From 4ac5ec8b048e4e1cab7d418b92949b54733836ed Mon Sep 17 00:00:00 2001
From: pca006132 <jl@m-labs.hk>
Date: Mon, 21 Dec 2020 13:53:59 +0800
Subject: [PATCH] virtual class

---
 toy-impl/inference.py  | 19 ++++++++++++++++---
 toy-impl/parse_expr.py |  2 +-
 toy-impl/test_expr.py  | 23 +++++++++++++++++++++++
 3 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/toy-impl/inference.py b/toy-impl/inference.py
index 30157e9..1d4441d 100644
--- a/toy-impl/inference.py
+++ b/toy-impl/inference.py
@@ -48,8 +48,20 @@ def find_subst(ctx: dict[str, Type],
         else:
             return f"{a} can take values other than {b}"
 
-    # TODO: virtual type is not handled currently
-    # we need to access the class dictionary to handle this
+    if isinstance(b, VirtualClassType):
+        if isinstance(a, ClassType):
+            parents = [a]
+        elif isinstance(a, VirtualClassType):
+            parents = [a.base]
+        else:
+            raise CustomError("cannot substitute non-class-type into virtual class")
+        while len(parents) > 0:
+            current = parents.pop(0)
+            if current == b.base:
+                return sub
+            else:
+                parents += current.parents
+
     if type(a) == type(b):
         if isinstance(a, ParametricType):
             if len(a.params) != len(b.params):
@@ -62,9 +74,10 @@ def find_subst(ctx: dict[str, Type],
             if a.name == b.name:
                 return sub
         elif isinstance(a, VirtualClassType):
-            return find_subst(a.base, b.base)
+            return find_subst(ctx, sub, a.base, b.base)
         else:
             raise Exception()
+
     return f"{a} != {b}"
 
 def resolve_call(obj,
diff --git a/toy-impl/parse_expr.py b/toy-impl/parse_expr.py
index 7e01072..4fd3047 100644
--- a/toy-impl/parse_expr.py
+++ b/toy-impl/parse_expr.py
@@ -162,7 +162,7 @@ def parse_call(ctx: Context,
     obj = None
     f = None
     if isinstance(node.func, ast.Attribute):
-        obj = parse_expr(node.func.value)
+        obj = parse_expr(ctx, sym_table, node.func.value)
         f = node.func.attr
     elif isinstance(node.func, ast.Name):
         f = node.func.id
diff --git a/toy-impl/test_expr.py b/toy-impl/test_expr.py
index a72c39c..102f928 100644
--- a/toy-impl/test_expr.py
+++ b/toy-impl/test_expr.py
@@ -111,8 +111,21 @@ class Foo:
     def __ge__(self, other: Foo) -> bool:
         pass
 
+    def foo(self) -> self:
+        pass
+
+class Bar(Foo):
+    def foo(self) -> self:
+        pass
+
 def find(ls: list[I], x: I) -> int32:
     pass
+
+def foobar(a: virtual[Foo]) -> virtual[Foo]:
+    pass
+
+def bar(a: virtual[Bar]) -> virtual[Bar]:
+    pass
 """
 ctx, _ = parse_top_level(ctx, ast.parse(test_classes))
 test_expr('Foo(1) + Foo(1)', {})
@@ -120,3 +133,13 @@ test_expr('Foo(1) + Foo(1) < Foo(2) + Foo(3) < Foo(4)', {})
 test_expr('find([1, 2, 3], 1)', {})
 test_expr('find([], 1)', {})
 
+test_expr('Foo(1).foo()', {})
+test_expr('foobar(1)', {})
+test_expr('foobar(Foo(1))', {})
+test_expr('foobar(Bar())', {})
+test_expr('foobar(foobar(Foo(1)))', {})
+test_expr('bar(foobar(Foo(1)))', {})
+test_expr('foobar(bar(Foo(1)))', {})
+test_expr('foobar(bar(Bar()))', {})
+
+