Update dependencies (#5574)

Update vendor

vendor/golang.org/x/tools/go/ast/astutil/enclosing.go

@@ -11,6 +11,8 @@ import (
 	"go/ast"
 	"go/token"
 	"sort"
+
+	"golang.org/x/tools/internal/typeparams"
 )
 
 // PathEnclosingInterval returns the node that encloses the source
@@ -20,9 +22,9 @@ import (
 // additional whitespace abutting a node to be enclosed by it.
 // In this example:
 //
-//              z := x + y // add them
-//                   <-A->
-//                  <----B----->
+//	z := x + y // add them
+//	     <-A->
+//	    <----B----->
 //
 // the ast.BinaryExpr(+) node is considered to enclose interval B
 // even though its [Pos()..End()) is actually only interval A.
@@ -41,10 +43,10 @@ import (
 // interior whitespace of path[0].
 // In this example:
 //
-//              z := x + y // add them
-//                <--C-->     <---E-->
-//                  ^
-//                  D
+//	z := x + y // add them
+//	  <--C-->     <---E-->
+//	    ^
+//	    D
 //
 // intervals C, D and E are inexact.  C is contained by the
 // z-assignment statement, because it spans three of its children (:=,
@@ -52,12 +54,11 @@ import (
 // interior whitespace of the assignment.  E is considered interior
 // whitespace of the BlockStmt containing the assignment.
 //
-// Precondition: [start, end) both lie within the same file as root.
-// TODO(adonovan): return (nil, false) in this case and remove precond.
-// Requires FileSet; see loader.tokenFileContainsPos.
-//
-// Postcondition: path is never nil; it always contains at least 'root'.
-//
+// The resulting path is never empty; it always contains at least the
+// 'root' *ast.File.  Ideally PathEnclosingInterval would reject
+// intervals that lie wholly or partially outside the range of the
+// file, but unfortunately ast.File records only the token.Pos of
+// the 'package' keyword, but not of the start of the file itself.
 func PathEnclosingInterval(root *ast.File, start, end token.Pos) (path []ast.Node, exact bool) {
 	// fmt.Printf("EnclosingInterval %d %d\n", start, end) // debugging
 
@@ -133,6 +134,7 @@ func PathEnclosingInterval(root *ast.File, start, end token.Pos) (path []ast.Nod
 		return false // inexact: overlaps multiple children
 	}
 
+	// Ensure [start,end) is nondecreasing.
 	if start > end {
 		start, end = end, start
 	}
@@ -160,7 +162,6 @@ func PathEnclosingInterval(root *ast.File, start, end token.Pos) (path []ast.Nod
 // tokenNode is a dummy implementation of ast.Node for a single token.
 // They are used transiently by PathEnclosingInterval but never escape
 // this package.
-//
 type tokenNode struct {
 	pos token.Pos
 	end token.Pos
@@ -181,7 +182,6 @@ func tok(pos token.Pos, len int) ast.Node {
 // childrenOf returns the direct non-nil children of ast.Node n.
 // It may include fake ast.Node implementations for bare tokens.
 // it is not safe to call (e.g.) ast.Walk on such nodes.
-//
 func childrenOf(n ast.Node) []ast.Node {
 	var children []ast.Node
 
@@ -294,8 +294,8 @@ func childrenOf(n ast.Node) []ast.Node {
 
 	case *ast.FieldList:
 		children = append(children,
-			tok(n.Opening, len("(")),
-			tok(n.Closing, len(")")))
+			tok(n.Opening, len("(")), // or len("[")
+			tok(n.Closing, len(")"))) // or len("]")
 
 	case *ast.File:
 		// TODO test: Doc
@@ -322,6 +322,9 @@ func childrenOf(n ast.Node) []ast.Node {
 			children = append(children, n.Recv)
 		}
 		children = append(children, n.Name)
+		if tparams := typeparams.ForFuncType(n.Type); tparams != nil {
+			children = append(children, tparams)
+		}
 		if n.Type.Params != nil {
 			children = append(children, n.Type.Params)
 		}
@@ -371,8 +374,13 @@ func childrenOf(n ast.Node) []ast.Node {
 
 	case *ast.IndexExpr:
 		children = append(children,
-			tok(n.Lbrack, len("{")),
-			tok(n.Rbrack, len("}")))
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
+
+	case *typeparams.IndexListExpr:
+		children = append(children,
+			tok(n.Lbrack, len("[")),
+			tok(n.Rbrack, len("]")))
 
 	case *ast.InterfaceType:
 		children = append(children,
@@ -478,7 +486,6 @@ func (sl byPos) Swap(i, j int) {
 // TODO(adonovan): in some cases (e.g. Field, FieldList, Ident,
 // StarExpr) we could be much more specific given the path to the AST
 // root.  Perhaps we should do that.
-//
 func NodeDescription(n ast.Node) string {
 	switch n := n.(type) {
 	case *ast.ArrayType:
@@ -581,6 +588,8 @@ func NodeDescription(n ast.Node) string {
 		return "decrement statement"
 	case *ast.IndexExpr:
 		return "index expression"
+	case *typeparams.IndexListExpr:
+		return "index list expression"
 	case *ast.InterfaceType:
 		return "interface type"
 	case *ast.KeyValueExpr:

vendor/golang.org/x/tools/go/ast/astutil/imports.go

@@ -22,8 +22,11 @@ func AddImport(fset *token.FileSet, f *ast.File, path string) (added bool) {
 // If name is not empty, it is used to rename the import.
 //
 // For example, calling
+//
 //	AddNamedImport(fset, f, "pathpkg", "path")
+//
 // adds
+//
 //	import pathpkg "path"
 func AddNamedImport(fset *token.FileSet, f *ast.File, name, path string) (added bool) {
 	if imports(f, name, path) {
@@ -270,14 +273,15 @@ func DeleteNamedImport(fset *token.FileSet, f *ast.File, name, path string) (del
 			}
 			if j > 0 {
 				lastImpspec := gen.Specs[j-1].(*ast.ImportSpec)
-				lastLine := fset.Position(lastImpspec.Path.ValuePos).Line
-				line := fset.Position(impspec.Path.ValuePos).Line
+				lastLine := fset.PositionFor(lastImpspec.Path.ValuePos, false).Line
+				line := fset.PositionFor(impspec.Path.ValuePos, false).Line
 
 				// We deleted an entry but now there may be
 				// a blank line-sized hole where the import was.
-				if line-lastLine > 1 {
+				if line-lastLine > 1 || !gen.Rparen.IsValid() {
 					// There was a blank line immediately preceding the deleted import,
-					// so there's no need to close the hole.
+					// so there's no need to close the hole. The right parenthesis is
+					// invalid after AddImport to an import statement without parenthesis.
 					// Do nothing.
 				} else if line != fset.File(gen.Rparen).LineCount() {
 					// There was no blank line. Close the hole.

vendor/golang.org/x/tools/go/ast/astutil/rewrite.go

@@ -9,6 +9,8 @@ import (
 	"go/ast"
 	"reflect"
 	"sort"
+
+	"golang.org/x/tools/internal/typeparams"
 )
 
 // An ApplyFunc is invoked by Apply for each node n, even if n is nil,
@@ -39,7 +41,6 @@ type ApplyFunc func(*Cursor) bool
 // Children are traversed in the order in which they appear in the
 // respective node's struct definition. A package's files are
 // traversed in the filenames' alphabetical order.
-//
 func Apply(root ast.Node, pre, post ApplyFunc) (result ast.Node) {
 	parent := &struct{ ast.Node }{root}
 	defer func() {
@@ -63,8 +64,8 @@ var abort = new(int) // singleton, to signal termination of Apply
 // c.Parent(), and f is the field identifier with name c.Name(),
 // the following invariants hold:
 //
-//   p.f            == c.Node()  if c.Index() <  0
-//   p.f[c.Index()] == c.Node()  if c.Index() >= 0
+//	p.f            == c.Node()  if c.Index() <  0
+//	p.f[c.Index()] == c.Node()  if c.Index() >= 0
 //
 // The methods Replace, Delete, InsertBefore, and InsertAfter
 // can be used to change the AST without disrupting Apply.
@@ -251,6 +252,10 @@ func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.
 		a.apply(n, "X", nil, n.X)
 		a.apply(n, "Index", nil, n.Index)
 
+	case *typeparams.IndexListExpr:
+		a.apply(n, "X", nil, n.X)
+		a.applyList(n, "Indices")
+
 	case *ast.SliceExpr:
 		a.apply(n, "X", nil, n.X)
 		a.apply(n, "Low", nil, n.Low)
@@ -288,6 +293,9 @@ func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.
 		a.apply(n, "Fields", nil, n.Fields)
 
 	case *ast.FuncType:
+		if tparams := typeparams.ForFuncType(n); tparams != nil {
+			a.apply(n, "TypeParams", nil, tparams)
+		}
 		a.apply(n, "Params", nil, n.Params)
 		a.apply(n, "Results", nil, n.Results)
 
@@ -400,6 +408,9 @@ func (a *application) apply(parent ast.Node, name string, iter *iterator, n ast.
 	case *ast.TypeSpec:
 		a.apply(n, "Doc", nil, n.Doc)
 		a.apply(n, "Name", nil, n.Name)
+		if tparams := typeparams.ForTypeSpec(n); tparams != nil {
+			a.apply(n, "TypeParams", nil, tparams)
+		}
 		a.apply(n, "Type", nil, n.Type)
 		a.apply(n, "Comment", nil, n.Comment)
 

vendor/golang.org/x/tools/go/ast/astutil/util.go

@@ -1,3 +1,7 @@
+// 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 astutil
 
 import "go/ast"

vendor/golang.org/x/tools/go/gcexportdata/gcexportdata.go

@@ -17,32 +17,46 @@
 // developer tools, which will then be able to consume both Go 1.7 and
 // Go 1.8 export data files, so they will work before and after the
 // Go update. (See discussion at https://golang.org/issue/15651.)
-//
 package gcexportdata // import "golang.org/x/tools/go/gcexportdata"
 
 import (
 	"bufio"
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"go/token"
 	"go/types"
 	"io"
-	"io/ioutil"
+	"os/exec"
 
-	"golang.org/x/tools/go/internal/gcimporter"
+	"golang.org/x/tools/internal/gcimporter"
 )
 
 // Find returns the name of an object (.o) or archive (.a) file
 // containing type information for the specified import path,
-// using the workspace layout conventions of go/build.
+// using the go command.
 // If no file was found, an empty filename is returned.
 //
 // A relative srcDir is interpreted relative to the current working directory.
 //
 // Find also returns the package's resolved (canonical) import path,
 // reflecting the effects of srcDir and vendoring on importPath.
+//
+// Deprecated: Use the higher-level API in golang.org/x/tools/go/packages,
+// which is more efficient.
 func Find(importPath, srcDir string) (filename, path string) {
-	return gcimporter.FindPkg(importPath, srcDir)
+	cmd := exec.Command("go", "list", "-json", "-export", "--", importPath)
+	cmd.Dir = srcDir
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return "", ""
+	}
+	var data struct {
+		ImportPath string
+		Export     string
+	}
+	json.Unmarshal(out, &data)
+	return data.Export, data.ImportPath
 }
 
 // NewReader returns a reader for the export data section of an object
@@ -50,16 +64,46 @@ func Find(importPath, srcDir string) (filename, path string) {
 // additional trailing data beyond the end of the export data.
 func NewReader(r io.Reader) (io.Reader, error) {
 	buf := bufio.NewReader(r)
-	_, err := gcimporter.FindExportData(buf)
-	// If we ever switch to a zip-like archive format with the ToC
-	// at the end, we can return the correct portion of export data,
-	// but for now we must return the entire rest of the file.
-	return buf, err
+	_, size, err := gcimporter.FindExportData(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	if size >= 0 {
+		// We were given an archive and found the __.PKGDEF in it.
+		// This tells us the size of the export data, and we don't
+		// need to return the entire file.
+		return &io.LimitedReader{
+			R: buf,
+			N: size,
+		}, nil
+	} else {
+		// We were given an object file. As such, we don't know how large
+		// the export data is and must return the entire file.
+		return buf, nil
+	}
+}
+
+// readAll works the same way as io.ReadAll, but avoids allocations and copies
+// by preallocating a byte slice of the necessary size if the size is known up
+// front. This is always possible when the input is an archive. In that case,
+// NewReader will return the known size using an io.LimitedReader.
+func readAll(r io.Reader) ([]byte, error) {
+	if lr, ok := r.(*io.LimitedReader); ok {
+		data := make([]byte, lr.N)
+		_, err := io.ReadFull(lr, data)
+		return data, err
+	}
+	return io.ReadAll(r)
 }
 
 // Read reads export data from in, decodes it, and returns type
 // information for the package.
-// The package name is specified by path.
+//
+// The package path (effectively its linker symbol prefix) is
+// specified by path, since unlike the package name, this information
+// may not be recorded in the export data.
+//
 // File position information is added to fset.
 //
 // Read may inspect and add to the imports map to ensure that references
@@ -70,7 +114,7 @@ func NewReader(r io.Reader) (io.Reader, error) {
 //
 // On return, the state of the reader is undefined.
 func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package, path string) (*types.Package, error) {
-	data, err := ioutil.ReadAll(in)
+	data, err := readAll(in)
 	if err != nil {
 		return nil, fmt.Errorf("reading export data for %q: %v", path, err)
 	}
@@ -79,31 +123,65 @@ func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package,
 		return nil, fmt.Errorf("can't read export data for %q directly from an archive file (call gcexportdata.NewReader first to extract export data)", path)
 	}
 
-	// The App Engine Go runtime v1.6 uses the old export data format.
-	// TODO(adonovan): delete once v1.7 has been around for a while.
-	if bytes.HasPrefix(data, []byte("package ")) {
-		return gcimporter.ImportData(imports, path, path, bytes.NewReader(data))
-	}
-
 	// The indexed export format starts with an 'i'; the older
 	// binary export format starts with a 'c', 'd', or 'v'
 	// (from "version"). Select appropriate importer.
-	if len(data) > 0 && data[0] == 'i' {
-		_, pkg, err := gcimporter.IImportData(fset, imports, data[1:], path)
-		return pkg, err
-	}
+	if len(data) > 0 {
+		switch data[0] {
+		case 'i':
+			_, pkg, err := gcimporter.IImportData(fset, imports, data[1:], path)
+			return pkg, err
 
-	_, pkg, err := gcimporter.BImportData(fset, imports, data, path)
-	return pkg, err
+		case 'v', 'c', 'd':
+			_, pkg, err := gcimporter.BImportData(fset, imports, data, path)
+			return pkg, err
+
+		case 'u':
+			_, pkg, err := gcimporter.UImportData(fset, imports, data[1:], path)
+			return pkg, err
+
+		default:
+			l := len(data)
+			if l > 10 {
+				l = 10
+			}
+			return nil, fmt.Errorf("unexpected export data with prefix %q for path %s", string(data[:l]), path)
+		}
+	}
+	return nil, fmt.Errorf("empty export data for %s", path)
 }
 
 // Write writes encoded type information for the specified package to out.
 // The FileSet provides file position information for named objects.
 func Write(out io.Writer, fset *token.FileSet, pkg *types.Package) error {
-	b, err := gcimporter.BExportData(fset, pkg)
-	if err != nil {
+	if _, err := io.WriteString(out, "i"); err != nil {
 		return err
 	}
-	_, err = out.Write(b)
-	return err
+	return gcimporter.IExportData(out, fset, pkg)
+}
+
+// ReadBundle reads an export bundle from in, decodes it, and returns type
+// information for the packages.
+// File position information is added to fset.
+//
+// ReadBundle may inspect and add to the imports map to ensure that references
+// within the export bundle to other packages are consistent.
+//
+// On return, the state of the reader is undefined.
+//
+// Experimental: This API is experimental and may change in the future.
+func ReadBundle(in io.Reader, fset *token.FileSet, imports map[string]*types.Package) ([]*types.Package, error) {
+	data, err := readAll(in)
+	if err != nil {
+		return nil, fmt.Errorf("reading export bundle: %v", err)
+	}
+	return gcimporter.IImportBundle(fset, imports, data)
+}
+
+// WriteBundle writes encoded type information for the specified packages to out.
+// The FileSet provides file position information for named objects.
+//
+// Experimental: This API is experimental and may change in the future.
+func WriteBundle(out io.Writer, fset *token.FileSet, pkgs []*types.Package) error {
+	return gcimporter.IExportBundle(out, fset, pkgs)
 }

vendor/golang.org/x/tools/go/gcexportdata/importer.go

@@ -23,6 +23,8 @@ import (
 // or to control the FileSet or access the imports map populated during
 // package loading.
 //
+// Deprecated: Use the higher-level API in golang.org/x/tools/go/packages,
+// which is more efficient.
 func NewImporter(fset *token.FileSet, imports map[string]*types.Package) types.ImporterFrom {
 	return importer{fset, imports}
 }

