go/types: add a test that generated files match types2

Adjust the go/types file generation to run in a test, so that we can
easily reuse the existing logic to verify that the current content of
go/types matches the expected result of generating from types2.

This test will enforce that we don't forget to regenerate go/types when
making changes to types2.

Change-Id: Iee14b1402065f7f0ecbcf28000e07a06c08fa42e
Reviewed-on: https://go-review.googlesource.com/c/go/+/462758
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Findley <rfindley@google.com>

39 files changed, 82 insertions, 70 deletions

diff --git a/src/go/types/array.go b/src/go/types/array.go
index 759e2f2e67..f19ce6e528 100644
--- a/src/go/types/array.go
+++ b/src/go/types/array.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/basic.go b/src/go/types/basic.go
index 7d6decdb1a..d483616413 100644
--- a/src/go/types/basic.go
+++ b/src/go/types/basic.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/chan.go b/src/go/types/chan.go
index 565e9d2e9d..940620067c 100644
--- a/src/go/types/chan.go
+++ b/src/go/types/chan.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/context.go b/src/go/types/context.go
index 81b2f139eb..56368e1060 100644
--- a/src/go/types/context.go
+++ b/src/go/types/context.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/context_test.go b/src/go/types/context_test.go
index 1340bf2053..c9f6dce728 100644
--- a/src/go/types/context_test.go
+++ b/src/go/types/context_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/gccgosizes.go b/src/go/types/gccgosizes.go
index d98105c69a..9152c811e1 100644
--- a/src/go/types/gccgosizes.go
+++ b/src/go/types/gccgosizes.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2019 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/generate.go b/src/go/types/generate.go
index 6759f117b9..7fec743170 100644
--- a/src/go/types/generate.go
+++ b/src/go/types/generate.go
@@ -3,6 +3,6 @@
 // license that can be found in the LICENSE file.
 
 // This file exists only to drive go:generate.
-//go:generate go run generator.go
+//go:generate go test -run=Generate -write=all
 
 package types
diff --git a/src/go/types/generator.go b/src/go/types/generate_test.go
index fc6295d3c8..b6942279a8 100644
--- a/src/go/types/generator.go
+++ b/src/go/types/generate_test.go
@@ -2,81 +2,93 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build ignore
-
 // This file implements a custom generator to create various go/types
 // source files from the corresponding types2 files.
 
-package main
+package types_test
 
 import (
 	"bytes"
 	"flag"
-	"fmt"
 	"go/ast"
 	"go/format"
 	"go/parser"
 	"go/token"
-	"log"
+	"internal/diff"
 	"os"
 	"path/filepath"
 	"runtime"
 	"strings"
+	"testing"
 )
 
+var filesToWrite = flag.String("write", "", `go/types files to generate, or "all" for all files`)
+
 const (
-	srcDir = "cmd/compile/internal/types2"
-	dstDir = "go/types"
+	srcDir = "/src/cmd/compile/internal/types2/"
+	dstDir = "/src/go/types/"
 )
 
-var fset = token.NewFileSet()
-
-func main() {
-	flag.Parse()
-
-	// process provided filenames, if any
-	if flag.NArg() > 0 {
-		for _, filename := range flag.Args() {
-			generate(filename, filemap[filename])
+// TestGenerate verifies that generated files in go/types match their types2
+// counterpart. If -write is set, this test actually writes the expected
+// content to go/types; otherwise, it just compares with the existing content.
+func TestGenerate(t *testing.T) {
+	// If filesToWrite is set, write the generated content to disk.
+	// In the special case of "all", write all files in filemap.
+	write := *filesToWrite != ""
+	var files []string // files to process
+	if *filesToWrite != "" && *filesToWrite != "all" {
+		files = strings.Split(*filesToWrite, ",")
+	} else {
+		for file := range filemap {
+			files = append(files, file)
 		}
-		fmt.Printf("generated %d files\n", flag.NArg())
-		return
 	}
 
-	// otherwise process per filemap below
-	for filename, action := range filemap {
-		generate(filename, action)
+	for _, filename := range files {
+		generate(t, filename, write)
 	}
-	fmt.Printf("generated %d files\n", len(filemap))
 }
 
