Initialize module and dependencies

vendor/golang.org/x/tools/internal/gcimporter/bimport.go

@@ -0,0 +1,89 @@
+// 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.
+
+// This file contains the remaining vestiges of
+// $GOROOT/src/go/internal/gcimporter/bimport.go.
+
+package gcimporter
+
+import (
+	"fmt"
+	"go/token"
+	"go/types"
+	"sync"
+)
+
+func errorf(format string, args ...any) {
+	panic(fmt.Sprintf(format, args...))
+}
+
+const deltaNewFile = -64 // see cmd/compile/internal/gc/bexport.go
+
+// Synthesize a token.Pos
+type fakeFileSet struct {
+	fset  *token.FileSet
+	files map[string]*fileInfo
+}
+
+type fileInfo struct {
+	file     *token.File
+	lastline int
+}
+
+const maxlines = 64 * 1024
+
+func (s *fakeFileSet) pos(file string, line, column int) token.Pos {
+	_ = column // TODO(mdempsky): Make use of column.
+
+	// Since we don't know the set of needed file positions, we reserve maxlines
+	// positions per file. We delay calling token.File.SetLines until all
+	// positions have been calculated (by way of fakeFileSet.setLines), so that
+	// we can avoid setting unnecessary lines. See also golang/go#46586.
+	f := s.files[file]
+	if f == nil {
+		f = &fileInfo{file: s.fset.AddFile(file, -1, maxlines)}
+		s.files[file] = f
+	}
+	if line > maxlines {
+		line = 1
+	}
+	if line > f.lastline {
+		f.lastline = line
+	}
+
+	// Return a fake position assuming that f.file consists only of newlines.
+	return token.Pos(f.file.Base() + line - 1)
+}
+
+func (s *fakeFileSet) setLines() {
+	fakeLinesOnce.Do(func() {
+		fakeLines = make([]int, maxlines)
+		for i := range fakeLines {
+			fakeLines[i] = i
+		}
+	})
+	for _, f := range s.files {
+		f.file.SetLines(fakeLines[:f.lastline])
+	}
+}
+
+var (
+	fakeLines     []int
+	fakeLinesOnce sync.Once
+)
+
+func chanDir(d int) types.ChanDir {
+	// tag values must match the constants in cmd/compile/internal/gc/go.go
+	switch d {
+	case 1 /* Crecv */ :
+		return types.RecvOnly
+	case 2 /* Csend */ :
+		return types.SendOnly
+	case 3 /* Cboth */ :
+		return types.SendRecv
+	default:
+		errorf("unexpected channel dir %d", d)
+		return 0
+	}
+}

vendor/golang.org/x/tools/internal/gcimporter/exportdata.go

@@ -0,0 +1,421 @@
+// Copyright 2011 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.
+
+// This file should be kept in sync with $GOROOT/src/internal/exportdata/exportdata.go.
+// This file also additionally implements FindExportData for gcexportdata.NewReader.
+
+package gcimporter
+
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"go/build"
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"sync"
+)
+
+// FindExportData positions the reader r at the beginning of the
+// export data section of an underlying cmd/compile created archive
+// file by reading from it. The reader must be positioned at the
+// start of the file before calling this function.
+// This returns the length of the export data in bytes.
+//
+// This function is needed by [gcexportdata.Read], which must
+// accept inputs produced by the last two releases of cmd/compile,
+// plus tip.
+func FindExportData(r *bufio.Reader) (size int64, err error) {
+	arsize, err := FindPackageDefinition(r)
+	if err != nil {
+		return
+	}
+	size = int64(arsize)
+
+	objapi, headers, err := ReadObjectHeaders(r)
+	if err != nil {
+		return
+	}
+	size -= int64(len(objapi))
+	for _, h := range headers {
+		size -= int64(len(h))
+	}
+
+	// Check for the binary export data section header "$$B\n".
+	// TODO(taking): Unify with ReadExportDataHeader so that it stops at the 'u' instead of reading
+	line, err := r.ReadSlice('\n')
+	if err != nil {
+		return
+	}
+	hdr := string(line)
+	if hdr != "$$B\n" {
+		err = fmt.Errorf("unknown export data header: %q", hdr)
+		return
+	}
+	size -= int64(len(hdr))
+
+	// For files with a binary export data header "$$B\n",
+	// these are always terminated by an end-of-section marker "\n$$\n".
+	// So the last bytes must always be this constant.
+	//
+	// The end-of-section marker is not a part of the export data itself.
+	// Do not include these in size.
+	//
+	// It would be nice to have sanity check that the final bytes after
+	// the export data are indeed the end-of-section marker. The split
+	// of gcexportdata.NewReader and gcexportdata.Read make checking this
+	// ugly so gcimporter gives up enforcing this. The compiler and go/types
+	// importer do enforce this, which seems good enough.
+	const endofsection = "\n$$\n"
+	size -= int64(len(endofsection))
+
+	if size < 0 {
+		err = fmt.Errorf("invalid size (%d) in the archive file: %d bytes remain without section headers (recompile package)", arsize, size)
+		return
+	}
+
+	return
+}
+
+// ReadUnified reads the contents of the unified export data from a reader r
+// that contains the contents of a GC-created archive file.
+//
+// On success, the reader will be positioned after the end-of-section marker "\n$$\n".
+//
+// Supported GC-created archive files have 4 layers of nesting:
+//   - An archive file containing a package definition file.
+//   - The package definition file contains headers followed by a data section.
+//     Headers are lines (≤ 4kb) that do not start with "$$".
+//   - The data section starts with "$$B\n" followed by export data followed
+//     by an end of section marker "\n$$\n". (The section start "$$\n" is no
+//     longer supported.)
+//   - The export data starts with a format byte ('u') followed by the <data> in
+//     the given format. (See ReadExportDataHeader for older formats.)
+//
+// Putting this together, the bytes in a GC-created archive files are expected
+// to look like the following.
+// See cmd/internal/archive for more details on ar file headers.
+//
+// | <!arch>\n             | ar file signature
+// | __.PKGDEF...size...\n | ar header for __.PKGDEF including size.
