Fix crash on TypeGuard plus "and" (#10496)

In python/typeshed#5473, I tried to switch a number of `inspect` functions to use the new `TypeGuard` functionality. Unfortunately, mypy-primer found a number of crashes in third-party libraries in places where a TypeGuard function was ANDed together with some other check. Examples:

- https://github.com/sphinx-doc/sphinx/blob/4.x/sphinx/util/inspect.py#L252
- https://github.com/sphinx-doc/sphinx/blob/4.x/sphinx/ext/coverage.py#L212
- https://github.com/streamlit/streamlit/blob/develop/lib/streamlit/elements/doc_string.py#L105

The problems trace back to the decision in #9865 to make TypeGuardType not inherit from ProperType: in various conditions that are more complicated than a simple `if` check, mypy wants everything to become a ProperType. Therefore, to fix the crashes I had to make TypeGuardType a ProperType and support it in various visitors.

mypy/constraints.py

@@ -7,7 +7,7 @@
     CallableType, Type, TypeVisitor, UnboundType, AnyType, NoneType, TypeVarType, Instance,
     TupleType, TypedDictType, UnionType, Overloaded, ErasedType, PartialType, DeletedType,
     UninhabitedType, TypeType, TypeVarId, TypeQuery, is_named_instance, TypeOfAny, LiteralType,
-    ProperType, get_proper_type, TypeAliasType
+    ProperType, get_proper_type, TypeAliasType, TypeGuardType
 )
 from mypy.maptype import map_instance_to_supertype
 import mypy.subtypes
@@ -534,6 +534,9 @@ def visit_union_type(self, template: UnionType) -> List[Constraint]:
     def visit_type_alias_type(self, template: TypeAliasType) -> List[Constraint]:
         assert False, "This should be never called, got {}".format(template)
 
+    def visit_type_guard_type(self, template: TypeGuardType) -> List[Constraint]:
+        assert False, "This should be never called, got {}".format(template)
+
     def infer_against_any(self, types: Iterable[Type], any_type: AnyType) -> List[Constraint]:
         res = []  # type: List[Constraint]
         for t in types:

mypy/erasetype.py

@@ -4,7 +4,7 @@
     Type, TypeVisitor, UnboundType, AnyType, NoneType, TypeVarId, Instance, TypeVarType,
     CallableType, TupleType, TypedDictType, UnionType, Overloaded, ErasedType, PartialType,
     DeletedType, TypeTranslator, UninhabitedType, TypeType, TypeOfAny, LiteralType, ProperType,
-    get_proper_type, TypeAliasType
+    get_proper_type, TypeAliasType, TypeGuardType
 )
 from mypy.nodes import ARG_STAR, ARG_STAR2
 
@@ -90,6 +90,9 @@ def visit_union_type(self, t: UnionType) -> ProperType:
         from mypy.typeops import make_simplified_union
         return make_simplified_union(erased_items)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> ProperType:
+        return TypeGuardType(t.type_guard.accept(self))
+
     def visit_type_type(self, t: TypeType) -> ProperType:
         return TypeType.make_normalized(t.item.accept(self), line=t.line)
 

mypy/expandtype.py

@@ -1,7 +1,7 @@
 from typing import Dict, Iterable, List, TypeVar, Mapping, cast
 
 from mypy.types import (
-    Type, Instance, CallableType, TypeVisitor, UnboundType, AnyType,
+    Type, Instance, CallableType, TypeGuardType, TypeVisitor, UnboundType, AnyType,
     NoneType, TypeVarType, Overloaded, TupleType, TypedDictType, UnionType,
     ErasedType, PartialType, DeletedType, UninhabitedType, TypeType, TypeVarId,
     FunctionLike, TypeVarDef, LiteralType, get_proper_type, ProperType,
@@ -126,6 +126,9 @@ def visit_union_type(self, t: UnionType) -> Type:
         from mypy.typeops import make_simplified_union  # asdf
         return make_simplified_union(self.expand_types(t.items), t.line, t.column)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> ProperType:
+        return TypeGuardType(t.type_guard.accept(self))
+
     def visit_partial_type(self, t: PartialType) -> Type:
         return t
 

