go/types, types2: introduce _Alias type node

[gostls13.git] / src / go / types / typexpr.go

diff --git a/src/go/types/typexpr.go b/src/go/types/typexpr.go
index d35c6d1263798854135ad0e014291f91691e1e51..5bc5a1f3ac72565c0e590f34391ecc87fd62ea74 100644 (file)
--- a/src/go/types/typexpr.go
+++ b/src/go/types/typexpr.go
@@ -95,7 +95,7 @@ func (check *Checker) ident(x *operand, e *ast.Ident, def *TypeName, wantType bo
                x.mode = constant_
 
        case *TypeName:
-               if check.isBrokenAlias(obj) {
+               if !check.conf._EnableAlias && check.isBrokenAlias(obj) {
                        check.errorf(e, InvalidDeclCycle, "invalid use of type alias %s in recursive type (see go.dev/issue/50729)", obj.name)
                        return
                }
@@ -394,7 +394,13 @@ func (check *Checker) typInternal(e0 ast.Expr, def *TypeName) (T Type) {
 func setDefType(def *TypeName, typ Type) {
        if def != nil {
                switch t := def.typ.(type) {
-               // case *_Alias:
+               case *_Alias:
+                       // t.fromRHS should always be set, either to an invalid type
+                       // in the beginning, or to typ in certain cyclic declarations.
+                       if t.fromRHS != Typ[Invalid] && t.fromRHS != typ {
+                               panic(sprintf(nil, nil, true, "t.fromRHS = %s, typ = %s\n", t.fromRHS, typ))
+                       }
+                       t.fromRHS = typ
                case *Basic:
                        assert(t == Typ[Invalid])
                case *Named: