go/types, types2: track gotypesalias non-default behavior

Fixes #66216.

Change-Id: I2750a744d0dcf636a00d388299e1f2f993e5ac26
Reviewed-on: https://go-review.googlesource.com/c/go/+/572575
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>

diff --git a/src/cmd/compile/internal/types2/check.go b/src/cmd/compile/internal/types2/check.go
index cc723f20127e2c1af7270aa12c2eeb8c2f0df089..17d1577ee1f2e0710bdc6d8dad320cbf58887ea8 100644 (file)
--- a/src/cmd/compile/internal/types2/check.go
+++ b/src/cmd/compile/internal/types2/check.go
@@ -102,6 +102,12 @@ type Checker struct {
        // If enableAlias is set, alias declarations produce an Alias type.
        // Otherwise the alias information is only in the type name, which
        // points directly to the actual (aliased) type.
+       // Starting with Go 1.23, enableAlias is set by default.
+       // Non-default behavior is tracked with gotypesalias.IncNonDefault()
+       // for each declaration of an alias type where enableAlias is not set.
+       //
+       // TODO(gri) Testing runs tests in both modes. Do we need to exclude
+       //           tracking of non-default behavior for tests?
        enableAlias bool
 
        conf *Config

diff --git a/src/cmd/compile/internal/types2/check_test.go b/src/cmd/compile/internal/types2/check_test.go
index 066218772ea97f4d236a06e5c36b4b8abd704a9d..f1b520d33c2d1ca6846328b8a44a6dc7b09e7f27 100644 (file)
--- a/src/cmd/compile/internal/types2/check_test.go
+++ b/src/cmd/compile/internal/types2/check_test.go
@@ -122,7 +122,7 @@ func parseFlags(src []byte, flags *flag.FlagSet) error {
 //
 // If provided, opts may be used to mutate the Config before type-checking.
 func testFiles(t *testing.T, filenames []string, srcs [][]byte, colDelta uint, manual bool, opts ...func(*Config)) {
-       // Alias types are enabled by default
+       // Alias types are enabled by default.
        testFilesImpl(t, filenames, srcs, colDelta, manual, opts...)
        if !manual {
                t.Setenv("GODEBUG", "gotypesalias=0")

diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go
index 26ce49d87a7abd1c27577edf12a9d8bdb2480b89..fff2da49532031ff8e4ba49223cb2340b676434f 100644 (file)
--- a/src/cmd/compile/internal/types2/decl.go
+++ b/src/cmd/compile/internal/types2/decl.go
@@ -532,6 +532,22 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *TypeN
                        alias.fromRHS = rhs
                        Unalias(alias) // resolve alias.actual
                } else {
+                       // With Go1.23, the default behavior is to use Alias nodes,
+                       // reflected by check.enableAlias. Signal non-default behavior
+                       // by calling gotypesalias.IncNonDefault().
+                       //
+                       // Note: As of Go 1.23, Settings.IncNonDefault is not present
+                       // in internal/godebug/godebug.go used during bootstrapping,
+                       // only after the tool chain is built and recompiles itself.
+                       // Check dynamically for the presence of IncNonDefault.
+                       // (This is not an issue for go/types because it is not used
+                       // during bootstrap.)
+                       //
+                       // TODO(gri) replace with direct call when we bootstrap with Go 1.20
+                       if s, ok := any(gotypesalias).(interface{ IncNonDefault() }); ok {
+                               s.IncNonDefault()
+                       }
+
                        if !versionErr && tparam0 != nil {
                                check.error(tdecl, UnsupportedFeature, "generic type alias requires GODEBUG=gotypesalias=1 or unset")
                                versionErr = true

diff --git a/src/go/types/check.go b/src/go/types/check.go
index be990eabfe58d4acc9f688376abaff290669672d..c651e57fa91aefc74546f68eaaae43a7fe8688f8 100644 (file)
--- a/src/go/types/check.go
+++ b/src/go/types/check.go
@@ -102,9 +102,15 @@ type Checker struct {
        // package information
        // (initialized by NewChecker, valid for the life-time of checker)
 