+// | go object <...>\n     | objabi header
+// | <optional headers>\n  | other headers such as build id
+// | $$B\n                 | binary format marker
+// | u<data>\n             | unified export <data>
+// | $$\n                  | end-of-section marker
+// | [optional padding]    | padding byte (0x0A) if size is odd
+// | [ar file header]      | other ar files
+// | [ar file data]        |
+func ReadUnified(r *bufio.Reader) (data []byte, err error) {
+	// We historically guaranteed headers at the default buffer size (4096) work.
+	// This ensures we can use ReadSlice throughout.
+	const minBufferSize = 4096
+	r = bufio.NewReaderSize(r, minBufferSize)
+
+	size, err := FindPackageDefinition(r)
+	if err != nil {
+		return
+	}
+	n := size
+
+	objapi, headers, err := ReadObjectHeaders(r)
+	if err != nil {
+		return
+	}
+	n -= len(objapi)
+	for _, h := range headers {
+		n -= len(h)
+	}
+
+	hdrlen, err := ReadExportDataHeader(r)
+	if err != nil {
+		return
+	}
+	n -= hdrlen
+
+	// size also includes the end of section marker. Remove that many bytes from the end.
+	const marker = "\n$$\n"
+	n -= len(marker)
+
+	if n < 0 {
+		err = fmt.Errorf("invalid size (%d) in the archive file: %d bytes remain without section headers (recompile package)", size, n)
+		return
+	}
+
+	// Read n bytes from buf.
+	data = make([]byte, n)
+	_, err = io.ReadFull(r, data)
+	if err != nil {
+		return
+	}
+
+	// Check for marker at the end.
+	var suffix [len(marker)]byte
+	_, err = io.ReadFull(r, suffix[:])
+	if err != nil {
+		return
+	}
+	if s := string(suffix[:]); s != marker {
+		err = fmt.Errorf("read %q instead of end-of-section marker (%q)", s, marker)
+		return
+	}
+
+	return
+}
+
+// FindPackageDefinition positions the reader r at the beginning of a package
+// definition file ("__.PKGDEF") within a GC-created archive by reading
+// from it, and returns the size of the package definition file in the archive.
+//
+// The reader must be positioned at the start of the archive file before calling
+// this function, and "__.PKGDEF" is assumed to be the first file in the archive.
+//
+// See cmd/internal/archive for details on the archive format.
+func FindPackageDefinition(r *bufio.Reader) (size int, err error) {
+	// Uses ReadSlice to limit risk of malformed inputs.
+
+	// Read first line to make sure this is an object file.
+	line, err := r.ReadSlice('\n')
+	if err != nil {
+		err = fmt.Errorf("can't find export data (%v)", err)
+		return
+	}
+
+	// Is the first line an archive file signature?
+	if string(line) != "!<arch>\n" {
+		err = fmt.Errorf("not the start of an archive file (%q)", line)
+		return
+	}
+
+	// package export block should be first
+	size = readArchiveHeader(r, "__.PKGDEF")
+	if size <= 0 {
+		err = fmt.Errorf("not a package file")
+		return
+	}
+
+	return
+}
+
+// ReadObjectHeaders reads object headers from the reader. Object headers are
+// lines that do not start with an end-of-section marker "$$". The first header
+// is the objabi header. On success, the reader will be positioned at the beginning
+// of the end-of-section marker.
+//
+// It returns an error if any header does not fit in r.Size() bytes.
+func ReadObjectHeaders(r *bufio.Reader) (objapi string, headers []string, err error) {
+	// line is a temporary buffer for headers.
+	// Use bounded reads (ReadSlice, Peek) to limit risk of malformed inputs.
+	var line []byte
+
+	// objapi header should be the first line
+	if line, err = r.ReadSlice('\n'); err != nil {
+		err = fmt.Errorf("can't find export data (%v)", err)
+		return
+	}
+	objapi = string(line)
+
+	// objapi header begins with "go object ".
+	if !strings.HasPrefix(objapi, "go object ") {
+		err = fmt.Errorf("not a go object file: %s", objapi)
+		return
+	}
+
+	// process remaining object header lines
+	for {
+		// check for an end of section marker "$$"
+		line, err = r.Peek(2)
+		if err != nil {
+			return
+		}
+		if string(line) == "$$" {
+			return // stop
+		}
+
+		// read next header
+		line, err = r.ReadSlice('\n')
+		if err != nil {
+			return
+		}
+		headers = append(headers, string(line))
+	}
+}
+
+// ReadExportDataHeader reads the export data header and format from r.
+// It returns the number of bytes read, or an error if the format is no longer
+// supported or it failed to read.
+//
+// The only currently supported format is binary export data in the
+// unified export format.
+func ReadExportDataHeader(r *bufio.Reader) (n int, err error) {
+	// Read export data header.
+	line, err := r.ReadSlice('\n')
+	if err != nil {
+		return
+	}
+
+	hdr := string(line)
+	switch hdr {
+	case "$$\n":
+		err = fmt.Errorf("old textual export format no longer supported (recompile package)")
+		return
+
+	case "$$B\n":
+		var format byte
+		format, err = r.ReadByte()
+		if err != nil {
+			return
+		}
+		// The unified export format starts with a 'u'.
+		switch format {
+		case 'u':
+		default:
+			// Older no longer supported export formats include:
+			// indexed export format which started with an 'i'; and
+			// the older binary export format which started with a 'c',
+			// 'd', or 'v' (from "version").
+			err = fmt.Errorf("binary export format %q is no longer supported (recompile package)", format)
+			return
+		}
+
+	default:
+		err = fmt.Errorf("unknown export data header: %q", hdr)
+		return
+	}
+
+	n = len(hdr) + 1 // + 1 is for 'u'
+	return
+}
+
+// FindPkg returns the filename and unique package id for an import
+// path based on package information provided by build.Import (using
+// the build.Default build.Context). A relative srcDir is interpreted
+// relative to the current working directory.
+//
+// FindPkg is only used in tests within x/tools.
