Guard destructuring initializer contextual typing

Co-authored-by: RyanCavanaugh <[email protected]>

Author: Copilot

src/compiler/checker.ts

@@ -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;
         }
 

tests/baselines/reference/destructuringContextualBindingStackOverflow.errors.txt

@@ -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.
+    

tests/baselines/reference/destructuringContextualBindingStackOverflow.js

@@ -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;

tests/baselines/reference/destructuringContextualBindingStackOverflow.symbols

@@ -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))
+

tests/baselines/reference/destructuringContextualBindingStackOverflow.types

@@ -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
+>  : ^^^
+