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

@@ -1,852 +0,0 @@
-// Copyright 2016 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.
-
-// Binary package export.
-// This file was derived from $GOROOT/src/cmd/compile/internal/gc/bexport.go;
-// see that file for specification of the format.
-
-package gcimporter
-
-import (
-	"bytes"
-	"encoding/binary"
-	"fmt"
-	"go/ast"
-	"go/constant"
-	"go/token"
-	"go/types"
-	"math"
-	"math/big"
-	"sort"
-	"strings"
-)
-
-// If debugFormat is set, each integer and string value is preceded by a marker
-// and position information in the encoding. This mechanism permits an importer
-// to recognize immediately when it is out of sync. The importer recognizes this
-// mode automatically (i.e., it can import export data produced with debugging
-// support even if debugFormat is not set at the time of import). This mode will
-// lead to massively larger export data (by a factor of 2 to 3) and should only
-// be enabled during development and debugging.
-//
-// NOTE: This flag is the first flag to enable if importing dies because of
-// (suspected) format errors, and whenever a change is made to the format.
-const debugFormat = false // default: false
-
-// If trace is set, debugging output is printed to std out.
-const trace = false // default: false
-
-// Current export format version. Increase with each format change.
-// Note: The latest binary (non-indexed) export format is at version 6.
-//       This exporter is still at level 4, but it doesn't matter since
-//       the binary importer can handle older versions just fine.
-// 6: package height (CL 105038) -- NOT IMPLEMENTED HERE
-// 5: improved position encoding efficiency (issue 20080, CL 41619) -- NOT IMPLEMEMTED HERE
-// 4: type name objects support type aliases, uses aliasTag
-// 3: Go1.8 encoding (same as version 2, aliasTag defined but never used)
-// 2: removed unused bool in ODCL export (compiler only)
-// 1: header format change (more regular), export package for _ struct fields
-// 0: Go1.7 encoding
-const exportVersion = 4
-
-// trackAllTypes enables cycle tracking for all types, not just named
-// types. The existing compiler invariants assume that unnamed types
-// that are not completely set up are not used, or else there are spurious
-// errors.
-// If disabled, only named types are tracked, possibly leading to slightly
-// less efficient encoding in rare cases. It also prevents the export of
-// some corner-case type declarations (but those are not handled correctly
-// with with the textual export format either).
-// TODO(gri) enable and remove once issues caused by it are fixed
-const trackAllTypes = false
-
-type exporter struct {
-	fset *token.FileSet
-	out  bytes.Buffer
-
-	// object -> index maps, indexed in order of serialization
-	strIndex map[string]int
-	pkgIndex map[*types.Package]int
-	typIndex map[types.Type]int
-
-	// position encoding
-	posInfoFormat bool
-	prevFile      string
-	prevLine      int
-
-	// debugging support
-	written int // bytes written
-	indent  int // for trace
-}
-
-// internalError represents an error generated inside this package.
-type internalError string
-
-func (e internalError) Error() string { return "gcimporter: " + string(e) }
-
-func internalErrorf(format string, args ...interface{}) error {
-	return internalError(fmt.Sprintf(format, args...))
-}
-
-// BExportData returns binary export data for pkg.
-// If no file set is provided, position info will be missing.
-func BExportData(fset *token.FileSet, pkg *types.Package) (b []byte, err error) {
-	defer func() {
-		if e := recover(); e != nil {
-			if ierr, ok := e.(internalError); ok {
-				err = ierr
-				return
-			}
-			// Not an internal error; panic again.
-			panic(e)
-		}
-	}()
-
-	p := exporter{
-		fset:          fset,
-		strIndex:      map[string]int{"": 0}, // empty string is mapped to 0
-		pkgIndex:      make(map[*types.Package]int),
-		typIndex:      make(map[types.Type]int),
-		posInfoFormat: true, // TODO(gri) might become a flag, eventually
-	}
-
-	// write version info
-	// The version string must start with "version %d" where %d is the version
-	// number. Additional debugging information may follow after a blank; that
-	// text is ignored by the importer.
-	p.rawStringln(fmt.Sprintf("version %d", exportVersion))
-	var debug string
-	if debugFormat {
-		debug = "debug"
-	}
-	p.rawStringln(debug) // cannot use p.bool since it's affected by debugFormat; also want to see this clearly
-	p.bool(trackAllTypes)
-	p.bool(p.posInfoFormat)
-
-	// --- generic export data ---
-
-	// populate type map with predeclared "known" types
-	for index, typ := range predeclared() {
-		p.typIndex[typ] = index
-	}
-	if len(p.typIndex) != len(predeclared()) {
-		return nil, internalError("duplicate entries in type map?")
-	}
-
-	// write package data
-	p.pkg(pkg, true)
-	if trace {
-		p.tracef("\n")
-	}
-
-	// write objects
-	objcount := 0
-	scope := pkg.Scope()
-	for _, name := range scope.Names() {
-		if !ast.IsExported(name) {
-			continue
-		}
-		if trace {
-			p.tracef("\n")
-		}
-		p.obj(scope.Lookup(name))
-		objcount++
-	}
-
-	// indicate end of list
-	if trace {
-		p.tracef("\n")
-	}
-	p.tag(endTag)
-
-	// for self-verification only (redundant)
-	p.int(objcount)
-
-	if trace {
-		p.tracef("\n")
-	}
-
-	// --- end of export data ---
-
-	return p.out.Bytes(), nil
-}
-
-func (p *exporter) pkg(pkg *types.Package, emptypath bool) {
-	if pkg == nil {
-		panic(internalError("unexpected nil pkg"))
-	}
-
-	// if we saw the package before, write its index (>= 0)
-	if i, ok := p.pkgIndex[pkg]; ok {
-		p.index('P', i)
-		return
-	}
-
-	// otherwise, remember the package, write the package tag (< 0) and package data
-	if trace {
-		p.tracef("P%d = { ", len(p.pkgIndex))
-		defer p.tracef("} ")
-	}
-	p.pkgIndex[pkg] = len(p.pkgIndex)
-
-	p.tag(packageTag)
-	p.string(pkg.Name())
-	if emptypath {
-		p.string("")
-	} else {
-		p.string(pkg.Path())
-	}
-}
-
-func (p *exporter) obj(obj types.Object) {
-	switch obj := obj.(type) {
-	case *types.Const:
-		p.tag(constTag)
-		p.pos(obj)
-		p.qualifiedName(obj)
-		p.typ(obj.Type())
-		p.value(obj.Val())
-
-	case *types.TypeName:
-		if obj.IsAlias() {
-			p.tag(aliasTag)
-			p.pos(obj)
-			p.qualifiedName(obj)
-		} else {
-			p.tag(typeTag)
-		}
-		p.typ(obj.Type())
-
-	case *types.Var:
-		p.tag(varTag)
-		p.pos(obj)
-		p.qualifiedName(obj)
-		p.typ(obj.Type())
-
-	case *types.Func:
-		p.tag(funcTag)
-		p.pos(obj)
-		p.qualifiedName(obj)
-		sig := obj.Type().(*types.Signature)
-		p.paramList(sig.Params(), sig.Variadic())
-		p.paramList(sig.Results(), false)
-
-	default:
-		panic(internalErrorf("unexpected object %v (%T)", obj, obj))
-	}
-}
-
-func (p *exporter) pos(obj types.Object) {
-	if !p.posInfoFormat {
-		return
-	}
-
-	file, line := p.fileLine(obj)
-	if file == p.prevFile {
-		// common case: write line delta
-		// delta == 0 means different file or no line change
-		delta := line - p.prevLine
-		p.int(delta)
-		if delta == 0 {
-			p.int(-1) // -1 means no file change
-		}
-	} else {
-		// different file
-		p.int(0)
-		// Encode filename as length of common prefix with previous
-		// filename, followed by (possibly empty) suffix. Filenames
-		// frequently share path prefixes, so this can save a lot
-		// of space and make export data size less dependent on file
-		// path length. The suffix is unlikely to be empty because
-		// file names tend to end in ".go".
-		n := commonPrefixLen(p.prevFile, file)
-		p.int(n)           // n >= 0
-		p.string(file[n:]) // write suffix only
-		p.prevFile = file
-		p.int(line)
-	}
-	p.prevLine = line
-}
-
-func (p *exporter) fileLine(obj types.Object) (file string, line int) {
-	if p.fset != nil {
-		pos := p.fset.Position(obj.Pos())
-		file = pos.Filename
-		line = pos.Line
-	}
-	return
-}
-
-func commonPrefixLen(a, b string) int {
-	if len(a) > len(b) {
-		a, b = b, a
-	}
-	// len(a) <= len(b)
-	i := 0
-	for i < len(a) && a[i] == b[i] {
-		i++
-	}
-	return i
-}
-
-func (p *exporter) qualifiedName(obj types.Object) {
-	p.string(obj.Name())
-	p.pkg(obj.Pkg(), false)
-}
-
-func (p *exporter) typ(t types.Type) {
-	if t == nil {
-		panic(internalError("nil type"))
-	}
-
-	// Possible optimization: Anonymous pointer types *T where
-	// T is a named type are common. We could canonicalize all
-	// such types *T to a single type PT = *T. This would lead
-	// to at most one *T entry in typIndex, and all future *T's
-	// would be encoded as the respective index directly. Would
-	// save 1 byte (pointerTag) per *T and reduce the typIndex
-	// size (at the cost of a canonicalization map). We can do
-	// this later, without encoding format change.
-
-	// if we saw the type before, write its index (>= 0)
-	if i, ok := p.typIndex[t]; ok {
-		p.index('T', i)
-		return
-	}
-
-	// otherwise, remember the type, write the type tag (< 0) and type data
-	if trackAllTypes {
-		if trace {
-			p.tracef("T%d = {>\n", len(p.typIndex))
-			defer p.tracef("<\n} ")
-		}
-		p.typIndex[t] = len(p.typIndex)
-	}
-
-	switch t := t.(type) {
-	case *types.Named:
-		if !trackAllTypes {
-			// if we don't track all types, track named types now
-			p.typIndex[t] = len(p.typIndex)
-		}
-
-		p.tag(namedTag)
-		p.pos(t.Obj())
-		p.qualifiedName(t.Obj())
-		p.typ(t.Underlying())
-		if !types.IsInterface(t) {
-			p.assocMethods(t)
-		}
-
-	case *types.Array:
-		p.tag(arrayTag)
-		p.int64(t.Len())
-		p.typ(t.Elem())
-
-	case *types.Slice:
-		p.tag(sliceTag)
-		p.typ(t.Elem())
-
-	case *dddSlice:
-		p.tag(dddTag)
-		p.typ(t.elem)
-
-	case *types.Struct:
-		p.tag(structTag)
-		p.fieldList(t)
-
-	case *types.Pointer:
-		p.tag(pointerTag)
-		p.typ(t.Elem())
-
-	case *types.Signature:
-		p.tag(signatureTag)
-		p.paramList(t.Params(), t.Variadic())
-		p.paramList(t.Results(), false)
-
-	case *types.Interface:
-		p.tag(interfaceTag)
-		p.iface(t)
-
-	case *types.Map:
-		p.tag(mapTag)
-		p.typ(t.Key())
-		p.typ(t.Elem())
-
-	case *types.Chan:
-		p.tag(chanTag)
-		p.int(int(3 - t.Dir())) // hack
-		p.typ(t.Elem())
-
-	default:
-		panic(internalErrorf("unexpected type %T: %s", t, t))
-	}
-}
-
-func (p *exporter) assocMethods(named *types.Named) {
-	// Sort methods (for determinism).
-	var methods []*types.Func
-	for i := 0; i < named.NumMethods(); i++ {
-		methods = append(methods, named.Method(i))
-	}
-	sort.Sort(methodsByName(methods))
-
-	p.int(len(methods))
-
-	if trace && methods != nil {
-		p.tracef("associated methods {>\n")
-	}
-
-	for i, m := range methods {
-		if trace && i > 0 {
-			p.tracef("\n")
-		}
-
-		p.pos(m)
-		name := m.Name()
-		p.string(name)
-		if !exported(name) {
-			p.pkg(m.Pkg(), false)
-		}
-
-		sig := m.Type().(*types.Signature)
-		p.paramList(types.NewTuple(sig.Recv()), false)
-		p.paramList(sig.Params(), sig.Variadic())
-		p.paramList(sig.Results(), false)
-		p.int(0) // dummy value for go:nointerface pragma - ignored by importer
-	}
-
-	if trace && methods != nil {
-		p.tracef("<\n} ")
-	}
-}
-
-type methodsByName []*types.Func
-
-func (x methodsByName) Len() int           { return len(x) }
-func (x methodsByName) Swap(i, j int)      { x[i], x[j] = x[j], x[i] }
-func (x methodsByName) Less(i, j int) bool { return x[i].Name() < x[j].Name() }
-
-func (p *exporter) fieldList(t *types.Struct) {
-	if trace && t.NumFields() > 0 {
-		p.tracef("fields {>\n")
-		defer p.tracef("<\n} ")
-	}
-
-	p.int(t.NumFields())
-	for i := 0; i < t.NumFields(); i++ {
-		if trace && i > 0 {
-			p.tracef("\n")
-		}
-		p.field(t.Field(i))
-		p.string(t.Tag(i))
-	}
-}
-
-func (p *exporter) field(f *types.Var) {
-	if !f.IsField() {
-		panic(internalError("field expected"))
-	}
-
-	p.pos(f)
-	p.fieldName(f)
-	p.typ(f.Type())
-}
-
-func (p *exporter) iface(t *types.Interface) {
-	// TODO(gri): enable importer to load embedded interfaces,
-	// then emit Embeddeds and ExplicitMethods separately here.
-	p.int(0)
-
-	n := t.NumMethods()
-	if trace && n > 0 {
-		p.tracef("methods {>\n")
-		defer p.tracef("<\n} ")
-	}
-	p.int(n)
-	for i := 0; i < n; i++ {
-		if trace && i > 0 {
-			p.tracef("\n")
-		}
-		p.method(t.Method(i))
-	}
-}
-
-func (p *exporter) method(m *types.Func) {
-	sig := m.Type().(*types.Signature)
-	if sig.Recv() == nil {
-		panic(internalError("method expected"))
-	}
-
-	p.pos(m)
-	p.string(m.Name())
-	if m.Name() != "_" && !ast.IsExported(m.Name()) {
-		p.pkg(m.Pkg(), false)
-	}
-
-	// interface method; no need to encode receiver.
-	p.paramList(sig.Params(), sig.Variadic())
-	p.paramList(sig.Results(), false)
-}
-
-func (p *exporter) fieldName(f *types.Var) {
-	name := f.Name()
-
-	if f.Anonymous() {
-		// anonymous field - we distinguish between 3 cases:
-		// 1) field name matches base type name and is exported
-		// 2) field name matches base type name and is not exported
-		// 3) field name doesn't match base type name (alias name)
-		bname := basetypeName(f.Type())
-		if name == bname {
-			if ast.IsExported(name) {
-				name = "" // 1) we don't need to know the field name or package
-			} else {
-				name = "?" // 2) use unexported name "?" to force package export
-			}
-		} else {
-			// 3) indicate alias and export name as is
-			// (this requires an extra "@" but this is a rare case)
-			p.string("@")
-		}
-	}
-
-	p.string(name)
-	if name != "" && !ast.IsExported(name) {
-		p.pkg(f.Pkg(), false)
-	}
-}
-
-func basetypeName(typ types.Type) string {
-	switch typ := deref(typ).(type) {
-	case *types.Basic:
-		return typ.Name()
-	case *types.Named:
-		return typ.Obj().Name()
-	default:
-		return "" // unnamed type
-	}
-}
-
-func (p *exporter) paramList(params *types.Tuple, variadic bool) {
-	// use negative length to indicate unnamed parameters
-	// (look at the first parameter only since either all
-	// names are present or all are absent)
-	n := params.Len()
-	if n > 0 && params.At(0).Name() == "" {
-		n = -n
-	}
-	p.int(n)
-	for i := 0; i < params.Len(); i++ {
-		q := params.At(i)
-		t := q.Type()
-		if variadic && i == params.Len()-1 {
-			t = &dddSlice{t.(*types.Slice).Elem()}
-		}
-		p.typ(t)
-		if n > 0 {
-			name := q.Name()
-			p.string(name)
-			if name != "_" {
-				p.pkg(q.Pkg(), false)
-			}
-		}
-		p.string("") // no compiler-specific info
-	}
-}
-
-func (p *exporter) value(x constant.Value) {
-	if trace {
-		p.tracef("= ")
-	}
-
-	switch x.Kind() {
-	case constant.Bool:
-		tag := falseTag
-		if constant.BoolVal(x) {
-			tag = trueTag
-		}
-		p.tag(tag)
-
-	case constant.Int:
-		if v, exact := constant.Int64Val(x); exact {
-			// common case: x fits into an int64 - use compact encoding
-			p.tag(int64Tag)
-			p.int64(v)
-			return
-		}
-		// uncommon case: large x - use float encoding
-		// (powers of 2 will be encoded efficiently with exponent)
-		p.tag(floatTag)
-		p.float(constant.ToFloat(x))
-
-	case constant.Float:
-		p.tag(floatTag)
-		p.float(x)
-
-	case constant.Complex:
-		p.tag(complexTag)
-		p.float(constant.Real(x))
-		p.float(constant.Imag(x))
-
-	case constant.String:
-		p.tag(stringTag)
-		p.string(constant.StringVal(x))
-
-	case constant.Unknown:
-		// package contains type errors
-		p.tag(unknownTag)
-
-	default:
-		panic(internalErrorf("unexpected value %v (%T)", x, x))
-	}
-}
-
-func (p *exporter) float(x constant.Value) {
-	if x.Kind() != constant.Float {
-		panic(internalErrorf("unexpected constant %v, want float", x))
-	}
-	// extract sign (there is no -0)
-	sign := constant.Sign(x)
-	if sign == 0 {
-		// x == 0
-		p.int(0)
-		return
-	}
-	// x != 0
-
-	var f big.Float
-	if v, exact := constant.Float64Val(x); exact {
-		// float64
-		f.SetFloat64(v)
-	} else if num, denom := constant.Num(x), constant.Denom(x); num.Kind() == constant.Int {
-		// TODO(gri): add big.Rat accessor to constant.Value.
-		r := valueToRat(num)
-		f.SetRat(r.Quo(r, valueToRat(denom)))
-	} else {
-		// Value too large to represent as a fraction => inaccessible.
-		// TODO(gri): add big.Float accessor to constant.Value.
-		f.SetFloat64(math.MaxFloat64) // FIXME
-	}
-
-	// extract exponent such that 0.5 <= m < 1.0
-	var m big.Float
-	exp := f.MantExp(&m)
-
-	// extract mantissa as *big.Int
-	// - set exponent large enough so mant satisfies mant.IsInt()
-	// - get *big.Int from mant
-	m.SetMantExp(&m, int(m.MinPrec()))
-	mant, acc := m.Int(nil)
-	if acc != big.Exact {
-		panic(internalError("internal error"))
-	}
-
-	p.int(sign)
-	p.int(exp)
-	p.string(string(mant.Bytes()))
-}
-
-func valueToRat(x constant.Value) *big.Rat {
-	// Convert little-endian to big-endian.
-	// I can't believe this is necessary.
-	bytes := constant.Bytes(x)
-	for i := 0; i < len(bytes)/2; i++ {
-		bytes[i], bytes[len(bytes)-1-i] = bytes[len(bytes)-1-i], bytes[i]
-	}
-	return new(big.Rat).SetInt(new(big.Int).SetBytes(bytes))
-}
-
-func (p *exporter) bool(b bool) bool {
-	if trace {
-		p.tracef("[")
-		defer p.tracef("= %v] ", b)
-	}
-
-	x := 0
-	if b {
-		x = 1
-	}
-	p.int(x)
-	return b
-}
-
-// ----------------------------------------------------------------------------
-// Low-level encoders
-
-func (p *exporter) index(marker byte, index int) {
-	if index < 0 {
-		panic(internalError("invalid index < 0"))
-	}
-	if debugFormat {
-		p.marker('t')
-	}
-	if trace {
-		p.tracef("%c%d ", marker, index)
-	}
-	p.rawInt64(int64(index))
-}
-
-func (p *exporter) tag(tag int) {
-	if tag >= 0 {
-		panic(internalError("invalid tag >= 0"))
-	}
-	if debugFormat {
-		p.marker('t')
-	}
-	if trace {
-		p.tracef("%s ", tagString[-tag])
-	}
-	p.rawInt64(int64(tag))
-}
-
-func (p *exporter) int(x int) {
-	p.int64(int64(x))
-}
-
-func (p *exporter) int64(x int64) {
-	if debugFormat {
-		p.marker('i')
-	}
-	if trace {
-		p.tracef("%d ", x)
-	}
-	p.rawInt64(x)
-}
-
-func (p *exporter) string(s string) {
-	if debugFormat {
-		p.marker('s')
-	}
-	if trace {
-		p.tracef("%q ", s)
-	}
-	// if we saw the string before, write its index (>= 0)
-	// (the empty string is mapped to 0)
-	if i, ok := p.strIndex[s]; ok {
-		p.rawInt64(int64(i))
-		return
-	}
-	// otherwise, remember string and write its negative length and bytes
-	p.strIndex[s] = len(p.strIndex)
-	p.rawInt64(-int64(len(s)))
-	for i := 0; i < len(s); i++ {
-		p.rawByte(s[i])
-	}
-}
-
-// marker emits a marker byte and position information which makes
-// it easy for a reader to detect if it is "out of sync". Used for
-// debugFormat format only.
-func (p *exporter) marker(m byte) {
-	p.rawByte(m)
-	// Enable this for help tracking down the location
-	// of an incorrect marker when running in debugFormat.
-	if false && trace {
-		p.tracef("#%d ", p.written)
-	}
-	p.rawInt64(int64(p.written))
-}
-
-// rawInt64 should only be used by low-level encoders.
-func (p *exporter) rawInt64(x int64) {
-	var tmp [binary.MaxVarintLen64]byte
-	n := binary.PutVarint(tmp[:], x)
-	for i := 0; i < n; i++ {
-		p.rawByte(tmp[i])
-	}
-}
-
-// rawStringln should only be used to emit the initial version string.
-func (p *exporter) rawStringln(s string) {
-	for i := 0; i < len(s); i++ {
-		p.rawByte(s[i])
-	}
-	p.rawByte('\n')
-}
-
-// rawByte is the bottleneck interface to write to p.out.
-// rawByte escapes b as follows (any encoding does that
-// hides '$'):
-//
-//	'$'  => '|' 'S'
-//	'|'  => '|' '|'
-//
-// Necessary so other tools can find the end of the
-// export data by searching for "$$".
-// rawByte should only be used by low-level encoders.
-func (p *exporter) rawByte(b byte) {
-	switch b {
-	case '$':
-		// write '$' as '|' 'S'
-		b = 'S'
-		fallthrough
-	case '|':
-		// write '|' as '|' '|'
-		p.out.WriteByte('|')
-		p.written++
-	}
-	p.out.WriteByte(b)
-	p.written++
-}
-
-// tracef is like fmt.Printf but it rewrites the format string
-// to take care of indentation.
-func (p *exporter) tracef(format string, args ...interface{}) {
-	if strings.ContainsAny(format, "<>\n") {
-		var buf bytes.Buffer
-		for i := 0; i < len(format); i++ {
-			// no need to deal with runes
-			ch := format[i]
-			switch ch {
-			case '>':
-				p.indent++
-				continue
-			case '<':
-				p.indent--
-				continue
-			}
-			buf.WriteByte(ch)
-			if ch == '\n' {
-				for j := p.indent; j > 0; j-- {
-					buf.WriteString(".  ")
-				}
-			}
-		}
-		format = buf.String()
-	}
-	fmt.Printf(format, args...)
-}
-
-// Debugging support.
-// (tagString is only used when tracing is enabled)
-var tagString = [...]string{
-	// Packages
-	-packageTag: "package",
-
-	// Types
-	-namedTag:     "named type",
-	-arrayTag:     "array",
-	-sliceTag:     "slice",
-	-dddTag:       "ddd",
-	-structTag:    "struct",
-	-pointerTag:   "pointer",
-	-signatureTag: "signature",
-	-interfaceTag: "interface",
-	-mapTag:       "map",
-	-chanTag:      "chan",
-
-	// Values
-	-falseTag:    "false",
-	-trueTag:     "true",
-	-int64Tag:    "int64",
-	-floatTag:    "float",
-	-fractionTag: "fraction",
-	-complexTag:  "complex",
-	-stringTag:   "string",
-	-unknownTag:  "unknown",
-
-	// Type aliases
-	-aliasTag: "alias",
-}

