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Do not mark indexed access object type comparisons as unreliable. (#54781)

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This commit is contained in:
Daniel Rosenwasser
2023-06-26 13:21:10 -07:00
committed by GitHub
parent 4cac28ed57
commit f762de5220
3 changed files with 36 additions and 6 deletions
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5
src/compiler/checker.ts
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@@ -21538,11 +21538,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
// Relate components directly before falling back to constraint relationships
// A type S[K] is related to a type T[J] if S is related to T and K is related to J.
if (result = isRelatedTo((source as IndexedAccessType).objectType, (target as IndexedAccessType).objectType, RecursionFlags.Both, reportErrors)) {
// This does _not_ generalize - specific instantiations of `S[K]` and `T[J]` may be related, even if the indexed accesses generally are not.
// For example, `S = {x: string, a: string}`, `T = {x: string, b: string}`, `K = J = "x"`. `S` and `T` are unrelated, but the result of executing
// `S["x"]` and `T["x"]` _are_. Given that, we have to flag the object type comparison here as "unreliable", since while the generic result can reliably
// be used in the affirmative case, it failing is not an indicator that the structural result will not succeed.
instantiateType((source as IndexedAccessType).objectType, reportUnreliableMapper);
result &= isRelatedTo((source as IndexedAccessType).indexType, (target as IndexedAccessType).indexType, RecursionFlags.Both, reportErrors);
}
if (result) {