6 files changed, 7 insertions, 27 deletions
diff --git a/src/cmd/compile/internal/noder/unified.go b/src/cmd/compile/internal/noder/unified.go
index 85982d7c18..05f4483d0d 100644
--- a/src/cmd/compile/internal/noder/unified.go
+++ b/src/cmd/compile/internal/noder/unified.go
@@ -7,7 +7,6 @@ package noder
 import (
 	"cmp"
 	"fmt"
-	"internal/buildcfg"
 	"internal/pkgbits"
 	"internal/types/errors"
 	"io"
@@ -464,11 +463,8 @@ func readPackage(pr *pkgReader, importpkg *types.Pkg, localStub bool) {
 // writeUnifiedExport writes to `out` the finalized, self-contained
 // Unified IR export data file for the current compilation unit.
 func writeUnifiedExport(out io.Writer) {
-	// Use V2 as the encoded version aliastypeparams GOEXPERIMENT is enabled.
-	version := pkgbits.V1
-	if buildcfg.Experiment.AliasTypeParams {
-		version = pkgbits.V2
-	}
+	// Use V2 as the encoded version for aliastypeparams.
+	version := pkgbits.V2
 	l := linker{
 		pw: pkgbits.NewPkgEncoder(version, base.Debug.SyncFrames),
 
diff --git a/src/cmd/compile/internal/noder/writer.go b/src/cmd/compile/internal/noder/writer.go
index baff0ceea0..54e5f1ea5f 100644
--- a/src/cmd/compile/internal/noder/writer.go
+++ b/src/cmd/compile/internal/noder/writer.go
@@ -96,11 +96,8 @@ type pkgWriter struct {
 // newPkgWriter returns an initialized pkgWriter for the specified
 // package.
 func newPkgWriter(m posMap, pkg *types2.Package, info *types2.Info, otherInfo map[*syntax.FuncLit]bool) *pkgWriter {
-	// Use V2 as the encoded version aliastypeparams GOEXPERIMENT is enabled.
-	version := pkgbits.V1
-	if buildcfg.Experiment.AliasTypeParams {
-		version = pkgbits.V2
-	}
+	// Use V2 as the encoded version for aliastypeparams.
+	version := pkgbits.V2
 	return &pkgWriter{
 		PkgEncoder: pkgbits.NewPkgEncoder(version, base.Debug.SyncFrames),
 
diff --git a/src/cmd/compile/internal/types2/decl.go b/src/cmd/compile/internal/types2/decl.go
index 64047aa84f..34105816a6 100644
--- a/src/cmd/compile/internal/types2/decl.go
+++ b/src/cmd/compile/internal/types2/decl.go
@@ -8,7 +8,6 @@ import (
 	"cmd/compile/internal/syntax"
 	"fmt"
 	"go/constant"
-	"internal/buildcfg"
 	. "internal/types/errors"
 	"slices"
 )
@@ -525,10 +524,6 @@ func (check *Checker) typeDecl(obj *TypeName, tdecl *syntax.TypeDecl, def *TypeN
 
 			// handle type parameters even if not allowed (Alias type is supported)
 			if tparam0 != nil {
-				if !versionErr && !buildcfg.Experiment.AliasTypeParams {
-					check.error(tdecl, UnsupportedFeature, "generic type alias requires GOEXPERIMENT=aliastypeparams")
-					versionErr = true
-				}
 				check.openScope(tdecl, "type parameters")
 				defer check.closeScope()
 				check.collectTypeParams(&alias.tparams, tdecl.TParamList)
diff --git a/src/cmd/compile/internal/types2/instantiate.go b/src/cmd/compile/internal/types2/instantiate.go
index f7346cab46..1c8c12d07c 100644
--- a/src/cmd/compile/internal/types2/instantiate.go
+++ b/src/cmd/compile/internal/types2/instantiate.go
@@ -11,7 +11,6 @@ import (
 	"cmd/compile/internal/syntax"
 	"errors"
 	"fmt"
-	"internal/buildcfg"
 	. "internal/types/errors"
 )
 
@@ -130,10 +129,6 @@ func (check *Checker) instance(pos syntax.Pos, orig genericType, targs []Type, e
 		res = check.newNamedInstance(pos, orig, targs, expanding) // substituted lazily
 
 	case *Alias:
-		if !buildcfg.Experiment.AliasTypeParams {
-			assert(expanding == nil) // Alias instances cannot be reached from Named types
-		}
-
 		// verify type parameter count (see go.dev/issue/71198 for a test case)
 		tparams := orig.TypeParams()
 		if !check.validateTArgLen(pos, orig.obj.Name(), tparams.Len(), len(targs)) {
diff --git a/src/cmd/compile/internal/types2/object_test.go b/src/cmd/compile/internal/types2/object_test.go
index f19264e4db..4f1a653ff3 100644
--- a/src/cmd/compile/internal/types2/object_test.go
+++ b/src/cmd/compile/internal/types2/object_test.go
@@ -99,8 +99,7 @@ var testObjects = []struct {
 	{"type t = struct{f int}", "t", "type p.t = struct{f int}", false},
 	{"type t = func(int)", "t", "type p.t = func(int)", false},
 	{"type A = B; type B = int", "A", "type p.A = p.B", true},
-	{"type A[P ~int] = struct{}", "A", "type p.A[P ~int] = struct{}", true}, // requires GOEXPERIMENT=aliastypeparams
-
+	{"type A[P ~int] = struct{}", "A", "type p.A[P ~int] = struct{}", true},
 	{"var v int", "v", "var p.v int", false},
 
 	{"func f(int) string", "f", "func p.f(int) string", false},
@@ -114,10 +113,6 @@ func TestObjectString(t *testing.T) {
 
 	for i, test := range testObjects {
 		t.Run(fmt.Sprint(i), func(t *testing.T) {
-			if test.alias {
-				revert := setGOEXPERIMENT("aliastypeparams")
-				defer revert()
-			}
 			src := "package p; " + test.src
 			conf := Config{Error: func(error) {}, Importer: defaultImporter(), EnableAlias: test.alias}
 			pkg, err := typecheck(src, &conf, nil)
diff --git a/src/cmd/compile/internal/types2/stdlib_test.go b/src/cmd/compile/internal/types2/stdlib_test.go
index 35e15d814d..365bc97462 100644
--- a/src/cmd/compile/internal/types2/stdlib_test.go
+++ b/src/cmd/compile/internal/types2/stdlib_test.go
@@ -332,6 +332,8 @@ func TestStdFixed(t *testing.T) {
 		"issue49814.go",  // go/types does not have constraints on array size
 		"issue56103.go",  // anonymous interface cycles; will be a type checker error in 1.22
 		"issue52697.go",  // types2 does not have constraints on stack size
+		"issue68054.go",  // this test requires GODEBUG=gotypesalias=1
+		"issue68580.go",  // this test requires GODEBUG=gotypesalias=1
 		"issue73309.go",  // this test requires GODEBUG=gotypesalias=1
 		"issue73309b.go", // this test requires GODEBUG=gotypesalias=1