+func FindPkg(path, srcDir string) (filename, id string, err error) {
+	// TODO(taking): Move internal/exportdata.FindPkg into its own file,
+	// and then this copy into a _test package.
+	if path == "" {
+		return "", "", errors.New("path is empty")
+	}
+
+	var noext string
+	switch {
+	default:
+		// "x" -> "$GOPATH/pkg/$GOOS_$GOARCH/x.ext", "x"
+		// Don't require the source files to be present.
+		if abs, err := filepath.Abs(srcDir); err == nil { // see issue 14282
+			srcDir = abs
+		}
+		var bp *build.Package
+		bp, err = build.Import(path, srcDir, build.FindOnly|build.AllowBinary)
+		if bp.PkgObj == "" {
+			if bp.Goroot && bp.Dir != "" {
+				filename, err = lookupGorootExport(bp.Dir)
+				if err == nil {
+					_, err = os.Stat(filename)
+				}
+				if err == nil {
+					return filename, bp.ImportPath, nil
+				}
+			}
+			goto notfound
+		} else {
+			noext = strings.TrimSuffix(bp.PkgObj, ".a")
+		}
+		id = bp.ImportPath
+
+	case build.IsLocalImport(path):
+		// "./x" -> "/this/directory/x.ext", "/this/directory/x"
+		noext = filepath.Join(srcDir, path)
+		id = noext
+
+	case filepath.IsAbs(path):
+		// for completeness only - go/build.Import
+		// does not support absolute imports
+		// "/x" -> "/x.ext", "/x"
+		noext = path
+		id = path
+	}
+
+	if false { // for debugging
+		if path != id {
+			fmt.Printf("%s -> %s\n", path, id)
+		}
+	}
+
+	// try extensions
+	for _, ext := range pkgExts {
+		filename = noext + ext
+		f, statErr := os.Stat(filename)
+		if statErr == nil && !f.IsDir() {
+			return filename, id, nil
+		}
+		if err == nil {
+			err = statErr
+		}
+	}
+
+notfound:
+	if err == nil {
+		return "", path, fmt.Errorf("can't find import: %q", path)
+	}
+	return "", path, fmt.Errorf("can't find import: %q: %w", path, err)
+}
+
+var pkgExts = [...]string{".a", ".o"} // a file from the build cache will have no extension
+
+var exportMap sync.Map // package dir → func() (string, error)
+
+// lookupGorootExport returns the location of the export data
+// (normally found in the build cache, but located in GOROOT/pkg
+// in prior Go releases) for the package located in pkgDir.
+//
+// (We use the package's directory instead of its import path
+// mainly to simplify handling of the packages in src/vendor
+// and cmd/vendor.)
+//
+// lookupGorootExport is only used in tests within x/tools.
+func lookupGorootExport(pkgDir string) (string, error) {
+	f, ok := exportMap.Load(pkgDir)
+	if !ok {
+		var (
+			listOnce   sync.Once
+			exportPath string
+			err        error
+		)
+		f, _ = exportMap.LoadOrStore(pkgDir, func() (string, error) {
+			listOnce.Do(func() {
+				cmd := exec.Command(filepath.Join(build.Default.GOROOT, "bin", "go"), "list", "-export", "-f", "{{.Export}}", pkgDir)
+				cmd.Dir = build.Default.GOROOT
+				cmd.Env = append(os.Environ(), "PWD="+cmd.Dir, "GOROOT="+build.Default.GOROOT)
+				var output []byte
+				output, err = cmd.Output()
+				if err != nil {
+					if ee, ok := err.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
+						err = errors.New(string(ee.Stderr))
+					}
+					return
+				}
+
+				exports := strings.Split(string(bytes.TrimSpace(output)), "\n")
+				if len(exports) != 1 {
+					err = fmt.Errorf("go list reported %d exports; expected 1", len(exports))
+					return
+				}
+
+				exportPath = exports[0]
+			})
+
+			return exportPath, err
+		})
+	}
+
+	return f.(func() (string, error))()
+}

vendor/golang.org/x/tools/internal/gcimporter/gcimporter.go

@@ -0,0 +1,108 @@
+// Copyright 2011 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.
+
+// This file is a reduced copy of $GOROOT/src/go/internal/gcimporter/gcimporter.go.
+
+// Package gcimporter provides various functions for reading
+// gc-generated object files that can be used to implement the
+// Importer interface defined by the Go 1.5 standard library package.
+//
+// The encoding is deterministic: if the encoder is applied twice to
+// the same types.Package data structure, both encodings are equal.
+// This property may be important to avoid spurious changes in
+// applications such as build systems.
+//
+// However, the encoder is not necessarily idempotent. Importing an
+// exported package may yield a types.Package that, while it
+// represents the same set of Go types as the original, may differ in
+// the details of its internal representation. Because of these
+// differences, re-encoding the imported package may yield a
+// different, but equally valid, encoding of the package.
+package gcimporter // import "golang.org/x/tools/internal/gcimporter"
+
+import (
+	"bufio"
+	"fmt"
+	"go/token"
+	"go/types"
+	"io"
+	"os"
+)
+
+const (
+	// Enable debug during development: it adds some additional checks, and
+	// prevents errors from being recovered.
+	debug = false
+
+	// If trace is set, debugging output is printed to std out.
+	trace = false
+)
+
+// Import imports a gc-generated package given its import path and srcDir, adds
+// the corresponding package object to the packages map, and returns the object.
+// The packages map must contain all packages already imported.
+//
+// Import is only used in tests.
+func Import(fset *token.FileSet, packages map[string]*types.Package, path, srcDir string, lookup func(path string) (io.ReadCloser, error)) (pkg *types.Package, err error) {
+	var rc io.ReadCloser
+	var id string
+	if lookup != nil {
+		// With custom lookup specified, assume that caller has
+		// converted path to a canonical import path for use in the map.
+		if path == "unsafe" {
+			return types.Unsafe, nil
+		}
+		id = path
+
+		// No need to re-import if the package was imported completely before.
