fix #5658

tests/types/thard_tyforward.nim

@@ -0,0 +1,22 @@
+type
+  Bar[T] = Foo[T, T]
+  Baz[T] = proc (x: Foo[T, T])
+  
+  GenericAlias[T] = Foo[T]
+  GenericAlias2[T] = Foo[Baz[T]]
+  
+  Concrete1 = Foo[int, float]
+  Concrete2 = proc(x: proc(a: Foo[int, float]))
+  
+  Foo[T, U] = object
+    x: T
+    y: U
+
+var
+  x1: Bar[float]
+  x2: Baz[int]
+  x3: Concrete1
+  x4: Concrete2
+  x5: GenericAlias[int]
+  x6: GenericAlias2[string]
+