From dd597102a4e8d308864fd886b41be47761a799fb Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Wed, 5 Jun 2024 15:43:11 -0700
Subject: [PATCH] Local declarations don't mutate captured outer variables

---
 src/compiler/binder.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 0b5f5a8f15b..0a9fcdbb464 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -1393,7 +1393,7 @@ function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
     function createFlowMutation(flags: FlowFlags.Assignment | FlowFlags.ArrayMutation, antecedent: FlowNode, node: Expression | VariableDeclaration | ArrayBindingElement) {
         setFlowNodeReferenced(antecedent);
         hasFlowEffects = true;
-        hasFlowMutation = true;
+        if (node.kind !== SyntaxKind.VariableDeclaration && node.kind !== SyntaxKind.BindingElement) hasFlowMutation = true;
         const result = createFlowNode(flags, node, antecedent) as FlowAssignment | FlowArrayMutation;
         if (currentExceptionTarget) {
             addAntecedent(currentExceptionTarget, result);