fix($compile): handle boolean attributes in @ bindings

Closes angular#13767

Author: petebacondarwin

src/ng/compile.js

@@ -2956,10 +2956,13 @@ function $CompileProvider($provide, $$sanitizeUriProvider) {
               }
             });
             attrs.$$observers[attrName].$$scope = scope;
-            if (isString(attrs[attrName])) {
+            lastValue = attrs[attrName];
+            if (isString(lastValue)) {
               // If the attribute has been provided then we trigger an interpolation to ensure
               // the value is there for use in the link fn
-              destination[scopeName] = $interpolate(attrs[attrName])(scope);
+              destination[scopeName] = $interpolate(lastValue)(scope);
+            } else if (isBoolean(lastValue)) {
+              destination[scopeName] = lastValue;
             }
             break;
 

test/ng/compileSpec.js

@@ -2694,6 +2694,24 @@ describe('$compile', function() {
                   expect(element.isolateScope()['watch']).toBe('watch');
                 })
             );
+
+            it('should handle @ bindings on BOOLEAN attributes', function() {
+              var checkedVal;
+              module(function($compileProvider) {
+                $compileProvider.directive('test', function() {
+                  return {
+                    scope: { checked: '@' },
+                    link: function(scope, element, attrs) {
+                      checkedVal = scope.checked;
+                    }
+                  };
+                });
+              });
+              inject(function($compile, $rootScope) {
+                $compile('<input test checked="checked">')($rootScope);
+                expect(checkedVal).toEqual(true);
+              });
+            });
           });