+		if pkg = packages[id]; pkg != nil && pkg.Complete() {
+			return
+		}
+		f, err := lookup(path)
+		if err != nil {
+			return nil, err
+		}
+		rc = f
+	} else {
+		var filename string
+		filename, id, err = FindPkg(path, srcDir)
+		if filename == "" {
+			if path == "unsafe" {
+				return types.Unsafe, nil
+			}
+			return nil, err
+		}
+
+		// no need to re-import if the package was imported completely before
+		if pkg = packages[id]; pkg != nil && pkg.Complete() {
+			return
+		}
+
+		// open file
+		f, err := os.Open(filename)
+		if err != nil {
+			return nil, err
+		}
+		defer func() {
+			if err != nil {
+				// add file name to error
+				err = fmt.Errorf("%s: %v", filename, err)
+			}
+		}()
+		rc = f
+	}
+	defer rc.Close()
+
+	buf := bufio.NewReader(rc)
+	data, err := ReadUnified(buf)
+	if err != nil {
+		err = fmt.Errorf("import %q: %v", path, err)
+		return
+	}
+
+	// unified: emitted by cmd/compile since go1.20.
+	_, pkg, err = UImportData(fset, packages, data, id)
+
+	return
+}

vendor/golang.org/x/tools/internal/gcimporter/predeclared.go

@@ -0,0 +1,91 @@
+// 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 gcimporter
+
+import (
+	"go/types"
+	"sync"
+)
+
+// predecl is a cache for the predeclared types in types.Universe.
+//
+// Cache a distinct result based on the runtime value of any.
+// The pointer value of the any type varies based on GODEBUG settings.
+var predeclMu sync.Mutex
+var predecl map[types.Type][]types.Type
+
+func predeclared() []types.Type {
+	anyt := types.Universe.Lookup("any").Type()
+
+	predeclMu.Lock()
+	defer predeclMu.Unlock()
+
+	if pre, ok := predecl[anyt]; ok {
+		return pre
+	}
+
+	if predecl == nil {
+		predecl = make(map[types.Type][]types.Type)
+	}
+
+	decls := []types.Type{ // basic types
+		types.Typ[types.Bool],
+		types.Typ[types.Int],
+		types.Typ[types.Int8],
+		types.Typ[types.Int16],
+		types.Typ[types.Int32],
+		types.Typ[types.Int64],
+		types.Typ[types.Uint],
+		types.Typ[types.Uint8],
+		types.Typ[types.Uint16],
+		types.Typ[types.Uint32],
+		types.Typ[types.Uint64],
+		types.Typ[types.Uintptr],
+		types.Typ[types.Float32],
+		types.Typ[types.Float64],
+		types.Typ[types.Complex64],
+		types.Typ[types.Complex128],
+		types.Typ[types.String],
+
+		// basic type aliases
+		types.Universe.Lookup("byte").Type(),
+		types.Universe.Lookup("rune").Type(),
+
+		// error
+		types.Universe.Lookup("error").Type(),
+
+		// untyped types
+		types.Typ[types.UntypedBool],
+		types.Typ[types.UntypedInt],
+		types.Typ[types.UntypedRune],
+		types.Typ[types.UntypedFloat],
+		types.Typ[types.UntypedComplex],
+		types.Typ[types.UntypedString],
+		types.Typ[types.UntypedNil],
+
+		// package unsafe
+		types.Typ[types.UnsafePointer],
+
+		// invalid type
+		types.Typ[types.Invalid], // only appears in packages with errors
+
+		// used internally by gc; never used by this package or in .a files
+		anyType{},
+
+		// comparable
+		types.Universe.Lookup("comparable").Type(),
+
+		// any
+		anyt,
+	}
+
+	predecl[anyt] = decls
+	return decls
+}
+
+type anyType struct{}
+
+func (t anyType) Underlying() types.Type { return t }
+func (t anyType) String() string         { return "any" }

vendor/golang.org/x/tools/internal/gcimporter/support.go

@@ -0,0 +1,30 @@
+// 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 gcimporter
+
+import (
+	"bufio"
+	"io"
+	"strconv"
+	"strings"
+)
+
+// Copy of $GOROOT/src/cmd/internal/archive.ReadHeader.
+func readArchiveHeader(b *bufio.Reader, name string) int {
+	// architecture-independent object file output
+	const HeaderSize = 60
+
+	var buf [HeaderSize]byte
+	if _, err := io.ReadFull(b, buf[:]); err != nil {
+		return -1
+	}
+	aname := strings.Trim(string(buf[0:16]), " ")
+	if !strings.HasPrefix(aname, name) {
+		return -1
+	}
+	asize := strings.Trim(string(buf[48:58]), " ")
+	i, _ := strconv.Atoi(asize)
+	return i
+}

vendor/golang.org/x/tools/internal/gcimporter/ureader_yes.go

@@ -0,0 +1,761 @@
+// Copyright 2021 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.
+
+// Derived from go/internal/gcimporter/ureader.go
+
+package gcimporter
+
+import (
+	"fmt"
+	"go/token"
+	"go/types"
+	"sort"
+
+	"golang.org/x/tools/internal/aliases"
+	"golang.org/x/tools/internal/pkgbits"
+	"golang.org/x/tools/internal/typesinternal"
+)
+
+// A pkgReader holds the shared state for reading a unified IR package
+// description.
+type pkgReader struct {
+	pkgbits.PkgDecoder
+
+	fake fakeFileSet
+
+	ctxt    *types.Context
+	imports map[string]*types.Package // previously imported packages, indexed by path
+	aliases bool                      // create types.Alias nodes
+
+	// lazily initialized arrays corresponding to the unified IR
+	// PosBase, Pkg, and Type sections, respectively.
+	posBases []string // position bases (i.e., file names)
+	pkgs     []*types.Package
+	typs     []types.Type
+
+	// laterFns holds functions that need to be invoked at the end of
+	// import reading.
+	laterFns []func()
+	// laterFors is used in case of 'type A B' to ensure that B is processed before A.
+	laterFors map[types.Type]int
+
+	// ifaces holds a list of constructed Interfaces, which need to have
+	// Complete called after importing is done.