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

@@ -1,93 +0,0 @@
-// 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 copy of $GOROOT/src/go/internal/gcimporter/exportdata.go.
-
-// This file implements FindExportData.
-
-package gcimporter
-
-import (
-	"bufio"
-	"fmt"
-	"io"
-	"strconv"
-	"strings"
-)
-
-func readGopackHeader(r *bufio.Reader) (name string, size int, err error) {
-	// See $GOROOT/include/ar.h.
-	hdr := make([]byte, 16+12+6+6+8+10+2)
-	_, err = io.ReadFull(r, hdr)
-	if err != nil {
-		return
-	}
-	// leave for debugging
-	if false {
-		fmt.Printf("header: %s", hdr)
-	}
-	s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10]))
-	size, err = strconv.Atoi(s)
-	if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
-		err = fmt.Errorf("invalid archive header")
-		return
-	}
-	name = strings.TrimSpace(string(hdr[:16]))
-	return
-}
-
-// FindExportData positions the reader r at the beginning of the
-// export data section of an underlying GC-created object/archive
-// file by reading from it. The reader must be positioned at the
-// start of the file before calling this function. The hdr result
-// is the string before the export data, either "$$" or "$$B".
-//
-func FindExportData(r *bufio.Reader) (hdr string, err error) {
-	// 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
-	}
-
-	if string(line) == "!<arch>\n" {
-		// Archive file. Scan to __.PKGDEF.
-		var name string
-		if name, _, err = readGopackHeader(r); err != nil {
-			return
-		}
-
-		// First entry should be __.PKGDEF.
-		if name != "__.PKGDEF" {
-			err = fmt.Errorf("go archive is missing __.PKGDEF")
-			return
-		}
-
-		// Read first line of __.PKGDEF data, so that line
-		// is once again the first line of the input.
-		if line, err = r.ReadSlice('\n'); err != nil {
-			err = fmt.Errorf("can't find export data (%v)", err)
-			return
-		}
-	}
-
-	// Now at __.PKGDEF in archive or still at beginning of file.
-	// Either way, line should begin with "go object ".
-	if !strings.HasPrefix(string(line), "go object ") {
-		err = fmt.Errorf("not a Go object file")
-		return
-	}
-
-	// Skip over object header to export data.
-	// Begins after first line starting with $$.
-	for line[0] != '$' {
-		if line, err = r.ReadSlice('\n'); err != nil {
-			err = fmt.Errorf("can't find export data (%v)", err)
-			return
-		}
-	}
-	hdr = string(line)
-
-	return
-}

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

@@ -1,723 +0,0 @@
-// Copyright 2019 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.
-
-// Indexed binary package export.
-// This file was derived from $GOROOT/src/cmd/compile/internal/gc/iexport.go;
-// see that file for specification of the format.
-
-// +build go1.11
-
-package gcimporter
-
-import (
-	"bytes"
-	"encoding/binary"
-	"go/ast"
-	"go/constant"
-	"go/token"
-	"go/types"
-	"io"
-	"math/big"
-	"reflect"
-	"sort"
-)
-
-// Current indexed export format version. Increase with each format change.
-// 0: Go1.11 encoding
-const iexportVersion = 0
-
-// IExportData returns the binary export data for pkg.
-// If no file set is provided, position info will be missing.
-func IExportData(fset *token.FileSet, pkg *types.Package) (b []byte, err error) {
-	defer func() {
-		if e := recover(); e != nil {
-			if ierr, ok := e.(internalError); ok {
-				err = ierr
-				return
-			}
-			// Not an internal error; panic again.
-			panic(e)
-		}
-	}()
-
-	p := iexporter{
-		out:         bytes.NewBuffer(nil),
-		fset:        fset,
-		allPkgs:     map[*types.Package]bool{},
-		stringIndex: map[string]uint64{},
-		declIndex:   map[types.Object]uint64{},
-		typIndex:    map[types.Type]uint64{},
-	}
-
-	for i, pt := range predeclared() {
-		p.typIndex[pt] = uint64(i)
-	}
-	if len(p.typIndex) > predeclReserved {
-		panic(internalErrorf("too many predeclared types: %d > %d", len(p.typIndex), predeclReserved))
-	}
-
-	// Initialize work queue with exported declarations.
-	scope := pkg.Scope()
-	for _, name := range scope.Names() {
-		if ast.IsExported(name) {
-			p.pushDecl(scope.Lookup(name))
-		}
-	}
-
-	// Loop until no more work.
-	for !p.declTodo.empty() {
-		p.doDecl(p.declTodo.popHead())
-	}
-
-	// Append indices to data0 section.
-	dataLen := uint64(p.data0.Len())
-	w := p.newWriter()
-	w.writeIndex(p.declIndex, pkg)
-	w.flush()
-
-	// Assemble header.
-	var hdr intWriter
-	hdr.WriteByte('i')
-	hdr.uint64(iexportVersion)
-	hdr.uint64(uint64(p.strings.Len()))
-	hdr.uint64(dataLen)
-
-	// Flush output.
-	io.Copy(p.out, &hdr)
-	io.Copy(p.out, &p.strings)
-	io.Copy(p.out, &p.data0)
-
-	return p.out.Bytes(), nil
-}
-
-// writeIndex writes out an object index. mainIndex indicates whether
-// we're writing out the main index, which is also read by
-// non-compiler tools and includes a complete package description
-// (i.e., name and height).
-func (w *exportWriter) writeIndex(index map[types.Object]uint64, localpkg *types.Package) {
-	// Build a map from packages to objects from that package.
-	pkgObjs := map[*types.Package][]types.Object{}
-
-	// For the main index, make sure to include every package that
-	// we reference, even if we're not exporting (or reexporting)
-	// any symbols from it.
-	pkgObjs[localpkg] = nil
-	for pkg := range w.p.allPkgs {
-		pkgObjs[pkg] = nil
-	}
-
-	for obj := range index {
-		pkgObjs[obj.Pkg()] = append(pkgObjs[obj.Pkg()], obj)
-	}
-
-	var pkgs []*types.Package
-	for pkg, objs := range pkgObjs {
-		pkgs = append(pkgs, pkg)
-
-		sort.Slice(objs, func(i, j int) bool {
-			return objs[i].Name() < objs[j].Name()
-		})
-	}
-
-	sort.Slice(pkgs, func(i, j int) bool {
-		return pkgs[i].Path() < pkgs[j].Path()
-	})
-
-	w.uint64(uint64(len(pkgs)))
-	for _, pkg := range pkgs {
-		w.string(pkg.Path())
-		w.string(pkg.Name())
-		w.uint64(uint64(0)) // package height is not needed for go/types
-
-		objs := pkgObjs[pkg]
-		w.uint64(uint64(len(objs)))
-		for _, obj := range objs {
-			w.string(obj.Name())
-			w.uint64(index[obj])
-		}
-	}
-}
-
-type iexporter struct {
-	fset *token.FileSet
-	out  *bytes.Buffer
-
-	// allPkgs tracks all packages that have been referenced by
-	// the export data, so we can ensure to include them in the
-	// main index.
-	allPkgs map[*types.Package]bool
-
-	declTodo objQueue
-
-	strings     intWriter
-	stringIndex map[string]uint64
-
-	data0     intWriter
-	declIndex map[types.Object]uint64
-	typIndex  map[types.Type]uint64
-}
-
-// stringOff returns the offset of s within the string section.
-// If not already present, it's added to the end.
-func (p *iexporter) stringOff(s string) uint64 {
-	off, ok := p.stringIndex[s]
-	if !ok {
-		off = uint64(p.strings.Len())
-		p.stringIndex[s] = off
-
-		p.strings.uint64(uint64(len(s)))
-		p.strings.WriteString(s)
-	}
-	return off
-}
-
-// pushDecl adds n to the declaration work queue, if not already present.
-func (p *iexporter) pushDecl(obj types.Object) {
-	// Package unsafe is known to the compiler and predeclared.
-	assert(obj.Pkg() != types.Unsafe)
-
-	if _, ok := p.declIndex[obj]; ok {
-		return
-	}
-
-	p.declIndex[obj] = ^uint64(0) // mark n present in work queue
-	p.declTodo.pushTail(obj)
-}
-
-// exportWriter handles writing out individual data section chunks.
-type exportWriter struct {
-	p *iexporter
-
-	data     intWriter
-	currPkg  *types.Package
-	prevFile string
-	prevLine int64
-}
-
-func (p *iexporter) doDecl(obj types.Object) {
-	w := p.newWriter()
-	w.setPkg(obj.Pkg(), false)
-
-	switch obj := obj.(type) {
-	case *types.Var:
-		w.tag('V')
-		w.pos(obj.Pos())
-		w.typ(obj.Type(), obj.Pkg())
-
-	case *types.Func:
-		sig, _ := obj.Type().(*types.Signature)
-		if sig.Recv() != nil {
-			panic(internalErrorf("unexpected method: %v", sig))
-		}
-		w.tag('F')
-		w.pos(obj.Pos())
-		w.signature(sig)
-
-	case *types.Const:
-		w.tag('C')
-		w.pos(obj.Pos())
-		w.value(obj.Type(), obj.Val())
-
-	case *types.TypeName:
-		if obj.IsAlias() {
-			w.tag('A')
-			w.pos(obj.Pos())
-			w.typ(obj.Type(), obj.Pkg())
-			break
-		}
-
-		// Defined type.
-		w.tag('T')
-		w.pos(obj.Pos())
-
-		underlying := obj.Type().Underlying()
-		w.typ(underlying, obj.Pkg())
-
-		t := obj.Type()
-		if types.IsInterface(t) {
-			break
-		}
-
-		named, ok := t.(*types.Named)
-		if !ok {
-			panic(internalErrorf("%s is not a defined type", t))
-		}
-
-		n := named.NumMethods()
-		w.uint64(uint64(n))
-		for i := 0; i < n; i++ {
-			m := named.Method(i)
-			w.pos(m.Pos())
-			w.string(m.Name())
-			sig, _ := m.Type().(*types.Signature)
-			w.param(sig.Recv())
-			w.signature(sig)
-		}
-
-	default:
-		panic(internalErrorf("unexpected object: %v", obj))
-	}
-
-	p.declIndex[obj] = w.flush()
-}
-
-func (w *exportWriter) tag(tag byte) {
-	w.data.WriteByte(tag)
-}
-
-func (w *exportWriter) pos(pos token.Pos) {
-	p := w.p.fset.Position(pos)
-	file := p.Filename
-	line := int64(p.Line)
-
-	// When file is the same as the last position (common case),
-	// we can save a few bytes by delta encoding just the line
-	// number.
-	//
-	// Note: Because data objects may be read out of order (or not
-	// at all), we can only apply delta encoding within a single
-	// object. This is handled implicitly by tracking prevFile and
-	// prevLine as fields of exportWriter.
-
-	if file == w.prevFile {
-		delta := line - w.prevLine
-		w.int64(delta)
-		if delta == deltaNewFile {
-			w.int64(-1)
-		}
-	} else {
-		w.int64(deltaNewFile)
-		w.int64(line) // line >= 0
-		w.string(file)
-		w.prevFile = file
-	}
-	w.prevLine = line
-}
-
-func (w *exportWriter) pkg(pkg *types.Package) {
-	// Ensure any referenced packages are declared in the main index.
-	w.p.allPkgs[pkg] = true
-
-	w.string(pkg.Path())
-}
-
-func (w *exportWriter) qualifiedIdent(obj types.Object) {
-	// Ensure any referenced declarations are written out too.
-	w.p.pushDecl(obj)
-
-	w.string(obj.Name())
-	w.pkg(obj.Pkg())
-}
-
-func (w *exportWriter) typ(t types.Type, pkg *types.Package) {
-	w.data.uint64(w.p.typOff(t, pkg))
-}
-
-func (p *iexporter) newWriter() *exportWriter {
-	return &exportWriter{p: p}
-}
-
-func (w *exportWriter) flush() uint64 {
-	off := uint64(w.p.data0.Len())
-	io.Copy(&w.p.data0, &w.data)
-	return off
-}
-
-func (p *iexporter) typOff(t types.Type, pkg *types.Package) uint64 {
-	off, ok := p.typIndex[t]
-	if !ok {
-		w := p.newWriter()
-		w.doTyp(t, pkg)
-		off = predeclReserved + w.flush()
-		p.typIndex[t] = off
-	}
-	return off
-}
-
-func (w *exportWriter) startType(k itag) {
-	w.data.uint64(uint64(k))
-}
-
-func (w *exportWriter) doTyp(t types.Type, pkg *types.Package) {
-	switch t := t.(type) {
-	case *types.Named:
-		w.startType(definedType)
-		w.qualifiedIdent(t.Obj())
-
-	case *types.Pointer:
-		w.startType(pointerType)
-		w.typ(t.Elem(), pkg)
-
-	case *types.Slice:
-		w.startType(sliceType)
-		w.typ(t.Elem(), pkg)
-
-	case *types.Array:
-		w.startType(arrayType)
-		w.uint64(uint64(t.Len()))
-		w.typ(t.Elem(), pkg)
-
-	case *types.Chan:
-		w.startType(chanType)
-		// 1 RecvOnly; 2 SendOnly; 3 SendRecv
-		var dir uint64
-		switch t.Dir() {
-		case types.RecvOnly:
-			dir = 1
-		case types.SendOnly:
-			dir = 2
-		case types.SendRecv:
-			dir = 3
-		}
-		w.uint64(dir)
-		w.typ(t.Elem(), pkg)
-
-	case *types.Map:
-		w.startType(mapType)
-		w.typ(t.Key(), pkg)
-		w.typ(t.Elem(), pkg)
-
-	case *types.Signature:
-		w.startType(signatureType)
-		w.setPkg(pkg, true)
-		w.signature(t)
-
-	case *types.Struct:
-		w.startType(structType)
-		w.setPkg(pkg, true)
-
-		n := t.NumFields()
-		w.uint64(uint64(n))
-		for i := 0; i < n; i++ {
-			f := t.Field(i)
-			w.pos(f.Pos())
-			w.string(f.Name())
-			w.typ(f.Type(), pkg)
-			w.bool(f.Embedded())
-			w.string(t.Tag(i)) // note (or tag)
-		}
-
-	case *types.Interface:
-		w.startType(interfaceType)
-		w.setPkg(pkg, true)
-
-		n := t.NumEmbeddeds()
-		w.uint64(uint64(n))
-		for i := 0; i < n; i++ {
-			f := t.Embedded(i)
-			w.pos(f.Obj().Pos())
-			w.typ(f.Obj().Type(), f.Obj().Pkg())
-		}
-
-		n = t.NumExplicitMethods()
-		w.uint64(uint64(n))
-		for i := 0; i < n; i++ {
-			m := t.ExplicitMethod(i)
-			w.pos(m.Pos())
-			w.string(m.Name())
-			sig, _ := m.Type().(*types.Signature)
-			w.signature(sig)
-		}
-
-	default:
-		panic(internalErrorf("unexpected type: %v, %v", t, reflect.TypeOf(t)))
-	}
-}
-
-func (w *exportWriter) setPkg(pkg *types.Package, write bool) {
-	if write {
-		w.pkg(pkg)
-	}
-
-	w.currPkg = pkg
-}
-
-func (w *exportWriter) signature(sig *types.Signature) {
-	w.paramList(sig.Params())
-	w.paramList(sig.Results())
-	if sig.Params().Len() > 0 {
-		w.bool(sig.Variadic())
-	}
-}
-
-func (w *exportWriter) paramList(tup *types.Tuple) {
-	n := tup.Len()
-	w.uint64(uint64(n))
-	for i := 0; i < n; i++ {
-		w.param(tup.At(i))
-	}
-}
-
-func (w *exportWriter) param(obj types.Object) {
-	w.pos(obj.Pos())
-	w.localIdent(obj)
-	w.typ(obj.Type(), obj.Pkg())
-}
-
-func (w *exportWriter) value(typ types.Type, v constant.Value) {
-	w.typ(typ, nil)
-
-	switch v.Kind() {
-	case constant.Bool:
-		w.bool(constant.BoolVal(v))
-	case constant.Int:
-		var i big.Int
-		if i64, exact := constant.Int64Val(v); exact {
-			i.SetInt64(i64)
-		} else if ui64, exact := constant.Uint64Val(v); exact {
-			i.SetUint64(ui64)
-		} else {
-			i.SetString(v.ExactString(), 10)
-		}
-		w.mpint(&i, typ)
-	case constant.Float:
-		f := constantToFloat(v)
-		w.mpfloat(f, typ)
-	case constant.Complex:
-		w.mpfloat(constantToFloat(constant.Real(v)), typ)
-		w.mpfloat(constantToFloat(constant.Imag(v)), typ)
-	case constant.String:
-		w.string(constant.StringVal(v))
-	case constant.Unknown:
-		// package contains type errors
-	default:
-		panic(internalErrorf("unexpected value %v (%T)", v, v))
-	}
-}
-
-// constantToFloat converts a constant.Value with kind constant.Float to a
-// big.Float.
-func constantToFloat(x constant.Value) *big.Float {
-	assert(x.Kind() == constant.Float)
-	// Use the same floating-point precision (512) as cmd/compile
-	// (see Mpprec in cmd/compile/internal/gc/mpfloat.go).
-	const mpprec = 512
-	var f big.Float
-	f.SetPrec(mpprec)
-	if v, exact := constant.Float64Val(x); exact {
-		// float64
-		f.SetFloat64(v)
-	} else if num, denom := constant.Num(x), constant.Denom(x); num.Kind() == constant.Int {
-		// TODO(gri): add big.Rat accessor to constant.Value.
-		n := valueToRat(num)
-		d := valueToRat(denom)
-		f.SetRat(n.Quo(n, d))
-	} else {
-		// Value too large to represent as a fraction => inaccessible.
-		// TODO(gri): add big.Float accessor to constant.Value.
-		_, ok := f.SetString(x.ExactString())
-		assert(ok)
-	}
-	return &f
-}
-
-// mpint exports a multi-precision integer.
-//
-// For unsigned types, small values are written out as a single
-// byte. Larger values are written out as a length-prefixed big-endian
-// byte string, where the length prefix is encoded as its complement.
-// For example, bytes 0, 1, and 2 directly represent the integer
-// values 0, 1, and 2; while bytes 255, 254, and 253 indicate a 1-,
-// 2-, and 3-byte big-endian string follow.
-//
-// Encoding for signed types use the same general approach as for
-// unsigned types, except small values use zig-zag encoding and the
-// bottom bit of length prefix byte for large values is reserved as a
-// sign bit.
-//
-// The exact boundary between small and large encodings varies
-// according to the maximum number of bytes needed to encode a value
-// of type typ. As a special case, 8-bit types are always encoded as a
-// single byte.
-//
-// TODO(mdempsky): Is this level of complexity really worthwhile?
-func (w *exportWriter) mpint(x *big.Int, typ types.Type) {
-	basic, ok := typ.Underlying().(*types.Basic)
-	if !ok {
-		panic(internalErrorf("unexpected type %v (%T)", typ.Underlying(), typ.Underlying()))
-	}
-
-	signed, maxBytes := intSize(basic)
-
-	negative := x.Sign() < 0
-	if !signed && negative {
-		panic(internalErrorf("negative unsigned integer; type %v, value %v", typ, x))
-	}
-
-	b := x.Bytes()
-	if len(b) > 0 && b[0] == 0 {
-		panic(internalErrorf("leading zeros"))
-	}
-	if uint(len(b)) > maxBytes {
-		panic(internalErrorf("bad mpint length: %d > %d (type %v, value %v)", len(b), maxBytes, typ, x))
-	}
-
-	maxSmall := 256 - maxBytes
-	if signed {
-		maxSmall = 256 - 2*maxBytes
-	}
-	if maxBytes == 1 {
-		maxSmall = 256
-	}
-
-	// Check if x can use small value encoding.
-	if len(b) <= 1 {
-		var ux uint
-		if len(b) == 1 {
-			ux = uint(b[0])
-		}
-		if signed {
-			ux <<= 1
-			if negative {
-				ux--
-			}
-		}
-		if ux < maxSmall {
-			w.data.WriteByte(byte(ux))
-			return
-		}
-	}
-
-	n := 256 - uint(len(b))
-	if signed {
-		n = 256 - 2*uint(len(b))
-		if negative {
-			n |= 1
-		}
-	}
-	if n < maxSmall || n >= 256 {
-		panic(internalErrorf("encoding mistake: %d, %v, %v => %d", len(b), signed, negative, n))
-	}
-
-	w.data.WriteByte(byte(n))
-	w.data.Write(b)
-}
-
-// mpfloat exports a multi-precision floating point number.
-//
-// The number's value is decomposed into mantissa × 2**exponent, where
-// mantissa is an integer. The value is written out as mantissa (as a
-// multi-precision integer) and then the exponent, except exponent is
-// omitted if mantissa is zero.
-func (w *exportWriter) mpfloat(f *big.Float, typ types.Type) {
-	if f.IsInf() {
-		panic("infinite constant")
-	}
-
-	// Break into f = mant × 2**exp, with 0.5 <= mant < 1.
-	var mant big.Float
-	exp := int64(f.MantExp(&mant))
-
-	// Scale so that mant is an integer.
-	prec := mant.MinPrec()
-	mant.SetMantExp(&mant, int(prec))
-	exp -= int64(prec)
-
-	manti, acc := mant.Int(nil)
-	if acc != big.Exact {
-		panic(internalErrorf("mantissa scaling failed for %f (%s)", f, acc))
-	}
-	w.mpint(manti, typ)
-	if manti.Sign() != 0 {
-		w.int64(exp)
-	}
-}
-
-func (w *exportWriter) bool(b bool) bool {
-	var x uint64
-	if b {
-		x = 1
-	}
-	w.uint64(x)
-	return b
-}
-
-func (w *exportWriter) int64(x int64)   { w.data.int64(x) }
-func (w *exportWriter) uint64(x uint64) { w.data.uint64(x) }
-func (w *exportWriter) string(s string) { w.uint64(w.p.stringOff(s)) }
-
-func (w *exportWriter) localIdent(obj types.Object) {
-	// Anonymous parameters.
-	if obj == nil {
-		w.string("")
-		return
-	}
-
-	name := obj.Name()
-	if name == "_" {
-		w.string("_")
-		return
-	}
-
-	w.string(name)
-}
-
-type intWriter struct {
-	bytes.Buffer
-}
-
-func (w *intWriter) int64(x int64) {
-	var buf [binary.MaxVarintLen64]byte
-	n := binary.PutVarint(buf[:], x)
-	w.Write(buf[:n])
-}
-
-func (w *intWriter) uint64(x uint64) {
-	var buf [binary.MaxVarintLen64]byte
-	n := binary.PutUvarint(buf[:], x)
-	w.Write(buf[:n])
-}
-
-func assert(cond bool) {
-	if !cond {
-		panic("internal error: assertion failed")
-	}
-}
-
-// The below is copied from go/src/cmd/compile/internal/gc/syntax.go.
-
-// objQueue is a FIFO queue of types.Object. The zero value of objQueue is
-// a ready-to-use empty queue.
-type objQueue struct {
-	ring       []types.Object
-	head, tail int
-}
-
-// empty returns true if q contains no Nodes.
-func (q *objQueue) empty() bool {
-	return q.head == q.tail
-}
-
-// pushTail appends n to the tail of the queue.
-func (q *objQueue) pushTail(obj types.Object) {
-	if len(q.ring) == 0 {
-		q.ring = make([]types.Object, 16)
-	} else if q.head+len(q.ring) == q.tail {
-		// Grow the ring.
-		nring := make([]types.Object, len(q.ring)*2)
-		// Copy the old elements.
-		part := q.ring[q.head%len(q.ring):]
-		if q.tail-q.head <= len(part) {
-			part = part[:q.tail-q.head]
-			copy(nring, part)
-		} else {
-			pos := copy(nring, part)
-			copy(nring[pos:], q.ring[:q.tail%len(q.ring)])
-		}
-		q.ring, q.head, q.tail = nring, 0, q.tail-q.head
-	}
-
-	q.ring[q.tail%len(q.ring)] = obj
-	q.tail++
-}
-
-// popHead pops a node from the head of the queue. It panics if q is empty.
-func (q *objQueue) popHead() types.Object {
-	if q.empty() {
-		panic("dequeue empty")
-	}
-	obj := q.ring[q.head%len(q.ring)]
-	q.head++
-	return obj
-}

