Contextually type array elements using index signatures #58288
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Andarist
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Apr 22, 2024
src/compiler/checker.ts
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| @@ -30694,8 +30694,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker { | |||
| } | |||
| // If element index is known and a contextual property with that name exists, return it. Otherwise return the | |||
| // iterated or element type of the contextual type. | |||
| return (!firstSpreadIndex || index < firstSpreadIndex) && getTypeOfPropertyOfContextualType(t, "" + index as __String) || | |||
| getIteratedTypeOrElementType(IterationUse.Element, t, undefinedType, /*errorNode*/ undefined, /*checkAssignability*/ false); | |||
| return (firstSpreadIndex === undefined || index < firstSpreadIndex) && getTypeOfPropertyOfContextualType(t, "" + index as __String) || | |||
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We have 2 fixes here
!firstSpreadIndex->firstSpreadIndex === undefined. This fixes contextual parameter type here. It is not assigned correctly today. This PR makes it an implicit any which is better than the incorrect assignment.- I also start using applicable index info as a fallback here. This covers cases when
tis just an array-like that uses index signatures - that's not something thatgetIteratedTypeOrElementTypehandles today.
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…t-types-from-index-signatures
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fixes #58286