mypy/fixup.py

@@ -9,7 +9,7 @@
     TypeVarExpr, ClassDef, Block, TypeAlias,
 )
 from mypy.types import (
-    CallableType, Instance, Overloaded, TupleType, TypedDictType,
+    CallableType, Instance, Overloaded, TupleType, TypeGuardType, TypedDictType,
     TypeVarType, UnboundType, UnionType, TypeVisitor, LiteralType,
     TypeType, NOT_READY, TypeAliasType, AnyType, TypeOfAny, TypeVarDef
 )
@@ -254,6 +254,9 @@ def visit_union_type(self, ut: UnionType) -> None:
             for it in ut.items:
                 it.accept(self)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> None:
+        t.type_guard.accept(self)
+
     def visit_void(self, o: Any) -> None:
         pass  # Nothing to descend into.
 

mypy/indirection.py

@@ -97,6 +97,9 @@ def visit_literal_type(self, t: types.LiteralType) -> Set[str]:
     def visit_union_type(self, t: types.UnionType) -> Set[str]:
         return self._visit(t.items)
 
+    def visit_type_guard_type(self, t: types.TypeGuardType) -> Set[str]:
+        return self._visit(t.type_guard)
+
     def visit_partial_type(self, t: types.PartialType) -> Set[str]:
         return set()
 

mypy/join.py

@@ -7,7 +7,7 @@
     Type, AnyType, NoneType, TypeVisitor, Instance, UnboundType, TypeVarType, CallableType,
     TupleType, TypedDictType, ErasedType, UnionType, FunctionLike, Overloaded, LiteralType,
     PartialType, DeletedType, UninhabitedType, TypeType, TypeOfAny, get_proper_type,
-    ProperType, get_proper_types, TypeAliasType, PlaceholderType
+    ProperType, get_proper_types, TypeAliasType, PlaceholderType, TypeGuardType
 )
 from mypy.maptype import map_instance_to_supertype
 from mypy.subtypes import (
@@ -340,6 +340,9 @@ def visit_type_type(self, t: TypeType) -> ProperType:
     def visit_type_alias_type(self, t: TypeAliasType) -> ProperType:
         assert False, "This should be never called, got {}".format(t)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> ProperType:
+        assert False, "This should be never called, got {}".format(t)
+
     def join(self, s: Type, t: Type) -> ProperType:
         return join_types(s, t)
 

mypy/meet.py

@@ -8,7 +8,7 @@
     Type, AnyType, TypeVisitor, UnboundType, NoneType, TypeVarType, Instance, CallableType,
     TupleType, TypedDictType, ErasedType, UnionType, PartialType, DeletedType,
     UninhabitedType, TypeType, TypeOfAny, Overloaded, FunctionLike, LiteralType,
-    ProperType, get_proper_type, get_proper_types, TypeAliasType
+    ProperType, get_proper_type, get_proper_types, TypeAliasType, TypeGuardType
 )
 from mypy.subtypes import is_equivalent, is_subtype, is_callable_compatible, is_proper_subtype
 from mypy.erasetype import erase_type
@@ -648,6 +648,9 @@ def visit_type_type(self, t: TypeType) -> ProperType:
     def visit_type_alias_type(self, t: TypeAliasType) -> ProperType:
         assert False, "This should be never called, got {}".format(t)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> ProperType:
+        assert False, "This should be never called, got {}".format(t)
+
     def meet(self, s: Type, t: Type) -> ProperType:
         return meet_types(s, t)
 

mypy/sametypes.py

@@ -1,7 +1,7 @@
 from typing import Sequence
 
 from mypy.types import (
-    Type, UnboundType, AnyType, NoneType, TupleType, TypedDictType,
+    Type, TypeGuardType, UnboundType, AnyType, NoneType, TupleType, TypedDictType,
     UnionType, CallableType, TypeVarType, Instance, TypeVisitor, ErasedType,
     Overloaded, PartialType, DeletedType, UninhabitedType, TypeType, LiteralType,
     ProperType, get_proper_type, TypeAliasType)
@@ -10,6 +10,7 @@
 
 def is_same_type(left: Type, right: Type) -> bool:
     """Is 'left' the same type as 'right'?"""
+
     left = get_proper_type(left)
     right = get_proper_type(right)
 
