Guido comments and polish

mypy/fastparse.py

@@ -3,7 +3,7 @@
 
 from typing import Tuple, Union, TypeVar, Callable, Sequence, Optional, Any, cast, List, Set
 from mypy.sharedparse import (
-    special_function_elide_names, argument_elide_name, is_overload_part,
+    special_function_elide_names, argument_elide_name,
 )
 from mypy.nodes import (
     MypyFile, Node, ImportBase, Import, ImportAll, ImportFrom, FuncDef,

mypy/fastparse2.py

@@ -19,7 +19,7 @@
 
 from typing import Tuple, Union, TypeVar, Callable, Sequence, Optional, Any, cast, List, Set
 from mypy.sharedparse import (
-    special_function_elide_names, argument_elide_name, is_overload_part,
+    special_function_elide_names, argument_elide_name,
 )
 from mypy.nodes import (
     MypyFile, Node, ImportBase, Import, ImportAll, ImportFrom, FuncDef, OverloadedFuncDef,

mypy/parse.py

@@ -15,7 +15,7 @@
     EllipsisToken
 )
 from mypy.sharedparse import (
-    special_function_elide_names, argument_elide_name, is_overload_part,
+    special_function_elide_names, argument_elide_name,
 )
 from mypy.nodes import (
     MypyFile, Import, ImportAll, ImportFrom, FuncDef, OverloadedFuncDef,

mypy/semanal.py

@@ -422,9 +422,14 @@ def is_defined_type_var(self, tvar: str, context: Context) -> bool:
         return self.lookup_qualified(tvar, context).kind == BOUND_TVAR
 
     def visit_overloaded_func_def(self, defn: OverloadedFuncDef) -> None:
-        # Decide whether to analyze this as a property or an overload.
-        # If an overload, and we're outside a stub, find the impl and set it.
-        # Remove it from the item list, it's special.
+        # OverloadedFuncDef refers to any legitimate situation where you have
+        # more than one declaration for the same function in a row.  This occurs
+        # with a @property with a setter or a deleter, and for a classic
+        # @overload.
+
+        # Decide whether to analyze this as a property or an overload.  If an
+        # overload, and we're outside a stub, find the impl and set it.  Remove
+        # the impl from the item list, it's special.
         t = []  # type: List[CallableType]
         non_overload_indexes = []
         for i, item in enumerate(defn.items):

mypy/sharedparse.py

@@ -1,7 +1,5 @@
 from typing import Union, Tuple
 
-from mypy.nodes import Decorator, NameExpr, Statement, MemberExpr, Expression
-
 """Shared logic between our three mypy parser files."""
 
 
@@ -100,15 +98,3 @@ def special_function_elide_names(name: str) -> bool:
 
 def argument_elide_name(name: Union[str, Tuple, None]) -> bool:
     return isinstance(name, str) and name.startswith("__")
-
-
-def _is_overload_decorator(dec: Expression) -> bool:
-    if isinstance(dec, NameExpr) and dec.name in {'overload', 'property', 'abstractproperty'}:
-        return True
-    elif isinstance(dec, MemberExpr) and dec.name in {'setter', 'deleter'}:
-        return True
-    return False
-
-
-def is_overload_part(stmt: Decorator) -> bool:
-    return any(_is_overload_decorator(dec) for dec in stmt.decorators)

test-data/unit/check-overloading.test

@@ -8,10 +8,7 @@ def f(x: 'A') -> 'B': ...
 def f(x: 'B') -> 'A': ...
 
 def f(x: Any) -> Any:
-   if isinstance(x, A):
-       return B()
-   else:
-       return A()
+    pass
 
 reveal_type(f(A())) # E: Revealed type is '__main__.B'
 reveal_type(f(B())) # E: Revealed type is '__main__.A'
@@ -20,6 +17,30 @@ class A: pass
 class B: pass
 [builtins fixtures/isinstance.pyi]
 
+[case testTypeCheckOverloadWithImplementationPy2]
+# flags: --python-version 2.7
+
+from typing import overload
+@overload
+def f(x):
+    # type: (A) -> B
+    pass
+
+@overload
+def f(x):
+    # type: (B) -> A
+    pass
+
+def f(x):
+    pass
+
+reveal_type(f(A()))  # E: Revealed type is '__main__.B'
+reveal_type(f(B()))  # E: Revealed type is '__main__.A'
+
+class A: pass
+class B: pass
+[builtins fixtures/isinstance.pyi]
+
 [case testTypeCheckOverloadWithImplementationError]
 from typing import overload, Any
 
@@ -29,15 +50,20 @@ def f(x: 'A') -> 'B': ...
 def f(x: 'B') -> 'A': ...
 
 def f(x: Any) -> Any:
-   if isinstance(x, A):
-       y = x
-       y = B() # E: Incompatible types in assignment (expression has type "B", variable has type "A")
-       return y
-   else:
-       return A()
+    foo = 1
+    foo = "bar"  # E: Incompatible types in assignment (expression has type "str", variable has type "int")
 
-reveal_type(f(A())) # E: Revealed type is '__main__.B'
-reveal_type(f(B())) # E: Revealed type is '__main__.A'
+@overload
+def g(x: 'A') -> 'B': ...
+@overload
+def g(x: 'B') -> 'A': ...
+
+def g(x):
+    foo = 1
+    foo = "bar"
+
+reveal_type(f(A()))  # E: Revealed type is '__main__.B'
+reveal_type(f(B()))  # E: Revealed type is '__main__.A'
 
 class A: pass
 class B: pass
@@ -57,10 +83,7 @@ def f(x: 'A') -> 'B': ...
 def f(x: 'B') -> 'A': ...
 
 def f(x: 'A') -> Any: # E: Overloaded function implementation cannot accept all possible arguments of signature 2
-   if x is a:
-       return B()
-   else:
-       return A()
+    pass
 
 reveal_type(f(A())) # E: Revealed type is '__main__.B'
 reveal_type(f(B())) # E: Revealed type is '__main__.A'

test-data/unit/semanal-errors.test

@@ -1082,7 +1082,7 @@ from typing import overload
 def dec(x): pass
 @dec
 def f(): pass
-@dec # E: Name 'f' already defined
+@dec  # E: Name 'f' already defined
 def f(): pass
 [out]