Fix overload interaction with Any (#5233)

Fixes #5232

This also makes few minor amendments to pythoneval tests.

Author: ilevkivskyi

mypy/checkexpr.py

@@ -1304,8 +1304,10 @@ def infer_overload_return_type(self,
             return None
         elif any_causes_overload_ambiguity(matches, return_types, arg_types, arg_kinds, arg_names):
             # An argument of type or containing the type 'Any' caused ambiguity.
-            if all(is_subtype(ret_type, return_types[-1]) for ret_type in return_types[:-1]):
-                # The last match is a supertype of all the previous ones, so it's safe
+            if all(is_subtype(ret_type, return_types[-1]) and
+                   is_subtype(return_types[-1], ret_type)
+                   for ret_type in return_types[:-1]):
+                # The last match is mutually compatible with all previous ones, so it's safe
                 # to return that inferred type.
                 return return_types[-1], inferred_types[-1]
             else:

test-data/unit/check-overloading.test

@@ -1276,7 +1276,7 @@ def f(x: object) -> object: ...
 def f(x): pass
 
 a: Any
-reveal_type(f(a))  # E: Revealed type is 'builtins.object'
+reveal_type(f(a))  # E: Revealed type is 'Any'
 
 [case testOverloadWithOverlappingItemsAndAnyArgument2]
 from typing import overload, Any
@@ -1288,7 +1288,7 @@ def f(x: float) -> float: ...
 def f(x): pass
 
 a: Any
-reveal_type(f(a))  # E: Revealed type is 'builtins.float'
+reveal_type(f(a))  # E: Revealed type is 'Any'
 
 [case testOverloadWithOverlappingItemsAndAnyArgument3]
 from typing import overload, Any
@@ -1312,17 +1312,16 @@ def f(x: object, y: int, z: str) -> object: ...
 def f(x): pass
 
 a: Any
-# Any causes ambiguity; we fall back to returning object since it's a
-# supertype of int
-reveal_type(f(a, 1, ''))  # E: Revealed type is 'builtins.object'
+# Any causes ambiguity
+reveal_type(f(a, 1, ''))  # E: Revealed type is 'Any'
 # Any causes no ambiguity
 reveal_type(f(1, a, a))  # E: Revealed type is 'builtins.int'
 reveal_type(f('', a, a))  # E: Revealed type is 'builtins.object'
 # Like above, but use keyword arguments.
-reveal_type(f(y=1, z='', x=a))  # E: Revealed type is 'builtins.object'
+reveal_type(f(y=1, z='', x=a))  # E: Revealed type is 'Any'
 reveal_type(f(y=a, z='', x=1))  # E: Revealed type is 'builtins.int'
 reveal_type(f(z='', x=1, y=a))  # E: Revealed type is 'builtins.int'
-reveal_type(f(z='', x=a, y=1))  # E: Revealed type is 'builtins.object'
+reveal_type(f(z='', x=a, y=1))  # E: Revealed type is 'Any'
 
 [case testOverloadWithOverlappingItemsAndAnyArgument5]
 from typing import overload, Any, Union
@@ -1334,7 +1333,7 @@ def f(x: Union[int, float]) -> float: ...
 def f(x): pass
 
 a: Any
-reveal_type(f(a))  # E: Revealed type is 'builtins.float'
+reveal_type(f(a))  # E: Revealed type is 'Any'
 
 [case testOverloadWithOverlappingItemsAndAnyArgument6]
 from typing import overload, Any
@@ -1372,7 +1371,7 @@ def g(x): pass
 
 a: Any
 reveal_type(f(1, *a))  # E: Revealed type is 'builtins.int'
-reveal_type(g(1, *a))  # E: Revealed type is 'builtins.object'
+reveal_type(g(1, *a))  # E: Revealed type is 'Any'
 
 [case testOverloadWithOverlappingItemsAndAnyArgument8]
 from typing import overload, Any

test-data/unit/python2eval.test

@@ -342,7 +342,7 @@ print b.x + 1
 [out]
 4
 
-[case testReModuleBytesPython2]
+[case testReModuleBytes_python2]
 # Regression tests for various overloads in the re module -- bytes version
 import re
 if False:
@@ -365,7 +365,7 @@ if False:
     re.subn(bpat, lambda m: b'', b'')[0] + b''
 [out]
 
-[case testReModuleStringPython2]
+[case testReModuleString_python2]
 # Regression tests for various overloads in the re module -- string version
 import re
 ure = u'a+'
@@ -393,3 +393,11 @@ def g():  # type: () -> int
     yield
 [out]
 _program.py:2: error: The return type of a generator function should be "Generator" or one of its supertypes
+
+[case testOsPathJoinWorksWithAny_python2]
+import os
+def f():  # no annotation
+   return 'tests'
+path = 'test'
+path = os.path.join(f(), 'test.py')
+[out]

test-data/unit/pythoneval.test

@@ -1109,9 +1109,11 @@ async def main() -> None:
     ((a_x, a_y),) = await asyncio.gather(get_location('start'))
     reveal_type(a_x)
     reveal_type(a_y)
+reveal_type(asyncio.gather(*[asyncio.sleep(1), asyncio.sleep(1)]))
 [out]
 _testAsyncioGatherPreciseType.py:9: error: Revealed type is 'builtins.str'
 _testAsyncioGatherPreciseType.py:10: error: Revealed type is 'builtins.str'
+_testAsyncioGatherPreciseType.py:11: error: Revealed type is 'asyncio.futures.Future[builtins.tuple[Any]]'
 
 [case testMultipleInheritanceWorksWithTupleTypeGeneric]
 from typing import SupportsAbs, NamedTuple