Apply generic class fix also to non-callable types (python#8030)

ilevkivskyi · web-flow · commit b5f4df9862f4 · 2019-11-29T14:16:51.000Z
This is a follow up for python#8021, that applies the fix also to non-callable types. Currently non-callable types are still wrong: ```python R = TypeVar('R') T = TypeVar('T') # Can be any decorator that makes type non-callable. def classproperty(f: Callable[..., R]) -> R: ... class C(Generic[T]): @classproperty def test(self) -> T: ... x: C[int] y: Type[C[int]] reveal_type(x.test) # Revealed type is 'int', OK reveal_type(y.test) # Revealed type is 'T' ??? ``` So, python#7724 strikes again. It turns out there is not only duplicated logic for attribute kinds (decorators vs normal methods), but also for callable vs non-callable types. In latter case we still need to expand the type (like in other places, e.g., `analyze_var`).
diff --git a/mypy/checkmember.py b/mypy/checkmember.py
@@ -764,8 +764,8 @@ def analyze_class_attribute_access(itype: Instance,
         t = get_proper_type(t)
         if isinstance(t, FunctionLike) and is_classmethod:
             t = check_self_arg(t, mx.self_type, False, mx.context, name, mx.msg)
-        result = add_class_tvars(t, itype, isuper, is_classmethod,
-                                 mx.builtin_type, mx.self_type, original_vars=original_vars)
+        result = add_class_tvars(t, isuper, is_classmethod,
+                                 mx.self_type, original_vars=original_vars)
         if not mx.is_lvalue:
             result = analyze_descriptor_access(mx.original_type, result, mx.builtin_type,
                                                mx.msg, mx.context, chk=mx.chk)
@@ -808,9 +808,8 @@ def analyze_class_attribute_access(itype: Instance,
         return typ
 
 
-def add_class_tvars(t: ProperType, itype: Instance, isuper: Optional[Instance],
+def add_class_tvars(t: ProperType, isuper: Optional[Instance],
                     is_classmethod: bool,
-                    builtin_type: Callable[[str], Instance],
                     original_type: Type,
                     original_vars: Optional[List[TypeVarDef]] = None) -> Type:
     """Instantiate type variables during analyze_class_attribute_access,
@@ -821,12 +820,18 @@ class A(Generic[T]):
         def foo(cls: Type[Q]) -> Tuple[T, Q]: ...
 
     class B(A[str]): pass
-
     B.foo()
 
-    original_type is the value of the type B in the expression B.foo() or the corresponding
-    component in case if a union (this is used to bind the self-types); original_vars are type
-    variables of the class callable on which the method was accessed.
+    Args:
+        t: Declared type of the method (or property)
+        isuper: Current instance mapped to the superclass where method was defined, this
+            is usually done by map_instance_to_supertype()
+        is_classmethod: True if this method is decorated with @classmethod
+        original_type: The value of the type B in the expression B.foo() or the corresponding
+            component in case of a union (this is used to bind the self-types)
+        original_vars: Type variables of the class callable on which the method was accessed
+    Returns:
+        Expanded method type with added type variables (when needed).
     """
     # TODO: verify consistency between Q and T
 
@@ -851,10 +856,12 @@ class B(A[str]): pass
             t = cast(CallableType, expand_type_by_instance(t, isuper))
         return t.copy_modified(variables=tvars + t.variables)
     elif isinstance(t, Overloaded):
-        return Overloaded([cast(CallableType, add_class_tvars(item, itype, isuper, is_classmethod,
-                                                              builtin_type, original_type,
+        return Overloaded([cast(CallableType, add_class_tvars(item, isuper,
+                                                              is_classmethod, original_type,
                                                               original_vars=original_vars))
                            for item in t.items()])
+    if isuper is not None:
+        t = cast(ProperType, expand_type_by_instance(t, isuper))
     return t
 
 
diff --git a/mypy/expandtype.py b/mypy/expandtype.py
@@ -19,6 +19,7 @@ def expand_type(typ: Type, env: Mapping[TypeVarId, Type]) -> Type:
 def expand_type_by_instance(typ: Type, instance: Instance) -> Type:
     """Substitute type variables in type using values from an Instance.
     Type variables are considered to be bound by the class declaration."""
+    # TODO: use an overloaded signature? (ProperType stays proper after expansion.)
     if instance.args == []:
         return typ
     else:
diff --git a/test-data/unit/check-generics.test b/test-data/unit/check-generics.test
@@ -2337,3 +2337,57 @@ class Test():
     reveal_type(MakeTwoAppliedSubAbstract()(2)) # N: Revealed type is '__main__.TwoTypes[builtins.str, builtins.int*]'
     reveal_type(MakeTwoGenericSubAbstract[str]()('foo')) # N: Revealed type is '__main__.TwoTypes[builtins.str, builtins.str*]'
     reveal_type(MakeTwoGenericSubAbstract[str]()(2)) # N: Revealed type is '__main__.TwoTypes[builtins.str, builtins.int*]'
+
+[case testGenericClassPropertyBound]
+from typing import Generic, TypeVar, Callable, Type, List, Dict
+
+T = TypeVar('T')
+U = TypeVar('U')
+
+def classproperty(f: Callable[..., U]) -> U: ...
+
+class C(Generic[T]):
+    @classproperty
+    def test(self) -> T: ...
+
+class D(C[str]): ...
+class E1(C[T], Generic[T, U]): ...
+class E2(C[U], Generic[T, U]): ...
+class G(C[List[T]]): ...
+
+x: C[int]
+y: Type[C[int]]
+reveal_type(x.test)  # N: Revealed type is 'builtins.int*'
+reveal_type(y.test)  # N: Revealed type is 'builtins.int*'
+
+xd: D
+yd: Type[D]
+reveal_type(xd.test)  # N: Revealed type is 'builtins.str*'
+reveal_type(yd.test)  # N: Revealed type is 'builtins.str*'
+
+ye1: Type[E1[int, str]]
+ye2: Type[E2[int, str]]
+reveal_type(ye1.test)  # N: Revealed type is 'builtins.int*'
+reveal_type(ye2.test)  # N: Revealed type is 'builtins.str*'
+
+xg: G[int]
+yg: Type[G[int]]
+reveal_type(xg.test)  # N: Revealed type is 'builtins.list*[builtins.int*]'
+reveal_type(yg.test)  # N: Revealed type is 'builtins.list*[builtins.int*]'
+
+class Sup:
+    attr: int
+S = TypeVar('S', bound=Sup)
+
+def func(tp: Type[C[S]]) -> S:
+    reveal_type(tp.test.attr)  # N: Revealed type is 'builtins.int'
+
+    reg: Dict[S, G[S]]
+    reveal_type(reg[tp.test])  # N: Revealed type is '__main__.G*[S`-1]'
+    reveal_type(reg[tp.test].test)  # N: Revealed type is 'builtins.list*[S`-1]'
+
+    if bool():
+        return tp.test
+    else:
+        return reg[tp.test].test[0]
+[builtins fixtures/dict.pyi]
