go/parser: Use test-specific filesets to avoid races.

Only affects test code.

Fixes issue 9025.
Fixes issue 9130.

LGTM=r, adonovan
R=adonovan, r
CC=golang-codereviews
https://codereview.appspot.com/180920043

2 files changed, 22 insertions, 25 deletions

diff --git a/src/go/parser/error_test.go b/src/go/parser/error_test.go
index 48fb53e5b..1a08d5a6b 100644
--- a/src/go/parser/error_test.go
+++ b/src/go/parser/error_test.go
@@ -34,11 +34,9 @@ import (
 
 const testdata = "testdata"
 
-var fsetErrs = token.NewFileSet()
-
 // getFile assumes that each filename occurs at most once
-func getFile(filename string) (file *token.File) {
-	fsetErrs.Iterate(func(f *token.File) bool {
+func getFile(fset *token.FileSet, filename string) (file *token.File) {
+	fset.Iterate(func(f *token.File) bool {
 		if f.Name() == filename {
 			if file != nil {
 				panic(filename + " used multiple times")
@@ -50,8 +48,8 @@ func getFile(filename string) (file *token.File) {
 	return file
 }
 
-func getPos(filename string, offset int) token.Pos {
-	if f := getFile(filename); f != nil {
+func getPos(fset *token.FileSet, filename string, offset int) token.Pos {
+	if f := getFile(fset, filename); f != nil {
 		return f.Pos(offset)
 	}
 	return token.NoPos
@@ -68,14 +66,14 @@ var errRx = regexp.MustCompile(`^/\* *ERROR *(HERE)? *"([^"]*)" *\*/$`)
 // expectedErrors collects the regular expressions of ERROR comments found
 // in files and returns them as a map of error positions to error messages.
 //
-func expectedErrors(t *testing.T, filename string, src []byte) map[token.Pos]string {
+func expectedErrors(t *testing.T, fset *token.FileSet, filename string, src []byte) map[token.Pos]string {
 	errors := make(map[token.Pos]string)
 
 	var s scanner.Scanner
 	// file was parsed already - do not add it again to the file
 	// set otherwise the position information returned here will
 	// not match the position information collected by the parser
-	s.Init(getFile(filename), src, nil, scanner.ScanComments)
+	s.Init(getFile(fset, filename), src, nil, scanner.ScanComments)
 	var prev token.Pos // position of last non-comment, non-semicolon token
 	var here token.Pos // position immediately after the token at position prev
 
@@ -109,11 +107,11 @@ func expectedErrors(t *testing.T, filename string, src []byte) map[token.Pos]str
 // compareErrors compares the map of expected error messages with the list
 // of found errors and reports discrepancies.
 //
-func compareErrors(t *testing.T, expected map[token.Pos]string, found scanner.ErrorList) {
+func compareErrors(t *testing.T, fset *token.FileSet, expected map[token.Pos]string, found scanner.ErrorList) {
 	for _, error := range found {
 		// error.Pos is a token.Position, but we want
 		// a token.Pos so we can do a map lookup
-		pos := getPos(error.Pos.Filename, error.Pos.Offset)
+		pos := getPos(fset, error.Pos.Filename, error.Pos.Offset)
 		if msg, found := expected[pos]; found {
 			// we expect a message at pos; check if it matches
 			rx, err := regexp.Compile(msg)
@@ -140,7 +138,7 @@ func compareErrors(t *testing.T, expected map[token.Pos]string, found scanner.Er
 	if len(expected) > 0 {
 		t.Errorf("%d errors not reported:", len(expected))
 		for pos, msg := range expected {
-			t.Errorf("%s: %s\n", fsetErrs.Position(pos), msg)
+			t.Errorf("%s: %s\n", fset.Position(pos), msg)
 		}
 	}
 }
@@ -152,7 +150,8 @@ func checkErrors(t *testing.T, filename string, input interface{}) {
 		return
 	}
 
-	_, err = ParseFile(fsetErrs, filename, src, DeclarationErrors|AllErrors)
+	fset := token.NewFileSet()
+	_, err = ParseFile(fset, filename, src, DeclarationErrors|AllErrors)
 	found, ok := err.(scanner.ErrorList)
 	if err != nil && !ok {
 		t.Error(err)
@@ -162,10 +161,10 @@ func checkErrors(t *testing.T, filename string, input interface{}) {
 