-func generate(filename string, action action) {
+func generate(t *testing.T, filename string, write bool) {
 	// parse src
-	srcFilename := filepath.FromSlash(runtime.GOROOT() + "/src/" + srcDir + "/" + filename)
+	srcFilename := filepath.FromSlash(runtime.GOROOT() + srcDir + filename)
 	file, err := parser.ParseFile(fset, srcFilename, nil, parser.ParseComments)
 	if err != nil {
-		log.Fatal(err)
+		t.Fatal(err)
 	}
 
 	// fix package name
 	file.Name.Name = strings.ReplaceAll(file.Name.Name, "types2", "types")
 
 	// rewrite AST as needed
-	if action != nil {
+	if action := filemap[filename]; action != nil {
 		action(file)
 	}
 
 	// format AST
 	var buf bytes.Buffer
-	buf.WriteString("// Code generated by \"go run generator.go\"; DO NOT EDIT.\n\n")
+	buf.WriteString("// Code generated by \"go test -run=Generate -write=all\"; DO NOT EDIT.\n\n")
 	if err := format.Node(&buf, fset, file); err != nil {
-		log.Fatal(err)
+		t.Fatal(err)
 	}
+	generatedContent := buf.Bytes()
 
-	// write dst
-	dstFilename := filepath.FromSlash(runtime.GOROOT() + "/src/" + dstDir + "/" + filename)
-	if err := os.WriteFile(dstFilename, buf.Bytes(), 0o644); err != nil {
-		log.Fatal(err)
+	dstFilename := filepath.FromSlash(runtime.GOROOT() + dstDir + filename)
+	onDiskContent, err := os.ReadFile(dstFilename)
+	if err != nil {
+		t.Fatalf("reading %q: %v", filename, err)
+	}
+
+	if d := diff.Diff(filename+" (on disk)", onDiskContent, filename+" (generated)", generatedContent); d != nil {
+		if write {
+			t.Logf("applying change:\n%s", d)
+			if err := os.WriteFile(dstFilename, generatedContent, 0o644); err != nil {
+				t.Fatalf("writing %q: %v", filename, err)
+			}
+		} else {
+			t.Errorf("generated file content does not match:\n%s", string(d))
+		}
 	}
 }
 
