python · JukkaL · Mar 19, 2017 · Mar 14, 2017 · Mar 14, 2017 · Mar 14, 2017
diff --git a/mypy/checker.py b/mypy/checker.py
@@ -2452,28 +2452,46 @@ def push_type_map(self, type_map: Optional[Dict[Expression, Type]]) -> None:
 
 TypeMap = Optional[Dict[Expression, Type]]
 
+# An object that represents either a precise type or a type with an upper bound;
+# it is important for correct type inference with isinstance.
+TypeRange = NamedTuple(
+    'TypeRange',
+    [
+        ('item', Type),
+        ('is_upper_bound', bool),  # False => precise type
+    ])
+
 
 def conditional_type_map(expr: Expression,
                          current_type: Optional[Type],
-                         proposed_type: Optional[Type],
+                         proposed_type_ranges: Optional[List[TypeRange]],
                          ) -> Tuple[TypeMap, TypeMap]:
     """Takes in an expression, the current type of the expression, and a
     proposed type of that expression.
 
     Returns a 2-tuple: The first element is a map from the expression to
     the proposed type, if the expression can be the proposed type.  The
     second element is a map from the expression to the type it would hold
-    if it was not the proposed type, if any."""
-    if proposed_type:
+    if it was not the proposed type, if any. None means bot, {} means top"""
+    if proposed_type_ranges:
+        if len(proposed_type_ranges) == 1:
+            proposed_type = proposed_type_ranges[0].item  # Union with a single type breaks tests
+        else:
+            proposed_type = UnionType([type_range.item for type_range in proposed_type_ranges])
         if current_type:
-            if is_proper_subtype(current_type, proposed_type):
-                # Expression is always of type proposed_type
+            if not any(type_range.is_upper_bound for type_range in proposed_type_ranges) \
+               and is_proper_subtype(current_type, proposed_type):
+                # Expression is always of one of the types in proposed_type_ranges
                 return {}, None
             elif not is_overlapping_types(current_type, proposed_type):
-                # Expression is never of type proposed_type
+                # Expression is never of any type in proposed_type_ranges
                 return None, {}
             else:
-                remaining_type = restrict_subtype_away(current_type, proposed_type)
+                # we can only restrict when the type is precise, not bounded
+                proposed_precise_type = UnionType([type_range.item
+                                          for type_range in proposed_type_ranges
+                                          if not type_range.is_upper_bound])
+                remaining_type = restrict_subtype_away(current_type, proposed_precise_type)
                 return {expr: proposed_type}, {expr: remaining_type}
         else:
             return {expr: proposed_type}, {}
@@ -2644,8 +2662,8 @@ def find_isinstance_check(node: Expression,
             expr = node.args[0]
             if expr.literal == LITERAL_TYPE:
                 vartype = type_map[expr]
-                type = get_isinstance_type(node.args[1], type_map)
-                return conditional_type_map(expr, vartype, type)
+                types = get_isinstance_type(node.args[1], type_map)
+                return conditional_type_map(expr, vartype, types)
         elif refers_to_fullname(node.callee, 'builtins.callable'):
             expr = node.args[0]
             if expr.literal == LITERAL_TYPE:
@@ -2663,7 +2681,8 @@ def find_isinstance_check(node: Expression,
                     # two elements in node.operands, and at least one of them
                     # should represent a None.
                     vartype = type_map[expr]
-                    if_vars, else_vars = conditional_type_map(expr, vartype, NoneTyp())
+                    none_typ = [TypeRange(NoneTyp(), is_upper_bound=False)]
+                    if_vars, else_vars = conditional_type_map(expr, vartype, none_typ)
                     break
 
             if is_not:
@@ -2725,26 +2744,22 @@ def flatten(t: Expression) -> List[Expression]:
         return [t]
 