 	// we are expecting the following errors
 	// (collect these after parsing a file so that it is found in the file set)
-	expected := expectedErrors(t, filename, src)
+	expected := expectedErrors(t, fset, filename, src)
 
 	// verify errors returned by the parser
-	compareErrors(t, expected, found)
+	compareErrors(t, fset, expected, found)
 }
 
 func TestErrors(t *testing.T) {
diff --git a/src/go/parser/parser_test.go b/src/go/parser/parser_test.go
index 85065fd18..51ce1a933 100644
--- a/src/go/parser/parser_test.go
+++ b/src/go/parser/parser_test.go
@@ -14,8 +14,6 @@ import (
 	"testing"
 )
 
-var fset = token.NewFileSet()
-
 var validFiles = []string{
 	"parser.go",
 	"parser_test.go",
@@ -25,7 +23,7 @@ var validFiles = []string{
 
 func TestParse(t *testing.T) {
 	for _, filename := range validFiles {
-		_, err := ParseFile(fset, filename, nil, DeclarationErrors)
+		_, err := ParseFile(token.NewFileSet(), filename, nil, DeclarationErrors)
 		if err != nil {
 			t.Fatalf("ParseFile(%s): %v", filename, err)
 		}
@@ -46,7 +44,7 @@ func dirFilter(f os.FileInfo) bool { return nameFilter(f.Name()) }
 
 func TestParseDir(t *testing.T) {
 	path := "."
-	pkgs, err := ParseDir(fset, path, dirFilter, 0)
+	pkgs, err := ParseDir(token.NewFileSet(), path, dirFilter, 0)
 	if err != nil {
 		t.Fatalf("ParseDir(%s): %v", path, err)
 	}
@@ -131,7 +129,7 @@ func TestParseExpr(t *testing.T) {
 }
 
 func TestColonEqualsScope(t *testing.T) {
-	f, err := ParseFile(fset, "", `package p; func f() { x, y, z := x, y, z }`, 0)
+	f, err := ParseFile(token.NewFileSet(), "", `package p; func f() { x, y, z := x, y, z }`, 0)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -153,7 +151,7 @@ func TestColonEqualsScope(t *testing.T) {
 }
 
 func TestVarScope(t *testing.T) {
-	f, err := ParseFile(fset, "", `package p; func f() { var x, y, z = x, y, z }`, 0)
+	f, err := ParseFile(token.NewFileSet(), "", `package p; func f() { var x, y, z = x, y, z }`, 0)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -183,7 +181,7 @@ var x int
 func f() { L: }
 `
 
-	f, err := ParseFile(fset, "", src, 0)
+	f, err := ParseFile(token.NewFileSet(), "", src, 0)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -221,7 +219,7 @@ func f() { L: }
 }
 
 func TestUnresolved(t *testing.T) {
-	f, err := ParseFile(fset, "", `
+	f, err := ParseFile(token.NewFileSet(), "", `
 package p
 //
 func f1a(int)
@@ -316,7 +314,7 @@ var imports = map[string]bool{
 func TestImports(t *testing.T) {
 	for path, isValid := range imports {
 		src := fmt.Sprintf("package p; import %s", path)
-		_, err := ParseFile(fset, "", src, 0)
+		_, err := ParseFile(token.NewFileSet(), "", src, 0)
 		switch {
 		case err != nil && isValid:
 			t.Errorf("ParseFile(%s): got %v; expected no error", src, err)
@@ -327,7 +325,7 @@ func TestImports(t *testing.T) {
 }
 
 func TestCommentGroups(t *testing.T) {
-	f, err := ParseFile(fset, "", `
+	f, err := ParseFile(token.NewFileSet(), "", `
 package p /* 1a */ /* 1b */      /* 1c */ // 1d
 /* 2a
 */
@@ -421,7 +419,7 @@ func checkFieldComments(t *testing.T, file *ast.File, fieldname, lead, line stri
 }
 
 func TestLeadAndLineComments(t *testing.T) {
-	f, err := ParseFile(fset, "", `
+	f, err := ParseFile(token.NewFileSet(), "", `
 package p
 type T struct {
 	/* F1 lead comment */