From 7c7e2aa032e6312a0ca4dcb3f2d7870153ca7298 Mon Sep 17 00:00:00 2001
From: Daniel Rosenwasser <drosen@microsoft.com>
Date: Thu, 28 Jan 2016 17:23:56 -0800
Subject: [PATCH] Error on nodes which should not have type predicates.

---
 src/compiler/checker.ts              | 5 ++++-
 src/compiler/diagnosticMessages.json | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 9b7b2bd12c8..3ee1f2c6b72 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -11563,11 +11563,14 @@ namespace ts {
             return -1;
         }
 
-        function checkTypePredicate(node: TypePredicateNode) {
+        function checkTypePredicate(node: TypePredicateNode): void {
             const parent = getTypePredicateParent(node);
             if (!parent) {
+                // The parent must not be valid.
+                error(node.parent, Diagnostics.A_type_predicate_is_only_allowed_in_return_type_position_for_functions_and_methods);
                 return;
             }
+
             const typePredicate = getSignatureFromDeclaration(parent).typePredicate;
             if (!typePredicate) {
                 return;
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 25b86e67d34..2c8de840fc0 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -723,6 +723,10 @@
         "category": "Error",
         "code": 1227
     },
+    "A type predicate is only allowed in return type position for functions and methods.": {
+        "category": "Error",
+        "code": 1228
+    },
     "A type predicate cannot reference a rest parameter.": {
         "category": "Error",
         "code": 1229