cmd/compile/internal/types2: remove asTypeParam and simplify some code

Because we do not permit a stand-alone type parameter on the RHS of
a type declaration, the underlying type of a (Named) type cannot be
a type parameter. This allows us to simplify some code.

Specifically, when parsing union elements, we don't need to delay
a check for later, which allows further simplifications when computing
type sets.

Change-Id: I4047c609f87ebb194ea8c1bad630a70d255b20cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/363438
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cmd/compile/internal/types2/predicates.go b/src/cmd/compile/internal/types2/predicates.go
index f1fd33c5de..5cb1c33814 100644
--- a/src/cmd/compile/internal/types2/predicates.go
+++ b/src/cmd/compile/internal/types2/predicates.go
@@ -90,7 +90,7 @@ func IsInterface(t Type) bool {
 
 // isTypeParam reports whether t is a type parameter.
 func isTypeParam(t Type) bool {
-	_, ok := under(t).(*TypeParam)
+	_, ok := t.(*TypeParam)
 	return ok
 }