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

@@ -1,606 +0,0 @@
-// Copyright 2018 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.
-
-// Indexed package import.
-// See cmd/compile/internal/gc/iexport.go for the export data format.
-
-// This file is a copy of $GOROOT/src/go/internal/gcimporter/iimport.go.
-
-package gcimporter
-
-import (
-	"bytes"
-	"encoding/binary"
-	"fmt"
-	"go/constant"
-	"go/token"
-	"go/types"
-	"io"
-	"sort"
-)
-
-type intReader struct {
-	*bytes.Reader
-	path string
-}
-
-func (r *intReader) int64() int64 {
-	i, err := binary.ReadVarint(r.Reader)
-	if err != nil {
-		errorf("import %q: read varint error: %v", r.path, err)
-	}
-	return i
-}
-
-func (r *intReader) uint64() uint64 {
-	i, err := binary.ReadUvarint(r.Reader)
-	if err != nil {
-		errorf("import %q: read varint error: %v", r.path, err)
-	}
-	return i
-}
-
-const predeclReserved = 32
-
-type itag uint64
-
-const (
-	// Types
-	definedType itag = iota
-	pointerType
-	sliceType
-	arrayType
-	chanType
-	mapType
-	signatureType
-	structType
-	interfaceType
-)
-
-// IImportData imports a package from the serialized package data
-// and returns the number of bytes consumed and a reference to the package.
-// If the export data version is not recognized or the format is otherwise
-// compromised, an error is returned.
-func IImportData(fset *token.FileSet, imports map[string]*types.Package, data []byte, path string) (_ int, pkg *types.Package, err error) {
-	const currentVersion = 0
-	version := -1
-	defer func() {
-		if e := recover(); e != nil {
-			if version > currentVersion {
-				err = fmt.Errorf("cannot import %q (%v), export data is newer version - update tool", path, e)
-			} else {
-				err = fmt.Errorf("cannot import %q (%v), possibly version skew - reinstall package", path, e)
-			}
-		}
-	}()
-
-	r := &intReader{bytes.NewReader(data), path}
-
-	version = int(r.uint64())
-	switch version {
-	case currentVersion:
-	default:
-		errorf("unknown iexport format version %d", version)
-	}
-
-	sLen := int64(r.uint64())
-	dLen := int64(r.uint64())
-
-	whence, _ := r.Seek(0, io.SeekCurrent)
-	stringData := data[whence : whence+sLen]
-	declData := data[whence+sLen : whence+sLen+dLen]
-	r.Seek(sLen+dLen, io.SeekCurrent)
-
-	p := iimporter{
-		ipath: path,
-
-		stringData:  stringData,
-		stringCache: make(map[uint64]string),
-		pkgCache:    make(map[uint64]*types.Package),
-
-		declData: declData,
-		pkgIndex: make(map[*types.Package]map[string]uint64),
-		typCache: make(map[uint64]types.Type),
-
-		fake: fakeFileSet{
-			fset:  fset,
-			files: make(map[string]*token.File),
-		},
-	}
-
-	for i, pt := range predeclared() {
-		p.typCache[uint64(i)] = pt
-	}
-
-	pkgList := make([]*types.Package, r.uint64())
-	for i := range pkgList {
-		pkgPathOff := r.uint64()
-		pkgPath := p.stringAt(pkgPathOff)
-		pkgName := p.stringAt(r.uint64())
-		_ = r.uint64() // package height; unused by go/types
-
-		if pkgPath == "" {
-			pkgPath = path
-		}
-		pkg := imports[pkgPath]
-		if pkg == nil {
-			pkg = types.NewPackage(pkgPath, pkgName)
-			imports[pkgPath] = pkg
-		} else if pkg.Name() != pkgName {
-			errorf("conflicting names %s and %s for package %q", pkg.Name(), pkgName, path)
-		}
-
-		p.pkgCache[pkgPathOff] = pkg
-
-		nameIndex := make(map[string]uint64)
-		for nSyms := r.uint64(); nSyms > 0; nSyms-- {
-			name := p.stringAt(r.uint64())
-			nameIndex[name] = r.uint64()
-		}
-
-		p.pkgIndex[pkg] = nameIndex
-		pkgList[i] = pkg
-	}
-	var localpkg *types.Package
-	for _, pkg := range pkgList {
-		if pkg.Path() == path {
-			localpkg = pkg
-		}
-	}
-
-	names := make([]string, 0, len(p.pkgIndex[localpkg]))
-	for name := range p.pkgIndex[localpkg] {
-		names = append(names, name)
-	}
-	sort.Strings(names)
-	for _, name := range names {
-		p.doDecl(localpkg, name)
-	}
-
-	for _, typ := range p.interfaceList {
-		typ.Complete()
-	}
-
-	// record all referenced packages as imports
-	list := append(([]*types.Package)(nil), pkgList[1:]...)
-	sort.Sort(byPath(list))
-	localpkg.SetImports(list)
-
-	// package was imported completely and without errors
-	localpkg.MarkComplete()
-
-	consumed, _ := r.Seek(0, io.SeekCurrent)
-	return int(consumed), localpkg, nil
-}
-
-type iimporter struct {
-	ipath string
-
-	stringData  []byte
-	stringCache map[uint64]string
-	pkgCache    map[uint64]*types.Package
-
-	declData []byte
-	pkgIndex map[*types.Package]map[string]uint64
-	typCache map[uint64]types.Type
-
-	fake          fakeFileSet
-	interfaceList []*types.Interface
-}
-
-func (p *iimporter) doDecl(pkg *types.Package, name string) {
-	// See if we've already imported this declaration.
-	if obj := pkg.Scope().Lookup(name); obj != nil {
-		return
-	}
-
-	off, ok := p.pkgIndex[pkg][name]
-	if !ok {
-		errorf("%v.%v not in index", pkg, name)
-	}
-
-	r := &importReader{p: p, currPkg: pkg}
-	r.declReader.Reset(p.declData[off:])
-
-	r.obj(name)
-}
-
-func (p *iimporter) stringAt(off uint64) string {
-	if s, ok := p.stringCache[off]; ok {
-		return s
-	}
-
-	slen, n := binary.Uvarint(p.stringData[off:])
-	if n <= 0 {
-		errorf("varint failed")
-	}
-	spos := off + uint64(n)
-	s := string(p.stringData[spos : spos+slen])
-	p.stringCache[off] = s
-	return s
-}
-
-func (p *iimporter) pkgAt(off uint64) *types.Package {
-	if pkg, ok := p.pkgCache[off]; ok {
-		return pkg
-	}
-	path := p.stringAt(off)
-	errorf("missing package %q in %q", path, p.ipath)
-	return nil
-}
-
-func (p *iimporter) typAt(off uint64, base *types.Named) types.Type {
-	if t, ok := p.typCache[off]; ok && (base == nil || !isInterface(t)) {
-		return t
-	}
-
-	if off < predeclReserved {
-		errorf("predeclared type missing from cache: %v", off)
-	}
-
-	r := &importReader{p: p}
-	r.declReader.Reset(p.declData[off-predeclReserved:])
-	t := r.doType(base)
-
-	if base == nil || !isInterface(t) {
-		p.typCache[off] = t
-	}
-	return t
-}
-
-type importReader struct {
-	p          *iimporter
-	declReader bytes.Reader
-	currPkg    *types.Package
-	prevFile   string
-	prevLine   int64
-}
-
-func (r *importReader) obj(name string) {
-	tag := r.byte()
-	pos := r.pos()
-
-	switch tag {
-	case 'A':
-		typ := r.typ()
-
-		r.declare(types.NewTypeName(pos, r.currPkg, name, typ))
-
-	case 'C':
-		typ, val := r.value()
-
-		r.declare(types.NewConst(pos, r.currPkg, name, typ, val))
-
-	case 'F':
-		sig := r.signature(nil)
-
-		r.declare(types.NewFunc(pos, r.currPkg, name, sig))
-
-	case 'T':
-		// Types can be recursive. We need to setup a stub
-		// declaration before recursing.
-		obj := types.NewTypeName(pos, r.currPkg, name, nil)
-		named := types.NewNamed(obj, nil, nil)
-		r.declare(obj)
-
-		underlying := r.p.typAt(r.uint64(), named).Underlying()
-		named.SetUnderlying(underlying)
-
-		if !isInterface(underlying) {
-			for n := r.uint64(); n > 0; n-- {
-				mpos := r.pos()
-				mname := r.ident()
-				recv := r.param()
-				msig := r.signature(recv)
-
-				named.AddMethod(types.NewFunc(mpos, r.currPkg, mname, msig))
-			}
-		}
-
-	case 'V':
-		typ := r.typ()
-
-		r.declare(types.NewVar(pos, r.currPkg, name, typ))
-
-	default:
-		errorf("unexpected tag: %v", tag)
-	}
-}
-
-func (r *importReader) declare(obj types.Object) {
-	obj.Pkg().Scope().Insert(obj)
-}
-
-func (r *importReader) value() (typ types.Type, val constant.Value) {
-	typ = r.typ()
-
-	switch b := typ.Underlying().(*types.Basic); b.Info() & types.IsConstType {
-	case types.IsBoolean:
-		val = constant.MakeBool(r.bool())
-
-	case types.IsString:
-		val = constant.MakeString(r.string())
-
-	case types.IsInteger:
-		val = r.mpint(b)
-
-	case types.IsFloat:
-		val = r.mpfloat(b)
-
-	case types.IsComplex:
-		re := r.mpfloat(b)
-		im := r.mpfloat(b)
-		val = constant.BinaryOp(re, token.ADD, constant.MakeImag(im))
-
-	default:
-		if b.Kind() == types.Invalid {
-			val = constant.MakeUnknown()
-			return
-		}
-		errorf("unexpected type %v", typ) // panics
-		panic("unreachable")
-	}
-
-	return
-}
-
-func intSize(b *types.Basic) (signed bool, maxBytes uint) {
-	if (b.Info() & types.IsUntyped) != 0 {
-		return true, 64
-	}
-
-	switch b.Kind() {
-	case types.Float32, types.Complex64:
-		return true, 3
-	case types.Float64, types.Complex128:
-		return true, 7
-	}
-
-	signed = (b.Info() & types.IsUnsigned) == 0
-	switch b.Kind() {
-	case types.Int8, types.Uint8:
-		maxBytes = 1
-	case types.Int16, types.Uint16:
-		maxBytes = 2
-	case types.Int32, types.Uint32:
-		maxBytes = 4
-	default:
-		maxBytes = 8
-	}
-
-	return
-}
-
-func (r *importReader) mpint(b *types.Basic) constant.Value {
-	signed, maxBytes := intSize(b)
-
-	maxSmall := 256 - maxBytes
-	if signed {
-		maxSmall = 256 - 2*maxBytes
-	}
-	if maxBytes == 1 {
-		maxSmall = 256
-	}
-
-	n, _ := r.declReader.ReadByte()
-	if uint(n) < maxSmall {
-		v := int64(n)
-		if signed {
-			v >>= 1
-			if n&1 != 0 {
-				v = ^v
-			}
-		}
-		return constant.MakeInt64(v)
-	}
-
-	v := -n
-	if signed {
-		v = -(n &^ 1) >> 1
-	}
-	if v < 1 || uint(v) > maxBytes {
-		errorf("weird decoding: %v, %v => %v", n, signed, v)
-	}
-
-	buf := make([]byte, v)
-	io.ReadFull(&r.declReader, buf)
-
-	// convert to little endian
-	// TODO(gri) go/constant should have a more direct conversion function
-	//           (e.g., once it supports a big.Float based implementation)
-	for i, j := 0, len(buf)-1; i < j; i, j = i+1, j-1 {
-		buf[i], buf[j] = buf[j], buf[i]
-	}
-
-	x := constant.MakeFromBytes(buf)
-	if signed && n&1 != 0 {
-		x = constant.UnaryOp(token.SUB, x, 0)
-	}
-	return x
-}
-
-func (r *importReader) mpfloat(b *types.Basic) constant.Value {
-	x := r.mpint(b)
-	if constant.Sign(x) == 0 {
-		return x
-	}
-
-	exp := r.int64()
-	switch {
-	case exp > 0:
-		x = constant.Shift(x, token.SHL, uint(exp))
-	case exp < 0:
-		d := constant.Shift(constant.MakeInt64(1), token.SHL, uint(-exp))
-		x = constant.BinaryOp(x, token.QUO, d)
-	}
-	return x
-}
-
-func (r *importReader) ident() string {
-	return r.string()
-}
-
-func (r *importReader) qualifiedIdent() (*types.Package, string) {
-	name := r.string()
-	pkg := r.pkg()
-	return pkg, name
-}
-
-func (r *importReader) pos() token.Pos {
-	delta := r.int64()
-	if delta != deltaNewFile {
-		r.prevLine += delta
-	} else if l := r.int64(); l == -1 {
-		r.prevLine += deltaNewFile
-	} else {
-		r.prevFile = r.string()
-		r.prevLine = l
-	}
-
-	if r.prevFile == "" && r.prevLine == 0 {
-		return token.NoPos
-	}
-
-	return r.p.fake.pos(r.prevFile, int(r.prevLine))
-}
-
-func (r *importReader) typ() types.Type {
-	return r.p.typAt(r.uint64(), nil)
-}
-
-func isInterface(t types.Type) bool {
-	_, ok := t.(*types.Interface)
-	return ok
-}
-
-func (r *importReader) pkg() *types.Package { return r.p.pkgAt(r.uint64()) }
-func (r *importReader) string() string      { return r.p.stringAt(r.uint64()) }
-
-func (r *importReader) doType(base *types.Named) types.Type {
-	switch k := r.kind(); k {
-	default:
-		errorf("unexpected kind tag in %q: %v", r.p.ipath, k)
-		return nil
-
-	case definedType:
-		pkg, name := r.qualifiedIdent()
-		r.p.doDecl(pkg, name)
-		return pkg.Scope().Lookup(name).(*types.TypeName).Type()
-	case pointerType:
-		return types.NewPointer(r.typ())
-	case sliceType:
-		return types.NewSlice(r.typ())
-	case arrayType:
-		n := r.uint64()
-		return types.NewArray(r.typ(), int64(n))
-	case chanType:
-		dir := chanDir(int(r.uint64()))
-		return types.NewChan(dir, r.typ())
-	case mapType:
-		return types.NewMap(r.typ(), r.typ())
-	case signatureType:
-		r.currPkg = r.pkg()
-		return r.signature(nil)
-
-	case structType:
-		r.currPkg = r.pkg()
-
-		fields := make([]*types.Var, r.uint64())
-		tags := make([]string, len(fields))
-		for i := range fields {
-			fpos := r.pos()
-			fname := r.ident()
-			ftyp := r.typ()
-			emb := r.bool()
-			tag := r.string()
-
-			fields[i] = types.NewField(fpos, r.currPkg, fname, ftyp, emb)
-			tags[i] = tag
-		}
-		return types.NewStruct(fields, tags)
-
-	case interfaceType:
-		r.currPkg = r.pkg()
-
-		embeddeds := make([]types.Type, r.uint64())
-		for i := range embeddeds {
-			_ = r.pos()
-			embeddeds[i] = r.typ()
-		}
-
-		methods := make([]*types.Func, r.uint64())
-		for i := range methods {
-			mpos := r.pos()
-			mname := r.ident()
-
-			// TODO(mdempsky): Matches bimport.go, but I
-			// don't agree with this.
-			var recv *types.Var
-			if base != nil {
-				recv = types.NewVar(token.NoPos, r.currPkg, "", base)
-			}
-
-			msig := r.signature(recv)
-			methods[i] = types.NewFunc(mpos, r.currPkg, mname, msig)
-		}
-
-		typ := newInterface(methods, embeddeds)
-		r.p.interfaceList = append(r.p.interfaceList, typ)
-		return typ
-	}
-}
-
-func (r *importReader) kind() itag {
-	return itag(r.uint64())
-}
-
-func (r *importReader) signature(recv *types.Var) *types.Signature {
-	params := r.paramList()
-	results := r.paramList()
-	variadic := params.Len() > 0 && r.bool()
-	return types.NewSignature(recv, params, results, variadic)
-}
-
-func (r *importReader) paramList() *types.Tuple {
-	xs := make([]*types.Var, r.uint64())
-	for i := range xs {
-		xs[i] = r.param()
-	}
-	return types.NewTuple(xs...)
-}
-
-func (r *importReader) param() *types.Var {
-	pos := r.pos()
-	name := r.ident()
-	typ := r.typ()
-	return types.NewParam(pos, r.currPkg, name, typ)
-}
-
-func (r *importReader) bool() bool {
-	return r.uint64() != 0
-}
-
-func (r *importReader) int64() int64 {
-	n, err := binary.ReadVarint(&r.declReader)
-	if err != nil {
-		errorf("readVarint: %v", err)
-	}
-	return n
-}
-
-func (r *importReader) uint64() uint64 {
-	n, err := binary.ReadUvarint(&r.declReader)
-	if err != nil {
-		errorf("readUvarint: %v", err)
-	}
-	return n
-}
-
-func (r *importReader) byte() byte {
-	x, err := r.declReader.ReadByte()
-	if err != nil {
-		errorf("declReader.ReadByte: %v", err)
-	}
-	return x
-}

