[dev.typeparams] cmd/compile/internal/types2: don't permit method calls on ptr to type parameter receivers

Simplify the implementation of asInterface while at it.

For #47031.

Change-Id: Ie7d4fbbab898d961ed3c0b7772ba9604641be13f
Reviewed-on: https://go-review.googlesource.com/c/go/+/332609
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/src/cmd/compile/internal/types2/type.go b/src/cmd/compile/internal/types2/type.go
index e3f63f63b5..c2da97605b 100644
--- a/src/cmd/compile/internal/types2/type.go
+++ b/src/cmd/compile/internal/types2/type.go
@@ -112,11 +112,6 @@ func asSignature(t Type) *Signature {
 	return op
 }
 
-func asInterface(t Type) *Interface {
-	op, _ := optype(t).(*Interface)
-	return op
-}
-
 func asMap(t Type) *Map {
 	op, _ := optype(t).(*Map)
 	return op
@@ -127,10 +122,16 @@ func asChan(t Type) *Chan {
 	return op
 }
 
-// If the argument to asNamed and asTypeParam is of the respective types
+// If the argument to asInterface, asNamed, or asTypeParam is of the respective type
 // (possibly after expanding an instance type), these methods return that type.
 // Otherwise the result is nil.
 
+// asInterface does not need to look at optype (type sets don't contain interfaces)
+func asInterface(t Type) *Interface {
+	u, _ := under(t).(*Interface)
+	return u
+}
+
 func asNamed(t Type) *Named {
 	e, _ := expand(t).(*Named)
 	return e