From 2fdb5b8659bbf909a90f11d1e31b43bbe0da934c Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <nathansa@microsoft.com>
Date: Mon, 11 Sep 2017 11:16:01 -0700
Subject: [PATCH] assignContextualParameterTypes handles arguments object

Previously, it would crash &mdash; the arguments object is a transient
symbol with no declaration, and `getEffectiveTypeAnnotationNode`
does not accept `undefined`.
---
 src/compiler/checker.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ff5d1c661e8..b8b2e8edb82 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -16665,8 +16665,9 @@ namespace ts {
                 }
             }
             if (signature.hasRestParameter && isRestParameterIndex(context, signature.parameters.length - 1)) {
+                // parameter might be a transient symbol generated by use of `arguments` in the function body.
                 const parameter = lastOrUndefined(signature.parameters);
-                if (!getEffectiveTypeAnnotationNode(<ParameterDeclaration>parameter.valueDeclaration)) {
+                if (isTransientSymbol(parameter) || !getEffectiveTypeAnnotationNode(<ParameterDeclaration>parameter.valueDeclaration)) {
                     const contextualParameterType = getTypeOfSymbol(lastOrUndefined(context.parameters));
                     assignTypeToParameterAndFixTypeParameters(parameter, contextualParameterType);
                 }