Initialize module and dependencies

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")
+}