vendor/golang.org/x/tools/go/internal/gcimporter/newInterface10.go

@@ -1,21 +0,0 @@
-// Copyright 2018 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.
-
-// +build !go1.11
-
-package gcimporter
-
-import "go/types"
-
-func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interface {
-	named := make([]*types.Named, len(embeddeds))
-	for i, e := range embeddeds {
-		var ok bool
-		named[i], ok = e.(*types.Named)
-		if !ok {
-			panic("embedding of non-defined interfaces in interfaces is not supported before Go 1.11")
-		}
-	}
-	return types.NewInterface(methods, named)
-}

vendor/golang.org/x/tools/go/internal/gcimporter/newInterface11.go

@@ -1,13 +0,0 @@
-// Copyright 2018 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.
-
-// +build go1.11
-
-package gcimporter
-
-import "go/types"
-
-func newInterface(methods []*types.Func, embeddeds []types.Type) *types.Interface {
-	return types.NewInterfaceType(methods, embeddeds)
-}

vendor/golang.org/x/tools/go/internal/packagesdriver/sizes.go

@@ -6,155 +6,44 @@
 package packagesdriver
 
 import (
-	"bytes"
 	"context"
-	"encoding/json"
 	"fmt"
 	"go/types"
-	"log"
-	"os"
-	"os/exec"
 	"strings"
-	"time"
+
+	"golang.org/x/tools/internal/gocommand"
 )
 
 var debug = false
 
-// GetSizes returns the sizes used by the underlying driver with the given parameters.
-func GetSizes(ctx context.Context, buildFlags, env []string, dir string, usesExportData bool) (types.Sizes, error) {
-	// TODO(matloob): Clean this up. This code is mostly a copy of packages.findExternalDriver.
-	const toolPrefix = "GOPACKAGESDRIVER="
-	tool := ""
-	for _, env := range env {
-		if val := strings.TrimPrefix(env, toolPrefix); val != env {
-			tool = val
+func GetSizesGolist(ctx context.Context, inv gocommand.Invocation, gocmdRunner *gocommand.Runner) (types.Sizes, error) {
+	inv.Verb = "list"
+	inv.Args = []string{"-f", "{{context.GOARCH}} {{context.Compiler}}", "--", "unsafe"}
+	stdout, stderr, friendlyErr, rawErr := gocmdRunner.RunRaw(ctx, inv)
+	var goarch, compiler string
+	if rawErr != nil {
+		if rawErrMsg := rawErr.Error(); strings.Contains(rawErrMsg, "cannot find main module") || strings.Contains(rawErrMsg, "go.mod file not found") {
+			// User's running outside of a module. All bets are off. Get GOARCH and guess compiler is gc.
+			// TODO(matloob): Is this a problem in practice?
+			inv.Verb = "env"
+			inv.Args = []string{"GOARCH"}
+			envout, enverr := gocmdRunner.Run(ctx, inv)
+			if enverr != nil {
+				return nil, enverr
+			}
+			goarch = strings.TrimSpace(envout.String())
+			compiler = "gc"
+		} else {
+			return nil, friendlyErr
 		}
-	}
-
-	if tool == "" {
-		var err error
-		tool, err = exec.LookPath("gopackagesdriver")
-		if err != nil {
-			// We did not find the driver, so use "go list".
-			tool = "off"
+	} else {
+		fields := strings.Fields(stdout.String())
+		if len(fields) < 2 {
+			return nil, fmt.Errorf("could not parse GOARCH and Go compiler in format \"<GOARCH> <compiler>\":\nstdout: <<%s>>\nstderr: <<%s>>",
+				stdout.String(), stderr.String())
 		}
+		goarch = fields[0]
+		compiler = fields[1]
 	}
-
-	if tool == "off" {
-		return GetSizesGolist(ctx, buildFlags, env, dir, usesExportData)
-	}
-
-	req, err := json.Marshal(struct {
-		Command    string   `json:"command"`
-		Env        []string `json:"env"`
-		BuildFlags []string `json:"build_flags"`
-	}{
-		Command:    "sizes",
-		Env:        env,
-		BuildFlags: buildFlags,
-	})
-	if err != nil {
-		return nil, fmt.Errorf("failed to encode message to driver tool: %v", err)
-	}
-
-	buf := new(bytes.Buffer)
-	cmd := exec.CommandContext(ctx, tool)
-	cmd.Dir = dir
-	cmd.Env = env
-	cmd.Stdin = bytes.NewReader(req)
-	cmd.Stdout = buf
-	cmd.Stderr = new(bytes.Buffer)
-	if err := cmd.Run(); err != nil {
-		return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
-	}
-	var response struct {
-		// Sizes, if not nil, is the types.Sizes to use when type checking.
-		Sizes *types.StdSizes
-	}
-	if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
-		return nil, err
-	}
-	return response.Sizes, nil
-}
-
-func GetSizesGolist(ctx context.Context, buildFlags, env []string, dir string, usesExportData bool) (types.Sizes, error) {
-	args := []string{"list", "-f", "{{context.GOARCH}} {{context.Compiler}}"}
-	args = append(args, buildFlags...)
-	args = append(args, "--", "unsafe")
-	stdout, err := InvokeGo(ctx, env, dir, usesExportData, args...)
-	if err != nil {
-		return nil, err
-	}
-	fields := strings.Fields(stdout.String())
-	if len(fields) < 2 {
-		return nil, fmt.Errorf("could not determine GOARCH and Go compiler")
-	}
-	goarch := fields[0]
-	compiler := fields[1]
 	return types.SizesFor(compiler, goarch), nil
 }
-
-// InvokeGo returns the stdout of a go command invocation.
-func InvokeGo(ctx context.Context, env []string, dir string, usesExportData bool, args ...string) (*bytes.Buffer, error) {
-	if debug {
-		defer func(start time.Time) { log.Printf("%s for %v", time.Since(start), cmdDebugStr(env, args...)) }(time.Now())
-	}
-	stdout := new(bytes.Buffer)
-	stderr := new(bytes.Buffer)
-	cmd := exec.CommandContext(ctx, "go", args...)
-	// On darwin the cwd gets resolved to the real path, which breaks anything that
-	// expects the working directory to keep the original path, including the
-	// go command when dealing with modules.
-	// The Go stdlib has a special feature where if the cwd and the PWD are the
-	// same node then it trusts the PWD, so by setting it in the env for the child
-	// process we fix up all the paths returned by the go command.
-	cmd.Env = append(append([]string{}, env...), "PWD="+dir)
-	cmd.Dir = dir
-	cmd.Stdout = stdout
-	cmd.Stderr = stderr
-	if err := cmd.Run(); err != nil {
-		exitErr, ok := err.(*exec.ExitError)
-		if !ok {
-			// Catastrophic error:
-			// - executable not found
-			// - context cancellation
-			return nil, fmt.Errorf("couldn't exec 'go %v': %s %T", args, err, err)
-		}
-
-		// Export mode entails a build.
-		// If that build fails, errors appear on stderr
-		// (despite the -e flag) and the Export field is blank.
-		// Do not fail in that case.
-		if !usesExportData {
-			return nil, fmt.Errorf("go %v: %s: %s", args, exitErr, stderr)
-		}
-	}
-
-	// As of writing, go list -export prints some non-fatal compilation
-	// errors to stderr, even with -e set. We would prefer that it put
-	// them in the Package.Error JSON (see https://golang.org/issue/26319).
-	// In the meantime, there's nowhere good to put them, but they can
-	// be useful for debugging. Print them if $GOPACKAGESPRINTGOLISTERRORS
-	// is set.
-	if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTGOLISTERRORS") != "" {
-		fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(env, args...), stderr)
-	}
-
-	// debugging
-	if false {
-		fmt.Fprintf(os.Stderr, "%s stdout: <<%s>>\n", cmdDebugStr(env, args...), stdout)
-	}
-
-	return stdout, nil
-}
-
-func cmdDebugStr(envlist []string, args ...string) string {
-	env := make(map[string]string)
-	for _, kv := range envlist {
-		split := strings.Split(kv, "=")
-		k, v := split[0], split[1]
-		env[k] = v
-	}
-
-	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v PWD=%v go %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["PWD"], args)
-}

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

@@ -60,15 +60,13 @@ causes Load to run in LoadFiles mode, collecting minimal information.
 See the documentation for type Config for details.
 
 As noted earlier, the Config.Mode controls the amount of detail
-reported about the loaded packages, with each mode returning all the data of the
-previous mode with some extra added. See the documentation for type LoadMode
+reported about the loaded packages. See the documentation for type LoadMode
 for details.
 
