cmd/compile/internal/types2: reduce output when describing type parameters

There's no need to say "type parameter" for a type parameter. The
name is sufficient (they are always named), and the prose is followed
by "constrained by".

Change-Id: I98df8caa1432b8b7a874e58da6e3ed6be102b4a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/357410
Trust: Robert Griesemer <[email protected]>
Run-TryBot: Robert Griesemer <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Robert Findley <[email protected]>

Author: griesemer

src/cmd/compile/internal/types2/operand.go

@@ -176,17 +176,14 @@ func operandString(x *operand, qf Qualifier) string {
 	if hasType {
 		if x.typ != Typ[Invalid] {
 			var intro string
-			var tpar *TypeParam
 			if isGeneric(x.typ) {
 				intro = " of parameterized type "
-			} else if tpar = asTypeParam(x.typ); tpar != nil {
-				intro = " of type parameter "
 			} else {
 				intro = " of type "
 			}
 			buf.WriteString(intro)
 			WriteType(&buf, x.typ, qf)
-			if tpar != nil {
+			if tpar := asTypeParam(x.typ); tpar != nil {
 				buf.WriteString(" constrained by ")
 				WriteType(&buf, tpar.bound, qf) // do not compute interface type sets here
 			}