From ea4b13bdf94fb2241f15874d9d0b0cead15d6784 Mon Sep 17 00:00:00 2001
From: Anders Hejlsberg <andersh@microsoft.com>
Date: Thu, 3 Mar 2016 11:18:12 -0800
Subject: [PATCH] Allow 'null' and 'undefined' as type names

---
 src/compiler/checker.ts            | 6 ++++++
 src/compiler/declarationEmitter.ts | 2 ++
 src/compiler/parser.ts             | 4 ++++
 src/compiler/scanner.ts            | 1 +
 src/compiler/types.ts              | 1 +
 src/compiler/utilities.ts          | 1 +
 6 files changed, 15 insertions(+)

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 89517b7539e..71ef823d137 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -3411,6 +3411,8 @@ namespace ts {
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.UndefinedKeyword:
+                case SyntaxKind.NullKeyword:
                 case SyntaxKind.StringLiteralType:
                     return true;
                 case SyntaxKind.ArrayType:
@@ -4935,6 +4937,10 @@ namespace ts {
                     return esSymbolType;
                 case SyntaxKind.VoidKeyword:
                     return voidType;
+                case SyntaxKind.UndefinedKeyword:
+                    return undefinedType;
+                case SyntaxKind.NullKeyword:
+                    return nullType;
                 case SyntaxKind.ThisType:
                     return getTypeFromThisTypeNode(node);
                 case SyntaxKind.StringLiteralType:
diff --git a/src/compiler/declarationEmitter.ts b/src/compiler/declarationEmitter.ts
index 1328a2e8484..d2031a7bad6 100644
--- a/src/compiler/declarationEmitter.ts
+++ b/src/compiler/declarationEmitter.ts
@@ -367,6 +367,8 @@ namespace ts {
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.UndefinedKeyword:
+                case SyntaxKind.NullKeyword:
                 case SyntaxKind.ThisType:
                 case SyntaxKind.StringLiteralType:
                     return writeTextOfNode(currentText, type);
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index a7e76ac3ae4..c2d3173a860 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -2379,12 +2379,14 @@ namespace ts {
                 case SyntaxKind.NumberKeyword:
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
+                case SyntaxKind.UndefinedKeyword:
                     // If these are followed by a dot, then parse these out as a dotted type reference instead.
                     const node = tryParse(parseKeywordAndNoDot);
                     return node || parseTypeReference();
                 case SyntaxKind.StringLiteral:
                     return parseStringLiteralTypeNode();
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.NullKeyword:
                     return parseTokenNode<TypeNode>();
                 case SyntaxKind.ThisKeyword: {
                     const thisKeyword = parseThisTypeNode();
@@ -2416,6 +2418,8 @@ namespace ts {
                 case SyntaxKind.BooleanKeyword:
                 case SyntaxKind.SymbolKeyword:
                 case SyntaxKind.VoidKeyword:
+                case SyntaxKind.UndefinedKeyword:
+                case SyntaxKind.NullKeyword:
                 case SyntaxKind.ThisKeyword:
                 case SyntaxKind.TypeOfKeyword:
                 case SyntaxKind.OpenBraceToken:
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index 64747fc638c..8979814a7a2 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -114,6 +114,7 @@ namespace ts {
         "try": SyntaxKind.TryKeyword,
         "type": SyntaxKind.TypeKeyword,
         "typeof": SyntaxKind.TypeOfKeyword,
+        "undefined": SyntaxKind.UndefinedKeyword,
         "var": SyntaxKind.VarKeyword,
         "void": SyntaxKind.VoidKeyword,
         "while": SyntaxKind.WhileKeyword,
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index ea3d95c49eb..9f709c8fa68 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -171,6 +171,7 @@ namespace ts {
         StringKeyword,
         SymbolKeyword,
         TypeKeyword,
+        UndefinedKeyword,
         FromKeyword,
         GlobalKeyword,
         OfKeyword, // LastKeyword and LastToken
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 7012326fa98..953e2a7c194 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -515,6 +515,7 @@ namespace ts {
             case SyntaxKind.StringKeyword:
             case SyntaxKind.BooleanKeyword:
             case SyntaxKind.SymbolKeyword:
+            case SyntaxKind.UndefinedKeyword:
                 return true;
             case SyntaxKind.VoidKeyword:
                 return node.parent.kind !== SyntaxKind.VoidExpression;