diff --git a/docs/type-concepts.md b/docs/type-concepts.md index 1367ab3fa..74624b150 100644 --- a/docs/type-concepts.md +++ b/docs/type-concepts.md @@ -171,6 +171,7 @@ In addition to assignment-based type narrowing, Pyright supports the following t * `type(x) is T` and `type(x) is not T` * `x is E` and `x is not E` (where E is a literal enum or bool) * `x == L` and `x != L` (where L is a literal expression) +* `x.y is None` and `x.y is not None` (where x is a type that is distinguished by a field with a None) * `x.y is E` and `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) * `x.y == L` and `x.y != L` (where L is a literal expression and x is a type that is distinguished by a field with a literal type) * `x[K] == V` and `x[K] != V` (where K and V are literal expressions and x is a type that is distinguished by a TypedDict field with a literal type) diff --git a/packages/pyright-internal/src/analyzer/typeGuards.ts b/packages/pyright-internal/src/analyzer/typeGuards.ts index 8be520b14..80db09c42 100644 --- a/packages/pyright-internal/src/analyzer/typeGuards.ts +++ b/packages/pyright-internal/src/analyzer/typeGuards.ts @@ -65,6 +65,7 @@ import { convertToInstance, convertToInstantiable, doForEachSubtype, + getSpecializedTupleType, getTypeCondition, getTypeVarScopeId, isLiteralType, @@ -355,6 +356,25 @@ export function getTypeNarrowingCallback( }; } } + + // Look for X.Y is None or X.Y is not None + // These are commonly-used patterns used in control flow. + if ( + testExpression.leftExpression.nodeType === ParseNodeType.MemberAccess && + ParseTreeUtils.isMatchingExpression(reference, testExpression.leftExpression.leftExpression) && + testExpression.rightExpression.nodeType === ParseNodeType.Constant && + testExpression.rightExpression.constType === KeywordType.None + ) { + const memberName = testExpression.leftExpression.memberName; + return (type: Type) => { + return narrowTypeForDiscriminatedFieldNoneComparison( + evaluator, + type, + memberName.value, + adjIsPositiveTest + ); + }; + } } if (testExpression.operator === OperatorType.In) { @@ -707,24 +727,20 @@ function narrowTypeForTruthiness(evaluator: TypeEvaluator, type: Type, isPositiv } // Handle type narrowing for expressions of the form "a[I] is None" and "a[I] is not None" where -// I is an integer and a is a union of Tuples with known lengths and entry types. +// I is an integer and a is a union of Tuples and NamedTuples with known lengths and entry types. function narrowTupleTypeForIsNone(evaluator: TypeEvaluator, type: Type, isPositiveTest: boolean, indexValue: number) { return evaluator.mapSubtypesExpandTypeVars(type, /* conditionFilter */ undefined, (subtype) => { - if ( - !isClassInstance(subtype) || - !isTupleClass(subtype) || - isUnboundedTupleClass(subtype) || - !subtype.tupleTypeArguments - ) { + const tupleType = getSpecializedTupleType(subtype); + if (!tupleType || isUnboundedTupleClass(tupleType) || !tupleType.tupleTypeArguments) { return subtype; } - const tupleLength = subtype.tupleTypeArguments.length; + const tupleLength = tupleType.tupleTypeArguments.length; if (indexValue < 0 || indexValue >= tupleLength) { return subtype; } - const typeOfEntry = evaluator.makeTopLevelTypeVarsConcrete(subtype.tupleTypeArguments[indexValue].type); + const typeOfEntry = evaluator.makeTopLevelTypeVarsConcrete(tupleType.tupleTypeArguments[indexValue].type); if (isPositiveTest) { if (!evaluator.canAssignType(typeOfEntry, NoneType.createInstance())) { @@ -1459,6 +1475,41 @@ function narrowTypeForDiscriminatedFieldComparison( return narrowedType; } +// Attempts to narrow a type based on a comparison (equal or not equal) +// between a discriminating field that has a declared None type to a +// None. +function narrowTypeForDiscriminatedFieldNoneComparison( + evaluator: TypeEvaluator, + referenceType: Type, + memberName: string, + isPositiveTest: boolean +): Type { + return mapSubtypes(referenceType, (subtype) => { + let memberInfo: ClassMember | undefined; + if (isClassInstance(subtype)) { + memberInfo = lookUpObjectMember(subtype, memberName); + } else if (isInstantiableClass(subtype)) { + memberInfo = lookUpClassMember(subtype, memberName); + } + + if (memberInfo && memberInfo.isTypeDeclared) { + const memberType = evaluator.getTypeOfMember(memberInfo); + + if (isPositiveTest) { + if (!evaluator.canAssignType(memberType, NoneType.createInstance())) { + return undefined; + } + } else { + if (isNoneInstance(memberType)) { + return undefined; + } + } + } + + return subtype; + }); +} + // Attempts to narrow a type based on a "type(x) is y" or "type(x) is not y" check. function narrowTypeForTypeIs(type: Type, classType: ClassType, isPositiveTest: boolean) { return mapSubtypes(type, (subtype) => { diff --git a/packages/pyright-internal/src/tests/samples/typeNarrowingIsNoneNamedTuple1.py b/packages/pyright-internal/src/tests/samples/typeNarrowingIsNoneNamedTuple1.py new file mode 100644 index 000000000..317128831 --- /dev/null +++ b/packages/pyright-internal/src/tests/samples/typeNarrowingIsNoneNamedTuple1.py @@ -0,0 +1,35 @@ +# This sample tests the type narrowing case for unions of NamedTuples +# where one or more of the entries is tested against type None by attribute. + +from typing import NamedTuple, Union + +IntFirst = NamedTuple("IntFirst", [ + ("first", int), + ("second", None), +]) + +StrSecond = NamedTuple("StrSecond", [ + ("first", None), + ("second", str), +]) + +def func1(a: Union[IntFirst, StrSecond]) -> IntFirst: + if a.second is None: + reveal_type(a, expected_text="IntFirst") + return a + else: + reveal_type(a, expected_text="StrSecond") + raise ValueError() + + +UnionFirst = NamedTuple("UnionFirst", [ + ("first", Union[None, int]), + ("second", None), +]) + +def func2(a: Union[UnionFirst, StrSecond]): + if a.first is None: + reveal_type(a, expected_text="UnionFirst | StrSecond") + else: + reveal_type(a, expected_text="UnionFirst") + diff --git a/packages/pyright-internal/src/tests/samples/typeNarrowingIsNoneNamedTuple2.py b/packages/pyright-internal/src/tests/samples/typeNarrowingIsNoneNamedTuple2.py new file mode 100644 index 000000000..f6f28274b --- /dev/null +++ b/packages/pyright-internal/src/tests/samples/typeNarrowingIsNoneNamedTuple2.py @@ -0,0 +1,35 @@ +# This sample tests the type narrowing case for unions of NamedTuples +# where one or more of the entries is tested against type None by index. + +from typing import NamedTuple, Union + +IntFirst = NamedTuple("IntFirst", [ + ("first", int), + ("second", None), +]) + +StrSecond = NamedTuple("StrSecond", [ + ("first", None), + ("second", str), +]) + +def func1(a: Union[IntFirst, StrSecond]) -> IntFirst: + if a[1] is None: + reveal_type(a, expected_text="IntFirst") + return a + else: + reveal_type(a, expected_text="StrSecond") + raise ValueError() + + +UnionFirst = NamedTuple("UnionFirst", [ + ("first", Union[None, int]), + ("second", None), +]) + +def func2(a: Union[UnionFirst, StrSecond]): + if a[0] is None: + reveal_type(a, expected_text="UnionFirst | StrSecond") + else: + reveal_type(a, expected_text="UnionFirst") + diff --git a/packages/pyright-internal/src/tests/typeEvaluator1.test.ts b/packages/pyright-internal/src/tests/typeEvaluator1.test.ts index 8afa59f49..874d004ad 100644 --- a/packages/pyright-internal/src/tests/typeEvaluator1.test.ts +++ b/packages/pyright-internal/src/tests/typeEvaluator1.test.ts @@ -302,6 +302,18 @@ test('TypeNarrowingIsNoneTuple1', () => { TestUtils.validateResults(analysisResults, 0); }); +test('TypeNarrowingIsNoneNamedTuple1', () => { + const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typeNarrowingIsNoneNamedTuple1.py']); + + TestUtils.validateResults(analysisResults, 0); +}); + +test('TypeNarrowingIsNoneNamedTuple2', () => { + const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typeNarrowingIsNoneNamedTuple2.py']); + + TestUtils.validateResults(analysisResults, 0); +}); + test('TypeNarrowingLiteral1', () => { const analysisResults = TestUtils.typeAnalyzeSampleFiles(['typeNarrowingLiteral1.py']);