@@ -150,6 +151,12 @@ def visit_union_type(self, left: UnionType) -> bool:
         else:
             return False
 
+    def visit_type_guard_type(self, left: TypeGuardType) -> bool:
+        if isinstance(self.right, TypeGuardType):
+            return is_same_type(left.type_guard, self.right.type_guard)
+        else:
+            return False
+
     def visit_overloaded(self, left: Overloaded) -> bool:
         if isinstance(self.right, Overloaded):
             return is_same_types(left.items(), self.right.items())

mypy/server/astdiff.py

@@ -57,7 +57,7 @@ class level -- these are handled at attribute level (say, 'mod.Cls.method'
     FuncBase, OverloadedFuncDef, FuncItem, MypyFile, UNBOUND_IMPORTED
 )
 from mypy.types import (
-    Type, TypeVisitor, UnboundType, AnyType, NoneType, UninhabitedType,
+    Type, TypeGuardType, TypeVisitor, UnboundType, AnyType, NoneType, UninhabitedType,
     ErasedType, DeletedType, Instance, TypeVarType, CallableType, TupleType, TypedDictType,
     UnionType, Overloaded, PartialType, TypeType, LiteralType, TypeAliasType
 )
@@ -335,6 +335,9 @@ def visit_union_type(self, typ: UnionType) -> SnapshotItem:
         normalized = tuple(sorted(items))
         return ('UnionType', normalized)
 
+    def visit_type_guard_type(self, typ: TypeGuardType) -> SnapshotItem:
+        return ('TypeGuardType', snapshot_type(typ.type_guard))
+
     def visit_overloaded(self, typ: Overloaded) -> SnapshotItem:
         return ('Overloaded', snapshot_types(typ.items()))
 

mypy/server/astmerge.py

@@ -59,7 +59,7 @@
     Type, SyntheticTypeVisitor, Instance, AnyType, NoneType, CallableType, ErasedType, DeletedType,
     TupleType, TypeType, TypeVarType, TypedDictType, UnboundType, UninhabitedType, UnionType,
     Overloaded, TypeVarDef, TypeList, CallableArgument, EllipsisType, StarType, LiteralType,
-    RawExpressionType, PartialType, PlaceholderType, TypeAliasType
+    RawExpressionType, PartialType, PlaceholderType, TypeAliasType, TypeGuardType
 )
 from mypy.util import get_prefix, replace_object_state
 from mypy.typestate import TypeState
@@ -389,6 +389,9 @@ def visit_erased_type(self, t: ErasedType) -> None:
     def visit_deleted_type(self, typ: DeletedType) -> None:
         pass
 
+    def visit_type_guard_type(self, typ: TypeGuardType) -> None:
+        raise RuntimeError
+
     def visit_partial_type(self, typ: PartialType) -> None:
         raise RuntimeError
 

mypy/server/deps.py

@@ -97,7 +97,8 @@ class 'mod.Cls'. This can also refer to an attribute inherited from a
     Type, Instance, AnyType, NoneType, TypeVisitor, CallableType, DeletedType, PartialType,
     TupleType, TypeType, TypeVarType, TypedDictType, UnboundType, UninhabitedType, UnionType,
     FunctionLike, Overloaded, TypeOfAny, LiteralType, ErasedType, get_proper_type, ProperType,
-    TypeAliasType)
+    TypeAliasType, TypeGuardType
+)
 from mypy.server.trigger import make_trigger, make_wildcard_trigger
 from mypy.util import correct_relative_import
 from mypy.scope import Scope
@@ -970,6 +971,9 @@ def visit_unbound_type(self, typ: UnboundType) -> List[str]:
     def visit_uninhabited_type(self, typ: UninhabitedType) -> List[str]:
         return []
 