-       // If EnableAlias is set, alias declarations produce an Alias type.
+       // If enableAlias is set, alias declarations produce an Alias type.
        // Otherwise the alias information is only in the type name, which
        // points directly to the actual (aliased) type.
+       // Starting with Go 1.23, enableAlias is set by default.
+       // Non-default behavior is tracked with gotypesalias.IncNonDefault()
+       // for each declaration of an alias type where enableAlias is not set.
+       //
+       // TODO(gri) Testing runs tests in both modes. Do we need to exclude
+       //           tracking of non-default behavior for tests?
        enableAlias bool
 
        conf *Config

diff --git a/src/go/types/check_test.go b/src/go/types/check_test.go
index 6ad7ef3a27b6810fafb3c23e538a2807c263a226..068507dade150394fd5445de2d39b0f6aba16098 100644 (file)
--- a/src/go/types/check_test.go
+++ b/src/go/types/check_test.go
@@ -134,7 +134,7 @@ func parseFlags(src []byte, flags *flag.FlagSet) error {
 //
 // If provided, opts may be used to mutate the Config before type-checking.
 func testFiles(t *testing.T, filenames []string, srcs [][]byte, manual bool, opts ...func(*Config)) {
-       // Alias types are enabled by default
+       // Alias types are enabled by default.
        testFilesImpl(t, filenames, srcs, manual, opts...)
        if !manual {
                t.Setenv("GODEBUG", "gotypesalias=0")

diff --git a/src/go/types/decl.go b/src/go/types/decl.go
index 937163fc7535f8fd13b17154bc25d6a4275d2338..3dab94aa0fa8fc1adfba7ff23601024ac9723654 100644 (file)
--- a/src/go/types/decl.go
+++ b/src/go/types/decl.go
@@ -607,6 +607,10 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *ast.TypeSpec, def *TypeName
                        alias.fromRHS = rhs
                        Unalias(alias) // resolve alias.actual
                } else {
+                       // With Go1.23, the default behavior is to use Alias nodes,
+                       // reflected by check.enableAlias. Signal non-default behavior.
+                       gotypesalias.IncNonDefault()
+
                        if !versionErr && tparam0 != nil {
                                check.error(tdecl, UnsupportedFeature, "generic type alias requires GODEBUG=gotypesalias=1 or unset")
                                versionErr = true

diff --git a/src/internal/godebugs/table.go b/src/internal/godebugs/table.go
index e9e043df4c764301dcbdde1978d288d6a56f929c..a95c8f2f9434e80bd95ec492567bef73f9d00f56 100644 (file)
--- a/src/internal/godebugs/table.go
+++ b/src/internal/godebugs/table.go
@@ -30,7 +30,7 @@ var All = []Info{
        {Name: "gocachehash", Package: "cmd/go"},
        {Name: "gocachetest", Package: "cmd/go"},
        {Name: "gocacheverify", Package: "cmd/go"},
-       {Name: "gotypesalias", Package: "go/types", Changed: 23, Old: "0", Opaque: true}, // bug #66216: remove Opaque
+       {Name: "gotypesalias", Package: "go/types", Changed: 23, Old: "0"},
        {Name: "http2client", Package: "net/http"},
        {Name: "http2debug", Package: "net/http", Opaque: true},
        {Name: "http2server", Package: "net/http"},

diff --git a/src/runtime/metrics/doc.go b/src/runtime/metrics/doc.go
index deb993241d9785636f76d6dc48dbb4509f9ebc2a..fbbeb1a4754cb20f65e4345a88bc24a28b817986 100644 (file)
--- a/src/runtime/metrics/doc.go
+++ b/src/runtime/metrics/doc.go
@@ -246,6 +246,10 @@ Below is the full list of supported metrics, ordered lexicographically.
                The number of non-default behaviors executed by the cmd/go
                package due to a non-default GODEBUG=gocacheverify=... setting.
 
+       /godebug/non-default-behavior/gotypesalias:events
+               The number of non-default behaviors executed by the go/types
+               package due to a non-default GODEBUG=gotypesalias=... setting.
+
        /godebug/non-default-behavior/http2client:events
                The number of non-default behaviors executed by the net/http
                package due to a non-default GODEBUG=http2client=... setting.