[BUGFIX release] Fix block params named attrs

Fixes #14678

packages/ember-glimmer/tests/integration/syntax/with-test.js

@@ -208,6 +208,26 @@ moduleFor('Syntax test: {{#with as}}', class extends IfUnlessWithSyntaxTest {
     this.assertText('Hello world');
   }
 
+  ['@test `attrs` can be used as a block param [GH#14678]']() {
+    this.render('{{#with hash as |attrs|}}[{{hash.foo}}-{{attrs.foo}}]{{/with}}', {
+      hash: { foo: 'foo' }
+    });
+
+    this.assertText('[foo-foo]');
+
+    this.runTask(() => this.rerender());
+
+    this.assertText('[foo-foo]');
+
+    this.runTask(() => this.context.set('hash.foo', 'FOO'));
+
+    this.assertText('[FOO-FOO]');
+
+    this.runTask(() => this.context.set('hash.foo', 'foo'));
+
+    this.assertText('[foo-foo]');
+  }
+
 });
 
 moduleFor('Syntax test: Multiple {{#with as}} helpers', class extends RenderingTest {

packages/ember-template-compiler/lib/plugins/transform-attrs-into-args.js

@@ -22,24 +22,67 @@
   @class TransformAttrsToProps
 */
 
+class SymbolTable {
+  constructor(symbols, parent = null) {
+    this.symbols = symbols;
+    this.parent = parent;
+  }
+
+  hasLocalVariable(name) {
+    let { symbols, parent } = this;
+    return symbols.indexOf(name) >= 0 || (parent && parent.hasLocalVariable(name));
+  }
+
+  child(symbols) {
+    return new SymbolTable(symbols, this);
+  }
+}
+
+class Stack {
+  constructor() {
+    this.items = [];
+    this.current = null;
+  }
+
+  peek() {
+    return this.current;
+  }
+
+  push(item) {
+    this.items.push(item);
+    this.current = item;
+    return item;
+  }
+
+  pop() {
+    this.current = this.items[this.items.length - 1];
+    return this.items.pop();
+  }
+}
+
 export default function TransformAttrsToProps() {
   // set later within Glimmer2 to the syntax package
   this.syntax = null;
 }
 
-function isAttrs(node) {
-  if (node.parts[0] === 'attrs') {
-    return true;
+function isAttrs(node, symbolTable) {
+  let name = node.parts[0];
+
+  if (symbolTable.hasLocalVariable(name)) {
+    return false;
   }
 
-  let _this = node.parts[0];
-  let attrs = node.parts[1];
+  if (name === 'attrs') {
+    return true;
+  }
 
-  if (_this === null && attrs === 'attrs') {
+  if (name === null && node.parts[1] === 'attrs') {
     node.parts.shift();
     node.original = node.original.slice(5);
     return true;
   }
+
+  return false;
 }
 
 /**
@@ -50,9 +93,26 @@ function isAttrs(node) {
 TransformAttrsToProps.prototype.transform = function TransformAttrsToProps_transform(ast) {
   let { traverse, builders: b } = this.syntax;
 
+  let stack = new Stack();
+
   traverse(ast, {
+    Program: {
+      enter(node) {
+        let parent = stack.peek();
+
+        if (parent) {
+          stack.push(parent.child(node.blockParams));
+        } else {
+          stack.push(new SymbolTable(node.blockParams));
+        }
+      },
+      exit(node) {
+        stack.pop();
+      }
+    },
+
     PathExpression(node) {
-      if (isAttrs(node)) {
+      if (isAttrs(node, stack.peek())) {
         let path = b.path(node.original.substr(6));
         path.original = `@${path.original}`;
         path.data = true;