 Most tools should pass their command-line arguments (after any flags)
 uninterpreted to the loader, so that the loader can interpret them
 according to the conventions of the underlying build system.
 See the Example function for typical usage.
-
 */
 package packages // import "golang.org/x/tools/go/packages"
 

vendor/golang.org/x/tools/go/packages/external.go

@@ -12,7 +12,8 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
-	"os/exec"
+	exec "golang.org/x/sys/execabs"
+	"os"
 	"strings"
 )
 
@@ -76,15 +77,21 @@ func findExternalDriver(cfg *Config) driver {
 		}
 
 		buf := new(bytes.Buffer)
+		stderr := new(bytes.Buffer)
 		cmd := exec.CommandContext(cfg.Context, tool, words...)
 		cmd.Dir = cfg.Dir
 		cmd.Env = cfg.Env
 		cmd.Stdin = bytes.NewReader(req)
 		cmd.Stdout = buf
-		cmd.Stderr = new(bytes.Buffer)
+		cmd.Stderr = stderr
+
 		if err := cmd.Run(); err != nil {
 			return nil, fmt.Errorf("%v: %v: %s", tool, err, cmd.Stderr)
 		}
+		if len(stderr.Bytes()) != 0 && os.Getenv("GOPACKAGESPRINTDRIVERERRORS") != "" {
+			fmt.Fprintf(os.Stderr, "%s stderr: <<%s>>\n", cmdDebugStr(cmd), stderr)
+		}
+
 		var response driverResponse
 		if err := json.Unmarshal(buf.Bytes(), &response); err != nil {
 			return nil, err

vendor/golang.org/x/tools/go/packages/golist_overlay.go

@@ -1,16 +1,22 @@
+// Copyright 2018 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 packages
 
 import (
-	"bytes"
 	"encoding/json"
 	"fmt"
 	"go/parser"
 	"go/token"
-	"path"
+	"os"
 	"path/filepath"
+	"regexp"
+	"sort"
 	"strconv"
 	"strings"
-	"sync"
+
+	"golang.org/x/tools/internal/gocommand"
 )
 
 // processGolistOverlay provides rudimentary support for adding
@@ -18,20 +24,25 @@ import (
 // sometimes incorrect.
 // TODO(matloob): Handle unsupported cases, including the following:
 // - determining the correct package to add given a new import path
-func processGolistOverlay(cfg *Config, response *responseDeduper) (modifiedPkgs, needPkgs []string, err error) {
+func (state *golistState) processGolistOverlay(response *responseDeduper) (modifiedPkgs, needPkgs []string, err error) {
 	havePkgs := make(map[string]string) // importPath -> non-test package ID
 	needPkgsSet := make(map[string]bool)
 	modifiedPkgsSet := make(map[string]bool)
 
+	pkgOfDir := make(map[string][]*Package)
 	for _, pkg := range response.dr.Packages {
 		// This is an approximation of import path to id. This can be
 		// wrong for tests, vendored packages, and a number of other cases.
 		havePkgs[pkg.PkgPath] = pkg.ID
+		dir, err := commonDir(pkg.GoFiles)
+		if err != nil {
+			return nil, nil, err
+		}
+		if dir != "" {
+			pkgOfDir[dir] = append(pkgOfDir[dir], pkg)
+		}
 	}
 
-	var rootDirs map[string]string
-	var onceGetRootDirs sync.Once
-
 	// If no new imports are added, it is safe to avoid loading any needPkgs.
 	// Otherwise, it's hard to tell which package is actually being loaded
 	// (due to vendoring) and whether any modified package will show up
@@ -39,34 +50,70 @@ func processGolistOverlay(cfg *Config, response *responseDeduper) (modifiedPkgs,
 	// potentially modifying the transitive set of dependencies).
 	var overlayAddsImports bool
 
-	for opath, contents := range cfg.Overlay {
+	// If both a package and its test package are created by the overlay, we
+	// need the real package first. Process all non-test files before test
+	// files, and make the whole process deterministic while we're at it.
+	var overlayFiles []string
+	for opath := range state.cfg.Overlay {
+		overlayFiles = append(overlayFiles, opath)
+	}
+	sort.Slice(overlayFiles, func(i, j int) bool {
+		iTest := strings.HasSuffix(overlayFiles[i], "_test.go")
+		jTest := strings.HasSuffix(overlayFiles[j], "_test.go")
+		if iTest != jTest {
+			return !iTest // non-tests are before tests.
+		}
+		return overlayFiles[i] < overlayFiles[j]
+	})
+	for _, opath := range overlayFiles {
+		contents := state.cfg.Overlay[opath]
 		base := filepath.Base(opath)
 		dir := filepath.Dir(opath)
-		var pkg *Package
+		var pkg *Package           // if opath belongs to both a package and its test variant, this will be the test variant
 		var testVariantOf *Package // if opath is a test file, this is the package it is testing
 		var fileExists bool
-		isTest := strings.HasSuffix(opath, "_test.go")
+		isTestFile := strings.HasSuffix(opath, "_test.go")
 		pkgName, ok := extractPackageName(opath, contents)
 		if !ok {
 			// Don't bother adding a file that doesn't even have a parsable package statement
 			// to the overlay.
 			continue
 		}
+		// If all the overlay files belong to a different package, change the
+		// package name to that package.
+		maybeFixPackageName(pkgName, isTestFile, pkgOfDir[dir])
 	nextPackage:
 		for _, p := range response.dr.Packages {
-			if pkgName != p.Name {
+			if pkgName != p.Name && p.ID != "command-line-arguments" {
 				continue
 			}
 			for _, f := range p.GoFiles {
 				if !sameFile(filepath.Dir(f), dir) {
 					continue
 				}
-				if isTest && !hasTestFiles(p) {
+				// Make sure to capture information on the package's test variant, if needed.
+				if isTestFile && !hasTestFiles(p) {
 					// TODO(matloob): Are there packages other than the 'production' variant
 					// of a package that this can match? This shouldn't match the test main package
 					// because the file is generated in another directory.
 					testVariantOf = p
 					continue nextPackage
+				} else if !isTestFile && hasTestFiles(p) {
+					// We're examining a test variant, but the overlaid file is
+					// a non-test file. Because the overlay implementation
+					// (currently) only adds a file to one package, skip this
+					// package, so that we can add the file to the production
+					// variant of the package. (https://golang.org/issue/36857
+					// tracks handling overlays on both the production and test
+					// variant of a package).
+					continue nextPackage
+				}
+				if pkg != nil && p != pkg && pkg.PkgPath == p.PkgPath {
+					// We have already seen the production version of the
+					// for which p is a test variant.
+					if hasTestFiles(p) {
+						testVariantOf = pkg
+					}
 				}
 				pkg = p
 				if filepath.Base(f) == base {
@@ -74,57 +121,68 @@ func processGolistOverlay(cfg *Config, response *responseDeduper) (modifiedPkgs,
 				}
 			}
 		}
-		// The overlay could have included an entirely new package.
-		if pkg == nil {
-			onceGetRootDirs.Do(func() {
-				rootDirs = determineRootDirs(cfg)
-			})
+		// The overlay could have included an entirely new package or an
+		// ad-hoc package. An ad-hoc package is one that we have manually
+		// constructed from inadequate `go list` results for a file= query.
+		// It will have the ID command-line-arguments.
+		if pkg == nil || pkg.ID == "command-line-arguments" {
 			// Try to find the module or gopath dir the file is contained in.
 			// Then for modules, add the module opath to the beginning.
-			var pkgPath string
-			for rdir, rpath := range rootDirs {
-				// TODO(matloob): This doesn't properly handle symlinks.
-				r, err := filepath.Rel(rdir, dir)
-				if err != nil {
-					continue
-				}
-				pkgPath = filepath.ToSlash(r)
-				if rpath != "" {
-					pkgPath = path.Join(rpath, pkgPath)
-				}
-				// We only create one new package even it can belong in multiple modules or GOPATH entries.
-				// This is okay because tools (such as the LSP) that use overlays will recompute the overlay
-				// once the file is saved, and golist will do the right thing.
-				// TODO(matloob): Implement module tiebreaking?
+			pkgPath, ok, err := state.getPkgPath(dir)
+			if err != nil {
+				return nil, nil, err
+			}
+			if !ok {
 				break
 			}
-			if pkgPath == "" {
-				continue
-			}
+			var forTest string // only set for x tests
 			isXTest := strings.HasSuffix(pkgName, "_test")
 			if isXTest {
+				forTest = pkgPath
 				pkgPath += "_test"
 			}
 			id := pkgPath
-			if isTest && !isXTest {
-				id = fmt.Sprintf("%s [%s.test]", pkgPath, pkgPath)
-			}
-			// Try to reclaim a package with the same id if it exists in the response.
-			for _, p := range response.dr.Packages {
-				if reclaimPackage(p, id, opath, contents) {
-					pkg = p
-					break
+			if isTestFile {
+				if isXTest {
+					id = fmt.Sprintf("%s [%s.test]", pkgPath, forTest)
+				} else {
+					id = fmt.Sprintf("%s [%s.test]", pkgPath, pkgPath)
 				}
 			}
-			// Otherwise, create a new package
-			if pkg == nil {
-				pkg = &Package{PkgPath: pkgPath, ID: id, Name: pkgName, Imports: make(map[string]*Package)}
-				response.addPackage(pkg)
-				havePkgs[pkg.PkgPath] = id
-				// Add the production package's sources for a test variant.
-				if isTest && !isXTest && testVariantOf != nil {
-					pkg.GoFiles = append(pkg.GoFiles, testVariantOf.GoFiles...)
-					pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, testVariantOf.CompiledGoFiles...)
+			if pkg != nil {
+				// TODO(rstambler): We should change the package's path and ID
+				// here. The only issue is that this messes with the roots.
+			} else {
+				// Try to reclaim a package with the same ID, if it exists in the response.
+				for _, p := range response.dr.Packages {
+					if reclaimPackage(p, id, opath, contents) {
+						pkg = p
+						break
+					}
+				}
+				// Otherwise, create a new package.
+				if pkg == nil {
+					pkg = &Package{
+						PkgPath: pkgPath,
+						ID:      id,
+						Name:    pkgName,
+						Imports: make(map[string]*Package),
+					}
+					response.addPackage(pkg)
+					havePkgs[pkg.PkgPath] = id
+					// Add the production package's sources for a test variant.
+					if isTestFile && !isXTest && testVariantOf != nil {
+						pkg.GoFiles = append(pkg.GoFiles, testVariantOf.GoFiles...)
+						pkg.CompiledGoFiles = append(pkg.CompiledGoFiles, testVariantOf.CompiledGoFiles...)
+						// Add the package under test and its imports to the test variant.
+						pkg.forTest = testVariantOf.PkgPath
+						for k, v := range testVariantOf.Imports {
+							pkg.Imports[k] = &Package{ID: v.ID}
+						}
+					}
+					if isXTest {
+						pkg.forTest = forTest
+					}
 				}
 			}
 		}
@@ -141,38 +199,47 @@ func processGolistOverlay(cfg *Config, response *responseDeduper) (modifiedPkgs,
 			continue
 		}
 		for _, imp := range imports {
-			_, found := pkg.Imports[imp]
-			if !found {
-				overlayAddsImports = true
-				// TODO(matloob): Handle cases when the following block isn't correct.
-				// These include imports of test variants, imports of vendored packages, etc.
-				id, ok := havePkgs[imp]
-				if !ok {
-					id = imp
+			// TODO(rstambler): If the package is an x test and the import has
+			// a test variant, make sure to replace it.
+			if _, found := pkg.Imports[imp]; found {
+				continue
+			}
+			overlayAddsImports = true
+			id, ok := havePkgs[imp]
+			if !ok {
+				var err error
+				id, err = state.resolveImport(dir, imp)
+				if err != nil {
+					return nil, nil, err
 				}
-				pkg.Imports[imp] = &Package{ID: id}
+			}
+			pkg.Imports[imp] = &Package{ID: id}
+			// Add dependencies to the non-test variant version of this package as well.
+			if testVariantOf != nil {
+				testVariantOf.Imports[imp] = &Package{ID: id}
 			}
 		}
-		continue
 	}
 
-	// toPkgPath tries to guess the package path given the id.
-	// This isn't always correct -- it's certainly wrong for
-	// vendored packages' paths.
-	toPkgPath := func(id string) string {
-		// TODO(matloob): Handle vendor paths.
-		i := strings.IndexByte(id, ' ')
-		if i >= 0 {
-			return id[:i]
+	// toPkgPath guesses the package path given the id.
+	toPkgPath := func(sourceDir, id string) (string, error) {
+		if i := strings.IndexByte(id, ' '); i >= 0 {
+			return state.resolveImport(sourceDir, id[:i])
 		}
-		return id
+		return state.resolveImport(sourceDir, id)
 	}
 
-	// Do another pass now that new packages have been created to determine the
-	// set of missing packages.
+	// Now that new packages have been created, do another pass to determine
+	// the new set of missing packages.
 	for _, pkg := range response.dr.Packages {
 		for _, imp := range pkg.Imports {
-			pkgPath := toPkgPath(imp.ID)
+			if len(pkg.GoFiles) == 0 {
+				return nil, nil, fmt.Errorf("cannot resolve imports for package %q with no Go files", pkg.PkgPath)
+			}
+			pkgPath, err := toPkgPath(filepath.Dir(pkg.GoFiles[0]), imp.ID)
+			if err != nil {
+				return nil, nil, err
+			}
 			if _, ok := havePkgs[pkgPath]; !ok {
 				needPkgsSet[pkgPath] = true
 			}
@@ -192,6 +259,52 @@ func processGolistOverlay(cfg *Config, response *responseDeduper) (modifiedPkgs,
 	return modifiedPkgs, needPkgs, err
 }
 
+// resolveImport finds the ID of a package given its import path.
+// In particular, it will find the right vendored copy when in GOPATH mode.
+func (state *golistState) resolveImport(sourceDir, importPath string) (string, error) {
+	env, err := state.getEnv()
+	if err != nil {
+		return "", err
+	}
+	if env["GOMOD"] != "" {
+		return importPath, nil
+	}
+
+	searchDir := sourceDir
+	for {
+		vendorDir := filepath.Join(searchDir, "vendor")
+		exists, ok := state.vendorDirs[vendorDir]
+		if !ok {
+			info, err := os.Stat(vendorDir)
+			exists = err == nil && info.IsDir()
+			state.vendorDirs[vendorDir] = exists
+		}
+
+		if exists {
+			vendoredPath := filepath.Join(vendorDir, importPath)
+			if info, err := os.Stat(vendoredPath); err == nil && info.IsDir() {
+				// We should probably check for .go files here, but shame on anyone who fools us.
+				path, ok, err := state.getPkgPath(vendoredPath)
+				if err != nil {
+					return "", err
+				}
+				if ok {
+					return path, nil
+				}
+			}
+		}
+
+		// We know we've hit the top of the filesystem when we Dir / and get /,
+		// or C:\ and get C:\, etc.
+		next := filepath.Dir(searchDir)
+		if next == searchDir {
+			break
+		}
+		searchDir = next
+	}
+	return importPath, nil
+}
+
 func hasTestFiles(p *Package) bool {
 	for _, f := range p.GoFiles {
 		if strings.HasSuffix(f, "_test.go") {
@@ -201,44 +314,75 @@ func hasTestFiles(p *Package) bool {
 	return false
 }
 
-// determineRootDirs returns a mapping from directories code can be contained in to the
-// corresponding import path prefixes of those directories.
-// Its result is used to try to determine the import path for a package containing
-// an overlay file.
-func determineRootDirs(cfg *Config) map[string]string {
-	// Assume modules first:
-	out, err := invokeGo(cfg, "list", "-m", "-json", "all")
+// determineRootDirs returns a mapping from absolute directories that could
+// contain code to their corresponding import path prefixes.
+func (state *golistState) determineRootDirs() (map[string]string, error) {
+	env, err := state.getEnv()
 	if err != nil {
-		return determineRootDirsGOPATH(cfg)
+		return nil, err
 	}
-	m := map[string]string{}
-	type jsonMod struct{ Path, Dir string }
+	if env["GOMOD"] != "" {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsModules()
+		})
+	} else {
+		state.rootsOnce.Do(func() {
+			state.rootDirs, state.rootDirsError = state.determineRootDirsGOPATH()
+		})
+	}
+	return state.rootDirs, state.rootDirsError
+}
+
+func (state *golistState) determineRootDirsModules() (map[string]string, error) {
+	// List all of the modules--the first will be the directory for the main
+	// module. Any replaced modules will also need to be treated as roots.
+	// Editing files in the module cache isn't a great idea, so we don't
+	// plan to ever support that.
+	out, err := state.invokeGo("list", "-m", "-json", "all")
+	if err != nil {
+		// 'go list all' will fail if we're outside of a module and
+		// GO111MODULE=on. Try falling back without 'all'.
+		var innerErr error
+		out, innerErr = state.invokeGo("list", "-m", "-json")
+		if innerErr != nil {
+			return nil, err
+		}
+	}
+	roots := map[string]string{}
+	modules := map[string]string{}
+	var i int
 	for dec := json.NewDecoder(out); dec.More(); {
-		mod := new(jsonMod)
+		mod := new(gocommand.ModuleJSON)
 		if err := dec.Decode(mod); err != nil {
-			return m // Give up and return an empty map. Package won't be found for overlay.
+			return nil, err
 		}
 		if mod.Dir != "" && mod.Path != "" {
 			// This is a valid module; add it to the map.
-			m[mod.Dir] = mod.Path
+			absDir, err := filepath.Abs(mod.Dir)
+			if err != nil {
+				return nil, err
+			}
+			modules[absDir] = mod.Path
+			// The first result is the main module.
+			if i == 0 || mod.Replace != nil && mod.Replace.Path != "" {
+				roots[absDir] = mod.Path
+			}
 		}
+		i++
 	}
-	return m
+	return roots, nil
 }
 
-func determineRootDirsGOPATH(cfg *Config) map[string]string {
+func (state *golistState) determineRootDirsGOPATH() (map[string]string, error) {
 	m := map[string]string{}
-	out, err := invokeGo(cfg, "env", "GOPATH")
-	if err != nil {
-		// Could not determine root dir mapping. Everything is best-effort, so just return an empty map.
-		// When we try to find the import path for a directory, there will be no root-dir match and
-		// we'll give up.
-		return m
+	for _, dir := range filepath.SplitList(state.mustGetEnv()["GOPATH"]) {
+		absDir, err := filepath.Abs(dir)
+		if err != nil {
+			return nil, err
+		}
+		m[filepath.Join(absDir, "src")] = ""
 	}
-	for _, p := range filepath.SplitList(string(bytes.TrimSpace(out.Bytes()))) {
-		m[filepath.Join(p, "src")] = ""
-	}
-	return m
+	return m, nil
 }
 
