go/types, types2: do not mutate arguments in NewChecker

CL 507975 resulted in new data races (as reported in golang#61212), because
the pkg argument to NewChecker was mutated.

Fix this by deferring the recording of the goVersion in pkg until type
checking is actually initiated via a call to Checker.Files.
Additionally, modify types2/check.go to bring it in sync with the
changes in go/types/check.go, and generate the new version_test.go from
the types2 file.

Also move parsing the version into checkFiles, for simplicity.

Fixes golang#61212

Change-Id: I15edb6c2cff3085622fe7c6a3b0dab531d27bd04
Reviewed-on: https://go-review.googlesource.com/c/go/+/508439
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>

Author: findleyr

src/cmd/compile/internal/types2/version_test.go

@@ -0,0 +1,24 @@
+// Copyright 2023 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 types2
+
+import "testing"
+
+var parseGoVersionTests = []struct {
+	in  string
+	out version
+}{
+	{"go1.21", version{1, 21}},
+	{"go1.21.0", version{1, 21}},
+	{"go1.21rc2", version{1, 21}},
+}
+
+func TestParseGoVersion(t *testing.T) {
+	for _, tt := range parseGoVersionTests {
+		if out, err := parseGoVersion(tt.in); out != tt.out || err != nil {
+			t.Errorf("parseGoVersion(%q) = %v, %v, want %v, nil", tt.in, out, err, tt.out)
+		}
+	}
+}

src/go/types/check.go

@@ -109,7 +109,11 @@ type Checker struct {
 	fset *token.FileSet
 	pkg  *Package
 	*Info
+<<<<<<< HEAD
 	version goVersion              // accepted language version
+=======
+	version version                // accepted language version
+>>>>>>> a87a31d520 (go/types, types2: do not mutate arguments in NewChecker)
 	nextID  uint64                 // unique Id for type parameters (first valid Id is 1)
 	objMap  map[Object]*declInfo   // maps package-level objects and (non-interface) methods to declaration info
 	impMap  map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
@@ -258,6 +262,7 @@ func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Ch
 	// (previously, pkg.goVersion was mutated here: go.dev/issue/61212)
 
 	return &Checker{
+<<<<<<< HEAD
 		enableAlias: gotypesalias.Value() == "1",
 		conf:        conf,
 		ctxt:        conf.Context,
@@ -267,6 +272,15 @@ func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Ch
 		version:     asGoVersion(conf.GoVersion),
 		objMap:      make(map[Object]*declInfo),
 		impMap:      make(map[importKey]*Package),
+=======
+		conf:   conf,
+		ctxt:   conf.Context,
+		fset:   fset,
+		pkg:    pkg,
+		Info:   info,
+		objMap: make(map[Object]*declInfo),
+		impMap: make(map[importKey]*Package),
+>>>>>>> a87a31d520 (go/types, types2: do not mutate arguments in NewChecker)
 	}
 }
 
@@ -379,6 +393,14 @@ func (check *Checker) checkFiles(files []*ast.File) (err error) {
 		// not be mutated. See https://go.dev/issue/61212 for an example of where
 		// Unsafe is passed to NewChecker.
 		return nil
+<<<<<<< HEAD
+=======
+	}
+
+	check.version, err = parseGoVersion(check.conf.GoVersion)
+	if err != nil {
+		return err
+>>>>>>> a87a31d520 (go/types, types2: do not mutate arguments in NewChecker)
 	}
 
 	// Note: NewChecker doesn't return an error, so we need to check the version here.

src/go/types/generate_test.go

@@ -143,6 +143,7 @@ var filemap = map[string]action{
 	"universe.go":      fixGlobalTypVarDecl,
 	"util_test.go":     fixTokenPos,
 	"validtype.go":     nil,
+	"version_test.go":  nil,
 }
 
 // TODO(gri) We should be able to make these rewriters more configurable/composable.