	if fn := alloc.Parent(); fn.Recover != nil {
+		if slices.Contains(fn.results, alloc) {
+			return false
+		}
+	}
+
+	// Compute defblocks, the set of blocks containing a
+	// definition of the alloc cell.
+	var defblocks blockSet
+	for _, instr := range *alloc.Referrers() {
+		// Bail out if we discover the alloc is not liftable;
+		// the only operations permitted to use the alloc are
+		// loads/stores into the cell, and DebugRef.
+		switch instr := instr.(type) {
+		case *Store:
+			if instr.Val == alloc {
+				return false // address used as value
+			}
+			if instr.Addr != alloc {
+				panic("Alloc.Referrers is inconsistent")
+			}
+			defblocks.add(instr.Block())
+		case *UnOp:
+			if instr.Op != token.MUL {
+				return false // not a load
+			}
+			if instr.X != alloc {
+				panic("Alloc.Referrers is inconsistent")
+			}
+		case *DebugRef:
+			// ok
+		default:
+			return false // some other instruction
+		}
+	}
+	// The Alloc itself counts as a (zero) definition of the cell.
+	defblocks.add(alloc.Block())
+
+	if debugLifting {
+		fmt.Fprintln(os.Stderr, "\tlifting ", alloc, alloc.Name())
+	}
+
+	fn := alloc.Parent()
+
+	// Φ-insertion.
+	//
+	// What follows is the body of the main loop of the insert-φ
+	// function described by Cytron et al, but instead of using
+	// counter tricks, we just reset the 'hasAlready' and 'work'
+	// sets each iteration.  These are bitmaps so it's pretty cheap.
+	//
+	// TODO(adonovan): opt: recycle slice storage for W,
+	// hasAlready, defBlocks across liftAlloc calls.
+	var hasAlready blockSet
+
+	// Initialize W and work to defblocks.
+	var work blockSet = defblocks // blocks seen
+	var W blockSet                // blocks to do
+	W.Set(&defblocks.Int)
+
+	// Traverse iterated dominance frontier, inserting φ-nodes.
+	for i := W.take(); i != -1; i = W.take() {
+		u := fn.Blocks[i]
+		for _, v := range df[u.Index] {
+			if hasAlready.add(v) {
+				// Create φ-node.
+				// It will be prepended to v.Instrs later, if needed.
+				phi := &Phi{
+					Edges:   make([]Value, len(v.Preds)),
+					Comment: alloc.Comment,
+				}
+				// This is merely a debugging aid:
+				phi.setNum(*fresh)
+				*fresh++
+
+				phi.pos = alloc.Pos()
+				phi.setType(typeparams.MustDeref(alloc.Type()))
+				phi.block = v
+				if debugLifting {
+					fmt.Fprintf(os.Stderr, "\tplace %s = %s at block %s\n", phi.Name(), phi, v)
+				}
+				newPhis[v] = append(newPhis[v], newPhi{phi, alloc})
+
+				if work.add(v) {
+					W.add(v)
+				}
+			}
+		}
+	}
+
+	return true
+}
+
+// replaceAll replaces all intraprocedural uses of x with y,
+// updating x.Referrers and y.Referrers.
+// Precondition: x.Referrers() != nil, i.e. x must be local to some function.
+func replaceAll(x, y Value) {
+	var rands []*Value
+	pxrefs := x.Referrers()
+	pyrefs := y.Referrers()
+	for _, instr := range *pxrefs {
+		rands = instr.Operands(rands[:0]) // recycle storage
+		for _, rand := range rands {
+			if *rand != nil {
+				if *rand == x {
+					*rand = y
+				}
+			}
+		}
+		if pyrefs != nil {
+			*pyrefs = append(*pyrefs, instr) // dups ok
+		}
+	}
+	*pxrefs = nil // x is now unreferenced
+}
+
+// renamed returns the value to which alloc is being renamed,
+// constructing it lazily if it's the implicit zero initialization.
+func renamed(renaming []Value, alloc *Alloc) Value {
+	v := renaming[alloc.index]
+	if v == nil {
+		v = zeroConst(typeparams.MustDeref(alloc.Type()))
+		renaming[alloc.index] = v
+	}
+	return v
+}
+
+// rename implements the (Cytron et al) SSA renaming algorithm, a
+// preorder traversal of the dominator tree replacing all loads of
+// Alloc cells with the value stored to that cell by the dominating
+// store instruction.  For lifting, we need only consider loads,
+// stores and φ-nodes.
+//
+// renaming is a map from *Alloc (keyed by index number) to its
+// dominating stored value; newPhis[x] is the set of new φ-nodes to be
+// prepended to block x.
+func rename(u *BasicBlock, renaming []Value, newPhis newPhiMap) {
+	// Each φ-node becomes the new name for its associated Alloc.
+	for _, np := range newPhis[u] {
+		phi := np.phi
+		alloc := np.alloc
+		renaming[alloc.index] = phi
+	}
+
+	// Rename loads and stores of allocs.
+	for i, instr := range u.Instrs {
+		switch instr := instr.(type) {
+		case *Alloc:
+			if instr.index >= 0 { // store of zero to Alloc cell
+				// Replace dominated loads by the zero value.
+				renaming[instr.index] = nil
+				if debugLifting {
+					fmt.Fprintf(os.Stderr, "\tkill alloc %s\n", instr)
+				}
+				// Delete the Alloc.
+				u.Instrs[i] = nil
+				u.gaps++
+			}
+
+		case *Store:
+			if alloc, ok := instr.Addr.(*Alloc); ok && alloc.index >= 0 { // store to Alloc cell
+				// Replace dominated loads by the stored value.
+				renaming[alloc.index] = instr.Val
+				if debugLifting {
+					fmt.Fprintf(os.Stderr, "\tkill store %s; new value: %s\n",
+						instr, instr.Val.Name())
+				}
+				// Remove the store from the referrer list of the stored value.
+				if refs := instr.Val.Referrers(); refs != nil {
+					*refs = removeInstr(*refs, instr)
+				}
+				// Delete the Store.
+				u.Instrs[i] = nil
+				u.gaps++
+			}
+
+		case *UnOp:
+			if instr.Op == token.MUL {
+				if alloc, ok := instr.X.(*Alloc); ok && alloc.index >= 0 { // load of Alloc cell
+					newval := renamed(renaming, alloc)
+					if debugLifting {
+						fmt.Fprintf(os.Stderr, "\tupdate load %s = %s with %s\n",
+							instr.Name(), instr, newval.Name())
+					}
+					// Replace all references to
+					// the loaded value by the
+					// dominating stored value.
+					replaceAll(instr, newval)
+					// Delete the Load.
+					u.Instrs[i] = nil
+					u.gaps++
+				}
+			}
+
+		case *DebugRef:
+			if alloc, ok := instr.X.(*Alloc); ok && alloc.index >= 0 { // ref of Alloc cell
+				if instr.IsAddr {
+					instr.X = renamed(renaming, alloc)
+					instr.IsAddr = false
+
+					// Add DebugRef to instr.X's referrers.
+					if refs := instr.X.Referrers(); refs != nil {
+						*refs = append(*refs, instr)
+					}
+				} else {
+					// A source expression denotes the address
+					// of an Alloc that was optimized away.
+					instr.X = nil
+
+					// Delete the DebugRef.
+					u.Instrs[i] = nil
+					u.gaps++
+				}
+			}
+		}
+	}
+
+	// For each φ-node in a CFG successor, rename the edge.
+	for _, v := range u.Succs {
+		phis := newPhis[v]
+		if len(phis) == 0 {
+			continue
+		}
+		i := v.predIndex(u)
+		for _, np := range phis {
+			phi := np.phi
+			alloc := np.alloc
+			newval := renamed(renaming, alloc)
+			if debugLifting {
+				fmt.Fprintf(os.Stderr, "\tsetphi %s edge %s -> %s (#%d) (alloc=%s) := %s\n",
+					phi.Name(), u, v, i, alloc.Name(), newval.Name())
+			}
+			phi.Edges[i] = newval
+			if prefs := newval.Referrers(); prefs != nil {
+				*prefs = append(*prefs, phi)
+			}
+		}
+	}
+
+	// Continue depth-first recursion over domtree, pushing a
+	// fresh copy of the renaming map for each subtree.
+	for i, v := range u.dom.children {
+		r := renaming
+		if i < len(u.dom.children)-1 {
+			// On all but the final iteration, we must make
+			// a copy to avoid destructive update.
+			r = make([]Value, len(renaming))
+			copy(r, renaming)
+		}
+		rename(v, r, newPhis)
+	}
+
+}
+
+// deferstackPreamble returns the *Alloc and ssa:deferstack() call for fn.deferstack.
+func deferstackPreamble(fn *Function) (*Alloc, *Call) {
+	if alloc, _ := fn.vars[fn.deferstack].(*Alloc); alloc != nil {
+		for _, ref := range *alloc.Referrers() {
+			if ref, _ := ref.(*Store); ref != nil && ref.Addr == alloc {
+				if call, _ := ref.Val.(*Call); call != nil {
+					return alloc, call
+				}
+			}
+		}
+	}
+	return nil, nil
+}

vendor/golang.org/x/tools/go/ssa/lvalue.go

@@ -0,0 +1,155 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// lvalues are the union of addressable expressions and map-index
+// expressions.
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// An lvalue represents an assignable location that may appear on the
+// left-hand side of an assignment.  This is a generalization of a
+// pointer to permit updates to elements of maps.
+type lvalue interface {
+	store(fn *Function, v Value) // stores v into the location
+	load(fn *Function) Value     // loads the contents of the location
+	address(fn *Function) Value  // address of the location
+	typ() types.Type             // returns the type of the location
+}
+
+// An address is an lvalue represented by a true pointer.
+type address struct {
+	addr Value     // must have a pointer core type.
+	pos  token.Pos // source position
+	expr ast.Expr  // source syntax of the value (not address) [debug mode]
+}
+
+func (a *address) load(fn *Function) Value {
+	load := emitLoad(fn, a.addr)
+	load.pos = a.pos
+	return load
+}
+
+func (a *address) store(fn *Function, v Value) {
+	store := emitStore(fn, a.addr, v, a.pos)
+	if a.expr != nil {
+		// store.Val is v, converted for assignability.
+		emitDebugRef(fn, a.expr, store.Val, false)
+	}
+}
+
+func (a *address) address(fn *Function) Value {
+	if a.expr != nil {
+		emitDebugRef(fn, a.expr, a.addr, true)
+	}
+	return a.addr
+}
+
+func (a *address) typ() types.Type {
+	return typeparams.MustDeref(a.addr.Type())
+}
+
+// An element is an lvalue represented by m[k], the location of an
+// element of a map.  These locations are not addressable
+// since pointers cannot be formed from them, but they do support
+// load() and store().
+type element struct {
+	m, k Value      // map
+	t    types.Type // map element type
+	pos  token.Pos  // source position of colon ({k:v}) or lbrack (m[k]=v)
+}
+
+func (e *element) load(fn *Function) Value {
+	l := &Lookup{
+		X:     e.m,
+		Index: e.k,
+	}
+	l.setPos(e.pos)
+	l.setType(e.t)
+	return fn.emit(l)
+}
+
+func (e *element) store(fn *Function, v Value) {
+	up := &MapUpdate{
+		Map:   e.m,
+		Key:   e.k,
+		Value: emitConv(fn, v, e.t),
+	}
+	up.pos = e.pos
+	fn.emit(up)
+}
+
+func (e *element) address(fn *Function) Value {
+	panic("map elements are not addressable")
+}
+
+func (e *element) typ() types.Type {
+	return e.t
+}
+
+// A lazyAddress is an lvalue whose address is the result of an instruction.
+// These work like an *address except a new address.address() Value
+// is created on each load, store and address call.
+// A lazyAddress can be used to control when a side effect (nil pointer
+// dereference, index out of bounds) of using a location happens.
+type lazyAddress struct {
+	addr func(fn *Function) Value // emit to fn the computation of the address
+	t    types.Type               // type of the location
+	pos  token.Pos                // source position
+	expr ast.Expr                 // source syntax of the value (not address) [debug mode]
+}
+
+func (l *lazyAddress) load(fn *Function) Value {
+	load := emitLoad(fn, l.addr(fn))
+	load.pos = l.pos
+	return load
+}
+
+func (l *lazyAddress) store(fn *Function, v Value) {
+	store := emitStore(fn, l.addr(fn), v, l.pos)
+	if l.expr != nil {
+		// store.Val is v, converted for assignability.
+		emitDebugRef(fn, l.expr, store.Val, false)
+	}
+}
+
+func (l *lazyAddress) address(fn *Function) Value {
+	addr := l.addr(fn)
+	if l.expr != nil {
+		emitDebugRef(fn, l.expr, addr, true)
+	}
+	return addr
+}
+
+func (l *lazyAddress) typ() types.Type { return l.t }
+
+// A blank is a dummy variable whose name is "_".
+// It is not reified: loads are illegal and stores are ignored.
+type blank struct{}
+
+func (bl blank) load(fn *Function) Value {
+	panic("blank.load is illegal")
+}
+
+func (bl blank) store(fn *Function, v Value) {
+	// no-op
+}
+
+func (bl blank) address(fn *Function) Value {
+	panic("blank var is not addressable")
+}
+
+func (bl blank) typ() types.Type {
+	// This should be the type of the blank Ident; the typechecker
+	// doesn't provide this yet, but fortunately, we don't need it
+	// yet either.
+	panic("blank.typ is unimplemented")
+}

vendor/golang.org/x/tools/go/ssa/methods.go

@@ -0,0 +1,180 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines utilities for population of method sets.
+
+import (
+	"fmt"
+	"go/types"
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typesinternal"
+)
+
+// MethodValue returns the Function implementing method sel, building
+// wrapper methods on demand. It returns nil if sel denotes an
+// interface or generic method.
+//
+// Precondition: sel.Kind() == MethodVal.
+//
+// Thread-safe.
+//
+// Acquires prog.methodsMu.
+func (prog *Program) MethodValue(sel *types.Selection) *Function {
+	if sel.Kind() != types.MethodVal {
+		panic(fmt.Sprintf("MethodValue(%s) kind != MethodVal", sel))
+	}
+	T := sel.Recv()
+	if types.IsInterface(T) {
+		return nil // interface method or type parameter
+	}
+
+	if prog.isParameterized(T) {
+		return nil // generic method
+	}
+
+	if prog.mode&LogSource != 0 {
+		defer logStack("MethodValue %s %v", T, sel)()
+	}
+
+	var b builder
+
+	m := func() *Function {
+		prog.methodsMu.Lock()
+		defer prog.methodsMu.Unlock()
+
+		// Get or create SSA method set.
+		mset, ok := prog.methodSets.At(T).(*methodSet)
+		if !ok {
+			mset = &methodSet{mapping: make(map[string]*Function)}
+			prog.methodSets.Set(T, mset)
+		}
+
+		// Get or create SSA method.
+		id := sel.Obj().Id()
+		fn, ok := mset.mapping[id]
+		if !ok {
+			obj := sel.Obj().(*types.Func)
+			needsPromotion := len(sel.Index()) > 1
+			needsIndirection := !isPointer(recvType(obj)) && isPointer(T)
+			if needsPromotion || needsIndirection {
+				fn = createWrapper(prog, toSelection(sel))
+				fn.buildshared = b.shared()
+				b.enqueue(fn)
+			} else {
+				fn = prog.objectMethod(obj, &b)
+			}
+			if fn.Signature.Recv() == nil {
+				panic(fn)
+			}
+			mset.mapping[id] = fn
+		} else {
+			b.waitForSharedFunction(fn)
+		}
+
+		return fn
+	}()
+
+	b.iterate()
+
+	return m
+}
+
+// objectMethod returns the Function for a given method symbol.
+// The symbol may be an instance of a generic function. It need not
+// belong to an existing SSA package created by a call to
+// prog.CreatePackage.
+//
+// objectMethod panics if the function is not a method.
+//
+// Acquires prog.objectMethodsMu.
+func (prog *Program) objectMethod(obj *types.Func, b *builder) *Function {
+	sig := obj.Type().(*types.Signature)
+	if sig.Recv() == nil {
+		panic("not a method: " + obj.String())
+	}
+
+	// Belongs to a created package?
+	if fn := prog.FuncValue(obj); fn != nil {
+		return fn
+	}
+
+	// Instantiation of generic?
+	if originObj := obj.Origin(); originObj != obj {
+		origin := prog.objectMethod(originObj, b)
+		assert(origin.typeparams.Len() > 0, "origin is not generic")
+		targs := receiverTypeArgs(obj)
+		return origin.instance(targs, b)
+	}
+
+	// Consult/update cache of methods created from types.Func.
+	prog.objectMethodsMu.Lock()
+	defer prog.objectMethodsMu.Unlock()
+	fn, ok := prog.objectMethods[obj]
+	if !ok {
+		fn = createFunction(prog, obj, obj.Name(), nil, nil, "")
+		fn.Synthetic = "from type information (on demand)"
+		fn.buildshared = b.shared()
+		b.enqueue(fn)
+
+		if prog.objectMethods == nil {
+			prog.objectMethods = make(map[*types.Func]*Function)
+		}
+		prog.objectMethods[obj] = fn
+	} else {
+		b.waitForSharedFunction(fn)
+	}
+	return fn
+}
+
+// LookupMethod returns the implementation of the method of type T
+// identified by (pkg, name).  It returns nil if the method exists but
+// is an interface method or generic method, and panics if T has no such method.
+func (prog *Program) LookupMethod(T types.Type, pkg *types.Package, name string) *Function {
+	sel := prog.MethodSets.MethodSet(T).Lookup(pkg, name)
+	if sel == nil {
+		panic(fmt.Sprintf("%s has no method %s", T, types.Id(pkg, name)))
+	}
+	return prog.MethodValue(sel)
+}
+
+// methodSet contains the (concrete) methods of a concrete type (non-interface, non-parameterized).
+type methodSet struct {
+	mapping map[string]*Function // populated lazily
+}
+
+// RuntimeTypes returns a new unordered slice containing all types in
+// the program for which a runtime type is required.
+//
+// A runtime type is required for any non-parameterized, non-interface
+// type that is converted to an interface, or for any type (including
+// interface types) derivable from one through reflection.
+//
+// The methods of such types may be reachable through reflection or
+// interface calls even if they are never called directly.
+//
+// Thread-safe.
+//
+// Acquires prog.makeInterfaceTypesMu.
+func (prog *Program) RuntimeTypes() []types.Type {
+	prog.makeInterfaceTypesMu.Lock()
+	defer prog.makeInterfaceTypesMu.Unlock()
+
+	// Compute the derived types on demand, since many SSA clients
+	// never call RuntimeTypes, and those that do typically call
+	// it once (often within ssautil.AllFunctions, which will
+	// eventually not use it; see Go issue #69291.) This
+	// eliminates the need to eagerly compute all the element
+	// types during SSA building.
+	var runtimeTypes []types.Type
+	add := func(t types.Type) { runtimeTypes = append(runtimeTypes, t) }
+	var set typeutil.Map // for de-duping identical types
+	for t := range prog.makeInterfaceTypes {
+		typesinternal.ForEachElement(&set, &prog.MethodSets, t, add)
+	}
+
+	return runtimeTypes
+}