diff --git a/src/go/types/hilbert_test.go b/src/go/types/hilbert_test.go
index 15e5ae3aca..7da2a7ded1 100644
--- a/src/go/types/hilbert_test.go
+++ b/src/go/types/hilbert_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/infer.go b/src/go/types/infer.go
index ef14353540..5f91b526d9 100644
--- a/src/go/types/infer.go
+++ b/src/go/types/infer.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/instantiate.go b/src/go/types/instantiate.go
index ab3a9451c0..11afb7a853 100644
--- a/src/go/types/instantiate.go
+++ b/src/go/types/instantiate.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/instantiate_test.go b/src/go/types/instantiate_test.go
index 91b2a1aaba..574f3aeb86 100644
--- a/src/go/types/instantiate_test.go
+++ b/src/go/types/instantiate_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/lookup.go b/src/go/types/lookup.go
index fa2b7b2f4b..2d6501b739 100644
--- a/src/go/types/lookup.go
+++ b/src/go/types/lookup.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/main_test.go b/src/go/types/main_test.go
index b0630947c1..fda9d102a3 100644
--- a/src/go/types/main_test.go
+++ b/src/go/types/main_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2022 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/map.go b/src/go/types/map.go
index 9827e8c147..febb0d3a0b 100644
--- a/src/go/types/map.go
+++ b/src/go/types/map.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/named.go b/src/go/types/named.go
index f1b2685ec3..413eaada27 100644
--- a/src/go/types/named.go
+++ b/src/go/types/named.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/object.go b/src/go/types/object.go
index 74b630af9e..e47ef2ebec 100644
--- a/src/go/types/object.go
+++ b/src/go/types/object.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/object_test.go b/src/go/types/object_test.go
index b0459260a1..bed8de3637 100644
--- a/src/go/types/object_test.go
+++ b/src/go/types/object_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2016 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/objset.go b/src/go/types/objset.go
index 4e7aaac500..e6ea37566e 100644
--- a/src/go/types/objset.go
+++ b/src/go/types/objset.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/package.go b/src/go/types/package.go
index 7a64aa9fe4..7aa62fb7a3 100644
--- a/src/go/types/package.go
+++ b/src/go/types/package.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/pointer.go b/src/go/types/pointer.go
index 091824c55e..5b45ab7755 100644
--- a/src/go/types/pointer.go
+++ b/src/go/types/pointer.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/predicates.go b/src/go/types/predicates.go
index c80d41d702..1927844732 100644
--- a/src/go/types/predicates.go
+++ b/src/go/types/predicates.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2012 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/scope.go b/src/go/types/scope.go
index 433f31a478..bf646f6882 100644
--- a/src/go/types/scope.go
+++ b/src/go/types/scope.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/selection.go b/src/go/types/selection.go
index bc26f39b3f..c79e13c6eb 100644
--- a/src/go/types/selection.go
+++ b/src/go/types/selection.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/sizes.go b/src/go/types/sizes.go
index fb7a16699a..d32866913e 100644
--- a/src/go/types/sizes.go
+++ b/src/go/types/sizes.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/slice.go b/src/go/types/slice.go
index 0fb8476d24..934549c2d4 100644
--- a/src/go/types/slice.go
+++ b/src/go/types/slice.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/subst.go b/src/go/types/subst.go
index 3be5c02be2..30c48e1bad 100644
--- a/src/go/types/subst.go
+++ b/src/go/types/subst.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/termlist.go b/src/go/types/termlist.go
index 46de92459b..9bc631c0e6 100644
--- a/src/go/types/termlist.go
+++ b/src/go/types/termlist.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/termlist_test.go b/src/go/types/termlist_test.go
index 7499fc6b9e..cf0c190516 100644
--- a/src/go/types/termlist_test.go
+++ b/src/go/types/termlist_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/tuple.go b/src/go/types/tuple.go
index 8ccf0289a3..e5e3914bb2 100644
--- a/src/go/types/tuple.go
+++ b/src/go/types/tuple.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/typelists.go b/src/go/types/typelists.go
index 864a34fa54..c000de2272 100644
--- a/src/go/types/typelists.go
+++ b/src/go/types/typelists.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/typeparam.go b/src/go/types/typeparam.go
index c573fa8633..763fcc61f0 100644
--- a/src/go/types/typeparam.go
+++ b/src/go/types/typeparam.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/typeterm.go b/src/go/types/typeterm.go
index d862add06e..c86442c43f 100644
--- a/src/go/types/typeterm.go
+++ b/src/go/types/typeterm.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/typeterm_test.go b/src/go/types/typeterm_test.go
index bf67f3872d..c6370f44fe 100644
--- a/src/go/types/typeterm_test.go
+++ b/src/go/types/typeterm_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2021 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/under.go b/src/go/types/under.go
index 0c2410e74e..f17d3bcda4 100644
--- a/src/go/types/under.go
+++ b/src/go/types/under.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/unify.go b/src/go/types/unify.go
index 9db63ca9ec..9fb0c75893 100644
--- a/src/go/types/unify.go
+++ b/src/go/types/unify.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2020 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/universe.go b/src/go/types/universe.go
index 6984cf849b..d32a8ed4e8 100644
--- a/src/go/types/universe.go
+++ b/src/go/types/universe.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2011 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/util_test.go b/src/go/types/util_test.go
index 4667451a97..205237211f 100644
--- a/src/go/types/util_test.go
+++ b/src/go/types/util_test.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2023 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
diff --git a/src/go/types/validtype.go b/src/go/types/validtype.go
index 5fd5f73cfa..d915fef825 100644
--- a/src/go/types/validtype.go
+++ b/src/go/types/validtype.go
@@ -1,4 +1,4 @@
-// Code generated by "go run generator.go"; DO NOT EDIT.
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
 
 // Copyright 2022 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style