From 354fd10a2e12e49407615648579c8c00ee34e94a Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Fri, 1 Apr 2016 09:53:44 -0700
Subject: [PATCH] Separate error messages for 'null', 'undefined', or both.

---
 src/compiler/checker.ts              | 10 ++++++++--
 src/compiler/diagnosticMessages.json | 10 +++++++++-
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index da6548f8c69..6fc60c5c78a 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9554,8 +9554,14 @@ namespace ts {
 
         function checkNonNullExpression(node: Expression | QualifiedName) {
             const type = checkExpression(node);
-            if (strictNullChecks && getNullableKind(type)) {
-                error(node, Diagnostics.Object_is_possibly_null_or_undefined);
+            if (strictNullChecks) {
+                const kind = getNullableKind(type);
+                if (kind) {
+                    error(node, kind & TypeFlags.Undefined ? kind & TypeFlags.Null ?
+                        Diagnostics.Object_is_possibly_null_or_undefined :
+                        Diagnostics.Object_is_possibly_undefined :
+                        Diagnostics.Object_is_possibly_null);
+                }
                 return getNonNullableType(type);
             }
             return type;
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index d7c2fac2710..ebd3202d3a7 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1727,10 +1727,18 @@
         "category": "Error",
         "code": 2530
     },
-    "Object is possibly 'null' or 'undefined'.": {
+    "Object is possibly 'null'.": {
         "category": "Error",
         "code": 2531
     },
+    "Object is possibly 'undefined'.": {
+        "category": "Error",
+        "code": 2532
+    },
+    "Object is possibly 'null' or 'undefined'.": {
+        "category": "Error",
+        "code": 2533
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600