+	ifaces []*types.Interface
+}
+
+// later adds a function to be invoked at the end of import reading.
+func (pr *pkgReader) later(fn func()) {
+	pr.laterFns = append(pr.laterFns, fn)
+}
+
+// See cmd/compile/internal/noder.derivedInfo.
+type derivedInfo struct {
+	idx pkgbits.Index
+}
+
+// See cmd/compile/internal/noder.typeInfo.
+type typeInfo struct {
+	idx     pkgbits.Index
+	derived bool
+}
+
+func UImportData(fset *token.FileSet, imports map[string]*types.Package, data []byte, path string) (_ int, pkg *types.Package, err error) {
+	if !debug {
+		defer func() {
+			if x := recover(); x != nil {
+				err = fmt.Errorf("internal error in importing %q (%v); please report an issue", path, x)
+			}
+		}()
+	}
+
+	s := string(data)
+	input := pkgbits.NewPkgDecoder(path, s)
+	pkg = readUnifiedPackage(fset, nil, imports, input)
+	return
+}
+
+// laterFor adds a function to be invoked at the end of import reading, and records the type that function is finishing.
+func (pr *pkgReader) laterFor(t types.Type, fn func()) {
+	if pr.laterFors == nil {
+		pr.laterFors = make(map[types.Type]int)
+	}
+	pr.laterFors[t] = len(pr.laterFns)
+	pr.laterFns = append(pr.laterFns, fn)
+}
+
+// readUnifiedPackage reads a package description from the given
+// unified IR export data decoder.
+func readUnifiedPackage(fset *token.FileSet, ctxt *types.Context, imports map[string]*types.Package, input pkgbits.PkgDecoder) *types.Package {
+	pr := pkgReader{
+		PkgDecoder: input,
+
+		fake: fakeFileSet{
+			fset:  fset,
+			files: make(map[string]*fileInfo),
+		},
+
+		ctxt:    ctxt,
+		imports: imports,
+		aliases: aliases.Enabled(),
+
+		posBases: make([]string, input.NumElems(pkgbits.RelocPosBase)),
+		pkgs:     make([]*types.Package, input.NumElems(pkgbits.RelocPkg)),
+		typs:     make([]types.Type, input.NumElems(pkgbits.RelocType)),
+	}
+	defer pr.fake.setLines()
+
+	r := pr.newReader(pkgbits.RelocMeta, pkgbits.PublicRootIdx, pkgbits.SyncPublic)
+	pkg := r.pkg()
+	if r.Version().Has(pkgbits.HasInit) {
+		r.Bool()
+	}
+
+	for i, n := 0, r.Len(); i < n; i++ {
+		// As if r.obj(), but avoiding the Scope.Lookup call,
+		// to avoid eager loading of imports.
+		r.Sync(pkgbits.SyncObject)
+		if r.Version().Has(pkgbits.DerivedFuncInstance) {
+			assert(!r.Bool())
+		}
+		r.p.objIdx(r.Reloc(pkgbits.RelocObj))
+		assert(r.Len() == 0)
+	}
+
+	r.Sync(pkgbits.SyncEOF)
+
+	for _, fn := range pr.laterFns {
+		fn()
+	}
+
+	for _, iface := range pr.ifaces {
+		iface.Complete()
+	}
+
+	// Imports() of pkg are all of the transitive packages that were loaded.
+	var imps []*types.Package
+	for _, imp := range pr.pkgs {
+		if imp != nil && imp != pkg {
+			imps = append(imps, imp)
+		}
+	}
+	sort.Sort(byPath(imps))
+	pkg.SetImports(imps)
+
+	pkg.MarkComplete()
+	return pkg
+}
+
+// A reader holds the state for reading a single unified IR element
+// within a package.
+type reader struct {
+	pkgbits.Decoder
+
+	p *pkgReader
+
+	dict *readerDict
+}
+
+// A readerDict holds the state for type parameters that parameterize
+// the current unified IR element.
+type readerDict struct {
+	// bounds is a slice of typeInfos corresponding to the underlying
+	// bounds of the element's type parameters.
+	bounds []typeInfo
+
+	// tparams is a slice of the constructed TypeParams for the element.
+	tparams []*types.TypeParam
+
+	// derived is a slice of types derived from tparams, which may be
+	// instantiated while reading the current element.
+	derived      []derivedInfo
+	derivedTypes []types.Type // lazily instantiated from derived
+}
+
+func (pr *pkgReader) newReader(k pkgbits.RelocKind, idx pkgbits.Index, marker pkgbits.SyncMarker) *reader {
+	return &reader{
+		Decoder: pr.NewDecoder(k, idx, marker),
+		p:       pr,
+	}
+}
+
+func (pr *pkgReader) tempReader(k pkgbits.RelocKind, idx pkgbits.Index, marker pkgbits.SyncMarker) *reader {
+	return &reader{
+		Decoder: pr.TempDecoder(k, idx, marker),
+		p:       pr,
+	}
+}
+
+func (pr *pkgReader) retireReader(r *reader) {
+	pr.RetireDecoder(&r.Decoder)
+}
+
+// @@@ Positions
+
+func (r *reader) pos() token.Pos {
+	r.Sync(pkgbits.SyncPos)
+	if !r.Bool() {
+		return token.NoPos
+	}
+
+	// TODO(mdempsky): Delta encoding.
+	posBase := r.posBase()
+	line := r.Uint()
+	col := r.Uint()
+	return r.p.fake.pos(posBase, int(line), int(col))
+}
+
+func (r *reader) posBase() string {
+	return r.p.posBaseIdx(r.Reloc(pkgbits.RelocPosBase))
+}
+
+func (pr *pkgReader) posBaseIdx(idx pkgbits.Index) string {
+	if b := pr.posBases[idx]; b != "" {
+		return b
+	}
+
+	var filename string
+	{
+		r := pr.tempReader(pkgbits.RelocPosBase, idx, pkgbits.SyncPosBase)
+
+		// Within types2, position bases have a lot more details (e.g.,
+		// keeping track of where //line directives appeared exactly).
