From c95c0f5fbe7ae37ff1dd3e4997c675e67eb5a925 Mon Sep 17 00:00:00 2001
From: dcode <dcode@dcode.io>
Date: Sun, 3 Feb 2019 13:37:32 +0100
Subject: [PATCH] Emit diagnostic when redeclaring a local name, fixes #452

---
 src/compiler.ts | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/compiler.ts b/src/compiler.ts
index 9e8b8678..0b28eb67 100644
--- a/src/compiler.ts
+++ b/src/compiler.ts
@@ -2244,7 +2244,14 @@ export class Compiler extends DiagnosticEmitter {
         ) { // here: not top-level
           local = flow.addScopedLocal(type, name, false, declaration); // reports
         } else {
-          local = currentFunction.addLocal(type, name, declaration); // reports
+          if (currentFunction.flow.getScopedLocal(name)) {
+            this.error(
+              DiagnosticCode.Duplicate_identifier_0,
+              declaration.name.range, name
+            );
+            continue;
+          }
+          local = currentFunction.addLocal(type, name, declaration);
         }
         if (initExpr) {
           initializers.push(this.compileAssignmentWithValue(declaration.name, initExpr));