vendor/golang.org/x/tools/go/ssa/mode.go

@@ -0,0 +1,111 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines the BuilderMode type and its command-line flag.
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// BuilderMode is a bitmask of options for diagnostics and checking.
+//
+// *BuilderMode satisfies the flag.Value interface.  Example:
+//
+//	var mode = ssa.BuilderMode(0)
+//	func init() { flag.Var(&mode, "build", ssa.BuilderModeDoc) }
+type BuilderMode uint
+
+const (
+	PrintPackages        BuilderMode = 1 << iota // Print package inventory to stdout
+	PrintFunctions                               // Print function SSA code to stdout
+	LogSource                                    // Log source locations as SSA builder progresses
+	SanityCheckFunctions                         // Perform sanity checking of function bodies
+	NaiveForm                                    // Build naïve SSA form: don't replace local loads/stores with registers
+	BuildSerially                                // Build packages serially, not in parallel.
+	GlobalDebug                                  // Enable debug info for all packages
+	BareInits                                    // Build init functions without guards or calls to dependent inits
+	InstantiateGenerics                          // Instantiate generics functions (monomorphize) while building
+)
+
+const BuilderModeDoc = `Options controlling the SSA builder.
+The value is a sequence of zero or more of these letters:
+C	perform sanity [C]hecking of the SSA form.
+D	include [D]ebug info for every function.
+P	print [P]ackage inventory.
+F	print [F]unction SSA code.
+S	log [S]ource locations as SSA builder progresses.
+L	build distinct packages seria[L]ly instead of in parallel.
+N	build [N]aive SSA form: don't replace local loads/stores with registers.
+I	build bare [I]nit functions: no init guards or calls to dependent inits.
+G   instantiate [G]eneric function bodies via monomorphization
+`
+
+func (m BuilderMode) String() string {
+	var buf bytes.Buffer
+	if m&GlobalDebug != 0 {
+		buf.WriteByte('D')
+	}
+	if m&PrintPackages != 0 {
+		buf.WriteByte('P')
+	}
+	if m&PrintFunctions != 0 {
+		buf.WriteByte('F')
+	}
+	if m&LogSource != 0 {
+		buf.WriteByte('S')
+	}
+	if m&SanityCheckFunctions != 0 {
+		buf.WriteByte('C')
+	}
+	if m&NaiveForm != 0 {
+		buf.WriteByte('N')
+	}
+	if m&BuildSerially != 0 {
+		buf.WriteByte('L')
+	}
+	if m&BareInits != 0 {
+		buf.WriteByte('I')
+	}
+	if m&InstantiateGenerics != 0 {
+		buf.WriteByte('G')
+	}
+	return buf.String()
+}
+
+// Set parses the flag characters in s and updates *m.
+func (m *BuilderMode) Set(s string) error {
+	var mode BuilderMode
+	for _, c := range s {
+		switch c {
+		case 'D':
+			mode |= GlobalDebug
+		case 'P':
+			mode |= PrintPackages
+		case 'F':
+			mode |= PrintFunctions
+		case 'S':
+			mode |= LogSource | BuildSerially
+		case 'C':
+			mode |= SanityCheckFunctions
+		case 'N':
+			mode |= NaiveForm
+		case 'L':
+			mode |= BuildSerially
+		case 'I':
+			mode |= BareInits
+		case 'G':
+			mode |= InstantiateGenerics
+		default:
+			return fmt.Errorf("unknown BuilderMode option: %q", c)
+		}
+	}
+	*m = mode
+	return nil
+}
+
+// Get returns m.
+func (m BuilderMode) Get() any { return m }

vendor/golang.org/x/tools/go/ssa/print.go

@@ -0,0 +1,462 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file implements the String() methods for all Value and
+// Instruction types.
+
+import (
+	"bytes"
+	"fmt"
+	"go/types"
+	"io"
+	"reflect"
+	"sort"
+	"strings"
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// relName returns the name of v relative to i.
+// In most cases, this is identical to v.Name(), but references to
+// Functions (including methods) and Globals use RelString and
+// all types are displayed with relType, so that only cross-package
+// references are package-qualified.
+func relName(v Value, i Instruction) string {
+	var from *types.Package
+	if i != nil {
+		from = i.Parent().relPkg()
+	}
+	switch v := v.(type) {
+	case Member: // *Function or *Global
+		return v.RelString(from)
+	case *Const:
+		return v.RelString(from)
+	}
+	return v.Name()
+}
+
+func relType(t types.Type, from *types.Package) string {
+	return types.TypeString(t, types.RelativeTo(from))
+}
+
+func relTerm(term *types.Term, from *types.Package) string {
+	s := relType(term.Type(), from)
+	if term.Tilde() {
+		return "~" + s
+	}
+	return s
+}
+
+func relString(m Member, from *types.Package) string {
+	// NB: not all globals have an Object (e.g. init$guard),
+	// so use Package().Object not Object.Package().
+	if pkg := m.Package().Pkg; pkg != nil && pkg != from {
+		return fmt.Sprintf("%s.%s", pkg.Path(), m.Name())
+	}
+	return m.Name()
+}
+
+// Value.String()
+//
+// This method is provided only for debugging.
+// It never appears in disassembly, which uses Value.Name().
+
+func (v *Parameter) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("parameter %s : %s", v.Name(), relType(v.Type(), from))
+}
+
+func (v *FreeVar) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("freevar %s : %s", v.Name(), relType(v.Type(), from))
+}
+
+func (v *Builtin) String() string {
+	return fmt.Sprintf("builtin %s", v.Name())
+}
+
+// Instruction.String()
+
+func (v *Alloc) String() string {
+	op := "local"
+	if v.Heap {
+		op = "new"
+	}
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("%s %s (%s)", op, relType(typeparams.MustDeref(v.Type()), from), v.Comment)
+}
+
+func (v *Phi) String() string {
+	var b bytes.Buffer
+	b.WriteString("phi [")
+	for i, edge := range v.Edges {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		// Be robust against malformed CFG.
+		if v.block == nil {
+			b.WriteString("??")
+			continue
+		}
+		block := -1
+		if i < len(v.block.Preds) {
+			block = v.block.Preds[i].Index
+		}
+		fmt.Fprintf(&b, "%d: ", block)
+		edgeVal := "<nil>" // be robust
+		if edge != nil {
+			edgeVal = relName(edge, v)
+		}
+		b.WriteString(edgeVal)
+	}
+	b.WriteString("]")
+	if v.Comment != "" {
+		b.WriteString(" #")
+		b.WriteString(v.Comment)
+	}
+	return b.String()
+}
+
+func printCall(v *CallCommon, prefix string, instr Instruction) string {
+	var b bytes.Buffer
+	b.WriteString(prefix)
+	if !v.IsInvoke() {
+		b.WriteString(relName(v.Value, instr))
+	} else {
+		fmt.Fprintf(&b, "invoke %s.%s", relName(v.Value, instr), v.Method.Name())
+	}
+	b.WriteString("(")
+	for i, arg := range v.Args {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		b.WriteString(relName(arg, instr))
+	}
+	if v.Signature().Variadic() {
+		b.WriteString("...")
+	}
+	b.WriteString(")")
+	return b.String()
+}
+
+func (c *CallCommon) String() string {
+	return printCall(c, "", nil)
+}
+
+func (v *Call) String() string {
+	return printCall(&v.Call, "", v)
+}
+
+func (v *BinOp) String() string {
+	return fmt.Sprintf("%s %s %s", relName(v.X, v), v.Op.String(), relName(v.Y, v))
+}
+
+func (v *UnOp) String() string {
+	return fmt.Sprintf("%s%s%s", v.Op, relName(v.X, v), commaOk(v.CommaOk))
+}
+
+func printConv(prefix string, v, x Value) string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("%s %s <- %s (%s)",
+		prefix,
+		relType(v.Type(), from),
+		relType(x.Type(), from),
+		relName(x, v.(Instruction)))
+}
+
+func (v *ChangeType) String() string          { return printConv("changetype", v, v.X) }
+func (v *Convert) String() string             { return printConv("convert", v, v.X) }
+func (v *ChangeInterface) String() string     { return printConv("change interface", v, v.X) }
+func (v *SliceToArrayPointer) String() string { return printConv("slice to array pointer", v, v.X) }
+func (v *MakeInterface) String() string       { return printConv("make", v, v.X) }
+
+func (v *MultiConvert) String() string {
+	from := v.Parent().relPkg()
+
+	var b strings.Builder
+	b.WriteString(printConv("multiconvert", v, v.X))
+	b.WriteString(" [")
+	for i, s := range termListOf(v.from) {
+		for j, d := range termListOf(v.to) {
+			if i != 0 || j != 0 {
+				b.WriteString(" | ")
+			}
+			fmt.Fprintf(&b, "%s <- %s", relTerm(d, from), relTerm(s, from))
+		}
+	}
+	b.WriteString("]")
+	return b.String()
+}
+
+func (v *MakeClosure) String() string {
+	var b bytes.Buffer
+	fmt.Fprintf(&b, "make closure %s", relName(v.Fn, v))
+	if v.Bindings != nil {
+		b.WriteString(" [")
+		for i, c := range v.Bindings {
+			if i > 0 {
+				b.WriteString(", ")
+			}
+			b.WriteString(relName(c, v))
+		}
+		b.WriteString("]")
+	}
+	return b.String()
+}
+
+func (v *MakeSlice) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("make %s %s %s",
+		relType(v.Type(), from),
+		relName(v.Len, v),
+		relName(v.Cap, v))
+}
+
+func (v *Slice) String() string {
+	var b bytes.Buffer
+	b.WriteString("slice ")
+	b.WriteString(relName(v.X, v))
+	b.WriteString("[")
+	if v.Low != nil {
+		b.WriteString(relName(v.Low, v))
+	}
+	b.WriteString(":")
+	if v.High != nil {
+		b.WriteString(relName(v.High, v))
+	}
+	if v.Max != nil {
+		b.WriteString(":")
+		b.WriteString(relName(v.Max, v))
+	}
+	b.WriteString("]")
+	return b.String()
+}
+
+func (v *MakeMap) String() string {
+	res := ""
+	if v.Reserve != nil {
+		res = relName(v.Reserve, v)
+	}
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("make %s %s", relType(v.Type(), from), res)
+}
+
+func (v *MakeChan) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("make %s %s", relType(v.Type(), from), relName(v.Size, v))
+}
+
+func (v *FieldAddr) String() string {
+	// Be robust against a bad index.
+	name := "?"
+	if fld := fieldOf(typeparams.MustDeref(v.X.Type()), v.Field); fld != nil {
+		name = fld.Name()
+	}
+	return fmt.Sprintf("&%s.%s [#%d]", relName(v.X, v), name, v.Field)
+}
+
+func (v *Field) String() string {
+	// Be robust against a bad index.
+	name := "?"
+	if fld := fieldOf(v.X.Type(), v.Field); fld != nil {
+		name = fld.Name()
+	}
+	return fmt.Sprintf("%s.%s [#%d]", relName(v.X, v), name, v.Field)
+}
+
+func (v *IndexAddr) String() string {
+	return fmt.Sprintf("&%s[%s]", relName(v.X, v), relName(v.Index, v))
+}
+
+func (v *Index) String() string {
+	return fmt.Sprintf("%s[%s]", relName(v.X, v), relName(v.Index, v))
+}
+
+func (v *Lookup) String() string {
+	return fmt.Sprintf("%s[%s]%s", relName(v.X, v), relName(v.Index, v), commaOk(v.CommaOk))
+}
+
+func (v *Range) String() string {
+	return "range " + relName(v.X, v)
+}
+
+func (v *Next) String() string {
+	return "next " + relName(v.Iter, v)
+}
+
+func (v *TypeAssert) String() string {
+	from := v.Parent().relPkg()
+	return fmt.Sprintf("typeassert%s %s.(%s)", commaOk(v.CommaOk), relName(v.X, v), relType(v.AssertedType, from))
+}
+
+func (v *Extract) String() string {
+	return fmt.Sprintf("extract %s #%d", relName(v.Tuple, v), v.Index)
+}
+
+func (s *Jump) String() string {
+	// Be robust against malformed CFG.
+	block := -1
+	if s.block != nil && len(s.block.Succs) == 1 {
+		block = s.block.Succs[0].Index
+	}
+	return fmt.Sprintf("jump %d", block)
+}
+
+func (s *If) String() string {
+	// Be robust against malformed CFG.
+	tblock, fblock := -1, -1
+	if s.block != nil && len(s.block.Succs) == 2 {
+		tblock = s.block.Succs[0].Index
+		fblock = s.block.Succs[1].Index
+	}
+	return fmt.Sprintf("if %s goto %d else %d", relName(s.Cond, s), tblock, fblock)
+}
+
+func (s *Go) String() string {
+	return printCall(&s.Call, "go ", s)
+}
+
+func (s *Panic) String() string {
+	return "panic " + relName(s.X, s)
+}
+
+func (s *Return) String() string {
+	var b bytes.Buffer
+	b.WriteString("return")
+	for i, r := range s.Results {
+		if i == 0 {
+			b.WriteString(" ")
+		} else {
+			b.WriteString(", ")
+		}
+		b.WriteString(relName(r, s))
+	}
+	return b.String()
+}
+
+func (*RunDefers) String() string {
+	return "rundefers"
+}
+
+func (s *Send) String() string {
+	return fmt.Sprintf("send %s <- %s", relName(s.Chan, s), relName(s.X, s))
+}
+
+func (s *Defer) String() string {
+	prefix := "defer "
+	if s.DeferStack != nil {
+		prefix += "[" + relName(s.DeferStack, s) + "] "
+	}
+	c := printCall(&s.Call, prefix, s)
+	return c
+}
+
+func (s *Select) String() string {
+	var b bytes.Buffer
+	for i, st := range s.States {
+		if i > 0 {
+			b.WriteString(", ")
+		}
+		if st.Dir == types.RecvOnly {
+			b.WriteString("<-")
+			b.WriteString(relName(st.Chan, s))
+		} else {
+			b.WriteString(relName(st.Chan, s))
+			b.WriteString("<-")
+			b.WriteString(relName(st.Send, s))
+		}
+	}
+	non := ""
+	if !s.Blocking {
+		non = "non"
+	}
+	return fmt.Sprintf("select %sblocking [%s]", non, b.String())
+}
+
+func (s *Store) String() string {
+	return fmt.Sprintf("*%s = %s", relName(s.Addr, s), relName(s.Val, s))
+}
+
+func (s *MapUpdate) String() string {
+	return fmt.Sprintf("%s[%s] = %s", relName(s.Map, s), relName(s.Key, s), relName(s.Value, s))
+}
+
+func (s *DebugRef) String() string {
+	p := s.Parent().Prog.Fset.Position(s.Pos())
+	var descr any
+	if s.object != nil {
+		descr = s.object // e.g. "var x int"
+	} else {
+		descr = reflect.TypeOf(s.Expr) // e.g. "*ast.CallExpr"
+	}
+	var addr string
+	if s.IsAddr {
+		addr = "address of "
+	}
+	return fmt.Sprintf("; %s%s @ %d:%d is %s", addr, descr, p.Line, p.Column, s.X.Name())
+}
+
+func (p *Package) String() string {
+	return "package " + p.Pkg.Path()
+}
+
+var _ io.WriterTo = (*Package)(nil) // *Package implements io.Writer
+
+func (p *Package) WriteTo(w io.Writer) (int64, error) {
+	var buf bytes.Buffer
+	WritePackage(&buf, p)
+	n, err := w.Write(buf.Bytes())
+	return int64(n), err
+}
+
+// WritePackage writes to buf a human-readable summary of p.
+func WritePackage(buf *bytes.Buffer, p *Package) {
+	fmt.Fprintf(buf, "%s:\n", p)
+
+	var names []string
+	maxname := 0
+	for name := range p.Members {
+		if l := len(name); l > maxname {
+			maxname = l
+		}
+		names = append(names, name)
+	}
+
+	from := p.Pkg
+	sort.Strings(names)
+	for _, name := range names {
+		switch mem := p.Members[name].(type) {
+		case *NamedConst:
+			fmt.Fprintf(buf, "  const %-*s %s = %s\n",
+				maxname, name, mem.Name(), mem.Value.RelString(from))
+
+		case *Function:
+			fmt.Fprintf(buf, "  func  %-*s %s\n",
+				maxname, name, relType(mem.Type(), from))
+
+		case *Type:
+			fmt.Fprintf(buf, "  type  %-*s %s\n",
+				maxname, name, relType(mem.Type().Underlying(), from))
+			for _, meth := range typeutil.IntuitiveMethodSet(mem.Type(), &p.Prog.MethodSets) {
+				fmt.Fprintf(buf, "    %s\n", types.SelectionString(meth, types.RelativeTo(from)))
+			}
+
+		case *Global:
+			fmt.Fprintf(buf, "  var   %-*s %s\n",
+				maxname, name, relType(typeparams.MustDeref(mem.Type()), from))
+		}
+	}
+
+	fmt.Fprintf(buf, "\n")
+}
+
+func commaOk(x bool) string {
+	if x {
+		return ",ok"
+	}
+	return ""
+}