+    def visit_type_guard_type(self, typ: TypeGuardType) -> List[str]:
+        return typ.type_guard.accept(self)
+
     def visit_union_type(self, typ: UnionType) -> List[str]:
         triggers = []
         for item in typ.items:

mypy/subtypes.py

@@ -4,7 +4,7 @@
 from typing_extensions import Final
 
 from mypy.types import (
-    Type, AnyType, UnboundType, TypeVisitor, FormalArgument, NoneType,
+    Type, AnyType, TypeGuardType, UnboundType, TypeVisitor, FormalArgument, NoneType,
     Instance, TypeVarType, CallableType, TupleType, TypedDictType, UnionType, Overloaded,
     ErasedType, PartialType, DeletedType, UninhabitedType, TypeType, is_named_instance,
     FunctionLike, TypeOfAny, LiteralType, get_proper_type, TypeAliasType
@@ -475,6 +475,9 @@ def visit_overloaded(self, left: Overloaded) -> bool:
     def visit_union_type(self, left: UnionType) -> bool:
         return all(self._is_subtype(item, self.orig_right) for item in left.items)
 
+    def visit_type_guard_type(self, left: TypeGuardType) -> bool:
+        raise RuntimeError("TypeGuard should not appear here")
+
     def visit_partial_type(self, left: PartialType) -> bool:
         # This is indeterminate as we don't really know the complete type yet.
         raise RuntimeError
@@ -1374,6 +1377,14 @@ def visit_overloaded(self, left: Overloaded) -> bool:
     def visit_union_type(self, left: UnionType) -> bool:
         return all([self._is_proper_subtype(item, self.orig_right) for item in left.items])
 
+    def visit_type_guard_type(self, left: TypeGuardType) -> bool:
+        if isinstance(self.right, TypeGuardType):
+            # TypeGuard[bool] is a subtype of TypeGuard[int]
+            return self._is_proper_subtype(left.type_guard, self.right.type_guard)
+        else:
+            # TypeGuards aren't a subtype of anything else for now (but see #10489)
+            return False
+
     def visit_partial_type(self, left: PartialType) -> bool:
         # TODO: What's the right thing to do here?
         return False

mypy/type_visitor.py

@@ -19,7 +19,7 @@
 T = TypeVar('T')
 
 from mypy.types import (
-    Type, AnyType, CallableType, Overloaded, TupleType, TypedDictType, LiteralType,
+    Type, AnyType, CallableType, Overloaded, TupleType, TypeGuardType, TypedDictType, LiteralType,
     RawExpressionType, Instance, NoneType, TypeType,
     UnionType, TypeVarType, PartialType, DeletedType, UninhabitedType, TypeVarLikeDef,
     UnboundType, ErasedType, StarType, EllipsisType, TypeList, CallableArgument,
@@ -103,6 +103,10 @@ def visit_type_type(self, t: TypeType) -> T:
     def visit_type_alias_type(self, t: TypeAliasType) -> T:
         pass
 
+    @abstractmethod
+    def visit_type_guard_type(self, t: TypeGuardType) -> T:
+        pass
+
 
 @trait
 @mypyc_attr(allow_interpreted_subclasses=True)
@@ -220,6 +224,9 @@ def visit_union_type(self, t: UnionType) -> Type:
     def translate_types(self, types: Iterable[Type]) -> List[Type]:
         return [t.accept(self) for t in types]
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> Type:
+        return TypeGuardType(t.type_guard.accept(self))
+
     def translate_variables(self,
                             variables: Sequence[TypeVarLikeDef]) -> Sequence[TypeVarLikeDef]:
         return variables
@@ -319,6 +326,9 @@ def visit_star_type(self, t: StarType) -> T:
     def visit_union_type(self, t: UnionType) -> T:
         return self.query_types(t.items)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> T:
+        return t.type_guard.accept(self)
+
     def visit_overloaded(self, t: Overloaded) -> T:
         return self.query_types(t.items())
 

