Allow undefined and null in helper names

spec/basic.js

@@ -74,6 +74,20 @@ describe("basic context", function() {
           }
         },
         'true true object');
+    shouldCompileTo('{{undefined}}',
+        {
+          undefined: function() {
+            return 'undefined!';
+          }
+        },
+        'undefined!');
+    shouldCompileTo('{{null}}',
+        {
+          null: function() {
+            return 'null!';
+          }
+        },
+        'null!');
   });
 
   it("newlines", function() {

spec/javascript-compiler.js

@@ -23,7 +23,7 @@ describe('javascript-compiler api', function() {
     // Tests nameLookup dot vs. bracket behavior.  Bracket is required in certain cases
     // to avoid errors in older browsers.
     it('should handle reserved words', function() {
-      shouldCompileTo("{{foo}} {{~[null]~}}", { foo: "food" }, "food");
+      shouldCompileTo("{{foo}} {{~null~}}", { foo: "food" }, "food");
     });
   });
   describe('#compilerInfo', function() {

spec/parser.js

@@ -58,6 +58,10 @@ describe('parser', function() {
     equals(ast_for("{{foo false}}"), "{{ PATH:foo [BOOLEAN{false}] }}\n");
   });
 
+  it('parses mustaches with undefined and null paths', function() {
+    equals(ast_for("{{undefined}}"), "{{ UNDEFINED [] }}\n");
+    equals(ast_for("{{null}}"), "{{ NULL [] }}\n");
+  });
   it('parses mustaches with undefined and null parameters', function() {
     equals(ast_for("{{foo undefined null}}"), "{{ PATH:foo [UNDEFINED, NULL] }}\n");
   });

src/handlebars.yy

@@ -83,8 +83,6 @@ partial
 param
   : helperName -> $1
   | sexpr -> $1
-  | UNDEFINED -> new yy.UndefinedLiteral(yy.locInfo(@$))
-  | NULL -> new yy.NullLiteral(yy.locInfo(@$))
   ;
 
 sexpr
@@ -109,6 +107,8 @@ helperName
   | STRING -> new yy.StringLiteral($1, yy.locInfo(@$))
   | NUMBER -> new yy.NumberLiteral($1, yy.locInfo(@$))
   | BOOLEAN -> new yy.BooleanLiteral($1, yy.locInfo(@$))
+  | UNDEFINED -> new yy.UndefinedLiteral(yy.locInfo(@$))
+  | NULL -> new yy.NullLiteral(yy.locInfo(@$))
   ;
 
 partialName