vendor/golang.org/x/tools/go/ssa/sanity.go

@@ -0,0 +1,637 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// An optional pass for sanity-checking invariants of the SSA representation.
+// Currently it checks CFG invariants but little at the instruction level.
+
+import (
+	"bytes"
+	"fmt"
+	"go/ast"
+	"go/types"
+	"io"
+	"os"
+	"slices"
+	"strings"
+)
+
+type sanity struct {
+	reporter io.Writer
+	fn       *Function
+	block    *BasicBlock
+	instrs   map[Instruction]unit
+	insane   bool
+}
+
+// sanityCheck performs integrity checking of the SSA representation
+// of the function fn (which must have been "built") and returns true
+// if it was valid. Diagnostics are written to reporter if non-nil,
+// os.Stderr otherwise. Some diagnostics are only warnings and do not
+// imply a negative result.
+//
+// Sanity-checking is intended to facilitate the debugging of code
+// transformation passes.
+func sanityCheck(fn *Function, reporter io.Writer) bool {
+	if reporter == nil {
+		reporter = os.Stderr
+	}
+	return (&sanity{reporter: reporter}).checkFunction(fn)
+}
+
+// mustSanityCheck is like sanityCheck but panics instead of returning
+// a negative result.
+func mustSanityCheck(fn *Function, reporter io.Writer) {
+	if !sanityCheck(fn, reporter) {
+		fn.WriteTo(os.Stderr)
+		panic("SanityCheck failed")
+	}
+}
+
+func (s *sanity) diagnostic(prefix, format string, args ...any) {
+	fmt.Fprintf(s.reporter, "%s: function %s", prefix, s.fn)
+	if s.block != nil {
+		fmt.Fprintf(s.reporter, ", block %s", s.block)
+	}
+	io.WriteString(s.reporter, ": ")
+	fmt.Fprintf(s.reporter, format, args...)
+	io.WriteString(s.reporter, "\n")
+}
+
+func (s *sanity) errorf(format string, args ...any) {
+	s.insane = true
+	s.diagnostic("Error", format, args...)
+}
+
+func (s *sanity) warnf(format string, args ...any) {
+	s.diagnostic("Warning", format, args...)
+}
+
+// findDuplicate returns an arbitrary basic block that appeared more
+// than once in blocks, or nil if all were unique.
+func findDuplicate(blocks []*BasicBlock) *BasicBlock {
+	if len(blocks) < 2 {
+		return nil
+	}
+	if blocks[0] == blocks[1] {
+		return blocks[0]
+	}
+	// Slow path:
+	m := make(map[*BasicBlock]bool)
+	for _, b := range blocks {
+		if m[b] {
+			return b
+		}
+		m[b] = true
+	}
+	return nil
+}
+
+func (s *sanity) checkInstr(idx int, instr Instruction) {
+	switch instr := instr.(type) {
+	case *If, *Jump, *Return, *Panic:
+		s.errorf("control flow instruction not at end of block")
+	case *Phi:
+		if idx == 0 {
+			// It suffices to apply this check to just the first phi node.
+			if dup := findDuplicate(s.block.Preds); dup != nil {
+				s.errorf("phi node in block with duplicate predecessor %s", dup)
+			}
+		} else {
+			prev := s.block.Instrs[idx-1]
+			if _, ok := prev.(*Phi); !ok {
+				s.errorf("Phi instruction follows a non-Phi: %T", prev)
+			}
+		}
+		if ne, np := len(instr.Edges), len(s.block.Preds); ne != np {
+			s.errorf("phi node has %d edges but %d predecessors", ne, np)
+
+		} else {
+			for i, e := range instr.Edges {
+				if e == nil {
+					s.errorf("phi node '%s' has no value for edge #%d from %s", instr.Comment, i, s.block.Preds[i])
+				} else if !types.Identical(instr.typ, e.Type()) {
+					s.errorf("phi node '%s' has a different type (%s) for edge #%d from %s (%s)",
+						instr.Comment, instr.Type(), i, s.block.Preds[i], e.Type())
+				}
+			}
+		}
+
+	case *Alloc:
+		if !instr.Heap {
+			found := slices.Contains(s.fn.Locals, instr)
+			if !found {
+				s.errorf("local alloc %s = %s does not appear in Function.Locals", instr.Name(), instr)
+			}
+		}
+
+	case *BinOp:
+	case *Call:
+		if common := instr.Call; common.IsInvoke() {
+			if !types.IsInterface(common.Value.Type()) {
+				s.errorf("invoke on %s (%s) which is not an interface type (or type param)", common.Value, common.Value.Type())
+			}
+		}
+	case *ChangeInterface:
+	case *ChangeType:
+	case *SliceToArrayPointer:
+	case *Convert:
+		if from := instr.X.Type(); !isBasicConvTypes(from) {
+			if to := instr.Type(); !isBasicConvTypes(to) {
+				s.errorf("convert %s -> %s: at least one type must be basic (or all basic, []byte, or []rune)", from, to)
+			}
+		}
+	case *MultiConvert:
+	case *Defer:
+	case *Extract:
+	case *Field:
+	case *FieldAddr:
+	case *Go:
+	case *Index:
+	case *IndexAddr:
+	case *Lookup:
+	case *MakeChan:
+	case *MakeClosure:
+		numFree := len(instr.Fn.(*Function).FreeVars)
+		numBind := len(instr.Bindings)
+		if numFree != numBind {
+			s.errorf("MakeClosure has %d Bindings for function %s with %d free vars",
+				numBind, instr.Fn, numFree)
+
+		}
+		if recv := instr.Type().(*types.Signature).Recv(); recv != nil {
+			s.errorf("MakeClosure's type includes receiver %s", recv.Type())
+		}
+
+	case *MakeInterface:
+	case *MakeMap:
+	case *MakeSlice:
+	case *MapUpdate:
+	case *Next:
+	case *Range:
+	case *RunDefers:
+	case *Select:
+	case *Send:
+	case *Slice:
+	case *Store:
+	case *TypeAssert:
+	case *UnOp:
+	case *DebugRef:
+		// TODO(adonovan): implement checks.
+	default:
+		panic(fmt.Sprintf("Unknown instruction type: %T", instr))
+	}
+
+	if call, ok := instr.(CallInstruction); ok {
+		if call.Common().Signature() == nil {
+			s.errorf("nil signature: %s", call)
+		}
+	}
+
+	// Check that value-defining instructions have valid types
+	// and a valid referrer list.
+	if v, ok := instr.(Value); ok {
+		t := v.Type()
+		if t == nil {
+			s.errorf("no type: %s = %s", v.Name(), v)
+		} else if t == tRangeIter || t == tDeferStack {
+			// not a proper type; ignore.
+		} else if b, ok := t.Underlying().(*types.Basic); ok && b.Info()&types.IsUntyped != 0 {
+			s.errorf("instruction has 'untyped' result: %s = %s : %s", v.Name(), v, t)
+		}
+		s.checkReferrerList(v)
+	}
+
+	// Untyped constants are legal as instruction Operands(),
+	// for example:
+	//   _ = "foo"[0]
+	// or:
+	//   if wordsize==64 {...}
+
+	// All other non-Instruction Values can be found via their
+	// enclosing Function or Package.
+}
+
+func (s *sanity) checkFinalInstr(instr Instruction) {
+	switch instr := instr.(type) {
+	case *If:
+		if nsuccs := len(s.block.Succs); nsuccs != 2 {
+			s.errorf("If-terminated block has %d successors; expected 2", nsuccs)
+			return
+		}
+		if s.block.Succs[0] == s.block.Succs[1] {
+			s.errorf("If-instruction has same True, False target blocks: %s", s.block.Succs[0])
+			return
+		}
+
+	case *Jump:
+		if nsuccs := len(s.block.Succs); nsuccs != 1 {
+			s.errorf("Jump-terminated block has %d successors; expected 1", nsuccs)
+			return
+		}
+
+	case *Return:
+		if nsuccs := len(s.block.Succs); nsuccs != 0 {
+			s.errorf("Return-terminated block has %d successors; expected none", nsuccs)
+			return
+		}
+		if na, nf := len(instr.Results), s.fn.Signature.Results().Len(); nf != na {
+			s.errorf("%d-ary return in %d-ary function", na, nf)
+		}
+
+	case *Panic:
+		if nsuccs := len(s.block.Succs); nsuccs != 0 {
+			s.errorf("Panic-terminated block has %d successors; expected none", nsuccs)
+			return
+		}
+
+	default:
+		s.errorf("non-control flow instruction at end of block")
+	}
+}
+
+func (s *sanity) checkBlock(b *BasicBlock, index int) {
+	s.block = b
+
+	if b.Index != index {
+		s.errorf("block has incorrect Index %d", b.Index)
+	}
+	if b.parent != s.fn {
+		s.errorf("block has incorrect parent %s", b.parent)
+	}
+
+	// Check all blocks are reachable.
+	// (The entry block is always implicitly reachable,
+	// as is the Recover block, if any.)
+	if (index > 0 && b != b.parent.Recover) && len(b.Preds) == 0 {
+		s.warnf("unreachable block")
+		if b.Instrs == nil {
+			// Since this block is about to be pruned,
+			// tolerating transient problems in it
+			// simplifies other optimizations.
+			return
+		}
+	}
+
+	// Check predecessor and successor relations are dual,
+	// and that all blocks in CFG belong to same function.
+	for _, a := range b.Preds {
+		found := slices.Contains(a.Succs, b)
+		if !found {
+			s.errorf("expected successor edge in predecessor %s; found only: %s", a, a.Succs)
+		}
+		if a.parent != s.fn {
+			s.errorf("predecessor %s belongs to different function %s", a, a.parent)
+		}
+	}
+	for _, c := range b.Succs {
+		found := slices.Contains(c.Preds, b)
+		if !found {
+			s.errorf("expected predecessor edge in successor %s; found only: %s", c, c.Preds)
+		}
+		if c.parent != s.fn {
+			s.errorf("successor %s belongs to different function %s", c, c.parent)
+		}
+	}
+
+	// Check each instruction is sane.
+	n := len(b.Instrs)
+	if n == 0 {
+		s.errorf("basic block contains no instructions")
+	}
+	var rands [10]*Value // reuse storage
+	for j, instr := range b.Instrs {
+		if instr == nil {
+			s.errorf("nil instruction at index %d", j)
+			continue
+		}
+		if b2 := instr.Block(); b2 == nil {
+			s.errorf("nil Block() for instruction at index %d", j)
+			continue
+		} else if b2 != b {
+			s.errorf("wrong Block() (%s) for instruction at index %d ", b2, j)
+			continue
+		}
+		if j < n-1 {
+			s.checkInstr(j, instr)
+		} else {
+			s.checkFinalInstr(instr)
+		}
+
+		// Check Instruction.Operands.
+	operands:
+		for i, op := range instr.Operands(rands[:0]) {
+			if op == nil {
+				s.errorf("nil operand pointer %d of %s", i, instr)
+				continue
+			}
+			val := *op
+			if val == nil {
+				continue // a nil operand is ok
+			}
+
+			// Check that "untyped" types only appear on constant operands.
+			if _, ok := (*op).(*Const); !ok {
+				if basic, ok := (*op).Type().Underlying().(*types.Basic); ok {
+					if basic.Info()&types.IsUntyped != 0 {
+						s.errorf("operand #%d of %s is untyped: %s", i, instr, basic)
+					}
+				}
+			}
+
+			// Check that Operands that are also Instructions belong to same function.
+			// TODO(adonovan): also check their block dominates block b.
+			if val, ok := val.(Instruction); ok {
+				if val.Block() == nil {
+					s.errorf("operand %d of %s is an instruction (%s) that belongs to no block", i, instr, val)
+				} else if val.Parent() != s.fn {
+					s.errorf("operand %d of %s is an instruction (%s) from function %s", i, instr, val, val.Parent())
+				}
+			}
+
+			// Check that each function-local operand of
+			// instr refers back to instr.  (NB: quadratic)
+			switch val := val.(type) {
+			case *Const, *Global, *Builtin:
+				continue // not local
+			case *Function:
+				if val.parent == nil {
+					continue // only anon functions are local
+				}
+			}
+
+			// TODO(adonovan): check val.Parent() != nil <=> val.Referrers() is defined.
+
+			if refs := val.Referrers(); refs != nil {
+				for _, ref := range *refs {
+					if ref == instr {
+						continue operands
+					}
+				}
+				s.errorf("operand %d of %s (%s) does not refer to us", i, instr, val)
+			} else {
+				s.errorf("operand %d of %s (%s) has no referrers", i, instr, val)
+			}
+		}
+	}
+}
+
+func (s *sanity) checkReferrerList(v Value) {
+	refs := v.Referrers()
+	if refs == nil {
+		s.errorf("%s has missing referrer list", v.Name())
+		return
+	}
+	for i, ref := range *refs {
+		if _, ok := s.instrs[ref]; !ok {
+			s.errorf("%s.Referrers()[%d] = %s is not an instruction belonging to this function", v.Name(), i, ref)
+		}
+	}
+}
+
+func (s *sanity) checkFunctionParams() {
+	signature := s.fn.Signature
+	params := s.fn.Params
+
+	// startSigParams is the start of signature.Params() within params.
+	startSigParams := 0
+	if signature.Recv() != nil {
+		startSigParams = 1
+	}
+
+	if startSigParams+signature.Params().Len() != len(params) {
+		s.errorf("function has %d parameters in signature but has %d after building",
+			startSigParams+signature.Params().Len(), len(params))
+		return
+	}
+
+	for i, param := range params {
+		var sigType types.Type
+		si := i - startSigParams
+		if si < 0 {
+			sigType = signature.Recv().Type()
+		} else {
+			sigType = signature.Params().At(si).Type()
+		}
+
+		if !types.Identical(sigType, param.Type()) {
+			s.errorf("expect type %s in signature but got type %s in param %d", param.Type(), sigType, i)
+		}
+	}
+}
+
+// checkTransientFields checks whether all transient fields of Function are cleared.
+func (s *sanity) checkTransientFields() {
+	fn := s.fn
+	if fn.build != nil {
+		s.errorf("function transient field 'build' is not nil")
+	}
+	if fn.currentBlock != nil {
+		s.errorf("function transient field 'currentBlock' is not nil")
+	}
+	if fn.vars != nil {
+		s.errorf("function transient field 'vars' is not nil")
+	}
+	if fn.results != nil {
+		s.errorf("function transient field 'results' is not nil")
+	}
+	if fn.returnVars != nil {
+		s.errorf("function transient field 'returnVars' is not nil")
+	}
+	if fn.targets != nil {
+		s.errorf("function transient field 'targets' is not nil")
+	}
+	if fn.lblocks != nil {
+		s.errorf("function transient field 'lblocks' is not nil")
+	}
+	if fn.subst != nil {
+		s.errorf("function transient field 'subst' is not nil")
+	}
+	if fn.jump != nil {
+		s.errorf("function transient field 'jump' is not nil")
+	}
+	if fn.deferstack != nil {
+		s.errorf("function transient field 'deferstack' is not nil")
+	}
+	if fn.source != nil {
+		s.errorf("function transient field 'source' is not nil")
+	}
+	if fn.exits != nil {
+		s.errorf("function transient field 'exits' is not nil")
+	}
+	if fn.uniq != 0 {
+		s.errorf("function transient field 'uniq' is not zero")
+	}
+}
+
+func (s *sanity) checkFunction(fn *Function) bool {
+	s.fn = fn
+	s.checkFunctionParams()
+	s.checkTransientFields()
+
+	// TODO(taking): Sanity check origin, typeparams, and typeargs.
+	if fn.Prog == nil {
+		s.errorf("nil Prog")
+	}
+
+	var buf bytes.Buffer
+	_ = fn.String()               // must not crash
+	_ = fn.RelString(fn.relPkg()) // must not crash
+	WriteFunction(&buf, fn)       // must not crash
+
+	// All functions have a package, except delegates (which are
+	// shared across packages, or duplicated as weak symbols in a
+	// separate-compilation model), and error.Error.
+	if fn.Pkg == nil {
+		if strings.HasPrefix(fn.Synthetic, "from type information (on demand)") ||
+			strings.HasPrefix(fn.Synthetic, "wrapper ") ||
+			strings.HasPrefix(fn.Synthetic, "bound ") ||
+			strings.HasPrefix(fn.Synthetic, "thunk ") ||
+			strings.HasSuffix(fn.name, "Error") ||
+			strings.HasPrefix(fn.Synthetic, "instance ") ||
+			strings.HasPrefix(fn.Synthetic, "instantiation ") ||
+			(fn.parent != nil && len(fn.typeargs) > 0) /* anon fun in instance */ {
+			// ok
+		} else {
+			s.errorf("nil Pkg")
+		}
+	}
+	if src, syn := fn.Synthetic == "", fn.Syntax() != nil; src != syn {
+		if len(fn.typeargs) > 0 && fn.Prog.mode&InstantiateGenerics != 0 {
+			// ok (instantiation with InstantiateGenerics on)
+		} else if fn.topLevelOrigin != nil && len(fn.typeargs) > 0 {
+			// ok (we always have the syntax set for instantiation)
+		} else if _, rng := fn.syntax.(*ast.RangeStmt); rng && fn.Synthetic == "range-over-func yield" {
+			// ok (range-func-yields are both synthetic and keep syntax)
+		} else {
+			s.errorf("got fromSource=%t, hasSyntax=%t; want same values", src, syn)
+		}
+	}
+
+	// Build the set of valid referrers.
+	s.instrs = make(map[Instruction]unit)
+
+	// instrs are the instructions that are present in the function.
+	for instr := range fn.instrs() {
+		s.instrs[instr] = unit{}
+	}
+
+	// Check all Locals allocations appear in the function instruction.
+	for i, l := range fn.Locals {
+		if _, present := s.instrs[l]; !present {
+			s.warnf("function doesn't contain Local alloc %s", l.Name())
+		}
+
+		if l.Parent() != fn {
+			s.errorf("Local %s at index %d has wrong parent", l.Name(), i)
+		}
+		if l.Heap {
+			s.errorf("Local %s at index %d has Heap flag set", l.Name(), i)
+		}
+	}
+	for i, p := range fn.Params {
+		if p.Parent() != fn {
+			s.errorf("Param %s at index %d has wrong parent", p.Name(), i)
+		}
+		// Check common suffix of Signature and Params match type.
+		if sig := fn.Signature; sig != nil {
+			j := i - len(fn.Params) + sig.Params().Len() // index within sig.Params
+			if j < 0 {
+				continue
+			}
+			if !types.Identical(p.Type(), sig.Params().At(j).Type()) {
+				s.errorf("Param %s at index %d has wrong type (%s, versus %s in Signature)", p.Name(), i, p.Type(), sig.Params().At(j).Type())
+
+			}
+		}
+		s.checkReferrerList(p)
+	}
+	for i, fv := range fn.FreeVars {
+		if fv.Parent() != fn {
+			s.errorf("FreeVar %s at index %d has wrong parent", fv.Name(), i)
+		}
+		s.checkReferrerList(fv)
+	}
+
+	if fn.Blocks != nil && len(fn.Blocks) == 0 {
+		// Function _had_ blocks (so it's not external) but
+		// they were "optimized" away, even the entry block.
+		s.errorf("Blocks slice is non-nil but empty")
+	}
+	for i, b := range fn.Blocks {
+		if b == nil {
+			s.warnf("nil *BasicBlock at f.Blocks[%d]", i)
+			continue
+		}
+		s.checkBlock(b, i)
+	}
+	if fn.Recover != nil && fn.Blocks[fn.Recover.Index] != fn.Recover {
+		s.errorf("Recover block is not in Blocks slice")
+	}
+
+	s.block = nil
+	for i, anon := range fn.AnonFuncs {
+		if anon.Parent() != fn {
+			s.errorf("AnonFuncs[%d]=%s but %s.Parent()=%s", i, anon, anon, anon.Parent())
+		}
+		if i != int(anon.anonIdx) {
+			s.errorf("AnonFuncs[%d]=%s but %s.anonIdx=%d", i, anon, anon, anon.anonIdx)
+		}
+	}
+	s.fn = nil
+	return !s.insane
+}
+
+// sanityCheckPackage checks invariants of packages upon creation.
+// It does not require that the package is built.
+// Unlike sanityCheck (for functions), it just panics at the first error.
+func sanityCheckPackage(pkg *Package) {
+	if pkg.Pkg == nil {
+		panic(fmt.Sprintf("Package %s has no Object", pkg))
+	}
+	if pkg.info != nil {
+		panic(fmt.Sprintf("package %s field 'info' is not cleared", pkg))
+	}
+	if pkg.files != nil {
+		panic(fmt.Sprintf("package %s field 'files' is not cleared", pkg))
+	}
+	if pkg.created != nil {
+		panic(fmt.Sprintf("package %s field 'created' is not cleared", pkg))
+	}
+	if pkg.initVersion != nil {
+		panic(fmt.Sprintf("package %s field 'initVersion' is not cleared", pkg))
+	}
+
+	_ = pkg.String() // must not crash
+
+	for name, mem := range pkg.Members {
+		if name != mem.Name() {
+			panic(fmt.Sprintf("%s: %T.Name() = %s, want %s",
+				pkg.Pkg.Path(), mem, mem.Name(), name))
+		}
+		obj := mem.Object()
+		if obj == nil {
+			// This check is sound because fields
+			// {Global,Function}.object have type
+			// types.Object.  (If they were declared as
+			// *types.{Var,Func}, we'd have a non-empty
+			// interface containing a nil pointer.)
+
+			continue // not all members have typechecker objects
+		}
+		if obj.Name() != name {
+			if obj.Name() == "init" && strings.HasPrefix(mem.Name(), "init#") {
+				// Ok.  The name of a declared init function varies between
+				// its types.Func ("init") and its ssa.Function ("init#%d").
+			} else {
+				panic(fmt.Sprintf("%s: %T.Object().Name() = %s, want %s",
+					pkg.Pkg.Path(), mem, obj.Name(), name))
+			}
+		}
+		if obj.Pos() != mem.Pos() {
+			panic(fmt.Sprintf("%s Pos=%d obj.Pos=%d", mem, mem.Pos(), obj.Pos()))
+		}
+	}
+}