+		//
+		// For go/types, we just track the file name.
+
+		filename = r.String()
+
+		if r.Bool() { // file base
+			// Was: "b = token.NewTrimmedFileBase(filename, true)"
+		} else { // line base
+			pos := r.pos()
+			line := r.Uint()
+			col := r.Uint()
+
+			// Was: "b = token.NewLineBase(pos, filename, true, line, col)"
+			_, _, _ = pos, line, col
+		}
+		pr.retireReader(r)
+	}
+	b := filename
+	pr.posBases[idx] = b
+	return b
+}
+
+// @@@ Packages
+
+func (r *reader) pkg() *types.Package {
+	r.Sync(pkgbits.SyncPkg)
+	return r.p.pkgIdx(r.Reloc(pkgbits.RelocPkg))
+}
+
+func (pr *pkgReader) pkgIdx(idx pkgbits.Index) *types.Package {
+	// TODO(mdempsky): Consider using some non-nil pointer to indicate
+	// the universe scope, so we don't need to keep re-reading it.
+	if pkg := pr.pkgs[idx]; pkg != nil {
+		return pkg
+	}
+
+	pkg := pr.newReader(pkgbits.RelocPkg, idx, pkgbits.SyncPkgDef).doPkg()
+	pr.pkgs[idx] = pkg
+	return pkg
+}
+
+func (r *reader) doPkg() *types.Package {
+	path := r.String()
+	switch path {
+	// cmd/compile emits path="main" for main packages because
+	// that's the linker symbol prefix it used; but we need
+	// the package's path as it would be reported by go list,
+	// hence "main" below.
+	// See test at go/packages.TestMainPackagePathInModeTypes.
+	case "", "main":
+		path = r.p.PkgPath()
+	case "builtin":
+		return nil // universe
+	case "unsafe":
+		return types.Unsafe
+	}
+
+	if pkg := r.p.imports[path]; pkg != nil {
+		return pkg
+	}
+
+	name := r.String()
+
+	pkg := types.NewPackage(path, name)
+	r.p.imports[path] = pkg
+
+	return pkg
+}
+
+// @@@ Types
+
+func (r *reader) typ() types.Type {
+	return r.p.typIdx(r.typInfo(), r.dict)
+}
+
+func (r *reader) typInfo() typeInfo {
+	r.Sync(pkgbits.SyncType)
+	if r.Bool() {
+		return typeInfo{idx: pkgbits.Index(r.Len()), derived: true}
+	}
+	return typeInfo{idx: r.Reloc(pkgbits.RelocType), derived: false}
+}
+
+func (pr *pkgReader) typIdx(info typeInfo, dict *readerDict) types.Type {
+	idx := info.idx
+	var where *types.Type
+	if info.derived {
+		where = &dict.derivedTypes[idx]
+		idx = dict.derived[idx].idx
+	} else {
+		where = &pr.typs[idx]
+	}
+
+	if typ := *where; typ != nil {
+		return typ
+	}
+
+	var typ types.Type
+	{
+		r := pr.tempReader(pkgbits.RelocType, idx, pkgbits.SyncTypeIdx)
+		r.dict = dict
+
+		typ = r.doTyp()
+		assert(typ != nil)
+		pr.retireReader(r)
+	}
+	// See comment in pkgReader.typIdx explaining how this happens.
+	if prev := *where; prev != nil {
+		return prev
+	}
+
+	*where = typ
+	return typ
+}
+
+func (r *reader) doTyp() (res types.Type) {
+	switch tag := pkgbits.CodeType(r.Code(pkgbits.SyncType)); tag {
+	default:
+		errorf("unhandled type tag: %v", tag)
+		panic("unreachable")
+
+	case pkgbits.TypeBasic:
+		return types.Typ[r.Len()]
+
+	case pkgbits.TypeNamed:
+		obj, targs := r.obj()
+		name := obj.(*types.TypeName)
+		if len(targs) != 0 {
+			t, _ := types.Instantiate(r.p.ctxt, name.Type(), targs, false)
+			return t
+		}
+		return name.Type()
+
+	case pkgbits.TypeTypeParam:
+		return r.dict.tparams[r.Len()]
+
+	case pkgbits.TypeArray:
+		len := int64(r.Uint64())
+		return types.NewArray(r.typ(), len)
+	case pkgbits.TypeChan:
+		dir := types.ChanDir(r.Len())
+		return types.NewChan(dir, r.typ())
+	case pkgbits.TypeMap:
+		return types.NewMap(r.typ(), r.typ())
+	case pkgbits.TypePointer:
+		return types.NewPointer(r.typ())
+	case pkgbits.TypeSignature:
+		return r.signature(nil, nil, nil)
+	case pkgbits.TypeSlice:
+		return types.NewSlice(r.typ())
+	case pkgbits.TypeStruct:
+		return r.structType()
+	case pkgbits.TypeInterface:
+		return r.interfaceType()
+	case pkgbits.TypeUnion:
+		return r.unionType()
+	}
+}
+
+func (r *reader) structType() *types.Struct {
+	fields := make([]*types.Var, r.Len())
+	var tags []string
+	for i := range fields {
+		pos := r.pos()
+		pkg, name := r.selector()
+		ftyp := r.typ()
+		tag := r.String()
+		embedded := r.Bool()
+
+		fields[i] = types.NewField(pos, pkg, name, ftyp, embedded)
+		if tag != "" {
+			for len(tags) < i {
+				tags = append(tags, "")
+			}
+			tags = append(tags, tag)
+		}
+	}
+	return types.NewStruct(fields, tags)
+}
+
+func (r *reader) unionType() *types.Union {
+	terms := make([]*types.Term, r.Len())
+	for i := range terms {
+		terms[i] = types.NewTerm(r.Bool(), r.typ())
+	}
+	return types.NewUnion(terms)
+}
+
+func (r *reader) interfaceType() *types.Interface {
+	methods := make([]*types.Func, r.Len())
+	embeddeds := make([]types.Type, r.Len())
+	implicit := len(methods) == 0 && len(embeddeds) == 1 && r.Bool()
+
+	for i := range methods {
+		pos := r.pos()
+		pkg, name := r.selector()
+		mtyp := r.signature(nil, nil, nil)
+		methods[i] = types.NewFunc(pos, pkg, name, mtyp)
+	}
+
+	for i := range embeddeds {
+		embeddeds[i] = r.typ()
+	}
+
+	iface := types.NewInterfaceType(methods, embeddeds)
+	if implicit {
+		iface.MarkImplicit()
+	}
+
+	// We need to call iface.Complete(), but if there are any embedded
+	// defined types, then we may not have set their underlying
+	// interface type yet. So we need to defer calling Complete until
+	// after we've called SetUnderlying everywhere.
