Disallow paths beginning with @ in templates

packages/ember-template-compiler/lib/plugins/assert-reserved-named-arguments.js

@@ -0,0 +1,28 @@
+import { assert } from 'ember-metal/debug';
+import calculateLocationDisplay from 'ember-template-compiler/system/calculate-location-display';
+
+export default function AssertReservedNamedArguments(options) {
+  this.syntax = null;
+  this.options = options;
+}
+
+AssertReservedNamedArguments.prototype.transform = function AssertReservedNamedArguments_transform(ast) {
+  let moduleName = this.options.moduleName;
+
+  this.syntax.traverse(ast, {
+    PathExpression: function(node) {
+      if (node.original[0] === '@') {
+        assert(assertMessage(moduleName, node));
+      }
+    }
+  });
+
+  return ast;
+};
+
+function assertMessage(moduleName, node) {
+  let path = node.original;
+  let source = calculateLocationDisplay(moduleName, node.loc);
+
+  return `'${path}' is not a valid path. ${source}`;
+}

packages/ember-template-compiler/lib/plugins/index.js

@@ -3,17 +3,19 @@ import TransformItemClass from 'ember-template-compiler/plugins/transform-item-c
 import TransformAngleBracketComponents from 'ember-template-compiler/plugins/transform-angle-bracket-components';
 import TransformInputOnToOnEvent from 'ember-template-compiler/plugins/transform-input-on-to-onEvent';
 import TransformTopLevelComponents from 'ember-template-compiler/plugins/transform-top-level-components';
-import DeprecateRenderModel from 'ember-template-compiler/plugins/deprecate-render-model';
 import TransformInlineLinkTo from 'ember-template-compiler/plugins/transform-inline-link-to';
 import TransformOldClassBindingSyntax from 'ember-template-compiler/plugins/transform-old-class-binding-syntax';
+import DeprecateRenderModel from 'ember-template-compiler/plugins/deprecate-render-model';
+import AssertReservedNamedArguments from 'ember-template-compiler/plugins/assert-reserved-named-arguments';
 
 export default Object.freeze([
   TransformOldBindingSyntax,
   TransformItemClass,
   TransformAngleBracketComponents,
   TransformInputOnToOnEvent,
   TransformTopLevelComponents,
-  DeprecateRenderModel,
   TransformInlineLinkTo,
-  TransformOldClassBindingSyntax
+  TransformOldClassBindingSyntax,
+  DeprecateRenderModel,
+  AssertReservedNamedArguments
 ]);

packages/ember-template-compiler/tests/plugins/assert-reserved-named-arguments-test.js

@@ -0,0 +1,26 @@
+import { compile } from '../utils/helpers';
+
+QUnit.module('ember-template-compiler: assert-reserved-named-arguments');
+
+QUnit.test('Paths beginning with @ are not valid', function() {
+  expect(3);
+
+  expectAssertion(() => {
+    compile('{{@foo}}', {
+      moduleName: 'baz/foo-bar'
+    });
+  }, `'@foo' is not a valid path. ('baz/foo-bar' @ L1:C2) `);
+
+  expectAssertion(() => {
+    compile('{{#if @foo}}Yup{{/if}}', {
+      moduleName: 'baz/foo-bar'
+    });
+  }, `'@foo' is not a valid path. ('baz/foo-bar' @ L1:C6) `);
+
+  expectAssertion(() => {
+    compile('{{input type=(if @foo "bar" "baz")}}', {
+      moduleName: 'baz/foo-bar'
+    });
+  }, `'@foo' is not a valid path. ('baz/foo-bar' @ L1:C17) `);
+});
+