Only extract transparent-alias versions of types when necessary

go/extractor/extractor.go

@@ -1513,17 +1513,96 @@ func extractType(tw *trap.Writer, tp types.Type) trap.Label {
 	return extractTypeWithFlags(tw, tp, false)
 }
 
+func containsAliasTypes(tp types.Type) bool {
+	switch tp := tp.(type) {
+	case *types.Basic:
+		return false
+	case *types.Array:
+		return containsAliasTypes(tp.Elem())
+	case *types.Slice:
+		return containsAliasTypes(tp.Elem())
+	case *types.Struct:
+		for i := 0; i < tp.NumFields(); i++ {
+			field := tp.Field(i)
+			if containsAliasTypes(field.Type()) {
+				return true
+			}
+		}
+		return false
+	case *types.Pointer:
+		return containsAliasTypes(tp.Elem())
+	case *types.Interface:
+		for i := 0; i < tp.NumMethods(); i++ {
+			meth := tp.Method(i)
+			if containsAliasTypes(meth.Type()) {
+				return true
+			}
+		}
+		for i := 0; i < tp.NumEmbeddeds(); i++ {
+			if containsAliasTypes(tp.EmbeddedType(i)) {
+				return true
+			}
+		}
+		return false
+	case *types.Tuple:
+		for i := 0; i < tp.Len(); i++ {
+			if containsAliasTypes(tp.At(i).Type()) {
+				return true
+			}
+		}
+		return false
+	case *types.Signature:
+		params, results := tp.Params(), tp.Results()
+		if params != nil {
+			for i := 0; i < params.Len(); i++ {
+				param := params.At(i)
+				if containsAliasTypes(param.Type()) {
+					return true
+				}
+			}
+		}
+		if results != nil {
+			for i := 0; i < results.Len(); i++ {
+				result := results.At(i)
+				if containsAliasTypes(result.Type()) {
+					return true
+				}
+			}
+		}
+		return false
+	case *types.Map:
+		return containsAliasTypes(tp.Key()) || containsAliasTypes(tp.Elem())
+	case *types.Chan:
+		return containsAliasTypes(tp.Elem())
+	case *types.Named:
+		return false
+	case *types.TypeParam:
+		return false
+	case *types.Union:
+		for i := 0; i < tp.Len(); i++ {
+			term := tp.Term(i)
+			if containsAliasTypes(term.Type()) {
+				return true
+			}
+		}
+		return false
+	case *types.Alias:
+		return true
+	default:
+		log.Fatalf("unexpected type %T", tp)
+	}
+	return false
+}
+
 func extractTypeWithFlags(tw *trap.Writer, tp types.Type, transparentAliases bool) trap.Label {
 	lbl, exists := getTypeLabelWithFlags(tw, tp, transparentAliases)
 	if !exists {
-		if !transparentAliases {
+		if !transparentAliases && containsAliasTypes(tp) {
 			// Ensure the (deep) underlying type is also extracted, so that it is
 			// possible to implement deepUnalias in QL.
 			// For example, if we had type A = int and type B = string, we would need
 			// to extract map[string]int so that deepUnalias(map[B]A) has a real member
 			// of @type to return.
-			//
-			// TODO: consider using a newtype to do this instead.
 			extractTypeWithFlags(tw, tp, true)
 		}
 		var kind int
@@ -1709,6 +1788,11 @@ func getTypeLabelWithFlags(tw *trap.Writer, tp types.Type, transparentAliases bo
 	typeLabelKey := trap.TypeLabelsKey{Type: tp, TransparentAliases: transparentAliases}
 	lbl, exists := tw.Labeler.TypeLabels[typeLabelKey]
 	if !exists {
+		if transparentAliases && !containsAliasTypes(tp) {
+			// No aliases involved, so the label is the same as the non-transparent version
+			// of the same type.
+			return getTypeLabelWithFlags(tw, tp, false)
+		}
 		switch tp := tp.(type) {
 		case *types.Basic:
 			lbl = tw.Labeler.GlobalID(fmt.Sprintf("%d;basictype", tp.Kind()))