vendor/golang.org/x/tools/go/ssa/source.go

@@ -0,0 +1,288 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines utilities for working with source positions
+// or source-level named entities ("objects").
+
+// TODO(adonovan): test that {Value,Instruction}.Pos() positions match
+// the originating syntax, as specified.
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+)
+
+// EnclosingFunction returns the function that contains the syntax
+// node denoted by path.
+//
+// Syntax associated with package-level variable specifications is
+// enclosed by the package's init() function.
+//
+// Returns nil if not found; reasons might include:
+//   - the node is not enclosed by any function.
+//   - the node is within an anonymous function (FuncLit) and
+//     its SSA function has not been created yet
+//     (pkg.Build() has not yet been called).
+func EnclosingFunction(pkg *Package, path []ast.Node) *Function {
+	// Start with package-level function...
+	fn := findEnclosingPackageLevelFunction(pkg, path)
+	if fn == nil {
+		return nil // not in any function
+	}
+
+	// ...then walk down the nested anonymous functions.
+	n := len(path)
+outer:
+	for i := range path {
+		if lit, ok := path[n-1-i].(*ast.FuncLit); ok {
+			for _, anon := range fn.AnonFuncs {
+				if anon.Pos() == lit.Type.Func {
+					fn = anon
+					continue outer
+				}
+			}
+			// SSA function not found:
+			// - package not yet built, or maybe
+			// - builder skipped FuncLit in dead block
+			//   (in principle; but currently the Builder
+			//   generates even dead FuncLits).
+			return nil
+		}
+	}
+	return fn
+}
+
+// HasEnclosingFunction returns true if the AST node denoted by path
+// is contained within the declaration of some function or
+// package-level variable.
+//
+// Unlike EnclosingFunction, the behaviour of this function does not
+// depend on whether SSA code for pkg has been built, so it can be
+// used to quickly reject check inputs that will cause
+// EnclosingFunction to fail, prior to SSA building.
+func HasEnclosingFunction(pkg *Package, path []ast.Node) bool {
+	return findEnclosingPackageLevelFunction(pkg, path) != nil
+}
+
+// findEnclosingPackageLevelFunction returns the Function
+// corresponding to the package-level function enclosing path.
+func findEnclosingPackageLevelFunction(pkg *Package, path []ast.Node) *Function {
+	if n := len(path); n >= 2 { // [... {Gen,Func}Decl File]
+		switch decl := path[n-2].(type) {
+		case *ast.GenDecl:
+			if decl.Tok == token.VAR && n >= 3 {
+				// Package-level 'var' initializer.
+				return pkg.init
+			}
+
+		case *ast.FuncDecl:
+			if decl.Recv == nil && decl.Name.Name == "init" {
+				// Explicit init() function.
+				for _, b := range pkg.init.Blocks {
+					for _, instr := range b.Instrs {
+						if instr, ok := instr.(*Call); ok {
+							if callee, ok := instr.Call.Value.(*Function); ok && callee.Pkg == pkg && callee.Pos() == decl.Name.NamePos {
+								return callee
+							}
+						}
+					}
+				}
+				// Hack: return non-nil when SSA is not yet
+				// built so that HasEnclosingFunction works.
+				return pkg.init
+			}
+			// Declared function/method.
+			return findNamedFunc(pkg, decl.Name.NamePos)
+		}
+	}
+	return nil // not in any function
+}
+
+// findNamedFunc returns the named function whose FuncDecl.Ident is at
+// position pos.
+func findNamedFunc(pkg *Package, pos token.Pos) *Function {
+	// Look at all package members and method sets of named types.
+	// Not very efficient.
+	for _, mem := range pkg.Members {
+		switch mem := mem.(type) {
+		case *Function:
+			if mem.Pos() == pos {
+				return mem
+			}
+		case *Type:
+			mset := pkg.Prog.MethodSets.MethodSet(types.NewPointer(mem.Type()))
+			for i, n := 0, mset.Len(); i < n; i++ {
+				// Don't call Program.Method: avoid creating wrappers.
+				obj := mset.At(i).Obj().(*types.Func)
+				if obj.Pos() == pos {
+					// obj from MethodSet may not be the origin type.
+					m := obj.Origin()
+					return pkg.objects[m].(*Function)
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// ValueForExpr returns the SSA Value that corresponds to non-constant
+// expression e.
+//
+// It returns nil if no value was found, e.g.
+//   - the expression is not lexically contained within f;
+//   - f was not built with debug information; or
+//   - e is a constant expression.  (For efficiency, no debug
+//     information is stored for constants. Use
+//     go/types.Info.Types[e].Value instead.)
+//   - e is a reference to nil or a built-in function.
+//   - the value was optimised away.
+//
+// If e is an addressable expression used in an lvalue context,
+// value is the address denoted by e, and isAddr is true.
+//
+// The types of e (or &e, if isAddr) and the result are equal
+// (modulo "untyped" bools resulting from comparisons).
+//
+// (Tip: to find the ssa.Value given a source position, use
+// astutil.PathEnclosingInterval to locate the ast.Node, then
+// EnclosingFunction to locate the Function, then ValueForExpr to find
+// the ssa.Value.)
+func (f *Function) ValueForExpr(e ast.Expr) (value Value, isAddr bool) {
+	if f.debugInfo() { // (opt)
+		e = ast.Unparen(e)
+		for _, b := range f.Blocks {
+			for _, instr := range b.Instrs {
+				if ref, ok := instr.(*DebugRef); ok {
+					if ref.Expr == e {
+						return ref.X, ref.IsAddr
+					}
+				}
+			}
+		}
+	}
+	return
+}
+
+// --- Lookup functions for source-level named entities (types.Objects) ---
+
+// Package returns the SSA Package corresponding to the specified
+// type-checker package. It returns nil if no such Package was
+// created by a prior call to prog.CreatePackage.
+func (prog *Program) Package(pkg *types.Package) *Package {
+	return prog.packages[pkg]
+}
+
+// packageLevelMember returns the package-level member corresponding
+// to the specified symbol, which may be a package-level const
+// (*NamedConst), var (*Global) or func/method (*Function) of some
+// package in prog.
+//
+// It returns nil if the object belongs to a package that has not been
+// created by prog.CreatePackage.
+func (prog *Program) packageLevelMember(obj types.Object) Member {
+	if pkg, ok := prog.packages[obj.Pkg()]; ok {
+		return pkg.objects[obj]
+	}
+	return nil
+}
+
+// FuncValue returns the SSA function or (non-interface) method
+// denoted by the specified func symbol. It returns nil if the symbol
+// denotes an interface method, or belongs to a package that was not
+// created by prog.CreatePackage.
+func (prog *Program) FuncValue(obj *types.Func) *Function {
+	fn, _ := prog.packageLevelMember(obj).(*Function)
+	return fn
+}
+
+// ConstValue returns the SSA constant denoted by the specified const symbol.
+func (prog *Program) ConstValue(obj *types.Const) *Const {
+	// TODO(adonovan): opt: share (don't reallocate)
+	// Consts for const objects and constant ast.Exprs.
+
+	// Universal constant? {true,false,nil}
+	if obj.Parent() == types.Universe {
+		return NewConst(obj.Val(), obj.Type())
+	}
+	// Package-level named constant?
+	if v := prog.packageLevelMember(obj); v != nil {
+		return v.(*NamedConst).Value
+	}
+	return NewConst(obj.Val(), obj.Type())
+}
+
+// VarValue returns the SSA Value that corresponds to a specific
+// identifier denoting the specified var symbol.
+//
+// VarValue returns nil if a local variable was not found, perhaps
+// because its package was not built, the debug information was not
+// requested during SSA construction, or the value was optimized away.
+//
+// ref is the path to an ast.Ident (e.g. from PathEnclosingInterval),
+// and that ident must resolve to obj.
+//
+// pkg is the package enclosing the reference.  (A reference to a var
+// always occurs within a function, so we need to know where to find it.)
+//
+// If the identifier is a field selector and its base expression is
+// non-addressable, then VarValue returns the value of that field.
+// For example:
+//
+//	func f() struct {x int}
+//	f().x  // VarValue(x) returns a *Field instruction of type int
+//
+// All other identifiers denote addressable locations (variables).
+// For them, VarValue may return either the variable's address or its
+// value, even when the expression is evaluated only for its value; the
+// situation is reported by isAddr, the second component of the result.
+//
+// If !isAddr, the returned value is the one associated with the
+// specific identifier.  For example,
+//
+//	var x int    // VarValue(x) returns Const 0 here
+//	x = 1        // VarValue(x) returns Const 1 here
+//
+// It is not specified whether the value or the address is returned in
+// any particular case, as it may depend upon optimizations performed
+// during SSA code generation, such as registerization, constant
+// folding, avoidance of materialization of subexpressions, etc.
+func (prog *Program) VarValue(obj *types.Var, pkg *Package, ref []ast.Node) (value Value, isAddr bool) {
+	// All references to a var are local to some function, possibly init.
+	fn := EnclosingFunction(pkg, ref)
+	if fn == nil {
+		return // e.g. def of struct field; SSA not built?
+	}
+
+	id := ref[0].(*ast.Ident)
+
+	// Defining ident of a parameter?
+	if id.Pos() == obj.Pos() {
+		for _, param := range fn.Params {
+			if param.Object() == obj {
+				return param, false
+			}
+		}
+	}
+
+	// Other ident?
+	for _, b := range fn.Blocks {
+		for _, instr := range b.Instrs {
+			if dr, ok := instr.(*DebugRef); ok {
+				if dr.Pos() == id.Pos() {
+					return dr.X, dr.IsAddr
+				}
+			}
+		}
+	}
+
+	// Defining ident of package-level var?
+	if v := prog.packageLevelMember(obj); v != nil {
+		return v.(*Global), true
+	}
+
+	return // e.g. debug info not requested, or var optimized away
+}

vendor/golang.org/x/tools/go/ssa/ssautil/deprecated.go

@@ -0,0 +1,36 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil
+
+// This file contains deprecated public APIs.
+// We discourage their use.
+
+import (
+	"golang.org/x/tools/go/loader"
+	"golang.org/x/tools/go/ssa"
+)
+
+// CreateProgram returns a new program in SSA form, given a program
+// loaded from source.  An SSA package is created for each transitively
+// error-free package of lprog.
+//
+// Code for bodies of functions is not built until Build is called
+// on the result.
+//
+// The mode parameter controls diagnostics and checking during SSA construction.
+//
+// Deprecated: Use [golang.org/x/tools/go/packages] and the [Packages]
+// function instead; see ssa.Example_loadPackages.
+func CreateProgram(lprog *loader.Program, mode ssa.BuilderMode) *ssa.Program {
+	prog := ssa.NewProgram(lprog.Fset, mode)
+
+	for _, info := range lprog.AllPackages {
+		if info.TransitivelyErrorFree {
+			prog.CreatePackage(info.Pkg, info.Files, &info.Info, info.Importable)
+		}
+	}
+
+	return prog
+}

