Describe the Bug
From https://microsoft.github.io/pyright/#/type-concepts-advanced?id=type-guards
Type guards of the form x.y or x[y] are all partially-supported: we currently apply the narrowing to the type of x[y], but do not narrow the type of x (if it's something that can be discriminated by that field/index/key)
x is None / x is not Nonex == None / x != Nonex is ... / x is not ... / x == ... / x != ... (where ... is an ellipsis token) Note: as far as I can tell, this is just for narrowing object or Any to Ellipsis x is S / x is not S (where S is a Sentinel) Note: Sentinel here refers to PEP 661, which was deferred As far as I know, this is a pyright-exclusive thing: Add experimental support for PEP 661 (Sentinels) microsoft/pyright#10565 type(x) is T / type(x) is not T Type narrowing via assert type(x) is X and assert type(x) == X #335 type(x) == T / type(x) != T Type narrowing via assert type(x) is X and assert type(x) == X #335 x is L / x is not L (where L is an expression that evaluates to a literal type)x is C / x is not C (where C is a class)x == L / x != L (where L is an expression that evaluates to a literal type)x.y is None / x.y is not None (where x is a type that is distinguished by a field with a None)x.y is E / x.y is not E (where E is a literal enum or bool and x is a type that is distinguished by a field with a literal type) [feature] Discriminated Union (narrow typed dicts based on field type) #418 x.y == LN / x.y != LN (where LN is a literal expression or None and x is a type that is distinguished by a field or property with a literal type) [feature] Discriminated Union (narrow typed dicts based on field type) #418 x[K] == V / x[K] != V / x[K] is V / x[K] is not V (where K and V are literal expressions and x is a type that is distinguished by a TypedDict field with a literal type) [feature] Discriminated Union (narrow typed dicts based on field type) #418 x[I] == V / x[I] != V (where I and V are literal expressions and x is a known-length tuple that is distinguished by the index indicated by I) [feature] Discriminated Union (narrow typed dicts based on field type) #418 x[I] is B / x[I] is not B (where I is a literal expression, B is a bool or enum literal, and x is a known-length tuple that is distinguished by the index indicated by I) [feature] Discriminated Union (narrow typed dicts based on field type) #418 x[I] is None / x[I] is not None (where I is a literal expression and x is a known-length tuple that is distinguished by the index indicated by I) [feature] Discriminated Union (narrow typed dicts based on field type) #418 len(x) == L, len(x) != L, len(x) < L, etc. (where x is tuple and L is an expression that evaluates to an int literal type)x in y / x not in y (where y is instance of list, set, frozenset, deque, tuple, dict, defaultdict, or OrderedDict)S in D / S not in D (where S is a string literal and D is a TypedDict) TypedDict NotRequired key narrowing + access error #84 isinstance(x, T) (where T is a type or a tuple of types)issubclass(x, T) (where T is a type or a tuple of types)f(x) (where f is a user-defined type guard as defined in PEP 647 or PEP 742)bool(x) (where x is any expression that is statically verifiable to be truthy or falsey in all cases)x (where x is any expression that is statically known to be truthy or falsy)
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Describe the Bug
From https://microsoft.github.io/pyright/#/type-concepts-advanced?id=type-guards
Type guards of the form
x.yorx[y]are all partially-supported: we currently apply the narrowing to the type ofx[y], but do not narrow the type ofx(if it's something that can be discriminated by that field/index/key)x is None/x is not Nonex == None/x != Nonex is .../x is not .../x == .../x != ...(where ... is an ellipsis token) Note: as far as I can tell, this is just for narrowingobjectorAnytoEllipsisx is S/x is not S(where S is a Sentinel) Note: Sentinel here refers to PEP 661, which was deferred As far as I know, this is a pyright-exclusive thing: Add experimental support for PEP 661 (Sentinels) microsoft/pyright#10565type(x) is T/type(x) is not TType narrowing viaassert type(x) is Xandassert type(x) == X#335type(x) == T/type(x) != TType narrowing viaassert type(x) is Xandassert type(x) == X#335x is L/x is not L(where L is an expression that evaluates to a literal type)x is C/x is not C(where C is a class)x == L/x != L(where L is an expression that evaluates to a literal type)x.y is None/x.y is not None(where x is a type that is distinguished by a field with a None)x.y is E/x.y is not E(where E is a literal enum or bool and x is a type that is distinguished by a field with a literal type) [feature] Discriminated Union (narrow typed dicts based on field type) #418x.y == LN/x.y != LN(where LN is a literal expression or None and x is a type that is distinguished by a field or property with a literal type) [feature] Discriminated Union (narrow typed dicts based on field type) #418x[K] == V/x[K] != V/x[K] is V/x[K] is not V(where K and V are literal expressions and x is a type that is distinguished by a TypedDict field with a literal type) [feature] Discriminated Union (narrow typed dicts based on field type) #418x[I] == V/x[I] != V(where I and V are literal expressions and x is a known-length tuple that is distinguished by the index indicated by I) [feature] Discriminated Union (narrow typed dicts based on field type) #418x[I] is B/x[I] is not B(where I is a literal expression, B is a bool or enum literal, and x is a known-length tuple that is distinguished by the index indicated by I) [feature] Discriminated Union (narrow typed dicts based on field type) #418x[I] is None/x[I] is not None(where I is a literal expression and x is a known-length tuple that is distinguished by the index indicated by I) [feature] Discriminated Union (narrow typed dicts based on field type) #418len(x) == L,len(x) != L,len(x) < L, etc. (where x is tuple and L is an expression that evaluates to an int literal type)x in y/x not in y(where y is instance of list, set, frozenset, deque, tuple, dict, defaultdict, or OrderedDict)S in D/S not in D(where S is a string literal and D is a TypedDict) TypedDictNotRequiredkey narrowing + access error #84isinstance(x, T)(where T is a type or a tuple of types)issubclass(x, T)(where T is a type or a tuple of types)f(x)(where f is a user-defined type guard as defined in PEP 647 or PEP 742)bool(x)(where x is any expression that is statically verifiable to be truthy or falsey in all cases)x(where x is any expression that is statically known to be truthy or falsy)Sandbox Link
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