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'in' should not operate on primitive types (#41928 + @andrewbranch) (#42288)

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* 'in' should not operate on primitive types

* accept baselines of failing tests

* review

* update error message

* check if constraint of right type is assignable to a non primitive or instantiable non primitive

* do not throw errors where narrowing is impossible

* accept baselines

* fix test case failures

* Add more accurate comment discussion and document failing edge case in test

* Update baselines

Co-authored-by: Jonas Hübotter <jonas.huebotter@gmail.com>
This commit is contained in:
Andrew Branch
2021-01-11 16:46:08 -08:00
committed by GitHub
parent c456bbd466
commit b0f5e35777
10 changed files with 656 additions and 26 deletions
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28
src/compiler/checker.ts
View File

@@ -30305,14 +30305,36 @@ namespace ts {
rightType = checkNonNullType(rightType, right);
// TypeScript 1.0 spec (April 2014): 4.15.5
// The in operator requires the left operand to be of type Any, the String primitive type, or the Number primitive type,
// and the right operand to be of type Any, an object type, or a type parameter type.
// and the right operand to be
//
// 1. assignable to the non-primitive type,
// 2. an unconstrained type parameter,
// 3. a union or intersection including one or more type parameters, whose constituents are all assignable to the
// the non-primitive type, or are unconstrainted type parameters, or have constraints assignable to the
// non-primitive type, or
// 4. a type parameter whose constraint is
// i. an object type,
// ii. the non-primitive type, or
// iii. a union or intersection with at least one constituent assignable to an object or non-primitive type.
//
// The divergent behavior for type parameters and unions containing type parameters is a workaround for type
// parameters not being narrowable. If the right operand is a concrete type, we can error if there is any chance
// it is a primitive. But if the operand is a type parameter, it cannot be narrowed, so we don't issue an error
// unless *all* instantiations would result in an error.
//
// The result is always of the Boolean primitive type.
if (!(allTypesAssignableToKind(leftType, TypeFlags.StringLike | TypeFlags.NumberLike | TypeFlags.ESSymbolLike) ||
isTypeAssignableToKind(leftType, TypeFlags.Index | TypeFlags.TemplateLiteral | TypeFlags.StringMapping | TypeFlags.TypeParameter))) {
error(left, Diagnostics.The_left_hand_side_of_an_in_expression_must_be_of_type_any_string_number_or_symbol);
}
if (!allTypesAssignableToKind(rightType, TypeFlags.NonPrimitive | TypeFlags.InstantiableNonPrimitive)) {
error(right, Diagnostics.The_right_hand_side_of_an_in_expression_must_be_of_type_any_an_object_type_or_a_type_parameter);
const rightTypeConstraint = getConstraintOfType(rightType);
if (!allTypesAssignableToKind(rightType, TypeFlags.NonPrimitive | TypeFlags.InstantiableNonPrimitive) ||
rightTypeConstraint && (
isTypeAssignableToKind(rightType, TypeFlags.UnionOrIntersection) && !allTypesAssignableToKind(rightTypeConstraint, TypeFlags.NonPrimitive | TypeFlags.InstantiableNonPrimitive) ||
!maybeTypeOfKind(rightTypeConstraint, TypeFlags.NonPrimitive | TypeFlags.InstantiableNonPrimitive | TypeFlags.Object)
)
) {
error(right, Diagnostics.The_right_hand_side_of_an_in_expression_must_not_be_a_primitive);
}
return booleanType;
}

2
src/compiler/diagnosticMessages.json
View File

@@ -1625,7 +1625,7 @@
"category": "Error",
"code": 2360
},
"The right-hand side of an 'in' expression must be of type 'any', an object type or a type parameter.": {
"The right-hand side of an 'in' expression must not be a primitive.": {
"category": "Error",
"code": 2361
},