mypy/typeanal.py

@@ -14,7 +14,7 @@
 from mypy.types import (
     Type, UnboundType, TypeVarType, TupleType, TypedDictType, UnionType, Instance, AnyType,
     CallableType, NoneType, ErasedType, DeletedType, TypeList, TypeVarDef, SyntheticTypeVisitor,
-    StarType, PartialType, EllipsisType, UninhabitedType, TypeType,
+    StarType, PartialType, EllipsisType, UninhabitedType, TypeType, TypeGuardType,
     CallableArgument, TypeQuery, union_items, TypeOfAny, LiteralType, RawExpressionType,
     PlaceholderType, Overloaded, get_proper_type, TypeAliasType, TypeVarLikeDef, ParamSpecDef
 )
@@ -542,6 +542,9 @@ def visit_callable_type(self, t: CallableType, nested: bool = True) -> Type:
                                   )
         return ret
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> Type:
+        return t
+
     def anal_type_guard(self, t: Type) -> Optional[Type]:
         if isinstance(t, UnboundType):
             sym = self.lookup_qualified(t.name, t)

mypy/types.py

@@ -270,7 +270,14 @@ def copy_modified(self, *,
             self.line, self.column)
 
 
-class TypeGuardType(Type):
+class ProperType(Type):
+    """Not a type alias.
+
+    Every type except TypeAliasType must inherit from this type.
+    """
+
+
+class TypeGuardType(ProperType):
     """Only used by find_instance_check() etc."""
     def __init__(self, type_guard: Type):
         super().__init__(line=type_guard.line, column=type_guard.column)
@@ -279,12 +286,8 @@ def __init__(self, type_guard: Type):
     def __repr__(self) -> str:
         return "TypeGuard({})".format(self.type_guard)
 
-
-class ProperType(Type):
-    """Not a type alias.
-
-    Every type except TypeAliasType must inherit from this type.
-    """
+    def accept(self, visitor: 'TypeVisitor[T]') -> T:
+        return visitor.visit_type_guard_type(self)
 
 
 class TypeVarId:
@@ -2183,6 +2186,9 @@ def visit_union_type(self, t: UnionType) -> str:
         s = self.list_str(t.items)
         return 'Union[{}]'.format(s)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> str:
+        return 'TypeGuard[{}]'.format(t.type_guard.accept(self))
+
     def visit_partial_type(self, t: PartialType) -> str:
         if t.type is None:
             return '<partial None>'

mypy/typetraverser.py

@@ -6,7 +6,7 @@
     Type, SyntheticTypeVisitor, AnyType, UninhabitedType, NoneType, ErasedType, DeletedType,
     TypeVarType, LiteralType, Instance, CallableType, TupleType, TypedDictType, UnionType,
     Overloaded, TypeType, CallableArgument, UnboundType, TypeList, StarType, EllipsisType,
-    PlaceholderType, PartialType, RawExpressionType, TypeAliasType
+    PlaceholderType, PartialType, RawExpressionType, TypeAliasType, TypeGuardType
 )
 
 
@@ -62,6 +62,9 @@ def visit_typeddict_type(self, t: TypedDictType) -> None:
     def visit_union_type(self, t: UnionType) -> None:
         self.traverse_types(t.items)
 
+    def visit_type_guard_type(self, t: TypeGuardType) -> None:
+        t.type_guard.accept(self)
+
     def visit_overloaded(self, t: Overloaded) -> None:
         self.traverse_types(t.items())
 

test-data/unit/check-typeguard.test

@@ -294,3 +294,24 @@ class C:
 class D(C):
     def is_float(self, a: object) -> bool: pass  # E: Signature of "is_float" incompatible with supertype "C"
 [builtins fixtures/tuple.pyi]
+
+[case testTypeGuardInAnd]
+from typing import Any
+from typing_extensions import TypeGuard
+import types
+def isclass(a: object) -> bool:
+    pass
+def ismethod(a: object) -> TypeGuard[float]:
+    pass
+def isfunction(a: object) -> TypeGuard[str]:
+    pass
+def isclassmethod(obj: Any) -> bool:
+    if ismethod(obj) and obj.__self__ is not None and isclass(obj.__self__):  # E: "float" has no attribute "__self__"
+        return True
+
+    return False
+def coverage(obj: Any) -> bool:
+    if not (ismethod(obj) or isfunction(obj)):
+        return True
+    return False
+[builtins fixtures/classmethod.pyi]