+	//
+	// TODO(mdempsky): After CL 424876 lands, it should be safe to call
+	// iface.Complete() immediately.
+	r.p.ifaces = append(r.p.ifaces, iface)
+
+	return iface
+}
+
+func (r *reader) signature(recv *types.Var, rtparams, tparams []*types.TypeParam) *types.Signature {
+	r.Sync(pkgbits.SyncSignature)
+
+	params := r.params()
+	results := r.params()
+	variadic := r.Bool()
+
+	return types.NewSignatureType(recv, rtparams, tparams, params, results, variadic)
+}
+
+func (r *reader) params() *types.Tuple {
+	r.Sync(pkgbits.SyncParams)
+
+	params := make([]*types.Var, r.Len())
+	for i := range params {
+		params[i] = r.param()
+	}
+
+	return types.NewTuple(params...)
+}
+
+func (r *reader) param() *types.Var {
+	r.Sync(pkgbits.SyncParam)
+
+	pos := r.pos()
+	pkg, name := r.localIdent()
+	typ := r.typ()
+
+	return types.NewParam(pos, pkg, name, typ)
+}
+
+// @@@ Objects
+
+func (r *reader) obj() (types.Object, []types.Type) {
+	r.Sync(pkgbits.SyncObject)
+
+	if r.Version().Has(pkgbits.DerivedFuncInstance) {
+		assert(!r.Bool())
+	}
+
+	pkg, name := r.p.objIdx(r.Reloc(pkgbits.RelocObj))
+	obj := pkgScope(pkg).Lookup(name)
+
+	targs := make([]types.Type, r.Len())
+	for i := range targs {
+		targs[i] = r.typ()
+	}
+
+	return obj, targs
+}
+
+func (pr *pkgReader) objIdx(idx pkgbits.Index) (*types.Package, string) {
+
+	var objPkg *types.Package
+	var objName string
+	var tag pkgbits.CodeObj
+	{
+		rname := pr.tempReader(pkgbits.RelocName, idx, pkgbits.SyncObject1)
+
+		objPkg, objName = rname.qualifiedIdent()
+		assert(objName != "")
+
+		tag = pkgbits.CodeObj(rname.Code(pkgbits.SyncCodeObj))
+		pr.retireReader(rname)
+	}
+
+	if tag == pkgbits.ObjStub {
+		assert(objPkg == nil || objPkg == types.Unsafe)
+		return objPkg, objName
+	}
+
+	// Ignore local types promoted to global scope (#55110).
+	if _, suffix := splitVargenSuffix(objName); suffix != "" {
+		return objPkg, objName
+	}
+
+	if objPkg.Scope().Lookup(objName) == nil {
+		dict := pr.objDictIdx(idx)
+
+		r := pr.newReader(pkgbits.RelocObj, idx, pkgbits.SyncObject1)
+		r.dict = dict
+
+		declare := func(obj types.Object) {
+			objPkg.Scope().Insert(obj)
+		}
+
+		switch tag {
+		default:
+			panic("weird")
+
+		case pkgbits.ObjAlias:
+			pos := r.pos()
+			var tparams []*types.TypeParam
+			if r.Version().Has(pkgbits.AliasTypeParamNames) {
+				tparams = r.typeParamNames()
+			}
+			typ := r.typ()
+			declare(aliases.NewAlias(r.p.aliases, pos, objPkg, objName, typ, tparams))
+
+		case pkgbits.ObjConst:
+			pos := r.pos()
+			typ := r.typ()
+			val := r.Value()
+			declare(types.NewConst(pos, objPkg, objName, typ, val))
+
+		case pkgbits.ObjFunc:
+			pos := r.pos()
+			tparams := r.typeParamNames()
+			sig := r.signature(nil, nil, tparams)
+			declare(types.NewFunc(pos, objPkg, objName, sig))
+
+		case pkgbits.ObjType:
+			pos := r.pos()
+
+			obj := types.NewTypeName(pos, objPkg, objName, nil)
+			named := types.NewNamed(obj, nil, nil)
+			declare(obj)
+
+			named.SetTypeParams(r.typeParamNames())
+
+			setUnderlying := func(underlying types.Type) {
+				// If the underlying type is an interface, we need to
+				// duplicate its methods so we can replace the receiver
+				// parameter's type (#49906).
+				if iface, ok := types.Unalias(underlying).(*types.Interface); ok && iface.NumExplicitMethods() != 0 {
+					methods := make([]*types.Func, iface.NumExplicitMethods())
+					for i := range methods {
+						fn := iface.ExplicitMethod(i)
+						sig := fn.Type().(*types.Signature)
+
+						recv := types.NewVar(fn.Pos(), fn.Pkg(), "", named)
+						typesinternal.SetVarKind(recv, typesinternal.RecvVar)
+						methods[i] = types.NewFunc(fn.Pos(), fn.Pkg(), fn.Name(), types.NewSignatureType(recv, nil, nil, sig.Params(), sig.Results(), sig.Variadic()))
+					}
+
+					embeds := make([]types.Type, iface.NumEmbeddeds())
+					for i := range embeds {
+						embeds[i] = iface.EmbeddedType(i)
+					}
+
+					newIface := types.NewInterfaceType(methods, embeds)
+					r.p.ifaces = append(r.p.ifaces, newIface)
+					underlying = newIface
+				}
+
+				named.SetUnderlying(underlying)
+			}
+
+			// Since go.dev/cl/455279, we can assume rhs.Underlying() will
+			// always be non-nil. However, to temporarily support users of
+			// older snapshot releases, we continue to fallback to the old
+			// behavior for now.
