optional virtual type annotation

hm-inference/ast_visitor.py

@@ -80,11 +80,14 @@ class Visitor(ast.NodeVisitor):
 
     def visit_Call(self, node):
         if ast.get_source_segment(self.source, node.func) == 'virtual':
-            if len(node.args) != 2:
+            if len(node.args) > 2 or len(node.args) < 1:
                 raise UnificationError('Incorrect argument number for virtual')
             self.visit(node.args[0])
-            ty = self.type_parser(ast.get_source_segment(self.source,
-                                                         node.args[1]))
+            if len(node.args) == 2:
+                ty = self.type_parser(ast.get_source_segment(self.source,
+                                                             node.args[1]))
+            else:
+                ty = TVar()
             self.virtuals.append((node.args[0].type, ty))
             node.type = TVirtual(ty)
             return

hm-inference/nac3_types.py

@@ -377,7 +377,7 @@ class TObj(Type):
 
 
 class TVirtual(Type):
-    def __init__(self, obj: TObj):
+    def __init__(self, obj: Type):
         self.obj = obj
         self.checked = False
 

hm-inference/test.py

@@ -5,13 +5,13 @@ from nac3_types import *
 from primitives import *
 
 src = """
-a = 1 // 1
+a = virtual(bar)
+b = test_virtual(a)
 
-if 1 <= 1 < 2:
-    pass
+a = virtual(foo)
+b = test_virtual(a)
 
-b = test_virtual(virtual(bar, Foo))
-b = test_virtual(virtual(foo, Foo))
+c = virtual(foo, Foo)
 """
 
 foo = TObj('Foo', {
@@ -53,7 +53,7 @@ v.visit(ast.parse(src))
 
 for a, b in v.virtuals:
     assert isinstance(a, TObj)
-    assert b is a or b in a.parents
+    assert b.find() is a or b.find() in a.parents
 
 print('-----------')
 print('calls')