vendor/golang.org/x/tools/go/ssa/ssautil/load.go

@@ -0,0 +1,189 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil
+
+// This file defines utility functions for constructing programs in SSA form.
+
+import (
+	"go/ast"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/go/packages"
+	"golang.org/x/tools/go/ssa"
+)
+
+// Packages creates an SSA program for a set of packages.
+//
+// The packages must have been loaded from source syntax using the
+// [packages.Load] function in [packages.LoadSyntax] or
+// [packages.LoadAllSyntax] mode.
+//
+// Packages creates an SSA package for each well-typed package in the
+// initial list, plus all their dependencies. The resulting list of
+// packages corresponds to the list of initial packages, and may contain
+// a nil if SSA code could not be constructed for the corresponding initial
+// package due to type errors.
+//
+// Code for bodies of functions is not built until [Program.Build] is
+// called on the resulting Program. SSA code is constructed only for
+// the initial packages with well-typed syntax trees.
+//
+// The mode parameter controls diagnostics and checking during SSA construction.
+func Packages(initial []*packages.Package, mode ssa.BuilderMode) (*ssa.Program, []*ssa.Package) {
+	// TODO(adonovan): opt: this calls CreatePackage far more than
+	// necessary: for all dependencies, not just the (non-initial)
+	// direct dependencies of the initial packages.
+	//
+	// But can it reasonably be changed without breaking the
+	// spirit and/or letter of the law above? Clients may notice
+	// if we call CreatePackage less, as methods like
+	// Program.FuncValue will return nil. Or must we provide a new
+	// function (and perhaps deprecate this one)? Is it worth it?
+	//
+	// Tim King makes the interesting point that it would be
+	// possible to entirely alleviate the client from the burden
+	// of calling CreatePackage for non-syntax packages, if we
+	// were to treat vars and funcs lazily in the same way we now
+	// treat methods. (In essence, try to move away from the
+	// notion of ssa.Packages, and make the Program answer
+	// all reasonable questions about any types.Object.)
+
+	return doPackages(initial, mode, false)
+}
+
+// AllPackages creates an SSA program for a set of packages plus all
+// their dependencies.
+//
+// The packages must have been loaded from source syntax using the
+// [packages.Load] function in [packages.LoadAllSyntax] mode.
+//
+// AllPackages creates an SSA package for each well-typed package in the
+// initial list, plus all their dependencies. The resulting list of
+// packages corresponds to the list of initial packages, and may contain
+// a nil if SSA code could not be constructed for the corresponding
+// initial package due to type errors.
+//
+// Code for bodies of functions is not built until Build is called on
+// the resulting Program. SSA code is constructed for all packages with
+// well-typed syntax trees.
+//
+// The mode parameter controls diagnostics and checking during SSA construction.
+func AllPackages(initial []*packages.Package, mode ssa.BuilderMode) (*ssa.Program, []*ssa.Package) {
+	return doPackages(initial, mode, true)
+}
+
+func doPackages(initial []*packages.Package, mode ssa.BuilderMode, deps bool) (*ssa.Program, []*ssa.Package) {
+
+	var fset *token.FileSet
+	if len(initial) > 0 {
+		fset = initial[0].Fset
+	}
+
+	prog := ssa.NewProgram(fset, mode)
+
+	isInitial := make(map[*packages.Package]bool, len(initial))
+	for _, p := range initial {
+		isInitial[p] = true
+	}
+
+	ssamap := make(map[*packages.Package]*ssa.Package)
+	packages.Visit(initial, nil, func(p *packages.Package) {
+		if p.Types != nil && !p.IllTyped {
+			var files []*ast.File
+			var info *types.Info
+			if deps || isInitial[p] {
+				files = p.Syntax
+				info = p.TypesInfo
+			}
+			ssamap[p] = prog.CreatePackage(p.Types, files, info, true)
+		}
+	})
+
+	var ssapkgs []*ssa.Package
+	for _, p := range initial {
+		ssapkgs = append(ssapkgs, ssamap[p]) // may be nil
+	}
+	return prog, ssapkgs
+}
+
+// BuildPackage builds an SSA program with SSA intermediate
+// representation (IR) for all functions of a single package.
+//
+// It populates pkg by type-checking the specified file syntax trees.  All
+// dependencies are loaded using the importer specified by tc, which
+// typically loads compiler export data; SSA code cannot be built for
+// those packages.  BuildPackage then constructs an [ssa.Program] with all
+// dependency packages created, and builds and returns the SSA package
+// corresponding to pkg.
+//
+// The caller must have set pkg.Path to the import path.
+//
+// The operation fails if there were any type-checking or import errors.
+//
+// See ../example_test.go for an example.
+func BuildPackage(tc *types.Config, fset *token.FileSet, pkg *types.Package, files []*ast.File, mode ssa.BuilderMode) (*ssa.Package, *types.Info, error) {
+	if fset == nil {
+		panic("no token.FileSet")
+	}
+	if pkg.Path() == "" {
+		panic("package has no import path")
+	}
+
+	info := &types.Info{
+		Types:        make(map[ast.Expr]types.TypeAndValue),
+		Defs:         make(map[*ast.Ident]types.Object),
+		Uses:         make(map[*ast.Ident]types.Object),
+		Implicits:    make(map[ast.Node]types.Object),
+		Instances:    make(map[*ast.Ident]types.Instance),
+		Scopes:       make(map[ast.Node]*types.Scope),
+		Selections:   make(map[*ast.SelectorExpr]*types.Selection),
+		FileVersions: make(map[*ast.File]string),
+	}
+	if err := types.NewChecker(tc, fset, pkg, info).Files(files); err != nil {
+		return nil, nil, err
+	}
+
+	prog := ssa.NewProgram(fset, mode)
+
+	// Create SSA packages for all imports.
+	// Order is not significant.
+	created := make(map[*types.Package]bool)
+	var createAll func(pkgs []*types.Package)
+	createAll = func(pkgs []*types.Package) {
+		for _, p := range pkgs {
+			if !created[p] {
+				created[p] = true
+				prog.CreatePackage(p, nil, nil, true)
+				createAll(p.Imports())
+			}
+		}
+	}
+	createAll(pkg.Imports())
+
+	// TODO(adonovan): we could replace createAll with just:
+	//
+	// // Create SSA packages for all imports.
+	// for _, p := range pkg.Imports() {
+	// 	prog.CreatePackage(p, nil, nil, true)
+	// }
+	//
+	// (with minor changes to changes to ../builder_test.go as
+	// shown in CL 511715 PS 10.) But this would strictly violate
+	// the letter of the doc comment above, which says "all
+	// dependencies created".
+	//
+	// Tim makes the good point with some extra work we could
+	// remove the need for any CreatePackage calls except the
+	// ones with syntax (i.e. primary packages). Of course
+	// You wouldn't have ssa.Packages and Members for as
+	// many things but no-one really uses that anyway.
+	// I wish I had done this from the outset.
+
+	// Create and build the primary package.
+	ssapkg := prog.CreatePackage(pkg, files, info, false)
+	ssapkg.Build()
+	return ssapkg, info, nil
+}

vendor/golang.org/x/tools/go/ssa/ssautil/switch.go

@@ -0,0 +1,230 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil
+
+// This file implements discovery of switch and type-switch constructs
+// from low-level control flow.
+//
+// Many techniques exist for compiling a high-level switch with
+// constant cases to efficient machine code.  The optimal choice will
+// depend on the data type, the specific case values, the code in the
+// body of each case, and the hardware.
+// Some examples:
+// - a lookup table (for a switch that maps constants to constants)
+// - a computed goto
+// - a binary tree
+// - a perfect hash
+// - a two-level switch (to partition constant strings by their first byte).
+
+import (
+	"bytes"
+	"fmt"
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/go/ssa"
+)
+
+// A ConstCase represents a single constant comparison.
+// It is part of a Switch.
+type ConstCase struct {
+	Block *ssa.BasicBlock // block performing the comparison
+	Body  *ssa.BasicBlock // body of the case
+	Value *ssa.Const      // case comparand
+}
+
+// A TypeCase represents a single type assertion.
+// It is part of a Switch.
+type TypeCase struct {
+	Block   *ssa.BasicBlock // block performing the type assert
+	Body    *ssa.BasicBlock // body of the case
+	Type    types.Type      // case type
+	Binding ssa.Value       // value bound by this case
+}
+
+// A Switch is a logical high-level control flow operation
+// (a multiway branch) discovered by analysis of a CFG containing
+// only if/else chains.  It is not part of the ssa.Instruction set.
+//
+// One of ConstCases and TypeCases has length >= 2;
+// the other is nil.
+//
+// In a value switch, the list of cases may contain duplicate constants.
+// A type switch may contain duplicate types, or types assignable
+// to an interface type also in the list.
+// TODO(adonovan): eliminate such duplicates.
+type Switch struct {
+	Start      *ssa.BasicBlock // block containing start of if/else chain
+	X          ssa.Value       // the switch operand
+	ConstCases []ConstCase     // ordered list of constant comparisons
+	TypeCases  []TypeCase      // ordered list of type assertions
+	Default    *ssa.BasicBlock // successor if all comparisons fail
+}
+
+func (sw *Switch) String() string {
+	// We represent each block by the String() of its
+	// first Instruction, e.g. "print(42:int)".
+	var buf bytes.Buffer
+	if sw.ConstCases != nil {
+		fmt.Fprintf(&buf, "switch %s {\n", sw.X.Name())
+		for _, c := range sw.ConstCases {
+			fmt.Fprintf(&buf, "case %s: %s\n", c.Value, c.Body.Instrs[0])
+		}
+	} else {
+		fmt.Fprintf(&buf, "switch %s.(type) {\n", sw.X.Name())
+		for _, c := range sw.TypeCases {
+			fmt.Fprintf(&buf, "case %s %s: %s\n",
+				c.Binding.Name(), c.Type, c.Body.Instrs[0])
+		}
+	}
+	if sw.Default != nil {
+		fmt.Fprintf(&buf, "default: %s\n", sw.Default.Instrs[0])
+	}
+	fmt.Fprintf(&buf, "}")
+	return buf.String()
+}
+
+// Switches examines the control-flow graph of fn and returns the
+// set of inferred value and type switches.  A value switch tests an
+// ssa.Value for equality against two or more compile-time constant
+// values.  Switches involving link-time constants (addresses) are
+// ignored.  A type switch type-asserts an ssa.Value against two or
+// more types.
+//
+// The switches are returned in dominance order.
+//
+// The resulting switches do not necessarily correspond to uses of the
+// 'switch' keyword in the source: for example, a single source-level
+// switch statement with non-constant cases may result in zero, one or
+// many Switches, one per plural sequence of constant cases.
+// Switches may even be inferred from if/else- or goto-based control flow.
+// (In general, the control flow constructs of the source program
+// cannot be faithfully reproduced from the SSA representation.)
+func Switches(fn *ssa.Function) []Switch {
+	// Traverse the CFG in dominance order, so we don't
+	// enter an if/else-chain in the middle.
+	var switches []Switch
+	seen := make(map[*ssa.BasicBlock]bool) // TODO(adonovan): opt: use ssa.blockSet
+	for _, b := range fn.DomPreorder() {
+		if x, k := isComparisonBlock(b); x != nil {
+			// Block b starts a switch.
+			sw := Switch{Start: b, X: x}
+			valueSwitch(&sw, k, seen)
+			if len(sw.ConstCases) > 1 {
+				switches = append(switches, sw)
+			}
+		}
+
+		if y, x, T := isTypeAssertBlock(b); y != nil {
+			// Block b starts a type switch.
+			sw := Switch{Start: b, X: x}
+			typeSwitch(&sw, y, T, seen)
+			if len(sw.TypeCases) > 1 {
+				switches = append(switches, sw)
+			}
+		}
+	}
+	return switches
+}
+
+func valueSwitch(sw *Switch, k *ssa.Const, seen map[*ssa.BasicBlock]bool) {
+	b := sw.Start
+	x := sw.X
+	for x == sw.X {
+		if seen[b] {
+			break
+		}
+		seen[b] = true
+
+		sw.ConstCases = append(sw.ConstCases, ConstCase{
+			Block: b,
+			Body:  b.Succs[0],
+			Value: k,
+		})
+		b = b.Succs[1]
+		if len(b.Instrs) > 2 {
+			// Block b contains not just 'if x == k',
+			// so it may have side effects that
+			// make it unsafe to elide.
+			break
+		}
+		if len(b.Preds) != 1 {
+			// Block b has multiple predecessors,
+			// so it cannot be treated as a case.
+			break
+		}
+		x, k = isComparisonBlock(b)
+	}
+	sw.Default = b
+}
+
+func typeSwitch(sw *Switch, y ssa.Value, T types.Type, seen map[*ssa.BasicBlock]bool) {
+	b := sw.Start
+	x := sw.X
+	for x == sw.X {
+		if seen[b] {
+			break
+		}
+		seen[b] = true
+
+		sw.TypeCases = append(sw.TypeCases, TypeCase{
+			Block:   b,
+			Body:    b.Succs[0],
+			Type:    T,
+			Binding: y,
+		})
+		b = b.Succs[1]
+		if len(b.Instrs) > 4 {
+			// Block b contains not just
+			//  {TypeAssert; Extract #0; Extract #1; If}
+			// so it may have side effects that
+			// make it unsafe to elide.
+			break
+		}
+		if len(b.Preds) != 1 {
+			// Block b has multiple predecessors,
+			// so it cannot be treated as a case.
+			break
+		}
+		y, x, T = isTypeAssertBlock(b)
+	}
+	sw.Default = b
+}
+
+// isComparisonBlock returns the operands (v, k) if a block ends with
+// a comparison v==k, where k is a compile-time constant.
+func isComparisonBlock(b *ssa.BasicBlock) (v ssa.Value, k *ssa.Const) {
+	if n := len(b.Instrs); n >= 2 {
+		if i, ok := b.Instrs[n-1].(*ssa.If); ok {
+			if binop, ok := i.Cond.(*ssa.BinOp); ok && binop.Block() == b && binop.Op == token.EQL {
+				if k, ok := binop.Y.(*ssa.Const); ok {
+					return binop.X, k
+				}
+				if k, ok := binop.X.(*ssa.Const); ok {
+					return binop.Y, k
+				}
+			}
+		}
+	}
+	return
+}
+
+// isTypeAssertBlock returns the operands (y, x, T) if a block ends with
+// a type assertion "if y, ok := x.(T); ok {".
+func isTypeAssertBlock(b *ssa.BasicBlock) (y, x ssa.Value, T types.Type) {
+	if n := len(b.Instrs); n >= 4 {
+		if i, ok := b.Instrs[n-1].(*ssa.If); ok {
+			if ext1, ok := i.Cond.(*ssa.Extract); ok && ext1.Block() == b && ext1.Index == 1 {
+				if ta, ok := ext1.Tuple.(*ssa.TypeAssert); ok && ta.Block() == b {
+					// hack: relies upon instruction ordering.
+					if ext0, ok := b.Instrs[n-3].(*ssa.Extract); ok {
+						return ext0, ta.X, ta.AssertedType
+					}
+				}
+			}
+		}
+	}
+	return
+}

vendor/golang.org/x/tools/go/ssa/ssautil/visit.go

@@ -0,0 +1,157 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssautil // import "golang.org/x/tools/go/ssa/ssautil"
+
+import (
+	"go/ast"
+	"go/types"
+
+	"golang.org/x/tools/go/ssa"
+
+	_ "unsafe" // for linkname hack
+)
+
+// This file defines utilities for visiting the SSA representation of
+// a Program.
+//
+// TODO(adonovan): test coverage.
+
+// AllFunctions finds and returns the set of functions potentially
+// needed by program prog, as determined by a simple linker-style
+// reachability algorithm starting from the members and method-sets of
+// each package.  The result may include anonymous functions and
+// synthetic wrappers.
+//
+// Precondition: all packages are built.
+//
+// TODO(adonovan): this function is underspecified. It doesn't
+// actually work like a linker, which computes reachability from main
+// using something like go/callgraph/cha (without materializing the
+// call graph). In fact, it treats all public functions and all
+// methods of public non-parameterized types as roots, even though
+// they may be unreachable--but only in packages created from syntax.
+//
+// I think we should deprecate AllFunctions function in favor of two
+// clearly defined ones:
+//
+//  1. The first would efficiently compute CHA reachability from a set
+//     of main packages, making it suitable for a whole-program
+//     analysis context with InstantiateGenerics, in conjunction with
+//     Program.Build.
+//
+//  2. The second would return only the set of functions corresponding
+//     to source Func{Decl,Lit} syntax, like SrcFunctions in
+//     go/analysis/passes/buildssa; this is suitable for
+//     package-at-a-time (or handful of packages) context.
+//     ssa.Package could easily expose it as a field.
+//
+// We could add them unexported for now and use them via the linkname hack.
+func AllFunctions(prog *ssa.Program) map[*ssa.Function]bool {
+	seen := make(map[*ssa.Function]bool)
+
+	var function func(fn *ssa.Function)
+	function = func(fn *ssa.Function) {
+		if !seen[fn] {
+			seen[fn] = true
+			var buf [10]*ssa.Value // avoid alloc in common case
+			for _, b := range fn.Blocks {
+				for _, instr := range b.Instrs {
+					for _, op := range instr.Operands(buf[:0]) {
+						if fn, ok := (*op).(*ssa.Function); ok {
+							function(fn)
+						}
+					}
+				}
+			}
+		}
+	}
+
+	// TODO(adonovan): opt: provide a way to share a builder
+	// across a sequence of MethodValue calls.
+
+	methodsOf := func(T types.Type) {
+		if !types.IsInterface(T) {
+			mset := prog.MethodSets.MethodSet(T)
+			for method := range mset.Methods() {
+				function(prog.MethodValue(method))
+			}
+		}
+	}
+
+	// Historically, Program.RuntimeTypes used to include the type
+	// of any exported member of a package loaded from syntax that
+	// has a non-parameterized type, plus all types
+	// reachable from that type using reflection, even though
+	// these runtime types may not be required for them.
+	//
+	// Rather than break existing programs that rely on
+	// AllFunctions visiting extra methods that are unreferenced
+	// by IR and unreachable via reflection, we moved the logic
+	// here, unprincipled though it is.
+	// (See doc comment for better ideas.)
+	//
+	// Nonetheless, after the move, we no longer visit every
+	// method of any type recursively reachable from T, only the
+	// methods of T and *T themselves, and we only apply this to
+	// named types T, and not to the type of every exported
+	// package member.
+	exportedTypeHack := func(t *ssa.Type) {
+		if isSyntactic(t.Package()) &&
+			ast.IsExported(t.Name()) &&
+			!types.IsInterface(t.Type()) {
+			// Consider only named types.
+			// (Ignore aliases and unsafe.Pointer.)
+			if named, ok := t.Type().(*types.Named); ok {
+				if named.TypeParams() == nil {
+					methodsOf(named)                   //  T
+					methodsOf(types.NewPointer(named)) // *T
+				}
+			}
+		}
+	}
+
+	for _, pkg := range prog.AllPackages() {
+		for _, mem := range pkg.Members {
+			switch mem := mem.(type) {
+			case *ssa.Function:
+				// Visit all package-level declared functions.
+				function(mem)
+
+			case *ssa.Type:
+				exportedTypeHack(mem)
+			}
+		}
+	}
+
+	// Visit all methods of types for which runtime types were
+	// materialized, as they are reachable through reflection.
+	for _, T := range prog.RuntimeTypes() {
+		methodsOf(T)
+	}
+
+	return seen
+}
+
+// MainPackages returns the subset of the specified packages
+// named "main" that define a main function.
+// The result may include synthetic "testmain" packages.
+func MainPackages(pkgs []*ssa.Package) []*ssa.Package {
+	var mains []*ssa.Package
+	for _, pkg := range pkgs {
+		if pkg.Pkg.Name() == "main" && pkg.Func("main") != nil {
+			mains = append(mains, pkg)
+		}
+	}
+	return mains
+}
+
+// TODO(adonovan): propose a principled API for this. One possibility
+// is a new field, Package.SrcFunctions []*Function, which would
+// contain the list of SrcFunctions described in point 2 of the
+// AllFunctions doc comment, or nil if the package is not from syntax.
+// But perhaps overloading nil vs empty slice is too subtle.
+//
+//go:linkname isSyntactic golang.org/x/tools/go/ssa.isSyntactic
+func isSyntactic(pkg *ssa.Package) bool

