cmd/compile/internal/types2: implement TypeList.String (debugging support)

Change-Id: Iaa203def3dac94a7d5ff6120e89315c3d7977ee1
Reviewed-on: https://go-review.googlesource.com/c/go/+/345471
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

3 files changed, 14 insertions, 7 deletions

diff --git a/src/cmd/compile/internal/types2/instantiate.go b/src/cmd/compile/internal/types2/instantiate.go
index f9cde24dfc..4113d248b8 100644
--- a/src/cmd/compile/internal/types2/instantiate.go
+++ b/src/cmd/compile/internal/types2/instantiate.go
@@ -75,7 +75,7 @@ func Instantiate(env *Environment, typ Type, targs []Type, validate bool) (Type,
 func (check *Checker) instantiate(pos syntax.Pos, typ Type, targs []Type, posList []syntax.Pos) (res Type) {
 	assert(check != nil)
 	if check.conf.Trace {
-		check.trace(pos, "-- instantiating %s with %s", typ, typeListString(targs))
+		check.trace(pos, "-- instantiating %s with %s", typ, NewTypeList(targs))
 		check.indent++
 		defer func() {
 			check.indent--
diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go
index ff8dd13b6d..7c33e7ade4 100644
--- a/src/cmd/compile/internal/types2/subst.go
+++ b/src/cmd/compile/internal/types2/subst.go
@@ -281,12 +281,6 @@ func instantiatedHash(typ *Named, targs []Type) string {
 	return string(res[:i])
 }
 
-func typeListString(list []Type) string {
-	var buf bytes.Buffer
-	writeTypeList(&buf, list, nil, nil)
-	return buf.String()
-}
-
 // typOrNil is like typ but if the argument is nil it is replaced with Typ[Invalid].
 // A nil type may appear in pathological cases such as type T[P any] []func(_ T([]_))
 // where an array/slice element is accessed before it is set up.
diff --git a/src/cmd/compile/internal/types2/typelists.go b/src/cmd/compile/internal/types2/typelists.go
index 3258a5e9f8..c3befb077f 100644
--- a/src/cmd/compile/internal/types2/typelists.go
+++ b/src/cmd/compile/internal/types2/typelists.go
@@ -4,6 +4,8 @@
 
 package types2
 
+import "bytes"
+
 // TParamList holds a list of type parameters.
 type TParamList struct{ tparams []*TypeParam }
 
@@ -52,6 +54,17 @@ func (l *TypeList) list() []Type {
 	return l.types
 }
 
+func (l *TypeList) String() string {
+	if l == nil || len(l.types) == 0 {
+		return "[]"
+	}
+	var buf bytes.Buffer
+	buf.WriteByte('[')
+	writeTypeList(&buf, l.types, nil, nil)
+	buf.WriteByte(']')
+	return buf.String()
+}
+
 // ----------------------------------------------------------------------------
 // Implementation