go/types: avoid importer.Default

It uses a throwaway FileSet, so all position info is
wrong, and potentially misleading.

(Various other helpers in go/types testing also use a
throwaway FileSet, and should really accept it as a parameter.)

Fixes #71272

Change-Id: I9d899b987837b4041a299aad5ec266cb4f5d125c
Reviewed-on: https://go-review.googlesource.com/c/go/+/643777
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

src/go/types/api_test.go

@@ -19,11 +19,16 @@ import (
 	"testing"
 
 	. "go/types"
+	"runtime"
 )
 
 // nopos indicates an unknown position
 var nopos token.Pos
 
+func defaultImporter(fset *token.FileSet) Importer {
+	return importer.ForCompiler(fset, runtime.Compiler, nil)
+}
+
 func mustParse(fset *token.FileSet, src string) *ast.File {
 	f, err := parser.ParseFile(fset, pkgName(src), src, parser.ParseComments)
 	if err != nil {
@@ -33,12 +38,13 @@ func mustParse(fset *token.FileSet, src string) *ast.File {
 }
 
 func typecheck(src string, conf *Config, info *Info) (*Package, error) {
+	// TODO(adonovan): plumb this from caller.
 	fset := token.NewFileSet()
 	f := mustParse(fset, src)
 	if conf == nil {
 		conf = &Config{
 			Error:    func(err error) {}, // collect all errors
-			Importer: importer.Default(),
+			Importer: defaultImporter(fset),
 		}
 	}
 	return conf.Check(f.Name.Name, fset, []*ast.File{f}, info)
@@ -1128,7 +1134,7 @@ var (
 		Implicits: make(map[ast.Node]Object),
 	}
 	var conf Config
-	conf.Importer = importer.Default()
+	conf.Importer = defaultImporter(fset)
 	_, err := conf.Check("p", fset, []*ast.File{f}, &info)
 	if err != nil {
 		t.Fatal(err)

src/go/types/check_test.go

@@ -34,7 +34,6 @@ import (
 	"flag"
 	"fmt"
 	"go/ast"
-	"go/importer"
 	"go/parser"
 	"go/scanner"
 	"go/token"
@@ -164,7 +163,7 @@ func testFilesImpl(t *testing.T, filenames []string, srcs [][]byte, manual bool,
 	// set up typechecker
 	var conf Config
 	*boolFieldAddr(&conf, "_Trace") = manual && testing.Verbose()
-	conf.Importer = importer.Default()
+	conf.Importer = defaultImporter(fset)
 	conf.Error = func(err error) {
 		if *haltOnError {
 			defer panic(err)

src/go/types/eval_test.go

@@ -9,7 +9,6 @@ package types_test
 import (
 	"fmt"
 	"go/ast"
-	"go/importer"
 	"go/parser"
 	"go/token"
 	"go/types"
@@ -188,7 +187,7 @@ func TestEvalPos(t *testing.T) {
 		files = append(files, file)
 	}
 
-	conf := Config{Importer: importer.Default()}
+	conf := Config{Importer: defaultImporter(fset)}
 	pkg, err := conf.Check("p", fset, files, nil)
 	if err != nil {
 		t.Fatal(err)
@@ -257,7 +256,7 @@ func f(a int, s string) S {
 		t.Fatal(err)
 	}
 
-	conf := Config{Importer: importer.Default()}
+	conf := Config{Importer: defaultImporter(fset)}
 	pkg, err := conf.Check("p", fset, []*ast.File{f}, nil)
 	if err != nil {
 		t.Fatal(err)

src/go/types/example_test.go

@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"go/ast"
 	"go/format"
-	"go/importer"
 	"go/parser"
 	"go/token"
 	"go/types"
@@ -57,7 +56,7 @@ func Unused() { {}; {{ var x int; _ = x }} } // make sure empty block scopes get
 	// Type-check a package consisting of these files.
 	// Type information for the imported "fmt" package
 	// comes from $GOROOT/pkg/$GOOS_$GOOARCH/fmt.a.
-	conf := types.Config{Importer: importer.Default()}
+	conf := types.Config{Importer: defaultImporter(fset)}
 	pkg, err := conf.Check("temperature", fset, files, nil)
 	if err != nil {
 		log.Fatal(err)
@@ -126,7 +125,7 @@ type I interface { m() byte }
 	// Type-check a package consisting of this file.
 	// Type information for the imported packages
 	// comes from $GOROOT/pkg/$GOOS_$GOOARCH/fmt.a.
-	conf := types.Config{Importer: importer.Default()}
+	conf := types.Config{Importer: defaultImporter(fset)}
 	pkg, err := conf.Check("temperature", fset, []*ast.File{f}, nil)
 	if err != nil {
 		log.Fatal(err)

src/go/types/issues_test.go

@@ -9,7 +9,6 @@ package types_test
 import (
 	"fmt"
 	"go/ast"
-	"go/importer"
 	"go/parser"
 	"go/token"
 	"internal/testenv"
@@ -291,7 +290,7 @@ func TestIssue25627(t *testing.T) {
 	} {
 		f := mustParse(fset, prefix+src)
 