vendor/golang.org/x/tools/go/ssa/subst.go

@@ -0,0 +1,567 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/aliases"
+)
+
+// subster defines a type substitution operation of a set of type parameters
+// to type parameter free replacement types. Substitution is done within
+// the context of a package-level function instantiation. *Named types
+// declared in the function are unique to the instantiation.
+//
+// For example, given a parameterized function F
+//
+//	  func F[S, T any]() any {
+//	    type X struct{ s S; next *X }
+//		var p *X
+//	    return p
+//	  }
+//
+// calling the instantiation F[string, int]() returns an interface
+// value (*X[string,int], nil) where the underlying value of
+// X[string,int] is a struct{s string; next *X[string,int]}.
+//
+// A nil *subster is a valid, empty substitution map. It always acts as
+// the identity function. This allows for treating parameterized and
+// non-parameterized functions identically while compiling to ssa.
+//
+// Not concurrency-safe.
+//
+// Note: Some may find it helpful to think through some of the most
+// complex substitution cases using lambda calculus inspired notation.
+// subst.typ() solves evaluating a type expression E
+// within the body of a function Fn[m] with the type parameters m
+// once we have applied the type arguments N.
+// We can succinctly write this as a function application:
+//
+//	((λm. E) N)
+//
+// go/types does not provide this interface directly.
+// So what subster provides is a type substitution operation
+//
+//	E[m:=N]
+type subster struct {
+	replacements map[*types.TypeParam]types.Type // values should contain no type params
+	cache        map[types.Type]types.Type       // cache of subst results
+	origin       *types.Func                     // types.Objects declared within this origin function are unique within this context
+	ctxt         *types.Context                  // speeds up repeated instantiations
+	uniqueness   typeutil.Map                    // determines the uniqueness of the instantiations within the function
+	// TODO(taking): consider adding Pos
+}
+
+// Returns a subster that replaces tparams[i] with targs[i]. Uses ctxt as a cache.
+// targs should not contain any types in tparams.
+// fn is the generic function for which we are substituting.
+func makeSubster(ctxt *types.Context, fn *types.Func, tparams *types.TypeParamList, targs []types.Type) *subster {
+	assert(tparams.Len() == len(targs), "makeSubster argument count must match")
+
+	subst := &subster{
+		replacements: make(map[*types.TypeParam]types.Type, tparams.Len()),
+		cache:        make(map[types.Type]types.Type),
+		origin:       fn.Origin(),
+		ctxt:         ctxt,
+	}
+	for i := 0; i < tparams.Len(); i++ {
+		subst.replacements[tparams.At(i)] = targs[i]
+	}
+	return subst
+}
+
+// typ returns the type of t with the type parameter tparams[i] substituted
+// for the type targs[i] where subst was created using tparams and targs.
+func (subst *subster) typ(t types.Type) (res types.Type) {
+	if subst == nil {
+		return t // A nil subst is type preserving.
+	}
+	if r, ok := subst.cache[t]; ok {
+		return r
+	}
+	defer func() {
+		subst.cache[t] = res
+	}()
+
+	switch t := t.(type) {
+	case *types.TypeParam:
+		if r := subst.replacements[t]; r != nil {
+			return r
+		}
+		return t
+
+	case *types.Basic:
+		return t
+
+	case *types.Array:
+		if r := subst.typ(t.Elem()); r != t.Elem() {
+			return types.NewArray(r, t.Len())
+		}
+		return t
+
+	case *types.Slice:
+		if r := subst.typ(t.Elem()); r != t.Elem() {
+			return types.NewSlice(r)
+		}
+		return t
+
+	case *types.Pointer:
+		if r := subst.typ(t.Elem()); r != t.Elem() {
+			return types.NewPointer(r)
+		}
+		return t
+
+	case *types.Tuple:
+		return subst.tuple(t)
+
+	case *types.Struct:
+		return subst.struct_(t)
+
+	case *types.Map:
+		key := subst.typ(t.Key())
+		elem := subst.typ(t.Elem())
+		if key != t.Key() || elem != t.Elem() {
+			return types.NewMap(key, elem)
+		}
+		return t
+
+	case *types.Chan:
+		if elem := subst.typ(t.Elem()); elem != t.Elem() {
+			return types.NewChan(t.Dir(), elem)
+		}
+		return t
+
+	case *types.Signature:
+		return subst.signature(t)
+
+	case *types.Union:
+		return subst.union(t)
+
+	case *types.Interface:
+		return subst.interface_(t)
+
+	case *types.Alias:
+		return subst.alias(t)
+
+	case *types.Named:
+		return subst.named(t)
+
+	case *opaqueType:
+		return t // opaque types are never substituted
+
+	default:
+		panic("unreachable")
+	}
+}
+
+// types returns the result of {subst.typ(ts[i])}.
+func (subst *subster) types(ts []types.Type) []types.Type {
+	res := make([]types.Type, len(ts))
+	for i := range ts {
+		res[i] = subst.typ(ts[i])
+	}
+	return res
+}
+
+func (subst *subster) tuple(t *types.Tuple) *types.Tuple {
+	if t != nil {
+		if vars := subst.varlist(t); vars != nil {
+			return types.NewTuple(vars...)
+		}
+	}
+	return t
+}
+
+type varlist interface {
+	At(i int) *types.Var
+	Len() int
+}
+
+// fieldlist is an adapter for structs for the varlist interface.
+type fieldlist struct {
+	str *types.Struct
+}
+
+func (fl fieldlist) At(i int) *types.Var { return fl.str.Field(i) }
+func (fl fieldlist) Len() int            { return fl.str.NumFields() }
+
+func (subst *subster) struct_(t *types.Struct) *types.Struct {
+	if t != nil {
+		if fields := subst.varlist(fieldlist{t}); fields != nil {
+			tags := make([]string, t.NumFields())
+			for i, n := 0, t.NumFields(); i < n; i++ {
+				tags[i] = t.Tag(i)
+			}
+			return types.NewStruct(fields, tags)
+		}
+	}
+	return t
+}
+
+// varlist returns subst(in[i]) or return nils if subst(v[i]) == v[i] for all i.
+func (subst *subster) varlist(in varlist) []*types.Var {
+	var out []*types.Var // nil => no updates
+	for i, n := 0, in.Len(); i < n; i++ {
+		v := in.At(i)
+		w := subst.var_(v)
+		if v != w && out == nil {
+			out = make([]*types.Var, n)
+			for j := 0; j < i; j++ {
+				out[j] = in.At(j)
+			}
+		}
+		if out != nil {
+			out[i] = w
+		}
+	}
+	return out
+}
+
+func (subst *subster) var_(v *types.Var) *types.Var {
+	if v != nil {
+		if typ := subst.typ(v.Type()); typ != v.Type() {
+			if v.IsField() {
+				return types.NewField(v.Pos(), v.Pkg(), v.Name(), typ, v.Embedded())
+			}
+			return types.NewParam(v.Pos(), v.Pkg(), v.Name(), typ)
+		}
+	}
+	return v
+}
+
+func (subst *subster) union(u *types.Union) *types.Union {
+	var out []*types.Term // nil => no updates
+
+	for i, n := 0, u.Len(); i < n; i++ {
+		t := u.Term(i)
+		r := subst.typ(t.Type())
+		if r != t.Type() && out == nil {
+			out = make([]*types.Term, n)
+			for j := 0; j < i; j++ {
+				out[j] = u.Term(j)
+			}
+		}
+		if out != nil {
+			out[i] = types.NewTerm(t.Tilde(), r)
+		}
+	}
+
+	if out != nil {
+		return types.NewUnion(out)
+	}
+	return u
+}
+
+func (subst *subster) interface_(iface *types.Interface) *types.Interface {
+	if iface == nil {
+		return nil
+	}
+
+	// methods for the interface. Initially nil if there is no known change needed.
+	// Signatures for the method where recv is nil. NewInterfaceType fills in the receivers.
+	var methods []*types.Func
+	initMethods := func(n int) { // copy first n explicit methods
+		methods = make([]*types.Func, iface.NumExplicitMethods())
+		for i := range n {
+			f := iface.ExplicitMethod(i)
+			norecv := changeRecv(f.Type().(*types.Signature), nil)
+			methods[i] = types.NewFunc(f.Pos(), f.Pkg(), f.Name(), norecv)
+		}
+	}
+	for i := 0; i < iface.NumExplicitMethods(); i++ {
+		f := iface.ExplicitMethod(i)
+		// On interfaces, we need to cycle break on anonymous interface types
+		// being in a cycle with their signatures being in cycles with their receivers
+		// that do not go through a Named.
+		norecv := changeRecv(f.Type().(*types.Signature), nil)
+		sig := subst.typ(norecv)
+		if sig != norecv && methods == nil {
+			initMethods(i)
+		}
+		if methods != nil {
+			methods[i] = types.NewFunc(f.Pos(), f.Pkg(), f.Name(), sig.(*types.Signature))
+		}
+	}
+
+	var embeds []types.Type
+	initEmbeds := func(n int) { // copy first n embedded types
+		embeds = make([]types.Type, iface.NumEmbeddeds())
+		for i := range n {
+			embeds[i] = iface.EmbeddedType(i)
+		}
+	}
+	for i := 0; i < iface.NumEmbeddeds(); i++ {
+		e := iface.EmbeddedType(i)
+		r := subst.typ(e)
+		if e != r && embeds == nil {
+			initEmbeds(i)
+		}
+		if embeds != nil {
+			embeds[i] = r
+		}
+	}
+
+	if methods == nil && embeds == nil {
+		return iface
+	}
+	if methods == nil {
+		initMethods(iface.NumExplicitMethods())
+	}
+	if embeds == nil {
+		initEmbeds(iface.NumEmbeddeds())
+	}
+	return types.NewInterfaceType(methods, embeds).Complete()
+}
+
+func (subst *subster) alias(t *types.Alias) types.Type {
+	// See subster.named. This follows the same strategy.
+	tparams := aliases.TypeParams(t)
+	targs := aliases.TypeArgs(t)
+	tname := t.Obj()
+	torigin := aliases.Origin(t)
+
+	if !declaredWithin(tname, subst.origin) {
+		// t is declared outside of the function origin. So t is a package level type alias.
+		if targs.Len() == 0 {
+			// No type arguments so no instantiation needed.
+			return t
+		}
+
+		// Instantiate with the substituted type arguments.
+		newTArgs := subst.typelist(targs)
+		return subst.instantiate(torigin, newTArgs)
+	}
+
+	if targs.Len() == 0 {
+		// t is declared within the function origin and has no type arguments.
+		//
+		// Example: This corresponds to A or B in F, but not A[int]:
+		//
+		//     func F[T any]() {
+		//       type A[S any] = struct{t T, s S}
+		//       type B = T
+		//       var x A[int]
+		//       ...
+		//     }
+		//
+		// This is somewhat different than *Named as *Alias cannot be created recursively.
+
+		// Copy and substitute type params.
+		var newTParams []*types.TypeParam
+		for cur := range tparams.TypeParams() {
+			cobj := cur.Obj()
+			cname := types.NewTypeName(cobj.Pos(), cobj.Pkg(), cobj.Name(), nil)
+			ntp := types.NewTypeParam(cname, nil)
+			subst.cache[cur] = ntp // See the comment "Note: Subtle" in subster.named.
+			newTParams = append(newTParams, ntp)
+		}
+
+		// Substitute rhs.
+		rhs := subst.typ(aliases.Rhs(t))
+
+		// Create the fresh alias.
+		//
+		// Until 1.27, the result of aliases.NewAlias(...).Type() cannot guarantee it is a *types.Alias.
+		// However, as t is an *alias.Alias and t is well-typed, then aliases must have been enabled.
+		// Follow this decision, and always enable aliases here.
+		const enabled = true
+		obj := aliases.NewAlias(enabled, tname.Pos(), tname.Pkg(), tname.Name(), rhs, newTParams)
+
+		// Substitute into all of the constraints after they are created.
+		for i, ntp := range newTParams {
+			bound := tparams.At(i).Constraint()
+			ntp.SetConstraint(subst.typ(bound))
+		}
+		return obj.Type()
+	}
+
+	// t is declared within the function origin and has type arguments.
+	//
+	// Example: This corresponds to A[int] in F. Cases A and B are handled above.
+	//     func F[T any]() {
+	//       type A[S any] = struct{t T, s S}
+	//       type B = T
+	//       var x A[int]
+	//       ...
+	//     }
+	subOrigin := subst.typ(torigin)
+	subTArgs := subst.typelist(targs)
+	return subst.instantiate(subOrigin, subTArgs)
+}
+
+func (subst *subster) named(t *types.Named) types.Type {
+	// A Named type is a user defined type.
+	// Ignoring generics, Named types are canonical: they are identical if
+	// and only if they have the same defining symbol.
+	// Generics complicate things, both if the type definition itself is
+	// parameterized, and if the type is defined within the scope of a
+	// parameterized function. In this case, two named types are identical if
+	// and only if their identifying symbols are identical, and all type
+	// arguments bindings in scope of the named type definition (including the
+	// type parameters of the definition itself) are equivalent.
+	//
+	// Notably:
+	// 1. For type definition type T[P1 any] struct{}, T[A] and T[B] are identical
+	//    only if A and B are identical.
+	// 2. Inside the generic func Fn[m any]() any { type T struct{}; return T{} },
+	//    the result of Fn[A] and Fn[B] have identical type if and only if A and
+	//    B are identical.
+	// 3. Both 1 and 2 could apply, such as in
+	//    func F[m any]() any { type T[x any] struct{}; return T{} }
+	//
+	// A subster replaces type parameters within a function scope, and therefore must
+	// also replace free type parameters in the definitions of local types.
+	//
+	// Note: There are some detailed notes sprinkled throughout that borrow from
+	// lambda calculus notation. These contain some over simplifying math.
+	//
+	// LC: One way to think about subster is that it is  a way of evaluating
+	//   ((λm. E) N) as E[m:=N].
+	// Each Named type t has an object *TypeName within a scope S that binds an
+	// underlying type expression U. U can refer to symbols within S (+ S's ancestors).
+	// Let x = t.TypeParams() and A = t.TypeArgs().
+	// Each Named type t is then either:
+	//   U              where len(x) == 0 && len(A) == 0
+	//   λx. U          where len(x) != 0 && len(A) == 0
+	//   ((λx. U) A)    where len(x) == len(A)
+	// In each case, we will evaluate t[m:=N].
+	tparams := t.TypeParams() // x
+	targs := t.TypeArgs()     // A
+
+	if !declaredWithin(t.Obj(), subst.origin) {
+		// t is declared outside of Fn[m].
+		//
+		// In this case, we can skip substituting t.Underlying().
+		// The underlying type cannot refer to the type parameters.
+		//
+		// LC: Let free(E) be the set of free type parameters in an expression E.
+		// Then whenever m ∉ free(E), then E = E[m:=N].
+		// t ∉ Scope(fn) so therefore m ∉ free(U) and m ∩ x = ∅.
+		if targs.Len() == 0 {
+			// t has no type arguments. So it does not need to be instantiated.
+			//
+			// This is the normal case in real Go code, where t is not parameterized,
+			// declared at some package scope, and m is a TypeParam from a parameterized
+			// function F[m] or method.
+			//
+			// LC: m ∉ free(A) lets us conclude m ∉ free(t). So t=t[m:=N].
+			return t
+		}
+
+		// t is declared outside of Fn[m] and has type arguments.
+		// The type arguments may contain type parameters m so
+		// substitute the type arguments, and instantiate the substituted
+		// type arguments.
+		//
+		// LC: Evaluate this as ((λx. U) A') where A' = A[m := N].
+		newTArgs := subst.typelist(targs)
+		return subst.instantiate(t.Origin(), newTArgs)
+	}
+
+	// t is declared within Fn[m].
+
+	if targs.Len() == 0 { // no type arguments?
+		assert(t == t.Origin(), "local parameterized type abstraction must be an origin type")
+
+		// t has no type arguments.
+		// The underlying type of t may contain the function's type parameters,
+		// replace these, and create a new type.
+		//
+		// Subtle: We short circuit substitution and use a newly created type in
+		// subst, i.e. cache[t]=fresh, to preemptively replace t with fresh
+		// in recursive types during traversal. This both breaks infinite cycles
+		// and allows for constructing types with the replacement applied in
+		// subst.typ(U).
+		//
+		// A new copy of the Named and Typename (and constraints) per function
+		// instantiation matches the semantics of Go, which treats all function
+		// instantiations F[N] as having distinct local types.
+		//
+		// LC: x.Len()=0 can be thought of as a special case of λx. U.
+		// LC: Evaluate (λx. U)[m:=N] as (λx'. U') where U'=U[x:=x',m:=N].
+		tname := t.Obj()
+		obj := types.NewTypeName(tname.Pos(), tname.Pkg(), tname.Name(), nil)
+		fresh := types.NewNamed(obj, nil, nil)
+		var newTParams []*types.TypeParam
+		for cur := range tparams.TypeParams() {
+			cobj := cur.Obj()
+			cname := types.NewTypeName(cobj.Pos(), cobj.Pkg(), cobj.Name(), nil)
+			ntp := types.NewTypeParam(cname, nil)
+			subst.cache[cur] = ntp
+			newTParams = append(newTParams, ntp)
+		}
+		fresh.SetTypeParams(newTParams)
+		subst.cache[t] = fresh
+		subst.cache[fresh] = fresh
+		fresh.SetUnderlying(subst.typ(t.Underlying()))
+		// Substitute into all of the constraints after they are created.
+		for i, ntp := range newTParams {
+			bound := tparams.At(i).Constraint()
+			ntp.SetConstraint(subst.typ(bound))
+		}
+		return fresh
+	}
+
+	// t is defined within Fn[m] and t has type arguments (an instantiation).
+	// We reduce this to the two cases above:
+	// (1) substitute the function's type parameters into t.Origin().
+	// (2) substitute t's type arguments A and instantiate the updated t.Origin() with these.
+	//
+	// LC: Evaluate ((λx. U) A)[m:=N] as (t' A') where t' = (λx. U)[m:=N] and A'=A [m:=N]
+	subOrigin := subst.typ(t.Origin())
+	subTArgs := subst.typelist(targs)
+	return subst.instantiate(subOrigin, subTArgs)
+}
+
+func (subst *subster) instantiate(orig types.Type, targs []types.Type) types.Type {
+	i, err := types.Instantiate(subst.ctxt, orig, targs, false)
+	assert(err == nil, "failed to Instantiate named (Named or Alias) type")
+	if c, _ := subst.uniqueness.At(i).(types.Type); c != nil {
+		return c.(types.Type)
+	}
+	subst.uniqueness.Set(i, i)
+	return i
+}
+
+func (subst *subster) typelist(l *types.TypeList) []types.Type {
+	res := make([]types.Type, l.Len())
+	for i := 0; i < l.Len(); i++ {
+		res[i] = subst.typ(l.At(i))
+	}
+	return res
+}
+
+func (subst *subster) signature(t *types.Signature) types.Type {
+	tparams := t.TypeParams()
+
+	// We are choosing not to support tparams.Len() > 0 until a need has been observed in practice.
+	//
+	// There are some known usages for types.Types coming from types.{Eval,CheckExpr}.
+	// To support tparams.Len() > 0, we just need to do the following [pseudocode]:
+	//   targs := {subst.replacements[tparams[i]]]}; Instantiate(ctxt, t, targs, false)
+
+	assert(tparams.Len() == 0, "Substituting types.Signatures with generic functions are currently unsupported.")
+
+	// Either:
+	// (1)non-generic function.
+	//    no type params to substitute
+	// (2)generic method and recv needs to be substituted.
+
+	// Receivers can be either:
+	// named
+	// pointer to named
+	// interface
+	// nil
+	// interface is the problematic case. We need to cycle break there!
+	recv := subst.var_(t.Recv())
+	params := subst.tuple(t.Params())
+	results := subst.tuple(t.Results())
+	if recv != t.Recv() || params != t.Params() || results != t.Results() {
+		return types.NewSignatureType(recv, nil, nil, params, results, t.Variadic())
+	}
+	return t
+}

