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Guard destructuring initializer contextual typing

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Co-authored-by: RyanCavanaugh <6685088+RyanCavanaugh@users.noreply.github.com>
This commit is contained in:
copilot-swe-agent[bot] 2026-01-16 18:18:37 +00:00
parent 43898d202f
commit 2abf5a1a7b
5 changed files with 67 additions and 2 deletions
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16
src/compiler/checker.ts
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@ -28312,7 +28312,19 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
// from its initializer, we'll already have cached the type. Otherwise we compute it now
// without caching such that transient types are reflected.
const links = getNodeLinks(node);
return links.resolvedType || getTypeOfExpression(node);
if (links.resolvedType) {
return links.resolvedType;
}
const pattern = isVariableDeclaration(node.parent) && node.parent.initializer === node && isBindingPattern(node.parent.name)
? node.parent.name
: undefined;
if (pattern) {
contextualBindingPatterns.push(pattern);
const type = getTypeOfExpression(node);
contextualBindingPatterns.pop();
return type;
}
return getTypeOfExpression(node);
}
function getInitialTypeOfVariableDeclaration(node: VariableDeclaration) {
@ -31023,7 +31035,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
// If the identifier is declared in a binding pattern for which we're currently computing the implied type and the
// reference occurs with the same binding pattern, return the non-inferrable any type. This for example occurs in
// 'const [a, b = a + 1] = [2]' when we're computing the contextual type for the array literal '[2]'.
if (declaration && declaration.kind === SyntaxKind.BindingElement && contains(contextualBindingPatterns, declaration.parent) && findAncestor(node, parent => parent === declaration!.parent)) {
if (declaration && declaration.kind === SyntaxKind.BindingElement && contains(contextualBindingPatterns, declaration.parent)) {
return nonInferrableAnyType;
}

18
tests/baselines/reference/destructuringContextualBindingStackOverflow.errors.txt Normal file
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@ -0,0 +1,18 @@
destructuringContextualBindingStackOverflow.ts(1,7): error TS2322: Type '{ c: number; f: any; }' is not assignable to type 'string | number | symbol'.
destructuringContextualBindingStackOverflow.ts(1,9): error TS2339: Property 'c' does not exist on type 'string | number | symbol'.
destructuringContextualBindingStackOverflow.ts(1,12): error TS2339: Property 'f' does not exist on type 'string | number | symbol'.
destructuringContextualBindingStackOverflow.ts(1,52): error TS2448: Block-scoped variable 'f' used before its declaration.
==== destructuringContextualBindingStackOverflow.ts (4 errors) ====
const { c, f }: string | number | symbol = { c: 0, f };
~~~~~~~~
!!! error TS2322: Type '{ c: number; f: any; }' is not assignable to type 'string | number | symbol'.
~
!!! error TS2339: Property 'c' does not exist on type 'string | number | symbol'.
~
!!! error TS2339: Property 'f' does not exist on type 'string | number | symbol'.
~
!!! error TS2448: Block-scoped variable 'f' used before its declaration.
!!! related TS2728 destructuringContextualBindingStackOverflow.ts:1:12: 'f' is declared here.

9
tests/baselines/reference/destructuringContextualBindingStackOverflow.js Normal file
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@ -0,0 +1,9 @@
//// [tests/cases/compiler/destructuringContextualBindingStackOverflow.ts] ////
//// [destructuringContextualBindingStackOverflow.ts]
const { c, f }: string | number | symbol = { c: 0, f };
//// [destructuringContextualBindingStackOverflow.js]
"use strict";
var _a = { c: 0, f: f }, c = _a.c, f = _a.f;

9
tests/baselines/reference/destructuringContextualBindingStackOverflow.symbols Normal file
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@ -0,0 +1,9 @@
//// [tests/cases/compiler/destructuringContextualBindingStackOverflow.ts] ////
=== destructuringContextualBindingStackOverflow.ts ===
const { c, f }: string | number | symbol = { c: 0, f };
>c : Symbol(c, Decl(destructuringContextualBindingStackOverflow.ts, 0, 7))
>f : Symbol(f, Decl(destructuringContextualBindingStackOverflow.ts, 0, 10))
>c : Symbol(c, Decl(destructuringContextualBindingStackOverflow.ts, 0, 44))
>f : Symbol(f, Decl(destructuringContextualBindingStackOverflow.ts, 0, 50))

17
tests/baselines/reference/destructuringContextualBindingStackOverflow.types Normal file
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@ -0,0 +1,17 @@
//// [tests/cases/compiler/destructuringContextualBindingStackOverflow.ts] ////
=== destructuringContextualBindingStackOverflow.ts ===
const { c, f }: string | number | symbol = { c: 0, f };
>c : any
> : ^^^
>f : any
> : ^^^
>{ c: 0, f } : { c: number; f: any; }
> : ^^^^^^^^^^^^^^^^^^^^^^
>c : number
> : ^^^^^^
>0 : 0
> : ^
>f : any
> : ^^^