 
-def get_isinstance_type(expr: Expression, type_map: Dict[Expression, Type]) -> Type:
+def get_isinstance_type(expr: Expression, type_map: Dict[Expression, Type]) -> List[TypeRange]:
     all_types = [type_map[e] for e in flatten(expr)]
-
-    types = []  # type: List[Type]
-
+    types = []  # type: List[TypeRange]
     for type in all_types:
         if isinstance(type, FunctionLike):
             if type.is_type_obj():
                 # Type variables may be present -- erase them, which is the best
                 # we can do (outside disallowing them here).
                 type = erase_typevars(type.items()[0].ret_type)
-
-            types.append(type)
-
-    if len(types) == 0:
-        return None
-    elif len(types) == 1:
-        return types[0]
-    else:
-        return UnionType(types)
+            types.append(TypeRange(type, is_upper_bound=False))
+        elif isinstance(type, TypeType):
+            types.append(TypeRange(type.item, is_upper_bound=True))
+        else:  # we didn't see an actual type, but rather a variable whose value is unknown to us
+            return None
+    assert len(types) != 0
+    return types
 
 
 def expand_func(defn: FuncItem, map: Dict[TypeVarId, Type]) -> FuncItem:

diff --git a/mypy/semanal.py b/mypy/semanal.py
@@ -2679,8 +2679,7 @@ def visit_member_expr(self, expr: MemberExpr) -> None:
             # This branch handles the case foo.bar where foo is a module.
             # In this case base.node is the module's MypyFile and we look up
             # bar in its namespace.  This must be done for all types of bar.
-            file = base.node
-            assert isinstance(file, (MypyFile, type(None)))
+            file = cast(Optional[MypyFile], base.node)  # can't use isinstance due to issue #2999
             n = file.names.get(expr.name, None) if file is not None else None
             if n:
                 n = self.normalize_type_alias(n, expr)