vendor/golang.org/x/tools/go/ssa/task.go

@@ -0,0 +1,103 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"sync/atomic"
+)
+
+// Each task has two states: it is initially "active",
+// and transitions to "done".
+//
+// tasks form a directed graph. An edge from x to y (with y in x.edges)
+// indicates that the task x waits on the task y to be done.
+// Cycles are permitted.
+//
+// Calling x.wait() blocks the calling goroutine until task x,
+// and all the tasks transitively reachable from x are done.
+//
+// The nil *task is always considered done.
+type task struct {
+	done       chan unit      // close when the task is done.
+	edges      map[*task]unit // set of predecessors of this task.
+	transitive atomic.Bool    // true once it is known all predecessors are done.
+}
+
+func (x *task) isTransitivelyDone() bool { return x == nil || x.transitive.Load() }
+
+// addEdge creates an edge from x to y, indicating that
+// x.wait() will not return before y is done.
+// All calls to x.addEdge(...) should happen before x.markDone().
+func (x *task) addEdge(y *task) {
+	if x == y || y.isTransitivelyDone() {
+		return // no work remaining
+	}
+
+	// heuristic done check
+	select {
+	case <-x.done:
+		panic("cannot add an edge to a done task")
+	default:
+	}
+
+	if x.edges == nil {
+		x.edges = make(map[*task]unit)
+	}
+	x.edges[y] = unit{}
+}
+
+// markDone changes the task's state to markDone.
+func (x *task) markDone() {
+	if x != nil {
+		close(x.done)
+	}
+}
+
+// wait blocks until x and all the tasks it can reach through edges are done.
+func (x *task) wait() {
+	if x.isTransitivelyDone() {
+		return // already known to be done. Skip allocations.
+	}
+
+	// Use BFS to wait on u.done to be closed, for all u transitively
+	// reachable from x via edges.
+	//
+	// This work can be repeated by multiple workers doing wait().
+	//
+	// Note: Tarjan's SCC algorithm is able to mark SCCs as transitively done
+	// as soon as the SCC has been visited. This is theoretically faster, but is
+	// a more complex algorithm. Until we have evidence, we need the more complex
+	// algorithm, the simpler algorithm BFS is implemented.
+	//
+	// In Go 1.23, ssa/TestStdlib reaches <=3 *tasks per wait() in most schedules
+	// On some schedules, there is a cycle building net/http and internal/trace/testtrace
+	// due to slices functions.
+	work := []*task{x}
+	enqueued := map[*task]unit{x: {}}
+	for i := 0; i < len(work); i++ {
+		u := work[i]
+		if u.isTransitivelyDone() { // already transitively done
+			work[i] = nil
+			continue
+		}
+		<-u.done // wait for u to be marked done.
+
+		for v := range u.edges {
+			if _, ok := enqueued[v]; !ok {
+				enqueued[v] = unit{}
+				work = append(work, v)
+			}
+		}
+	}
+
+	// work is transitively closed over dependencies.
+	// u in work is done (or transitively done and skipped).
+	// u is transitively done.
+	for _, u := range work {
+		if u != nil {
+			x.transitive.Store(true)
+		}
+	}
+}

vendor/golang.org/x/tools/go/ssa/typeset.go

@@ -0,0 +1,179 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+import (
+	"go/types"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// Utilities for dealing with type sets.
+
+const debug = false
+
+// typeset is an iterator over the (type/underlying type) pairs of the
+// specific type terms of the type set implied by t.
+// If t is a type parameter, the implied type set is the type set of t's constraint.
+// In that case, if there are no specific terms, typeset calls yield with (nil, nil).
+// If t is not a type parameter, the implied type set consists of just t.
+// In any case, typeset is guaranteed to call yield at least once.
+func typeset(typ types.Type, yield func(t, u types.Type) bool) {
+	switch typ := types.Unalias(typ).(type) {
+	case *types.TypeParam, *types.Interface:
+		terms := termListOf(typ)
+		if len(terms) == 0 {
+			yield(nil, nil)
+			return
+		}
+		for _, term := range terms {
+			u := types.Unalias(term.Type())
+			if !term.Tilde() {
+				u = u.Underlying()
+			}
+			if debug {
+				assert(types.Identical(u, u.Underlying()), "Unalias(x) == under(x) for ~x terms")
+			}
+			if !yield(term.Type(), u) {
+				break
+			}
+		}
+		return
+	default:
+		yield(typ, typ.Underlying())
+	}
+}
+
+// termListOf returns the type set of typ as a normalized term set. Returns an empty set on an error.
+func termListOf(typ types.Type) []*types.Term {
+	terms, err := typeparams.NormalTerms(typ)
+	if err != nil {
+		return nil
+	}
+	return terms
+}
+
+// typeSetIsEmpty returns true if a typeset is empty.
+func typeSetIsEmpty(typ types.Type) bool {
+	var empty bool
+	typeset(typ, func(t, _ types.Type) bool {
+		empty = t == nil
+		return false
+	})
+	return empty
+}
+
+// isBytestring returns true if T has the same terms as interface{[]byte | string}.
+// These act like a core type for some operations: slice expressions, append and copy.
+//
+// See https://go.dev/ref/spec#Core_types for the details on bytestring.
+func isBytestring(T types.Type) bool {
+	U := T.Underlying()
+	if _, ok := U.(*types.Interface); !ok {
+		return false
+	}
+
+	hasBytes, hasString := false, false
+	ok := underIs(U, func(t types.Type) bool {
+		switch {
+		case isString(t):
+			hasString = true
+			return true
+		case isByteSlice(t):
+			hasBytes = true
+			return true
+		default:
+			return false
+		}
+	})
+	return ok && hasBytes && hasString
+}
+
+// underIs calls f with the underlying types of the type terms
+// of the type set of typ and reports whether all calls to f returned true.
+// If there are no specific terms, underIs returns the result of f(nil).
+func underIs(typ types.Type, f func(types.Type) bool) bool {
+	var ok bool
+	typeset(typ, func(t, u types.Type) bool {
+		ok = f(u)
+		return ok
+	})
+	return ok
+}
+
+// indexType returns the element type and index mode of a IndexExpr over a type.
+// It returns an invalid mode if the type is not indexable; this should never occur in a well-typed program.
+func indexType(typ types.Type) (types.Type, indexMode) {
+	switch U := typ.Underlying().(type) {
+	case *types.Array:
+		return U.Elem(), ixArrVar
+	case *types.Pointer:
+		if arr, ok := U.Elem().Underlying().(*types.Array); ok {
+			return arr.Elem(), ixVar
+		}
+	case *types.Slice:
+		return U.Elem(), ixVar
+	case *types.Map:
+		return U.Elem(), ixMap
+	case *types.Basic:
+		return tByte, ixValue // must be a string
+	case *types.Interface:
+		var elem types.Type
+		mode := ixInvalid
+		typeset(typ, func(t, _ types.Type) bool {
+			if t == nil {
+				return false // empty set
+			}
+			e, m := indexType(t)
+			if elem == nil {
+				elem, mode = e, m
+			}
+			if debug && !types.Identical(elem, e) { // if type checked, just a sanity check
+				mode = ixInvalid
+				return false
+			}
+			// Update the mode to the most constrained address type.
+			mode = mode.meet(m)
+			return mode != ixInvalid
+		})
+		return elem, mode
+	}
+	return nil, ixInvalid
+}
+
+// An indexMode specifies the (addressing) mode of an index operand.
+//
+// Addressing mode of an index operation is based on the set of
+// underlying types.
+// Hasse diagram of the indexMode meet semi-lattice:
+//
+//	ixVar     ixMap
+//	  |          |
+//	ixArrVar     |
+//	  |          |
+//	ixValue      |
+//	   \        /
+//	  ixInvalid
+type indexMode byte
+
+const (
+	ixInvalid indexMode = iota // index is invalid
+	ixValue                    // index is a computed value (not addressable)
+	ixArrVar                   // like ixVar, but index operand contains an array
+	ixVar                      // index is an addressable variable
+	ixMap                      // index is a map index expression (acts like a variable on lhs, commaok on rhs of an assignment)
+)
+
+// meet is the address type that is constrained by both x and y.
+func (x indexMode) meet(y indexMode) indexMode {
+	if (x == ixMap || y == ixMap) && x != y {
+		return ixInvalid
+	}
+	// Use int representation and return min.
+	if x < y {
+		return y
+	}
+	return x
+}

