x/tools: make tests agnostic as to whether gotypesalias="" => 0 or 1

This is required temporarily as we flip the default.

Updates golang/go#65294

Change-Id: I552e40475cc48b949e2307af347ca98a428c55ea
Reviewed-on: https://go-review.googlesource.com/c/tools/+/578041
Reviewed-by: Robert Findley <rfindley@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Alan Donovan <adonovan@google.com>

gopls/internal/analysis/fillreturns/fillreturns_test.go

@@ -5,19 +5,17 @@
 package fillreturns_test
 
 import (
-	"os"
-	"strings"
 	"testing"
 
 	"golang.org/x/tools/go/analysis/analysistest"
 	"golang.org/x/tools/gopls/internal/analysis/fillreturns"
+	"golang.org/x/tools/internal/testenv"
 )
 
 func Test(t *testing.T) {
-	// TODO(golang/go#65294): delete once gotypesalias=1 is the default.
-	if strings.Contains(os.Getenv("GODEBUG"), "gotypesalias=1") {
-		t.Skip("skipping due to gotypesalias=1, which changes (improves) the result; reenable and update the expectations once it is the default")
-	}
+	// TODO(golang/go#65294): delete (and update expectations)
+	// once gotypesalias=1 is the default.
+	testenv.SkipMaterializedAliases(t, "expectations need updating for materialized aliases")
 
 	testdata := analysistest.TestData()
 	analysistest.RunWithSuggestedFixes(t, testdata, fillreturns.Analyzer, "a", "typeparams")

gopls/internal/test/integration/misc/staticcheck_test.go

@@ -5,8 +5,6 @@
 package misc
 
 import (
-	"os"
-	"strings"
 	"testing"
 
 	"golang.org/x/tools/internal/testenv"
@@ -18,9 +16,7 @@ func TestStaticcheckGenerics(t *testing.T) {
 	testenv.NeedsGo1Point(t, 20) // staticcheck requires go1.20+
 
 	// TODO(golang/go#65249): re-enable and fix this test with gotypesalias=1.
-	if strings.Contains(os.Getenv("GODEBUG"), "gotypesalias=1") {
-		t.Skipf("staticcheck needs updates for materialized aliases")
-	}
+	testenv.SkipMaterializedAliases(t, "staticcheck needs updates for materialized aliases")
 
 	const files = `
 -- go.mod --
@@ -88,9 +84,7 @@ func TestStaticcheckRelatedInfo(t *testing.T) {
 	testenv.NeedsGo1Point(t, 20) // staticcheck is only supported at Go 1.20+
 
 	// TODO(golang/go#65249): re-enable and fix this test with gotypesalias=1.
-	if strings.Contains(os.Getenv("GODEBUG"), "gotypesalias=1") {
-		t.Skipf("staticcheck needs updates for materialized aliases")
-	}
+	testenv.SkipMaterializedAliases(t, "staticcheck needs updates for materialized aliases")
 
 	const files = `
 -- go.mod --

internal/aliases/aliases.go

@@ -16,7 +16,7 @@ import (
 // NewAlias creates a new TypeName in Package pkg that
 // is an alias for the type rhs.
 //
-// When GoVersion>=1.22 and GODEBUG=gotypesalias=1,
+// When GoVersion>=1.22 and GODEBUG=gotypesalias=1 (or unset),
 // the Type() of the return value is a *types.Alias.
 func NewAlias(pos token.Pos, pkg *types.Package, name string, rhs types.Type) *types.TypeName {
 	if enabled() {

internal/aliases/aliases_test.go

@@ -20,7 +20,7 @@ var _ func(*aliases.Alias) *types.TypeName = (*aliases.Alias).Obj
 
 // TestNewAlias tests that alias.NewAlias creates an alias of a type
 // whose underlying and Unaliased type is *Named.
-// When gotypesalias=1 and GoVersion >= 1.22, the type will
+// When gotypesalias=1 (or unset) and GoVersion >= 1.22, the type will
 // be an *aliases.Alias.
 func TestNewAlias(t *testing.T) {
 	const source = `
@@ -46,7 +46,10 @@ func TestNewAlias(t *testing.T) {
 		t.Fatalf("Eval(%s) failed: %v", expr, err)
 	}
 
-	for _, godebug := range []string{"", "gotypesalias=1"} {
+	for _, godebug := range []string{
+		// "", // The default is in transition; suppress this case for now
+		"gotypesalias=0",
+		"gotypesalias=1"} {
 		t.Run(godebug, func(t *testing.T) {
 			t.Setenv("GODEBUG", godebug)
 
@@ -62,7 +65,7 @@ func TestNewAlias(t *testing.T) {
 				t.Errorf("Expected Unalias(A)==%q. got %q", want, got)
 			}
 
-			if testenv.Go1Point() >= 22 && godebug == "gotypesalias=1" {
+			if testenv.Go1Point() >= 22 && godebug != "gotypesalias=0" {
 				if _, ok := A.Type().(*aliases.Alias); !ok {
 					t.Errorf("Expected A.Type() to be a types.Alias(). got %q", A.Type())
 				}

internal/testenv/exec.go

@@ -12,6 +12,7 @@ import (
 	"reflect"
 	"runtime"
 	"strconv"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -190,3 +191,22 @@ func Command(t testing.TB, name string, args ...string) *exec.Cmd {
 	t.Helper()
 	return CommandContext(t, context.Background(), name, args...)
 }
+
+// SkipMaterializedAliases skips the test if go/types would create
+// instances of types.Alias, which some tests do not yet handle
+// correctly.
+func SkipMaterializedAliases(t *testing.T, message string) {
+	if hasMaterializedAliases(Go1Point()) {
+		t.Skipf("%s", message)
+	}
+}
+
+func hasMaterializedAliases(minor int) bool {
+	if minor >= 23 && !strings.Contains(os.Getenv("GODEBUG"), "gotypesalias=0") {
+		return true // gotypesalias=1 became the default in go1.23
+	}
+	if minor == 22 && strings.Contains(os.Getenv("GODEBUG"), "gotypesalias=1") {
+		return true // gotypesalias=0 was the default in go1.22
+	}
+	return false // types.Alias didn't exist in go1.21
+}