cmd/compile/internal/types2: use []*TypeParam rather than []*TypeName for type param lists

This is a port of CL 343932 from go/types, with the necessary adjustments
to the compiler.

This change improves type safety slightly, avoids many internal type
assertions, and simplifies some code paths.

Change-Id: Ie9c4734814f49cd248927152d7b3264d3578428c
Reviewed-on: https://go-review.googlesource.com/c/go/+/344614
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Dan Scales <danscales@google.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/src/cmd/compile/internal/types2/typestring.go b/src/cmd/compile/internal/types2/typestring.go
index cb7cf73a62..5759118c94 100644
--- a/src/cmd/compile/internal/types2/typestring.go
+++ b/src/cmd/compile/internal/types2/typestring.go
@@ -242,14 +242,13 @@ func writeTypeList(buf *bytes.Buffer, list []Type, qf Qualifier, visited []Type)
 	}
 }
 
-func writeTParamList(buf *bytes.Buffer, list []*TypeName, qf Qualifier, visited []Type) {
+func writeTParamList(buf *bytes.Buffer, list []*TypeParam, qf Qualifier, visited []Type) {
 	buf.WriteString("[")
 	var prev Type
-	for i, p := range list {
+	for i, tpar := range list {
 		// Determine the type parameter and its constraint.
 		// list is expected to hold type parameter names,
 		// but don't crash if that's not the case.
-		tpar, _ := p.typ.(*TypeParam)
 		var bound Type
 		if tpar != nil {
 			bound = tpar.bound // should not be nil but we want to see it if it is
@@ -268,7 +267,7 @@ func writeTParamList(buf *bytes.Buffer, list []*TypeName, qf Qualifier, visited
 		if tpar != nil {
 			writeType(buf, tpar, qf, visited)
 		} else {
-			buf.WriteString(p.name)
+			buf.WriteString(tpar.obj.name)
 		}
 	}
 	if prev != nil {