diff --git a/test-data/unit/check-isinstance.test b/test-data/unit/check-isinstance.test
@@ -1360,3 +1360,31 @@ def f(x: object) -> None:
     reveal_type(b)  # E: Revealed type is '__main__.A'
 [builtins fixtures/isinstance.pyi]
 [out]
+
+[case testIsInstanceWithUnknownType]
+from typing import Union
+def f(x: Union[int, str], typ: type) -> None:
+    if isinstance(x, (typ, int)):
+        x + 1  # E: Unsupported operand types for + (likely involving Union)
+        reveal_type(x)  # E: Revealed type is 'Union[builtins.int, builtins.str]'
+    else:
+        reveal_type(x)  # E: Revealed type is 'Union[builtins.int, builtins.str]'
+[builtins fixtures/isinstancelist.pyi]
+
+
+[case testIsInstanceWithTypeObject]
+from typing import Union, Type
+
+class A: pass
+
+def f(x: Union[int, A], a: Type[A]) -> None:
+    if isinstance(x, a):
+        reveal_type(x)  # E: Revealed type is '__main__.A'
+    elif isinstance(x, int):
+        reveal_type(x)  # E: Revealed type is 'builtins.int'
+    else:
+        reveal_type(x)  # E: Revealed type is '__main__.A'
+    reveal_type(x)  # E: Revealed type is 'Union[builtins.int, __main__.A]'
+
+[builtins fixtures/isinstancelist.pyi]
+
diff --git a/typeshed b/typeshed
+2 −2		.travis.yml
+0 −1		CONTRIBUTING.md
+5 −5		requirements-tests-py3.txt
+11 −11		stdlib/2/ConfigParser.pyi
+21 −22		stdlib/2/__builtin__.pyi
+20 −20		stdlib/2/array.pyi
+10 −12		stdlib/2/codecs.pyi
+5 −8		stdlib/2/compileall.pyi
+9 −6		stdlib/2/datetime.pyi
+3 −3		stdlib/2/encodings/utf_8.pyi
+5 −5		stdlib/2/pickle.pyi
+1 −3		stdlib/2/socket.pyi
+2 −2		stdlib/2/spwd.pyi
+3 −3		stdlib/2/tempfile.pyi
+1 −1		stdlib/2/types.pyi
+40 −0		stdlib/2/unicodedata.pyi
+7 −7		stdlib/2and3/_bisect.pyi
+1 −1		stdlib/2and3/asynchat.pyi
+1 −1		stdlib/2and3/asyncore.pyi
+3 −3		stdlib/2and3/fractions.pyi
+0 −134		stdlib/2and3/ftplib.pyi
+3 −3		stdlib/2and3/logging/__init__.pyi
+1 −1		stdlib/2and3/logging/handlers.pyi
+2 −2		stdlib/2and3/opcode.pyi
+0 −38		stdlib/2and3/unicodedata.pyi
+28 −65		stdlib/3.4/asyncio/events.pyi
+5 −5		stdlib/3.4/asyncio/locks.pyi
+8 −8		stdlib/3.4/asyncio/queues.pyi
+1 −1		stdlib/3.4/asyncio/tasks.pyi
+2 −2		stdlib/3.4/pathlib.pyi
+0 −24		stdlib/3.4/statistics.pyi
+1 −1		stdlib/3/_markupbase.pyi
+4 −5		stdlib/3/_posixsubprocess.pyi
+1 −1		stdlib/3/base64.pyi
+20 −24		stdlib/3/builtins.pyi
+1 −1		stdlib/3/calendar.pyi
+194 −0		stdlib/3/codecs.pyi
+12 −13		stdlib/3/collections/__init__.pyi
+0 −18		stdlib/3/compileall.pyi
+1 −1		stdlib/3/datetime.pyi
+1 −1		stdlib/3/difflib.pyi
+45 −47		stdlib/3/dis.pyi
+1 −1		stdlib/3/email/message.pyi
+3 −3		stdlib/3/encodings/utf_8.pyi
+2 −3		stdlib/3/http/client.pyi
+1 −1		stdlib/3/inspect.pyi
+2 −2		stdlib/3/json.pyi
+3 −3		stdlib/3/linecache.pyi
+0 −6		stdlib/3/os/__init__.pyi
+1 −1		stdlib/3/queue.pyi
+2 −2		stdlib/3/shlex.pyi
+1 −3		stdlib/3/socket.pyi
+2 −0		stdlib/3/ssl.pyi
+41 −87		stdlib/3/subprocess.pyi
+39 −78		stdlib/3/tempfile.pyi
+3 −3		stdlib/3/token.pyi
+17 −30		stdlib/3/tokenize.pyi
+1 −1		stdlib/3/types.pyi
+5 −12		stdlib/3/typing.pyi
+37 −0		stdlib/3/unicodedata.pyi
+17 −18		stdlib/3/unittest/__init__.pyi
+2 −3		stdlib/3/urllib/parse.pyi
+2 −2		third_party/2/concurrent/futures/__init__.pyi
+1 −1		third_party/2/requests/packages/urllib3/connection.pyi
+1 −1		third_party/2/requests/packages/urllib3/packages/ssl_match_hostname/__init__.pyi
+55 −62		third_party/2/werkzeug/wrappers.pyi
+2 −2		third_party/2and3/characteristic/__init__.pyi
+2 −2		third_party/2and3/mypy_extensions.pyi
+5 −5		third_party/3.6/click/core.pyi
+13 −13		third_party/3.6/click/decorators.pyi
+4 −4		third_party/3.6/click/termui.pyi
+11 −11		third_party/3.6/click/types.pyi
+4 −4		third_party/3.6/click/utils.pyi
+4 −4		third_party/3/dateutil/parser.pyi
+2 −2		third_party/3/dateutil/relativedelta.pyi
+1 −1		third_party/3/dateutil/tz/_common.pyi
+1 −1		third_party/3/dateutil/tz/tz.pyi
+48 −49		third_party/3/itsdangerous.pyi
+24 −24		third_party/3/lxml/etree.pyi
+4 −4		third_party/3/requests/adapters.pyi
+17 −17		third_party/3/requests/api.pyi
+4 −6		third_party/3/requests/cookies.pyi
+4 −4		third_party/3/requests/models.pyi
+6 −13		third_party/3/requests/packages/urllib3/connection.pyi
+4 −2		third_party/3/requests/packages/urllib3/response.pyi
+22 −24		third_party/3/requests/sessions.pyi
+3 −3		third_party/3/requests/structures.pyi
+55 −62		third_party/3/werkzeug/wrappers.pyi