+			//
+			// TODO(mdempsky): Remove fallback code and simplify after
+			// allowing time for snapshot users to upgrade.
+			rhs := r.typ()
+			if underlying := rhs.Underlying(); underlying != nil {
+				setUnderlying(underlying)
+			} else {
+				pk := r.p
+				pk.laterFor(named, func() {
+					// First be sure that the rhs is initialized, if it needs to be initialized.
+					delete(pk.laterFors, named) // prevent cycles
+					if i, ok := pk.laterFors[rhs]; ok {
+						f := pk.laterFns[i]
+						pk.laterFns[i] = func() {} // function is running now, so replace it with a no-op
+						f()                        // initialize RHS
+					}
+					setUnderlying(rhs.Underlying())
+				})
+			}
+
+			for i, n := 0, r.Len(); i < n; i++ {
+				named.AddMethod(r.method())
+			}
+
+		case pkgbits.ObjVar:
+			pos := r.pos()
+			typ := r.typ()
+			v := types.NewVar(pos, objPkg, objName, typ)
+			typesinternal.SetVarKind(v, typesinternal.PackageVar)
+			declare(v)
+		}
+	}
+
+	return objPkg, objName
+}
+
+func (pr *pkgReader) objDictIdx(idx pkgbits.Index) *readerDict {
+
+	var dict readerDict
+
+	{
+		r := pr.tempReader(pkgbits.RelocObjDict, idx, pkgbits.SyncObject1)
+		if implicits := r.Len(); implicits != 0 {
+			errorf("unexpected object with %v implicit type parameter(s)", implicits)
+		}
+
+		dict.bounds = make([]typeInfo, r.Len())
+		for i := range dict.bounds {
+			dict.bounds[i] = r.typInfo()
+		}
+
+		dict.derived = make([]derivedInfo, r.Len())
+		dict.derivedTypes = make([]types.Type, len(dict.derived))
+		for i := range dict.derived {
+			dict.derived[i] = derivedInfo{idx: r.Reloc(pkgbits.RelocType)}
+			if r.Version().Has(pkgbits.DerivedInfoNeeded) {
+				assert(!r.Bool())
+			}
+		}
+
+		pr.retireReader(r)
+	}
+	// function references follow, but reader doesn't need those
+
+	return &dict
+}
+
+func (r *reader) typeParamNames() []*types.TypeParam {
+	r.Sync(pkgbits.SyncTypeParamNames)
+
+	// Note: This code assumes it only processes objects without
+	// implement type parameters. This is currently fine, because
+	// reader is only used to read in exported declarations, which are
+	// always package scoped.
+
+	if len(r.dict.bounds) == 0 {
+		return nil
+	}
+
+	// Careful: Type parameter lists may have cycles. To allow for this,
+	// we construct the type parameter list in two passes: first we
+	// create all the TypeNames and TypeParams, then we construct and
+	// set the bound type.
+
+	r.dict.tparams = make([]*types.TypeParam, len(r.dict.bounds))
+	for i := range r.dict.bounds {
+		pos := r.pos()
+		pkg, name := r.localIdent()
+
+		tname := types.NewTypeName(pos, pkg, name, nil)
+		r.dict.tparams[i] = types.NewTypeParam(tname, nil)
+	}
+
+	typs := make([]types.Type, len(r.dict.bounds))
+	for i, bound := range r.dict.bounds {
+		typs[i] = r.p.typIdx(bound, r.dict)
+	}
+
+	// TODO(mdempsky): This is subtle, elaborate further.
+	//
+	// We have to save tparams outside of the closure, because
+	// typeParamNames() can be called multiple times with the same
+	// dictionary instance.
+	//
+	// Also, this needs to happen later to make sure SetUnderlying has
+	// been called.
+	//
+	// TODO(mdempsky): Is it safe to have a single "later" slice or do
+	// we need to have multiple passes? See comments on CL 386002 and
+	// go.dev/issue/52104.
+	tparams := r.dict.tparams
+	r.p.later(func() {
+		for i, typ := range typs {
+			tparams[i].SetConstraint(typ)
+		}
+	})
+
+	return r.dict.tparams
+}
+
+func (r *reader) method() *types.Func {
+	r.Sync(pkgbits.SyncMethod)
+	pos := r.pos()
+	pkg, name := r.selector()
+
+	rparams := r.typeParamNames()
+	sig := r.signature(r.param(), rparams, nil)
+
+	_ = r.pos() // TODO(mdempsky): Remove; this is a hacker for linker.go.
+	return types.NewFunc(pos, pkg, name, sig)
+}
+
+func (r *reader) qualifiedIdent() (*types.Package, string) { return r.ident(pkgbits.SyncSym) }
+func (r *reader) localIdent() (*types.Package, string)     { return r.ident(pkgbits.SyncLocalIdent) }
+func (r *reader) selector() (*types.Package, string)       { return r.ident(pkgbits.SyncSelector) }
+
+func (r *reader) ident(marker pkgbits.SyncMarker) (*types.Package, string) {
+	r.Sync(marker)
+	return r.pkg(), r.String()
+}
+
+// pkgScope returns pkg.Scope().
+// If pkg is nil, it returns types.Universe instead.
+//
+// TODO(mdempsky): Remove after x/tools can depend on Go 1.19.
+func pkgScope(pkg *types.Package) *types.Scope {
+	if pkg != nil {
+		return pkg.Scope()
+	}
+	return types.Universe
+}
+
+// See cmd/compile/internal/types.SplitVargenSuffix.
+func splitVargenSuffix(name string) (base, suffix string) {
+	i := len(name)
+	for i > 0 && name[i-1] >= '0' && name[i-1] <= '9' {
+		i--
+	}
+	const dot = "·"
+	if i >= len(dot) && name[i-len(dot):i] == dot {
+		i -= len(dot)
+		return name[:i], name[i:]
+	}
+	return name, ""
+}