vendor/golang.org/x/tools/go/ssa/util.go

@@ -0,0 +1,413 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines a number of miscellaneous utility functions.
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"go/types"
+	"io"
+	"os"
+	"sync"
+	_ "unsafe" // for go:linkname hack
+
+	"golang.org/x/tools/go/types/typeutil"
+	"golang.org/x/tools/internal/typeparams"
+	"golang.org/x/tools/internal/typesinternal"
+)
+
+type unit struct{}
+
+//// Sanity checking utilities
+
+// assert panics with the message msg if p is false.
+// Avoid combining with expensive string formatting.
+func assert(p bool, msg string) {
+	if !p {
+		panic(msg)
+	}
+}
+
+//// AST utilities
+
+// isBlankIdent returns true iff e is an Ident with name "_".
+// They have no associated types.Object, and thus no type.
+func isBlankIdent(e ast.Expr) bool {
+	id, ok := e.(*ast.Ident)
+	return ok && id.Name == "_"
+}
+
+//// Type utilities.  Some of these belong in go/types.
+
+// isNonTypeParamInterface reports whether t is an interface type but not a type parameter.
+func isNonTypeParamInterface(t types.Type) bool {
+	return !typeparams.IsTypeParam(t) && types.IsInterface(t)
+}
+
+// isBasic reports whether t is a basic type.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isBasic(t types.Type) bool {
+	_, ok := t.(*types.Basic)
+	return ok
+}
+
+// isString reports whether t is exactly a string type.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isString(t types.Type) bool {
+	basic, ok := t.(*types.Basic)
+	return ok && basic.Info()&types.IsString != 0
+}
+
+// isByteSlice reports whether t is of the form []~bytes.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isByteSlice(t types.Type) bool {
+	if b, ok := t.(*types.Slice); ok {
+		e, _ := b.Elem().Underlying().(*types.Basic)
+		return e != nil && e.Kind() == types.Byte
+	}
+	return false
+}
+
+// isRuneSlice reports whether t is of the form []~runes.
+// t is assumed to be an Underlying type (not Named or Alias).
+func isRuneSlice(t types.Type) bool {
+	if b, ok := t.(*types.Slice); ok {
+		e, _ := b.Elem().Underlying().(*types.Basic)
+		return e != nil && e.Kind() == types.Rune
+	}
+	return false
+}
+
+// isBasicConvTypes returns true when the type set of a type
+// can be one side of a Convert operation. This is when:
+// - All are basic, []byte, or []rune.
+// - At least 1 is basic.
+// - At most 1 is []byte or []rune.
+func isBasicConvTypes(typ types.Type) bool {
+	basics, cnt := 0, 0
+	ok := underIs(typ, func(t types.Type) bool {
+		cnt++
+		if isBasic(t) {
+			basics++
+			return true
+		}
+		return isByteSlice(t) || isRuneSlice(t)
+	})
+	return ok && basics >= 1 && cnt-basics <= 1
+}
+
+// isPointer reports whether t's underlying type is a pointer.
+func isPointer(t types.Type) bool {
+	return is[*types.Pointer](t.Underlying())
+}
+
+// isPointerCore reports whether t's core type is a pointer.
+//
+// (Most pointer manipulation is related to receivers, in which case
+// isPointer is appropriate. tecallers can use isPointer(t).
+func isPointerCore(t types.Type) bool {
+	return is[*types.Pointer](typeparams.CoreType(t))
+}
+
+func is[T any](x any) bool {
+	_, ok := x.(T)
+	return ok
+}
+
+// recvType returns the receiver type of method obj.
+func recvType(obj *types.Func) types.Type {
+	return obj.Signature().Recv().Type()
+}
+
+// fieldOf returns the index'th field of the (core type of) a struct type;
+// otherwise returns nil.
+func fieldOf(typ types.Type, index int) *types.Var {
+	if st, ok := typeparams.CoreType(typ).(*types.Struct); ok {
+		if 0 <= index && index < st.NumFields() {
+			return st.Field(index)
+		}
+	}
+	return nil
+}
+
+// isUntyped reports whether typ is the type of an untyped constant.
+func isUntyped(typ types.Type) bool {
+	// No Underlying/Unalias: untyped constant types cannot be Named or Alias.
+	b, ok := typ.(*types.Basic)
+	return ok && b.Info()&types.IsUntyped != 0
+}
+
+// declaredWithin reports whether an object is declared within a function.
+//
+// obj must not be a method or a field.
+func declaredWithin(obj types.Object, fn *types.Func) bool {
+	if obj.Pos() != token.NoPos {
+		return fn.Scope().Contains(obj.Pos()) // trust the positions if they exist.
+	}
+	if fn.Pkg() != obj.Pkg() {
+		return false // fast path for different packages
+	}
+
+	// Traverse Parent() scopes for fn.Scope().
+	for p := obj.Parent(); p != nil; p = p.Parent() {
+		if p == fn.Scope() {
+			return true
+		}
+	}
+	return false
+}
+
+// logStack prints the formatted "start" message to stderr and
+// returns a closure that prints the corresponding "end" message.
+// Call using 'defer logStack(...)()' to show builder stack on panic.
+// Don't forget trailing parens!
+func logStack(format string, args ...any) func() {
+	msg := fmt.Sprintf(format, args...)
+	io.WriteString(os.Stderr, msg)
+	io.WriteString(os.Stderr, "\n")
+	return func() {
+		io.WriteString(os.Stderr, msg)
+		io.WriteString(os.Stderr, " end\n")
+	}
+}
+
+// newVar creates a 'var' for use in a types.Tuple.
+func newVar(name string, typ types.Type) *types.Var {
+	return types.NewParam(token.NoPos, nil, name, typ)
+}
+
+// anonVar creates an anonymous 'var' for use in a types.Tuple.
+func anonVar(typ types.Type) *types.Var {
+	return newVar("", typ)
+}
+
+var lenResults = types.NewTuple(anonVar(tInt))
+
+// makeLen returns the len builtin specialized to type func(T)int.
+func makeLen(T types.Type) *Builtin {
+	lenParams := types.NewTuple(anonVar(T))
+	return &Builtin{
+		name: "len",
+		sig:  types.NewSignatureType(nil, nil, nil, lenParams, lenResults, false),
+	}
+}
+
+// receiverTypeArgs returns the type arguments to a method's receiver.
+// Returns an empty list if the receiver does not have type arguments.
+func receiverTypeArgs(method *types.Func) []types.Type {
+	recv := method.Signature().Recv()
+	_, named := typesinternal.ReceiverNamed(recv)
+	if named == nil {
+		return nil // recv is anonymous struct/interface
+	}
+	ts := named.TypeArgs()
+	if ts.Len() == 0 {
+		return nil
+	}
+	targs := make([]types.Type, ts.Len())
+	for i := 0; i < ts.Len(); i++ {
+		targs[i] = ts.At(i)
+	}
+	return targs
+}
+
+// recvAsFirstArg takes a method signature and returns a function
+// signature with receiver as the first parameter.
+func recvAsFirstArg(sig *types.Signature) *types.Signature {
+	params := make([]*types.Var, 0, 1+sig.Params().Len())
+	params = append(params, sig.Recv())
+	for v := range sig.Params().Variables() {
+		params = append(params, v)
+	}
+	return types.NewSignatureType(nil, nil, nil, types.NewTuple(params...), sig.Results(), sig.Variadic())
+}
+
+// instance returns whether an expression is a simple or qualified identifier
+// that is a generic instantiation.
+func instance(info *types.Info, expr ast.Expr) bool {
+	// Compare the logic here against go/types.instantiatedIdent,
+	// which also handles  *IndexExpr and *IndexListExpr.
+	var id *ast.Ident
+	switch x := expr.(type) {
+	case *ast.Ident:
+		id = x
+	case *ast.SelectorExpr:
+		id = x.Sel
+	default:
+		return false
+	}
+	_, ok := info.Instances[id]
+	return ok
+}
+
+// instanceArgs returns the Instance[id].TypeArgs as a slice.
+func instanceArgs(info *types.Info, id *ast.Ident) []types.Type {
+	targList := info.Instances[id].TypeArgs
+	if targList == nil {
+		return nil
+	}
+
+	targs := make([]types.Type, targList.Len())
+	for i, n := 0, targList.Len(); i < n; i++ {
+		targs[i] = targList.At(i)
+	}
+	return targs
+}
+
+// Mapping of a type T to a canonical instance C s.t. types.Identical(T, C).
+// Thread-safe.
+type canonizer struct {
+	mu    sync.Mutex
+	types typeutil.Map // map from type to a canonical instance
+	lists typeListMap  // map from a list of types to a canonical instance
+}
+
+func newCanonizer() *canonizer {
+	c := &canonizer{}
+	h := typeutil.MakeHasher()
+	c.types.SetHasher(h)
+	c.lists.hasher = h
+	return c
+}
+
+// List returns a canonical representative of a list of types.
+// Representative of the empty list is nil.
+func (c *canonizer) List(ts []types.Type) *typeList {
+	if len(ts) == 0 {
+		return nil
+	}
+
+	unaliasAll := func(ts []types.Type) []types.Type {
+		// Is there some top level alias?
+		var found bool
+		for _, t := range ts {
+			if _, ok := t.(*types.Alias); ok {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return ts // no top level alias
+		}
+
+		cp := make([]types.Type, len(ts)) // copy with top level aliases removed.
+		for i, t := range ts {
+			cp[i] = types.Unalias(t)
+		}
+		return cp
+	}
+	l := unaliasAll(ts)
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.lists.rep(l)
+}
+
+// Type returns a canonical representative of type T.
+// Removes top-level aliases.
+//
+// For performance, reasons the canonical instance is order-dependent,
+// and may contain deeply nested aliases.
+func (c *canonizer) Type(T types.Type) types.Type {
+	T = types.Unalias(T) // remove the top level alias.
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	if r := c.types.At(T); r != nil {
+		return r.(types.Type)
+	}
+	c.types.Set(T, T)
+	return T
+}
+
+// A type for representing a canonized list of types.
+type typeList []types.Type
+
+func (l *typeList) identical(ts []types.Type) bool {
+	if l == nil {
+		return len(ts) == 0
+	}
+	n := len(*l)
+	if len(ts) != n {
+		return false
+	}
+	for i, left := range *l {
+		right := ts[i]
+		if !types.Identical(left, right) {
+			return false
+		}
+	}
+	return true
+}
+
+type typeListMap struct {
+	hasher  typeutil.Hasher
+	buckets map[uint32][]*typeList
+}
+
+// rep returns a canonical representative of a slice of types.
+func (m *typeListMap) rep(ts []types.Type) *typeList {
+	if m == nil || len(ts) == 0 {
+		return nil
+	}
+
+	if m.buckets == nil {
+		m.buckets = make(map[uint32][]*typeList)
+	}
+
+	h := m.hash(ts)
+	bucket := m.buckets[h]
+	for _, l := range bucket {
+		if l.identical(ts) {
+			return l
+		}
+	}
+
+	// not present. create a representative.
+	cp := make(typeList, len(ts))
+	copy(cp, ts)
+	rep := &cp
+
+	m.buckets[h] = append(bucket, rep)
+	return rep
+}
+
+func (m *typeListMap) hash(ts []types.Type) uint32 {
+	if m == nil {
+		return 0
+	}
+	// Some smallish prime far away from typeutil.Hash.
+	n := len(ts)
+	h := uint32(13619) + 2*uint32(n)
+	for i := range n {
+		h += 3 * m.hasher.Hash(ts[i])
+	}
+	return h
+}
+
+// instantiateMethod instantiates m with targs and returns a canonical representative for this method.
+func (canon *canonizer) instantiateMethod(m *types.Func, targs []types.Type, ctxt *types.Context) *types.Func {
+	recv := recvType(m)
+	if p, ok := types.Unalias(recv).(*types.Pointer); ok {
+		recv = p.Elem()
+	}
+	named := types.Unalias(recv).(*types.Named)
+	inst, err := types.Instantiate(ctxt, named.Origin(), targs, false)
+	if err != nil {
+		panic(err)
+	}
+	rep := canon.Type(inst)
+	obj, _, _ := types.LookupFieldOrMethod(rep, true, m.Pkg(), m.Name())
+	return obj.(*types.Func)
+}
+
+// Exposed to ssautil using the linkname hack.
+//
+//go:linkname isSyntactic golang.org/x/tools/go/ssa.isSyntactic
+func isSyntactic(pkg *Package) bool { return pkg.syntax }

vendor/golang.org/x/tools/go/ssa/wrappers.go

@@ -0,0 +1,346 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssa
+
+// This file defines synthesis of Functions that delegate to declared
+// methods; they come in three kinds:
+//
+// (1) wrappers: methods that wrap declared methods, performing
+//     implicit pointer indirections and embedded field selections.
+//
+// (2) thunks: funcs that wrap declared methods.  Like wrappers,
+//     thunks perform indirections and field selections. The thunk's
+//     first parameter is used as the receiver for the method call.
+//
+// (3) bounds: funcs that wrap declared methods.  The bound's sole
+//     free variable, supplied by a closure, is used as the receiver
+//     for the method call.  No indirections or field selections are
+//     performed since they can be done before the call.
+
+import (
+	"fmt"
+
+	"go/token"
+	"go/types"
+
+	"golang.org/x/tools/internal/typeparams"
+)
+
+// -- wrappers -----------------------------------------------------------
+
+// createWrapper returns a synthetic method that delegates to the
+// declared method denoted by meth.Obj(), first performing any
+// necessary pointer indirections or field selections implied by meth.
+//
+// The resulting method's receiver type is meth.Recv().
+//
+// This function is versatile but quite subtle!  Consider the
+// following axes of variation when making changes:
+//   - optional receiver indirection
+//   - optional implicit field selections
+//   - meth.Obj() may denote a concrete or an interface method
+//   - the result may be a thunk or a wrapper.
+func createWrapper(prog *Program, sel *selection) *Function {
+	obj := sel.obj.(*types.Func)      // the declared function
+	sig := sel.typ.(*types.Signature) // type of this wrapper
+
+	var recv *types.Var // wrapper's receiver or thunk's params[0]
+	name := obj.Name()
+	var description string
+	if sel.kind == types.MethodExpr {
+		name += "$thunk"
+		description = "thunk"
+		recv = sig.Params().At(0)
+	} else {
+		description = "wrapper"
+		recv = sig.Recv()
+	}
+
+	description = fmt.Sprintf("%s for %s", description, sel.obj)
+	if prog.mode&LogSource != 0 {
+		defer logStack("create %s to (%s)", description, recv.Type())()
+	}
+	/* method wrapper */
+	return &Function{
+		name:      name,
+		method:    sel,
+		object:    obj,
+		Signature: sig,
+		Synthetic: description,
+		Prog:      prog,
+		pos:       obj.Pos(),
+		// wrappers have no syntax
+		build:     (*builder).buildWrapper,
+		syntax:    nil,
+		info:      nil,
+		goversion: "",
+	}
+}
+
+// buildWrapper builds fn.Body for a method wrapper.
+func (b *builder) buildWrapper(fn *Function) {
+	var recv *types.Var // wrapper's receiver or thunk's params[0]
+	var start int       // first regular param
+	if fn.method.kind == types.MethodExpr {
+		recv = fn.Signature.Params().At(0)
+		start = 1
+	} else {
+		recv = fn.Signature.Recv()
+	}
+
+	fn.startBody()
+	fn.addSpilledParam(recv)
+	createParams(fn, start)
+
+	indices := fn.method.index
+
+	var v Value = fn.Locals[0] // spilled receiver
+	if isPointer(fn.method.recv) {
+		v = emitLoad(fn, v)
+
+		// For simple indirection wrappers, perform an informative nil-check:
+		// "value method (T).f called using nil *T pointer"
+		if len(indices) == 1 && !isPointer(recvType(fn.object)) {
+			var c Call
+			c.Call.Value = &Builtin{
+				name: "ssa:wrapnilchk",
+				sig:  types.NewSignatureType(nil, nil, nil, types.NewTuple(anonVar(fn.method.recv), anonVar(tString), anonVar(tString)), types.NewTuple(anonVar(fn.method.recv)), false),
+			}
+			c.Call.Args = []Value{
+				v,
+				stringConst(typeparams.MustDeref(fn.method.recv).String()),
+				stringConst(fn.method.obj.Name()),
+			}
+			c.setType(v.Type())
+			v = fn.emit(&c)
+		}
+	}
+
+	// Invariant: v is a pointer, either
+	//   value of *A receiver param, or
+	// address of  A spilled receiver.
+
+	// We use pointer arithmetic (FieldAddr possibly followed by
+	// Load) in preference to value extraction (Field possibly
+	// preceded by Load).
+
+	v = emitImplicitSelections(fn, v, indices[:len(indices)-1], token.NoPos)
+
+	// Invariant: v is a pointer, either
+	//   value of implicit *C field, or
+	// address of implicit  C field.
+
+	var c Call
+	if r := recvType(fn.object); !types.IsInterface(r) { // concrete method
+		if !isPointer(r) {
+			v = emitLoad(fn, v)
+		}
+		c.Call.Value = fn.Prog.objectMethod(fn.object, b)
+		c.Call.Args = append(c.Call.Args, v)
+	} else {
+		c.Call.Method = fn.object
+		c.Call.Value = emitLoad(fn, v) // interface (possibly a typeparam)
+	}
+	for _, arg := range fn.Params[1:] {
+		c.Call.Args = append(c.Call.Args, arg)
+	}
+	emitTailCall(fn, &c)
+	fn.finishBody()
+}
+
+// createParams creates parameters for wrapper method fn based on its
+// Signature.Params, which do not include the receiver.
+// start is the index of the first regular parameter to use.
+func createParams(fn *Function, start int) {
+	tparams := fn.Signature.Params()
+	for i, n := start, tparams.Len(); i < n; i++ {
+		fn.addParamVar(tparams.At(i))
+	}
+}
+
+// -- bounds -----------------------------------------------------------
+
+// createBound returns a bound method wrapper (or "bound"), a synthetic
+// function that delegates to a concrete or interface method denoted
+// by obj.  The resulting function has no receiver, but has one free
+// variable which will be used as the method's receiver in the
+// tail-call.
+//
+// Use MakeClosure with such a wrapper to construct a bound method
+// closure.  e.g.:
+//
+//	type T int          or:  type T interface { meth() }
+//	func (t T) meth()
+//	var t T
+//	f := t.meth
+//	f() // calls t.meth()
+//
+// f is a closure of a synthetic wrapper defined as if by:
+//
+//	f := func() { return t.meth() }
+//
+// Unlike createWrapper, createBound need perform no indirection or field
+// selections because that can be done before the closure is
+// constructed.
+func createBound(prog *Program, obj *types.Func) *Function {
+	description := fmt.Sprintf("bound method wrapper for %s", obj)
+	if prog.mode&LogSource != 0 {
+		defer logStack("%s", description)()
+	}
+	/* bound method wrapper */
+	fn := &Function{
+		name:      obj.Name() + "$bound",
+		object:    obj,
+		Signature: changeRecv(obj.Type().(*types.Signature), nil), // drop receiver
+		Synthetic: description,
+		Prog:      prog,
+		pos:       obj.Pos(),
+		// wrappers have no syntax
+		build:     (*builder).buildBound,
+		syntax:    nil,
+		info:      nil,
+		goversion: "",
+	}
+	fn.FreeVars = []*FreeVar{{name: "recv", typ: recvType(obj), parent: fn}} // (cyclic)
+	return fn
+}
+
+// buildBound builds fn.Body for a bound method closure.
+func (b *builder) buildBound(fn *Function) {
+	fn.startBody()
+	createParams(fn, 0)
+	var c Call
+
+	recv := fn.FreeVars[0]
+	if !types.IsInterface(recvType(fn.object)) { // concrete
+		c.Call.Value = fn.Prog.objectMethod(fn.object, b)
+		c.Call.Args = []Value{recv}
+	} else {
+		c.Call.Method = fn.object
+		c.Call.Value = recv // interface (possibly a typeparam)
+	}
+	for _, arg := range fn.Params {
+		c.Call.Args = append(c.Call.Args, arg)
+	}
+	emitTailCall(fn, &c)
+	fn.finishBody()
+}
+
+// -- thunks -----------------------------------------------------------
+
+// createThunk returns a thunk, a synthetic function that delegates to a
+// concrete or interface method denoted by sel.obj.  The resulting
+// function has no receiver, but has an additional (first) regular
+// parameter.
+//
+// Precondition: sel.kind == types.MethodExpr.
+//
+//	type T int          or:  type T interface { meth() }
+//	func (t T) meth()
+//	f := T.meth
+//	var t T
+//	f(t) // calls t.meth()
+//
+// f is a synthetic wrapper defined as if by:
+//
+//	f := func(t T) { return t.meth() }
+func createThunk(prog *Program, sel *selection) *Function {
+	if sel.kind != types.MethodExpr {
+		panic(sel)
+	}
+
+	fn := createWrapper(prog, sel)
+	if fn.Signature.Recv() != nil {
+		panic(fn) // unexpected receiver
+	}
+
+	return fn
+}
+
+func changeRecv(s *types.Signature, recv *types.Var) *types.Signature {
+	return types.NewSignatureType(recv, nil, nil, s.Params(), s.Results(), s.Variadic())
+}
+
+// A local version of *types.Selection.
+// Needed for some additional control, such as creating a MethodExpr for an instantiation.
+type selection struct {
+	kind     types.SelectionKind
+	recv     types.Type
+	typ      types.Type
+	obj      types.Object
+	index    []int
+	indirect bool
+}
+
+func toSelection(sel *types.Selection) *selection {
+	return &selection{
+		kind:     sel.Kind(),
+		recv:     sel.Recv(),
+		typ:      sel.Type(),
+		obj:      sel.Obj(),
+		index:    sel.Index(),
+		indirect: sel.Indirect(),
+	}
+}
+
+// -- instantiations --------------------------------------------------
+
+// buildInstantiationWrapper builds the body of an instantiation
+// wrapper fn. The body calls the original generic function,
+// bracketed by ChangeType conversions on its arguments and results.
+func (b *builder) buildInstantiationWrapper(fn *Function) {
+	orig := fn.topLevelOrigin
+	sig := fn.Signature
+
+	fn.startBody()
+	if sig.Recv() != nil {
+		fn.addParamVar(sig.Recv())
+	}
+	createParams(fn, 0)
+
+	// Create body. Add a call to origin generic function
+	// and make type changes between argument and parameters,
+	// as well as return values.
+	var c Call
+	c.Call.Value = orig
+	if res := orig.Signature.Results(); res.Len() == 1 {
+		c.typ = res.At(0).Type()
+	} else {
+		c.typ = res
+	}
+
+	// parameter of instance becomes an argument to the call
+	// to the original generic function.
+	argOffset := 0
+	for i, arg := range fn.Params {
+		var typ types.Type
+		if i == 0 && sig.Recv() != nil {
+			typ = orig.Signature.Recv().Type()
+			argOffset = 1
+		} else {
+			typ = orig.Signature.Params().At(i - argOffset).Type()
+		}
+		c.Call.Args = append(c.Call.Args, emitTypeCoercion(fn, arg, typ))
+	}
+
+	results := fn.emit(&c)
+	var ret Return
+	switch res := sig.Results(); res.Len() {
+	case 0:
+		// no results, do nothing.
+	case 1:
+		ret.Results = []Value{emitTypeCoercion(fn, results, res.At(0).Type())}
+	default:
+		for i := 0; i < sig.Results().Len(); i++ {
+			v := emitExtract(fn, results, i)
+			ret.Results = append(ret.Results, emitTypeCoercion(fn, v, res.At(i).Type()))
+		}
+	}
+
+	fn.emit(&ret)
+	fn.currentBlock = nil
+
+	fn.finishBody()
+}