 func extractImports(filename string, contents []byte) ([]string, error) {
@@ -298,3 +442,134 @@ func extractPackageName(filename string, contents []byte) (string, bool) {
 	}
 	return f.Name.Name, true
 }
+
+// commonDir returns the directory that all files are in, "" if files is empty,
+// or an error if they aren't in the same directory.
+func commonDir(files []string) (string, error) {
+	seen := make(map[string]bool)
+	for _, f := range files {
+		seen[filepath.Dir(f)] = true
+	}
+	if len(seen) > 1 {
+		return "", fmt.Errorf("files (%v) are in more than one directory: %v", files, seen)
+	}
+	for k := range seen {
+		// seen has only one element; return it.
+		return k, nil
+	}
+	return "", nil // no files
+}
+
+// It is possible that the files in the disk directory dir have a different package
+// name from newName, which is deduced from the overlays. If they all have a different
+// package name, and they all have the same package name, then that name becomes
+// the package name.
+// It returns true if it changes the package name, false otherwise.
+func maybeFixPackageName(newName string, isTestFile bool, pkgsOfDir []*Package) {
+	names := make(map[string]int)
+	for _, p := range pkgsOfDir {
+		names[p.Name]++
+	}
+	if len(names) != 1 {
+		// some files are in different packages
+		return
+	}
+	var oldName string
+	for k := range names {
+		oldName = k
+	}
+	if newName == oldName {
+		return
+	}
+	// We might have a case where all of the package names in the directory are
+	// the same, but the overlay file is for an x test, which belongs to its
+	// own package. If the x test does not yet exist on disk, we may not yet
+	// have its package name on disk, but we should not rename the packages.
+	//
+	// We use a heuristic to determine if this file belongs to an x test:
+	// The test file should have a package name whose package name has a _test
+	// suffix or looks like "newName_test".
+	maybeXTest := strings.HasPrefix(oldName+"_test", newName) || strings.HasSuffix(newName, "_test")
+	if isTestFile && maybeXTest {
+		return
+	}
+	for _, p := range pkgsOfDir {
+		p.Name = newName
+	}
+}
+
+// This function is copy-pasted from
+// https://github.com/golang/go/blob/9706f510a5e2754595d716bd64be8375997311fb/src/cmd/go/internal/search/search.go#L360.
+// It should be deleted when we remove support for overlays from go/packages.
+//
+// NOTE: This does not handle any ./... or ./ style queries, as this function
+// doesn't know the working directory.
+//
+// matchPattern(pattern)(name) reports whether
+// name matches pattern. Pattern is a limited glob
+// pattern in which '...' means 'any string' and there
+// is no other special syntax.
+// Unfortunately, there are two special cases. Quoting "go help packages":
+//
+// First, /... at the end of the pattern can match an empty string,
+// so that net/... matches both net and packages in its subdirectories, like net/http.
+// Second, any slash-separated pattern element containing a wildcard never
+// participates in a match of the "vendor" element in the path of a vendored
+// package, so that ./... does not match packages in subdirectories of
+// ./vendor or ./mycode/vendor, but ./vendor/... and ./mycode/vendor/... do.
+// Note, however, that a directory named vendor that itself contains code
+// is not a vendored package: cmd/vendor would be a command named vendor,
+// and the pattern cmd/... matches it.
+func matchPattern(pattern string) func(name string) bool {
+	// Convert pattern to regular expression.
+	// The strategy for the trailing /... is to nest it in an explicit ? expression.
+	// The strategy for the vendor exclusion is to change the unmatchable
+	// vendor strings to a disallowed code point (vendorChar) and to use
+	// "(anything but that codepoint)*" as the implementation of the ... wildcard.
+	// This is a bit complicated but the obvious alternative,
+	// namely a hand-written search like in most shell glob matchers,
+	// is too easy to make accidentally exponential.
+	// Using package regexp guarantees linear-time matching.
+
+	const vendorChar = "\x00"
+
+	if strings.Contains(pattern, vendorChar) {
+		return func(name string) bool { return false }
+	}
+
+	re := regexp.QuoteMeta(pattern)
+	re = replaceVendor(re, vendorChar)
+	switch {
+	case strings.HasSuffix(re, `/`+vendorChar+`/\.\.\.`):
+		re = strings.TrimSuffix(re, `/`+vendorChar+`/\.\.\.`) + `(/vendor|/` + vendorChar + `/\.\.\.)`
+	case re == vendorChar+`/\.\.\.`:
+		re = `(/vendor|/` + vendorChar + `/\.\.\.)`
+	case strings.HasSuffix(re, `/\.\.\.`):
+		re = strings.TrimSuffix(re, `/\.\.\.`) + `(/\.\.\.)?`
+	}
+	re = strings.ReplaceAll(re, `\.\.\.`, `[^`+vendorChar+`]*`)
+
+	reg := regexp.MustCompile(`^` + re + `$`)
+
+	return func(name string) bool {
+		if strings.Contains(name, vendorChar) {
+			return false
+		}
+		return reg.MatchString(replaceVendor(name, vendorChar))
+	}
+}
+
+// replaceVendor returns the result of replacing
+// non-trailing vendor path elements in x with repl.
+func replaceVendor(x, repl string) string {
+	if !strings.Contains(x, "vendor") {
+		return x
+	}
+	elem := strings.Split(x, "/")
+	for i := 0; i < len(elem)-1; i++ {
+		if elem[i] == "vendor" {
+			elem[i] = repl
+		}
+	}
+	return strings.Join(elem, "/")
+}

vendor/golang.org/x/tools/go/packages/loadmode_string.go

@@ -0,0 +1,57 @@
+// Copyright 2019 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 packages
+
+import (
+	"fmt"
+	"strings"
+)
+
+var allModes = []LoadMode{
+	NeedName,
+	NeedFiles,
+	NeedCompiledGoFiles,
+	NeedImports,
+	NeedDeps,
+	NeedExportFile,
+	NeedTypes,
+	NeedSyntax,
+	NeedTypesInfo,
+	NeedTypesSizes,
+}
+
+var modeStrings = []string{
+	"NeedName",
+	"NeedFiles",
+	"NeedCompiledGoFiles",
+	"NeedImports",
+	"NeedDeps",
+	"NeedExportFile",
+	"NeedTypes",
+	"NeedSyntax",
+	"NeedTypesInfo",
+	"NeedTypesSizes",
+}
+
+func (mod LoadMode) String() string {
+	m := mod
+	if m == 0 {
+		return "LoadMode(0)"
+	}
+	var out []string
+	for i, x := range allModes {
+		if x > m {
+			break
+		}
+		if (m & x) != 0 {
+			out = append(out, modeStrings[i])
+			m = m ^ x
+		}
+	}
+	if m != 0 {
+		out = append(out, "Unknown")
+	}
+	return fmt.Sprintf("LoadMode(%s)", strings.Join(out, "|"))
+}

vendor/golang.org/x/tools/go/packages/packages.go

@@ -15,14 +15,21 @@ import (
 	"go/scanner"
 	"go/token"
 	"go/types"
+	"io"
 	"io/ioutil"
 	"log"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 	"sync"
+	"time"
 
 	"golang.org/x/tools/go/gcexportdata"
+	"golang.org/x/tools/internal/gocommand"
+	"golang.org/x/tools/internal/packagesinternal"
+	"golang.org/x/tools/internal/typeparams"
+	"golang.org/x/tools/internal/typesinternal"
 )
 
 // A LoadMode controls the amount of detail to return when loading.
@@ -48,12 +55,11 @@ const (
 	// "placeholder" Packages with only the ID set.
 	NeedImports
 
-	// NeedDeps adds the fields requested by the LoadMode in the packages in Imports. If NeedImports
-	// is not set NeedDeps has no effect.
+	// NeedDeps adds the fields requested by the LoadMode in the packages in Imports.
 	NeedDeps
 
-	// NeedExportsFile adds ExportsFile.
-	NeedExportsFile
+	// NeedExportFile adds ExportFile.
+	NeedExportFile
 
 	// NeedTypes adds Types, Fset, and IllTyped.
 	NeedTypes
@@ -66,6 +72,26 @@ const (
 
 	// NeedTypesSizes adds TypesSizes.
 	NeedTypesSizes
+
+	// needInternalDepsErrors adds the internal deps errors field for use by gopls.
+	needInternalDepsErrors
+
+	// needInternalForTest adds the internal forTest field.
+	// Tests must also be set on the context for this field to be populated.
+	needInternalForTest
+
+	// typecheckCgo enables full support for type checking cgo. Requires Go 1.15+.
+	// Modifies CompiledGoFiles and Types, and has no effect on its own.
+	typecheckCgo
+
+	// NeedModule adds Module.
+	NeedModule
+
+	// NeedEmbedFiles adds EmbedFiles.
+	NeedEmbedFiles
+
+	// NeedEmbedPatterns adds EmbedPatterns.
+	NeedEmbedPatterns
 )
 
 const (
@@ -75,7 +101,7 @@ const (
 
 	// Deprecated: LoadImports exists for historical compatibility
 	// and should not be used. Please directly specify the needed fields using the Need values.
-	LoadImports = LoadFiles | NeedImports | NeedDeps
+	LoadImports = LoadFiles | NeedImports
 
 	// Deprecated: LoadTypes exists for historical compatibility
 	// and should not be used. Please directly specify the needed fields using the Need values.
@@ -87,7 +113,10 @@ const (
 
 	// Deprecated: LoadAllSyntax exists for historical compatibility
 	// and should not be used. Please directly specify the needed fields using the Need values.
-	LoadAllSyntax = LoadSyntax
+	LoadAllSyntax = LoadSyntax | NeedDeps
+
+	// Deprecated: NeedExportsFile is a historical misspelling of NeedExportFile.
+	NeedExportsFile = NeedExportFile
 )
 
 // A Config specifies details about how packages should be loaded.
@@ -103,6 +132,12 @@ type Config struct {
 	// If Context is nil, the load cannot be cancelled.
 	Context context.Context
 
+	// Logf is the logger for the config.
+	// If the user provides a logger, debug logging is enabled.
+	// If the GOPACKAGESDEBUG environment variable is set to true,
+	// but the logger is nil, default to log.Printf.
+	Logf func(format string, args ...interface{})
+
 	// Dir is the directory in which to run the build system's query tool
 	// that provides information about the packages.
 	// If Dir is empty, the tool is run in the current directory.
@@ -118,10 +153,19 @@ type Config struct {
 	//
 	Env []string
 
+	// gocmdRunner guards go command calls from concurrency errors.
+	gocmdRunner *gocommand.Runner
+
 	// BuildFlags is a list of command-line flags to be passed through to
 	// the build system's query tool.
 	BuildFlags []string
 
+	// modFile will be used for -modfile in go command invocations.
+	modFile string
+
+	// modFlag will be used for -modfile in go command invocations.
+	modFlag string
+
 	// Fset provides source position information for syntax trees and types.
 	// If Fset is nil, Load will use a new fileset, but preserve Fset's value.
 	Fset *token.FileSet
@@ -155,7 +199,7 @@ type Config struct {
 	Tests bool
 
 	// Overlay provides a mapping of absolute file paths to file contents.
-	// If the file  with the given path already exists, the parser will use the
+	// If the file with the given path already exists, the parser will use the
 	// alternative file contents provided by the map.
 	//
 	// Overlays provide incomplete support for when a given file doesn't
@@ -169,6 +213,13 @@ type driver func(cfg *Config, patterns ...string) (*driverResponse, error)
 
 // driverResponse contains the results for a driver query.
 type driverResponse struct {
+	// NotHandled is returned if the request can't be handled by the current
+	// driver. If an external driver returns a response with NotHandled, the
+	// rest of the driverResponse is ignored, and go/packages will fallback
+	// to the next driver. If go/packages is extended in the future to support
+	// lists of multiple drivers, go/packages will fall back to the next driver.
+	NotHandled bool
+
 	// Sizes, if not nil, is the types.Sizes to use when type checking.
 	Sizes *types.StdSizes
 
@@ -184,6 +235,11 @@ type driverResponse struct {
 	// Imports will be connected and then type and syntax information added in a
 	// later pass (see refine).
 	Packages []*Package
+
+	// GoVersion is the minor version number used by the driver
+	// (e.g. the go command on the PATH) when selecting .go files.
+	// Zero means unknown.
+	GoVersion int
 }
 
 // Load loads and returns the Go packages named by the given patterns.
@@ -207,17 +263,25 @@ func Load(cfg *Config, patterns ...string) ([]*Package, error) {
 		return nil, err
 	}
 	l.sizes = response.Sizes
-	return l.refine(response.Roots, response.Packages...)
+	return l.refine(response)
 }
 
-// defaultDriver is a driver that looks for an external driver binary, and if
-// it does not find it falls back to the built in go list driver.
+// defaultDriver is a driver that implements go/packages' fallback behavior.
+// It will try to request to an external driver, if one exists. If there's
+// no external driver, or the driver returns a response with NotHandled set,
+// defaultDriver will fall back to the go list driver.
 func defaultDriver(cfg *Config, patterns ...string) (*driverResponse, error) {
 	driver := findExternalDriver(cfg)
 	if driver == nil {
 		driver = goListDriver
 	}
-	return driver(cfg, patterns...)
+	response, err := driver(cfg, patterns...)
+	if err != nil {
+		return response, err
+	} else if response.NotHandled {
+		return goListDriver(cfg, patterns...)
+	}
+	return response, nil
 }
 
 // A Package describes a loaded Go package.
@@ -240,11 +304,14 @@ type Package struct {
 	// of the package, or while parsing or type-checking its files.
 	Errors []Error
 
+	// TypeErrors contains the subset of errors produced during type checking.
+	TypeErrors []types.Error
+
 	// GoFiles lists the absolute file paths of the package's Go source files.
 	GoFiles []string
 
 	// CompiledGoFiles lists the absolute file paths of the package's source
-	// files that were presented to the compiler.
+	// files that are suitable for type checking.
 	// This may differ from GoFiles if files are processed before compilation.
 	CompiledGoFiles []string
 
@@ -252,6 +319,19 @@ type Package struct {
 	// including assembly, C, C++, Fortran, Objective-C, SWIG, and so on.
 	OtherFiles []string
 
+	// EmbedFiles lists the absolute file paths of the package's files
+	// embedded with go:embed.
+	EmbedFiles []string
+
+	// EmbedPatterns lists the absolute file patterns of the package's
+	// files embedded with go:embed.
+	EmbedPatterns []string
+
+	// IgnoredFiles lists source files that are not part of the package
+	// using the current build configuration but that might be part of
+	// the package using other build configurations.
+	IgnoredFiles []string
+
 	// ExportFile is the absolute path to a file containing type
 	// information for the package as provided by the build system.
 	ExportFile string
@@ -279,6 +359,9 @@ type Package struct {
 	// The NeedSyntax LoadMode bit populates this field for packages matching the patterns.
 	// If NeedDeps and NeedImports are also set, this field will also be populated
 	// for dependencies.
+	//
+	// Syntax is kept in the same order as CompiledGoFiles, with the caveat that nils are
+	// removed.  If parsing returned nil, Syntax may be shorter than CompiledGoFiles.
 	Syntax []*ast.File
 
 	// TypesInfo provides type information about the package's syntax trees.
@@ -287,6 +370,58 @@ type Package struct {
 
 	// TypesSizes provides the effective size function for types in TypesInfo.
 	TypesSizes types.Sizes
+
+	// forTest is the package under test, if any.
+	forTest string
+
+	// depsErrors is the DepsErrors field from the go list response, if any.
+	depsErrors []*packagesinternal.PackageError
+
+	// module is the module information for the package if it exists.
+	Module *Module
+}
+
+// Module provides module information for a package.
+type Module struct {
+	Path      string       // module path
+	Version   string       // module version
+	Replace   *Module      // replaced by this module
+	Time      *time.Time   // time version was created
+	Main      bool         // is this the main module?
+	Indirect  bool         // is this module only an indirect dependency of main module?
+	Dir       string       // directory holding files for this module, if any
+	GoMod     string       // path to go.mod file used when loading this module, if any
+	GoVersion string       // go version used in module
+	Error     *ModuleError // error loading module
+}
+
+// ModuleError holds errors loading a module.
+type ModuleError struct {
+	Err string // the error itself
+}
+
+func init() {
+	packagesinternal.GetForTest = func(p interface{}) string {
+		return p.(*Package).forTest
+	}
+	packagesinternal.GetDepsErrors = func(p interface{}) []*packagesinternal.PackageError {
+		return p.(*Package).depsErrors
+	}
+	packagesinternal.GetGoCmdRunner = func(config interface{}) *gocommand.Runner {
+		return config.(*Config).gocmdRunner
+	}
+	packagesinternal.SetGoCmdRunner = func(config interface{}, runner *gocommand.Runner) {
+		config.(*Config).gocmdRunner = runner
+	}
+	packagesinternal.SetModFile = func(config interface{}, value string) {
+		config.(*Config).modFile = value
+	}
+	packagesinternal.SetModFlag = func(config interface{}, value string) {
+		config.(*Config).modFlag = value
+	}
+	packagesinternal.TypecheckCgo = int(typecheckCgo)
+	packagesinternal.DepsErrors = int(needInternalDepsErrors)
+	packagesinternal.ForTest = int(needInternalForTest)
 }
 
 // An Error describes a problem with a package's metadata, syntax, or types.
@@ -329,6 +464,9 @@ type flatPackage struct {
 	GoFiles         []string          `json:",omitempty"`
 	CompiledGoFiles []string          `json:",omitempty"`
 	OtherFiles      []string          `json:",omitempty"`
+	EmbedFiles      []string          `json:",omitempty"`
+	EmbedPatterns   []string          `json:",omitempty"`
+	IgnoredFiles    []string          `json:",omitempty"`
 	ExportFile      string            `json:",omitempty"`
 	Imports         map[string]string `json:",omitempty"`
 }
@@ -351,6 +489,9 @@ func (p *Package) MarshalJSON() ([]byte, error) {
 		GoFiles:         p.GoFiles,
 		CompiledGoFiles: p.CompiledGoFiles,
 		OtherFiles:      p.OtherFiles,
+		EmbedFiles:      p.EmbedFiles,
+		EmbedPatterns:   p.EmbedPatterns,
+		IgnoredFiles:    p.IgnoredFiles,
 		ExportFile:      p.ExportFile,
 	}
 	if len(p.Imports) > 0 {
@@ -377,6 +518,8 @@ func (p *Package) UnmarshalJSON(b []byte) error {
 		GoFiles:         flat.GoFiles,
 		CompiledGoFiles: flat.CompiledGoFiles,
 		OtherFiles:      flat.OtherFiles,
+		EmbedFiles:      flat.EmbedFiles,
+		EmbedPatterns:   flat.EmbedPatterns,
 		ExportFile:      flat.ExportFile,
 	}
 	if len(flat.Imports) > 0 {
@@ -399,6 +542,7 @@ type loaderPackage struct {
 	needsrc      bool  // load from source (Mode >= LoadTypes)
 	needtypes    bool  // type information is either requested or depended on
 	initial      bool  // package was matched by a pattern
+	goVersion    int   // minor version number of go command on PATH
 }
 
 // loader holds the working state of a single call to load.
@@ -410,11 +554,13 @@ type loader struct {
 	parseCacheMu sync.Mutex
 	exportMu     sync.Mutex // enforces mutual exclusion of exportdata operations
 
-	// TODO(matloob): Add an implied mode here and use that instead of mode.
-	// Implied mode would contain all the fields we need the data for so we can
-	// get the actually requested fields. We'll zero them out before returning
-	// packages to the user. This will make it easier for us to get the conditions
-	// where we need certain modes right.
+	// Config.Mode contains the implied mode (see impliedLoadMode).
+	// Implied mode contains all the fields we need the data for.
+	// In requestedMode there are the actually requested fields.
+	// We'll zero them out before returning packages to the user.
+	// This makes it easier for us to get the conditions where
+	// we need certain modes right.
+	requestedMode LoadMode
 }
 
 type parseValue struct {
@@ -429,6 +575,17 @@ func newLoader(cfg *Config) *loader {
 	}
 	if cfg != nil {
 		ld.Config = *cfg
+		// If the user has provided a logger, use it.
+		ld.Config.Logf = cfg.Logf
+	}
+	if ld.Config.Logf == nil {
+		// If the GOPACKAGESDEBUG environment variable is set to true,
+		// but the user has not provided a logger, default to log.Printf.
+		if debug {
+			ld.Config.Logf = log.Printf
+		} else {
+			ld.Config.Logf = func(format string, args ...interface{}) {}
+		}
 	}
 	if ld.Config.Mode == 0 {
 		ld.Config.Mode = NeedName | NeedFiles | NeedCompiledGoFiles // Preserve zero behavior of Mode for backwards compatibility.
@@ -436,6 +593,9 @@ func newLoader(cfg *Config) *loader {
 	if ld.Config.Env == nil {
 		ld.Config.Env = os.Environ()
 	}
+	if ld.Config.gocmdRunner == nil {
+		ld.Config.gocmdRunner = &gocommand.Runner{}
+	}
 	if ld.Context == nil {
 		ld.Context = context.Background()
 	}
@@ -445,7 +605,11 @@ func newLoader(cfg *Config) *loader {
 		}
 	}
 
