From: Robert Findley <rfindley@google.com>
Date: Mon, 16 Aug 2021 01:22:38 +0000 (-0400)
Subject: go/types: minor cleanup of writeTParamList
X-Git-Tag: go1.18beta1~1777
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=11a43df461;p=gostls13.git

go/types: minor cleanup of writeTParamList

This is a port of CL 339903 to go/types.

Change-Id: Iaf5fe7321d907df4421128c66cf8c58129eaae8b
Reviewed-on: https://go-review.googlesource.com/c/go/+/342435
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
---

diff --git a/src/go/types/infer.go b/src/go/types/infer.go
index eb0d75e46f..ea1057fe07 100644
--- a/src/go/types/infer.go
+++ b/src/go/types/infer.go
@@ -82,7 +82,7 @@ func (check *Checker) infer(posn positioner, tparams []*TypeName, targs []Type,
 
 	// Substitute type arguments for their respective type parameters in params,
 	// if any. Note that nil targs entries are ignored by check.subst.
-	// TODO(gri) Can we avoid this (we're setting known type argumemts below,
+	// TODO(gri) Can we avoid this (we're setting known type arguments below,
 	//           but that doesn't impact the isParameterized check for now).
 	if params.Len() > 0 {
 		smap := makeSubstMap(tparams, targs)
diff --git a/src/go/types/typestring.go b/src/go/types/typestring.go
index 975bba633a..fa29d75fe2 100644
--- a/src/go/types/typestring.go
+++ b/src/go/types/typestring.go
@@ -249,23 +249,27 @@ func writeTParamList(buf *bytes.Buffer, list []*TypeName, qf Qualifier, visited
 	buf.WriteString("[")
 	var prev Type
 	for i, p := range list {
-		// TODO(rFindley) support 'any' sugar here.
-		var b Type = &emptyInterface
-		if t, _ := p.typ.(*TypeParam); t != nil && t.bound != nil {
-			b = t.bound
+		// 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
 		}
+
 		if i > 0 {
-			if b != prev {
-				// type bound changed - write previous one before advancing
+			if bound != prev {
+				// bound changed - write previous one before advancing
 				buf.WriteByte(' ')
 				writeType(buf, prev, qf, visited)
 			}
 			buf.WriteString(", ")
 		}
-		prev = b
+		prev = bound
 
-		if t, _ := p.typ.(*TypeParam); t != nil {
-			writeType(buf, t, qf, visited)
+		if tpar != nil {
+			writeType(buf, tpar, qf, visited)
 		} else {
 			buf.WriteString(p.name)
 		}