Make bare None a partial type again

python · ddfisher · Jul 22, 2017 · Jul 22, 2017 · 111619ca81aaa849ef89c9db1a7e5d95f8d65a58
commit 111619ca81aaa849ef89c9db1a7e5d95f8d65a58
diff --git a/mypy/checker.py b/mypy/checker.py
@@ -2545,12 +2545,8 @@ def enter_partial_types(self) -> Iterator[None]:
         partial_types = self.partial_types.pop()
         if not self.current_node_deferred:
             for var, context in partial_types.items():
-                if isinstance(var.type, PartialType) and var.type.type is None:
-                    # None partial type: assume variable is intended to have type None
-                    var.type = NoneTyp()
-                else:
-                    self.msg.fail(messages.NEED_ANNOTATION_FOR_VAR, context)
-                    var.type = AnyType()
+                self.msg.fail(messages.NEED_ANNOTATION_FOR_VAR, context)
+                var.type = AnyType()
 
     def find_partial_types(self, var: Var) -> Optional[Dict[Var, Context]]:
         for partial_types in reversed(self.partial_types):
@@ -3144,10 +3140,6 @@ def is_valid_inferred_type(typ: Type) -> bool:
     incompletely defined (i.e. contain UninhabitedType) are invalid.
     """
     if is_same_type(typ, NoneTyp()):
-        # With strict Optional checking, we *may* eventually infer NoneTyp, but
-        # we only do that if we can't infer a specific Optional type.  This
-        # resolution happens in leave_partial_types when we pop a partial types
-        # scope.
         return False
     return is_valid_inferred_type_component(typ)
 

diff --git a/mypy/checkexpr.py b/mypy/checkexpr.py
@@ -2390,6 +2390,7 @@ def visit_yield_from_expr(self, e: YieldFromExpr, allow_none_return: bool = Fals
 
         if not allow_none_return and isinstance(expr_type, NoneTyp):
             self.chk.msg.does_not_return_value(None, e)
+            return AnyType(implicit=True)
         return expr_type
 
     def visit_temp_node(self, e: TempNode) -> Type:

diff --git a/test-data/unit/check-inference.test b/test-data/unit/check-inference.test
@@ -246,16 +246,16 @@ class C: pass
 [case testInferringLvarTypesInMultiDefWithNoneTypes]
 import typing
 def f() -> None:
-    a, b = A(), None
-    c, d = None, A()
+    a, b = A(), None  # E: Need type annotation for variable
+    c, d = None, A()  # E: Need type annotation for variable
 
 class A: pass
 [out]
 
 [case testInferringLvarTypesInNestedTupleAssignmentWithNoneTypes]
 import typing
 def f() -> None:
-    a1, (a2, b) = A(), (A(), None)
+    a1, (a2, b) = A(), (A(), None)  # E: Need type annotation for variable
 
 class A: pass
 [out]
@@ -874,7 +874,7 @@ for x in [A()]:
     b = x # E: Incompatible types in assignment (expression has type "A", variable has type "B")
     a = x
 
-for y in []:
+for y in []:  # E: Need type annotation for variable
     a = y
     reveal_type(y)  # E: Revealed type is 'builtins.None'
 
@@ -896,7 +896,7 @@ for xx, yy, zz in [(A(), B())]: # Fail
     pass
 for xx, (yy, zz) in [(A(), B())]: # Fail
     pass
-for xxx, yyy in [(None, None)]:
+for xxx, yyy in [(None, None)]: # Needs type annotation
     pass
 
 class A: pass
@@ -909,6 +909,7 @@ main:5: error: Incompatible types in assignment (expression has type "B", variab
 main:6: error: Incompatible types in assignment (expression has type "C", variable has type "A")
 main:10: error: Need more than 2 values to unpack (3 expected)
 main:12: error: '__main__.B' object is not iterable
+main:14: error: Need type annotation for variable
 
 [case testInferenceOfFor3]
 
@@ -920,7 +921,7 @@ for x, y in [[A()]]:
     a = x
     a = y
 
-for e, f in [[]]:
+for e, f in [[]]:  # E: Need type annotation for variable
     reveal_type(e)  # E: Revealed type is 'builtins.None'
     reveal_type(f)  # E: Revealed type is 'builtins.None'
 