-	if ld.Mode&NeedTypes != 0 {
+	// Save the actually requested fields. We'll zero them out before returning packages to the user.
+	ld.requestedMode = ld.Mode
+	ld.Mode = impliedLoadMode(ld.Mode)
+
+	if ld.Mode&NeedTypes != 0 || ld.Mode&NeedSyntax != 0 {
 		if ld.Fset == nil {
 			ld.Fset = token.NewFileSet()
 		}
@@ -459,12 +623,14 @@ func newLoader(cfg *Config) *loader {
 			}
 		}
 	}
+
 	return ld
 }
 
 // refine connects the supplied packages into a graph and then adds type and
 // and syntax information as requested by the LoadMode.
-func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
+func (ld *loader) refine(response *driverResponse) ([]*Package, error) {
+	roots := response.Roots
 	rootMap := make(map[string]int, len(roots))
 	for i, root := range roots {
 		rootMap[root] = i
@@ -472,17 +638,29 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 	ld.pkgs = make(map[string]*loaderPackage)
 	// first pass, fixup and build the map and roots
 	var initial = make([]*loaderPackage, len(roots))
-	for _, pkg := range list {
+	for _, pkg := range response.Packages {
 		rootIndex := -1
 		if i, found := rootMap[pkg.ID]; found {
 			rootIndex = i
 		}
+
+		// Overlays can invalidate export data.
+		// TODO(matloob): make this check fine-grained based on dependencies on overlaid files
+		exportDataInvalid := len(ld.Overlay) > 0 || pkg.ExportFile == "" && pkg.PkgPath != "unsafe"
+		// This package needs type information if the caller requested types and the package is
+		// either a root, or it's a non-root and the user requested dependencies ...
+		needtypes := (ld.Mode&NeedTypes|NeedTypesInfo != 0 && (rootIndex >= 0 || ld.Mode&NeedDeps != 0))
+		// This package needs source if the call requested source (or types info, which implies source)
+		// and the package is either a root, or itas a non- root and the user requested dependencies...
+		needsrc := ((ld.Mode&(NeedSyntax|NeedTypesInfo) != 0 && (rootIndex >= 0 || ld.Mode&NeedDeps != 0)) ||
+			// ... or if we need types and the exportData is invalid. We fall back to (incompletely)
+			// typechecking packages from source if they fail to compile.
+			(ld.Mode&(NeedTypes|NeedTypesInfo) != 0 && exportDataInvalid)) && pkg.PkgPath != "unsafe"
 		lpkg := &loaderPackage{
 			Package:   pkg,
-			needtypes: (ld.Mode&(NeedTypes|NeedTypesInfo) != 0 && rootIndex < 0) || rootIndex >= 0,
-			needsrc: (ld.Mode&(NeedSyntax|NeedTypesInfo) != 0 && rootIndex < 0) || rootIndex >= 0 ||
-				len(ld.Overlay) > 0 || // Overlays can invalidate export data. TODO(matloob): make this check fine-grained based on dependencies on overlaid files
-				pkg.ExportFile == "" && pkg.PkgPath != "unsafe",
+			needtypes: needtypes,
+			needsrc:   needsrc,
+			goVersion: response.GoVersion,
 		}
 		ld.pkgs[lpkg.ID] = lpkg
 		if rootIndex >= 0 {
@@ -528,8 +706,7 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 		stack = append(stack, lpkg) // push
 		stubs := lpkg.Imports       // the structure form has only stubs with the ID in the Imports
 		// If NeedImports isn't set, the imports fields will all be zeroed out.
-		// If NeedDeps isn't also set we want to keep the stubs.
-		if ld.Mode&NeedImports != 0 && ld.Mode&NeedDeps != 0 {
+		if ld.Mode&NeedImports != 0 {
 			lpkg.Imports = make(map[string]*Package, len(stubs))
 			for importPath, ipkg := range stubs {
 				var importErr error
@@ -566,7 +743,7 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 		return lpkg.needsrc
 	}
 
-	if ld.Mode&(NeedImports|NeedDeps) == 0 {
+	if ld.Mode&NeedImports == 0 {
 		// We do this to drop the stub import packages that we are not even going to try to resolve.
 		for _, lpkg := range initial {
 			lpkg.Imports = nil
@@ -577,7 +754,7 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 			visit(lpkg)
 		}
 	}
-	if ld.Mode&NeedDeps != 0 { // TODO(matloob): This is only the case if NeedTypes is also set, right?
+	if ld.Mode&NeedImports != 0 && ld.Mode&NeedTypes != 0 {
 		for _, lpkg := range srcPkgs {
 			// Complete type information is required for the
 			// immediate dependencies of each source package.
@@ -587,9 +764,9 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 			}
 		}
 	}
-	// Load type data if needed, starting at
+	// Load type data and syntax if needed, starting at
 	// the initial packages (roots of the import DAG).
-	if ld.Mode&NeedTypes != 0 {
+	if ld.Mode&NeedTypes != 0 || ld.Mode&NeedSyntax != 0 {
 		var wg sync.WaitGroup
 		for _, lpkg := range initial {
 			wg.Add(1)
@@ -602,54 +779,55 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 	}
 
 	result := make([]*Package, len(initial))
-	importPlaceholders := make(map[string]*Package)
 	for i, lpkg := range initial {
 		result[i] = lpkg.Package
 	}
 	for i := range ld.pkgs {
-		// Clear all unrequested fields, for extra de-Hyrum-ization.
-		if ld.Mode&NeedName == 0 {
+		// Clear all unrequested fields,
+		// to catch programs that use more than they request.
+		if ld.requestedMode&NeedName == 0 {
 			ld.pkgs[i].Name = ""
 			ld.pkgs[i].PkgPath = ""
 		}
-		if ld.Mode&NeedFiles == 0 {
+		if ld.requestedMode&NeedFiles == 0 {
 			ld.pkgs[i].GoFiles = nil
 			ld.pkgs[i].OtherFiles = nil
+			ld.pkgs[i].IgnoredFiles = nil
 		}
-		if ld.Mode&NeedCompiledGoFiles == 0 {
+		if ld.requestedMode&NeedEmbedFiles == 0 {
+			ld.pkgs[i].EmbedFiles = nil
+		}
+		if ld.requestedMode&NeedEmbedPatterns == 0 {
+			ld.pkgs[i].EmbedPatterns = nil
+		}
+		if ld.requestedMode&NeedCompiledGoFiles == 0 {
 			ld.pkgs[i].CompiledGoFiles = nil
 		}
-		if ld.Mode&NeedImports == 0 {
+		if ld.requestedMode&NeedImports == 0 {
 			ld.pkgs[i].Imports = nil
 		}
-		if ld.Mode&NeedExportsFile == 0 {
+		if ld.requestedMode&NeedExportFile == 0 {
 			ld.pkgs[i].ExportFile = ""
 		}
-		if ld.Mode&NeedTypes == 0 {
+		if ld.requestedMode&NeedTypes == 0 {
 			ld.pkgs[i].Types = nil
 			ld.pkgs[i].Fset = nil
 			ld.pkgs[i].IllTyped = false
 		}
-		if ld.Mode&NeedSyntax == 0 {
+		if ld.requestedMode&NeedSyntax == 0 {
 			ld.pkgs[i].Syntax = nil
 		}
-		if ld.Mode&NeedTypesInfo == 0 {
+		if ld.requestedMode&NeedTypesInfo == 0 {
 			ld.pkgs[i].TypesInfo = nil
 		}
-		if ld.Mode&NeedTypesSizes == 0 {
+		if ld.requestedMode&NeedTypesSizes == 0 {
 			ld.pkgs[i].TypesSizes = nil
 		}
-		if ld.Mode&NeedDeps == 0 {
-			for j, pkg := range ld.pkgs[i].Imports {
-				ph, ok := importPlaceholders[pkg.ID]
-				if !ok {
-					ph = &Package{ID: pkg.ID}
-					importPlaceholders[pkg.ID] = ph
-				}
-				ld.pkgs[i].Imports[j] = ph
-			}
+		if ld.requestedMode&NeedModule == 0 {
+			ld.pkgs[i].Module = nil
 		}
 	}
+
 	return result, nil
 }
 
@@ -670,7 +848,6 @@ func (ld *loader) loadRecursive(lpkg *loaderPackage) {
 			}(imp)
 		}
 		wg.Wait()
-
 		ld.loadPackage(lpkg)
 	})
 }
@@ -701,12 +878,19 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 	// never has to create a types.Package for an indirect dependency,
 	// which would then require that such created packages be explicitly
 	// inserted back into the Import graph as a final step after export data loading.
+	// (Hence this return is after the Types assignment.)
 	// The Diamond test exercises this case.
-	if !lpkg.needtypes {
+	if !lpkg.needtypes && !lpkg.needsrc {
 		return
 	}
 	if !lpkg.needsrc {
-		ld.loadFromExportData(lpkg)
+		if err := ld.loadFromExportData(lpkg); err != nil {
+			lpkg.Errors = append(lpkg.Errors, Error{
+				Pos:  "-",
+				Msg:  err.Error(),
+				Kind: UnknownError, // e.g. can't find/open/parse export data
+			})
+		}
 		return // not a source package, don't get syntax trees
 	}
 
@@ -738,6 +922,7 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 
 		case types.Error:
 			// from type checker
+			lpkg.TypeErrors = append(lpkg.TypeErrors, err)
 			errs = append(errs, Error{
 				Pos:  err.Fset.Position(err.Pos).String(),
 				Msg:  err.Msg,
@@ -759,12 +944,53 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 		lpkg.Errors = append(lpkg.Errors, errs...)
 	}
 
+	// If the go command on the PATH is newer than the runtime,
+	// then the go/{scanner,ast,parser,types} packages from the
+	// standard library may be unable to process the files
+	// selected by go list.
+	//
+	// There is currently no way to downgrade the effective
+	// version of the go command (see issue 52078), so we proceed
+	// with the newer go command but, in case of parse or type
+	// errors, we emit an additional diagnostic.
+	//
+	// See:
+	// - golang.org/issue/52078 (flag to set release tags)
+	// - golang.org/issue/50825 (gopls legacy version support)
+	// - golang.org/issue/55883 (go/packages confusing error)
+	//
+	// Should we assert a hard minimum of (currently) go1.16 here?
+	var runtimeVersion int
+	if _, err := fmt.Sscanf(runtime.Version(), "go1.%d", &runtimeVersion); err == nil && runtimeVersion < lpkg.goVersion {
+		defer func() {
+			if len(lpkg.Errors) > 0 {
+				appendError(Error{
+					Pos:  "-",
+					Msg:  fmt.Sprintf("This application uses version go1.%d of the source-processing packages but runs version go1.%d of 'go list'. It may fail to process source files that rely on newer language features. If so, rebuild the application using a newer version of Go.", runtimeVersion, lpkg.goVersion),
+					Kind: UnknownError,
+				})
+			}
+		}()
+	}
+
+	if ld.Config.Mode&NeedTypes != 0 && len(lpkg.CompiledGoFiles) == 0 && lpkg.ExportFile != "" {
+		// The config requested loading sources and types, but sources are missing.
+		// Add an error to the package and fall back to loading from export data.
+		appendError(Error{"-", fmt.Sprintf("sources missing for package %s", lpkg.ID), ParseError})
+		_ = ld.loadFromExportData(lpkg) // ignore any secondary errors
+
+		return // can't get syntax trees for this package
+	}
+
 	files, errs := ld.parseFiles(lpkg.CompiledGoFiles)
 	for _, err := range errs {
 		appendError(err)
 	}
 
 	lpkg.Syntax = files
+	if ld.Config.Mode&NeedTypes == 0 {
+		return
+	}
 
 	lpkg.TypesInfo = &types.Info{
 		Types:      make(map[ast.Expr]types.TypeAndValue),
@@ -774,6 +1000,7 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 		Scopes:     make(map[ast.Node]*types.Scope),
 		Selections: make(map[*ast.SelectorExpr]*types.Selection),
 	}
+	typeparams.InitInstanceInfo(lpkg.TypesInfo)
 	lpkg.TypesSizes = ld.sizes
 
 	importer := importerFunc(func(path string) (*types.Package, error) {
@@ -797,7 +1024,7 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 		if ipkg.Types != nil && ipkg.Types.Complete() {
 			return ipkg.Types, nil
 		}
-		log.Fatalf("internal error: nil Pkg importing %q from %q", path, lpkg)
+		log.Fatalf("internal error: package %q without types was imported from %q", path, lpkg)
 		panic("unreachable")
 	})
 
@@ -805,14 +1032,23 @@ func (ld *loader) loadPackage(lpkg *loaderPackage) {
 	tc := &types.Config{
 		Importer: importer,
 
-		// Type-check bodies of functions only in non-initial packages.
+		// Type-check bodies of functions only in initial packages.
 		// Example: for import graph A->B->C and initial packages {A,C},
 		// we can ignore function bodies in B.
-		IgnoreFuncBodies: (ld.Mode&(NeedDeps|NeedTypesInfo) == 0) && !lpkg.initial,
+		IgnoreFuncBodies: ld.Mode&NeedDeps == 0 && !lpkg.initial,
 
 		Error: appendError,
 		Sizes: ld.sizes,
 	}
+	if (ld.Mode & typecheckCgo) != 0 {
+		if !typesinternal.SetUsesCgo(tc) {
+			appendError(Error{
+				Msg:  "typecheckCgo requires Go 1.15+",
+				Kind: ListError,
+			})
+			return
+		}
+	}
 	types.NewChecker(tc, ld.Fset, lpkg.Types, lpkg.TypesInfo).Files(lpkg.Syntax)
 
 	lpkg.importErrors = nil // no longer needed
@@ -903,7 +1139,6 @@ func (ld *loader) parseFile(filename string) (*ast.File, error) {
 //
 // Because files are scanned in parallel, the token.Pos
 // positions of the resulting ast.Files are not ordered.
-//
 func (ld *loader) parseFiles(filenames []string) ([]*ast.File, []error) {
 	var wg sync.WaitGroup
 	n := len(filenames)
@@ -947,7 +1182,6 @@ func (ld *loader) parseFiles(filenames []string) ([]*ast.File, []error) {
 
 // sameFile returns true if x and y have the same basename and denote
 // the same file.
-//
 func sameFile(x, y string) bool {
 	if x == y {
 		// It could be the case that y doesn't exist.
@@ -968,9 +1202,10 @@ func sameFile(x, y string) bool {
 	return false
 }
 
-// loadFromExportData returns type information for the specified
+// loadFromExportData ensures that type information is present for the specified
 // package, loading it from an export data file on the first request.
-func (ld *loader) loadFromExportData(lpkg *loaderPackage) (*types.Package, error) {
+// On success it sets lpkg.Types to a new Package.
+func (ld *loader) loadFromExportData(lpkg *loaderPackage) error {
 	if lpkg.PkgPath == "" {
 		log.Fatalf("internal error: Package %s has no PkgPath", lpkg)
 	}
@@ -981,8 +1216,8 @@ func (ld *loader) loadFromExportData(lpkg *loaderPackage) (*types.Package, error
 	// must be sequential. (Finer-grained locking would require
 	// changes to the gcexportdata API.)
 	//
-	// The exportMu lock guards the Package.Pkg field and the
-	// types.Package it points to, for each Package in the graph.
+	// The exportMu lock guards the lpkg.Types field and the
+	// types.Package it points to, for each loaderPackage in the graph.
 	//
 	// Not all accesses to Package.Pkg need to be protected by exportMu:
 	// graph ordering ensures that direct dependencies of source
@@ -991,18 +1226,18 @@ func (ld *loader) loadFromExportData(lpkg *loaderPackage) (*types.Package, error
 	defer ld.exportMu.Unlock()
 
 	if tpkg := lpkg.Types; tpkg != nil && tpkg.Complete() {
-		return tpkg, nil // cache hit
+		return nil // cache hit
 	}
 
 	lpkg.IllTyped = true // fail safe
 
 	if lpkg.ExportFile == "" {
 		// Errors while building export data will have been printed to stderr.
-		return nil, fmt.Errorf("no export data file")
+		return fmt.Errorf("no export data file")
 	}
 	f, err := os.Open(lpkg.ExportFile)
 	if err != nil {
-		return nil, err
+		return err
 	}
 	defer f.Close()
 
@@ -1014,7 +1249,7 @@ func (ld *loader) loadFromExportData(lpkg *loaderPackage) (*types.Package, error
 	// queries.)
 	r, err := gcexportdata.NewReader(f)
 	if err != nil {
-		return nil, fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
+		return fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
 	}
 
 	// Build the view.
@@ -1058,18 +1293,34 @@ func (ld *loader) loadFromExportData(lpkg *loaderPackage) (*types.Package, error
 	// (May modify incomplete packages in view but not create new ones.)
 	tpkg, err := gcexportdata.Read(r, ld.Fset, view, lpkg.PkgPath)
 	if err != nil {
-		return nil, fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
+		return fmt.Errorf("reading %s: %v", lpkg.ExportFile, err)
+	}
+	if _, ok := view["go.shape"]; ok {
+		// Account for the pseudopackage "go.shape" that gets
+		// created by generic code.
+		viewLen++
 	}
 	if viewLen != len(view) {
-		log.Fatalf("Unexpected package creation during export data loading")
+		log.Panicf("golang.org/x/tools/go/packages: unexpected new packages during load of %s", lpkg.PkgPath)
 	}
 
 	lpkg.Types = tpkg
 	lpkg.IllTyped = false
+	return nil
+}
 
-	return tpkg, nil
+// impliedLoadMode returns loadMode with its dependencies.
+func impliedLoadMode(loadMode LoadMode) LoadMode {
+	if loadMode&(NeedDeps|NeedTypes|NeedTypesInfo) != 0 {
+		// All these things require knowing the import graph.
+		loadMode |= NeedImports
+	}
+
+	return loadMode
 }
 
 func usesExportData(cfg *Config) bool {
-	return cfg.Mode&NeedExportsFile != 0 || cfg.Mode&NeedTypes != 0 && cfg.Mode&NeedTypesInfo == 0
+	return cfg.Mode&NeedExportFile != 0 || cfg.Mode&NeedTypes != 0 && cfg.Mode&NeedDeps == 0
 }
+
+var _ interface{} = io.Discard // assert build toolchain is go1.16 or later

vendor/golang.org/x/tools/go/packages/visit.go

@@ -1,3 +1,7 @@
+// Copyright 2018 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 packages
 
 import (