-		cfg := Config{Importer: importer.Default(), Error: func(err error) {}}
+		cfg := Config{Importer: defaultImporter(fset), Error: func(err error) {}}
 		info := &Info{Types: make(map[ast.Expr]TypeAndValue)}
 		_, err := cfg.Check(f.Name.Name, fset, []*ast.File{f}, info)
 		if err != nil {
@@ -595,7 +594,11 @@ var _ T = template /* ERRORx "cannot use.*text/template.* as T value" */.Templat
 	)
 
 	a := mustTypecheck(asrc, nil, nil)
-	imp := importHelper{pkg: a, fallback: importer.Default()}
+	imp := importHelper{
+		pkg: a,
+		// TODO(adonovan): use same FileSet as mustTypecheck.
+		fallback: defaultImporter(token.NewFileSet()),
+	}
 
 	withImporter := func(cfg *Config) {
 		cfg.Importer = imp

src/go/types/lookup_test.go

@@ -5,7 +5,6 @@
 package types_test
 
 import (
-	"go/importer"
 	"go/token"
 	"path/filepath"
 	"runtime"
@@ -28,7 +27,7 @@ func BenchmarkLookupFieldOrMethod(b *testing.B) {
 	}
 
 	conf := Config{
-		Importer: importer.Default(),
+		Importer: defaultImporter(fset),
 	}
 
 	pkg, err := conf.Check("http", fset, files, nil)

src/go/types/mono_test.go

@@ -7,7 +7,6 @@ package types_test
 import (
 	"errors"
 	"fmt"
-	"go/importer"
 	"go/types"
 	"strings"
 	"testing"
@@ -19,7 +18,7 @@ func checkMono(t *testing.T, body string) error {
 	var buf strings.Builder
 	conf := types.Config{
 		Error:    func(err error) { fmt.Fprintln(&buf, err) },
-		Importer: importer.Default(),
+		Importer: defaultImporter(fset), // TODO(adonovan): use same FileSet as typecheck
 	}
 	typecheck(src, &conf, nil)
 	if buf.Len() == 0 {

src/go/types/resolver_test.go

@@ -7,7 +7,6 @@ package types_test
 import (
 	"fmt"
 	"go/ast"
-	"go/importer"
 	"go/token"
 	"internal/testenv"
 	"slices"
@@ -17,6 +16,7 @@ import (
 )
 
 type resolveTestImporter struct {
+	fset     *token.FileSet
 	importer ImporterFrom
 	imported map[string]bool
 }
@@ -30,7 +30,7 @@ func (imp *resolveTestImporter) ImportFrom(path, srcDir string, mode ImportMode)
 		panic("mode must be 0")
 	}
 	if imp.importer == nil {
-		imp.importer = importer.Default().(ImporterFrom)
+		imp.importer = defaultImporter(fset).(ImporterFrom)
 		imp.imported = make(map[string]bool)
 	}
 	pkg, err := imp.importer.ImportFrom(path, srcDir, mode)
@@ -124,7 +124,7 @@ func TestResolveIdents(t *testing.T) {
 	}
 
 	// resolve and type-check package AST
-	importer := new(resolveTestImporter)
+	importer := &resolveTestImporter{fset: fset}
 	conf := Config{Importer: importer}
 	uses := make(map[*ast.Ident]Object)
 	defs := make(map[*ast.Ident]Object)

src/go/types/self_test.go

@@ -6,7 +6,6 @@ package types_test
 
 import (
 	"go/ast"
-	"go/importer"
 	"go/parser"
 	"go/token"
 	"internal/testenv"
@@ -27,7 +26,7 @@ func TestSelf(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	conf := Config{Importer: importer.Default()}
+	conf := Config{Importer: defaultImporter(fset)}
 	_, err = conf.Check("go/types", fset, files, nil)
 	if err != nil {
 		t.Fatal(err)
@@ -82,7 +81,7 @@ func runbench(b *testing.B, path string, ignoreFuncBodies, writeInfo bool) {
 	for i := 0; i < b.N; i++ {
 		conf := Config{
 			IgnoreFuncBodies: ignoreFuncBodies,
-			Importer:         importer.Default(),
+			Importer:         defaultImporter(fset),
 		}
 		var info *Info
 		if writeInfo {

src/go/types/sizes_test.go

@@ -8,7 +8,7 @@ package types_test
 
 import (
 	"go/ast"
-	"go/importer"
+	"go/token"
 	"go/types"
 	"internal/testenv"
 	"testing"
@@ -87,7 +87,8 @@ const _ = unsafe.Offsetof(struct{ x int64 }{}.x)
 `
 	info := types.Info{Types: make(map[ast.Expr]types.TypeAndValue)}
 	conf := types.Config{
-		Importer: importer.Default(),
+		// TODO(adonovan): use same FileSet as mustTypecheck.
+		Importer: defaultImporter(token.NewFileSet()),
 		Sizes:    &types.StdSizes{WordSize: 8, MaxAlign: 8},
 	}
 	mustTypecheck(src, &conf, &info)
@@ -117,7 +118,8 @@ var s struct {
 	for _, arch := range []string{"386", "amd64"} {
 		t.Run(arch, func(t *testing.T) {
 			conf := types.Config{
-				Importer: importer.Default(),
+				// TODO(adonovan): use same FileSet as findStructTypeConfig.
+				Importer: defaultImporter(token.NewFileSet()),
 				Sizes:    types.SizesFor("gc", arch),
 			}
 			ts := findStructTypeConfig(t, src, &conf)
@@ -188,7 +190,11 @@ func TestGCSizes(t *testing.T) {
 		tc := tc
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
-			conf := types.Config{Importer: importer.Default(), Sizes: types.SizesFor("gc", "amd64")}
+			conf := types.Config{
+				// TODO(adonovan): use same FileSet as mustTypecheck.
+				Importer: defaultImporter(token.NewFileSet()),
+				Sizes:    types.SizesFor("gc", "amd64"),
+			}
 			mustTypecheck(tc.src, &conf, nil)
 		})
 	}