@@ -1446,7 +1447,7 @@ def f() -> None:
 [case testLvarInitializedToNoneWithoutType]
 import typing
 def f() -> None:
-    a = None
+    a = None  # E: Need type annotation for variable
     a.x() # E: None has no attribute "x"
 [out]
 
@@ -1494,13 +1495,13 @@ if object():
 
 [case testPartiallyInitializedVariableDoesNotEscapeScope1]
 def f() -> None:
-    x = None
+    x = None  # E: Need type annotation for variable
     reveal_type(x)  # E: Revealed type is 'builtins.None'
 x = 1
 [out]
 
 [case testPartiallyInitializedVariableDoesNotEscapeScope2]
-x = None
+x = None  # E: Need type annotation for variable
 def f() -> None:
     x = None
     x = 1
@@ -1523,8 +1524,8 @@ class A:
         self.x = 1
         self.x()
 [out]
-main:6: error: Incompatible types in assignment (expression has type "int", variable has type None)
-main:7: error: None not callable
+main:3: error: Need type annotation for variable
+main:7: error: "int" not callable
 
 [case testGlobalInitializedToNoneSetFromFunction]
 a = None
@@ -1553,6 +1554,7 @@ class A:
             pass
 [builtins fixtures/for.pyi]
 [out]
+main:3: error: Need type annotation for variable
 main:5: error: None has no attribute "__iter__"
 
 [case testPartialTypeErrorSpecialCase2]
@@ -1574,6 +1576,7 @@ class A:
             pass
 [builtins fixtures/for.pyi]
 [out]
+main:2: error: Need type annotation for variable
 main:4: error: None has no attribute "__iter__"
 
 

diff --git a/test-data/unit/check-modules.test b/test-data/unit/check-modules.test
@@ -511,7 +511,7 @@ x = 1
 
 [case testAssignToFuncDefViaImport]
 from m import *  # E: Incompatible import of "x" (imported name has type "int", local name has type "str")
-f = None
+f = None  # E: Need type annotation for variable
 x = ''
 [file m.py]
 def f(): pass

diff --git a/test-data/unit/check-optional.test b/test-data/unit/check-optional.test
@@ -1,7 +1,7 @@
 -- Tests for strict Optional behavior
 
 [case testImplicitNoneType]
-x = None
+x = None  # E: Need type annotation for variable
 x()  # E: None not callable
 
 [case testExplicitNoneType]
@@ -285,7 +285,7 @@ main:4: error: Incompatible return value type (got "Optional[T]", expected "T")
 
 [case testNoneOrStringIsString]
 def f() -> str:
-    a = None
+    a = None  # type: None

1E0A
     b = ''
     return a or b
 [out]
@@ -294,7 +294,7 @@ def f() -> str:
 from typing import TypeVar
 T = TypeVar('T')
 def f(b: T) -> T:
-    a = None
+    a = None  # type: None
     return a or b
 [out]
 
@@ -305,7 +305,7 @@ def f() -> Generator[None, None, None]:
 [out]
 
 [case testNoneAndStringIsNone]
-a = None
+a = None  # type: None
 b = "foo"
 reveal_type(a and b)  # E: Revealed type is 'builtins.None'
 
@@ -559,7 +559,7 @@ x is not None and x + '42'  # E: Unsupported operand types for + ("int" and "str
 [case testInvalidBooleanBranchIgnored]
 from typing import Optional
 
-x = None
+x = None  # type: None
 x is not None and x + 42
 [builtins fixtures/isinstance.pyi]
 

diff --git a/test-data/unit/check-tuples.test b/test-data/unit/check-tuples.test
@@ -633,13 +633,15 @@ for x in t:
 [case testForLoopOverEmptyTuple]
 import typing
 t = ()
-for x in t: pass
+for x in t:  # E: Need type annotation for variable
+  pass
 [builtins fixtures/for.pyi]
 
 [case testForLoopOverNoneValuedTuple]
 import typing
 t = ()
-for x in None, None: pass
+for x in None, None:  # E: Need type annotation for variable
+  pass
 [builtins fixtures/for.pyi]
 
 [case testForLoopOverTupleAndSubtyping]