1 files changed, 33 insertions, 23 deletions

diff --git a/src/go/types/testdata/examples/types.go2 b/src/go/types/testdata/examples/types.go2
index 59c8804ad2..a7544f79ea 100644
--- a/src/go/types/testdata/examples/types.go2
+++ b/src/go/types/testdata/examples/types.go2
@@ -161,30 +161,40 @@ type _ struct {
 	* /* ERROR List redeclared */ List[int]
 }
 
+// Issue #45639: We don't allow this anymore. Keep this code
+//               in case we decide to revisit this decision.
+//
 // It's possible to declare local types whose underlying types
 // are type parameters. As with ordinary type definitions, the
 // types underlying properties are "inherited" but the methods
 // are not.
-func _[T interface{ m(); type int }]() {
-	type L T
-	var x L
-
-	// m is not defined on L (it is not "inherited" from
-	// its underlying type).
-	x.m /* ERROR x.m undefined */ ()
-
-	// But the properties of T, such that as that it supports
-	// the operations of the types given by its type bound,
-	// are also the properties of L.
-	x++
-	_ = x - x
-
-	// On the other hand, if we define a local alias for T,
-	// that alias stands for T as expected.
-	type A = T
-	var y A
-	y.m()
-	_ = y < 0
+//func _[T interface{ m(); ~int }]() {
+//	type L T
+//	var x L
+//
+//	// m is not defined on L (it is not "inherited" from
+//	// its underlying type).
+//	x.m /* ERROR x.m undefined */ ()
+//
+//	// But the properties of T, such that as that it supports
+//	// the operations of the types given by its type bound,
+//	// are also the properties of L.
+//	x++
+//	_ = x - x
+//
+//	// On the other hand, if we define a local alias for T,
+//	// that alias stands for T as expected.
+//	type A = T
+//	var y A
+//	y.m()
+//	_ = y < 0
+//}
+
+// It is not permitted to declare a local type whose underlying
+// type is a type parameters not declared by that type declaration.
+func _[T any]() {
+	type _ T         // ERROR cannot use function type parameter T as RHS in type declaration
+	type _ [_ any] T // ERROR cannot use function type parameter T as RHS in type declaration
 }
 
 // As a special case, an explicit type argument may be omitted
@@ -238,11 +248,11 @@ func _[A Adder[A], B Adder[B], C Adder[A]]() {
 // The type of variables (incl. parameters and return values) cannot
 // be an interface with type constraints or be/embed comparable.
 type I interface {
-	type int
+	~int
 }
 
 var (
-	_ interface /* ERROR contains type constraints */ {type int}
+	_ interface /* ERROR contains type constraints */ {~int}
 	_ I /* ERROR contains type constraints */
 )
 
@@ -273,7 +283,7 @@ func _() {
 // (If a type list contains just a single const type, we could
 // allow it, but such type lists don't make much sense in the
 // first place.)
-func _[T interface { type int, float64 }]() {
+func _[T interface {~int|~float64}]() {
 	// not valid
 	const _ = T /* ERROR not constant */ (0)
 	const _ T /* ERROR invalid constant type T */ = 1