(unrelated tidy up) resolveTypeAlias not needed

`types.Unalias` already does the same thing

Author: owen-mc

go/extractor/extractor.go

@@ -1582,18 +1582,10 @@ func isAlias(tp types.Type) bool {
 	return ok
 }
 
-// If the given type is a type alias, this function resolves it to its underlying type.
-func resolveTypeAlias(tp types.Type) types.Type {
-	if isAlias(tp) {
-		return types.Unalias(tp) // tp.Underlying()
-	}
-	return tp
-}
-
 // extractType extracts type information for `tp` and returns its associated label;
 // types are only extracted once, so the second time `extractType` is invoked it simply returns the label
 func extractType(tw *trap.Writer, tp types.Type) trap.Label {
-	tp = resolveTypeAlias(tp)
+	tp = types.Unalias(tp)
 	lbl, exists := getTypeLabel(tw, tp)
 	if !exists {
 		var kind int
@@ -1771,7 +1763,7 @@ func extractType(tw *trap.Writer, tp types.Type) trap.Label {
 // is constructed from their globally unique ID. This prevents cyclic type keys
 // since type recursion in Go always goes through defined types.
 func getTypeLabel(tw *trap.Writer, tp types.Type) (trap.Label, bool) {
-	tp = resolveTypeAlias(tp)
+	tp = types.Unalias(tp)
 	lbl, exists := tw.Labeler.TypeLabels[tp]
 	if !exists {
 		switch tp := tp.(type) {