escape @ sigils in block comments (#3173)

Author: Conduitry

src/compiler/compile/render_dom/Block.ts

@@ -2,6 +2,7 @@ import CodeBuilder from '../utils/CodeBuilder';
 import deindent from '../utils/deindent';
 import Renderer from './Renderer';
 import Wrapper from './wrappers/shared/Wrapper';
+import { escape } from '../utils/stringify';
 
 export interface BlockOptions {
 	parent?: Block;
@@ -408,7 +409,7 @@ export default class Block {
 		const local_key = this.key && this.get_unique_name('key');
 
 		return deindent`
-			${this.comment && `// ${this.comment}`}
+			${this.comment && `// ${escape(this.comment, { only_escape_at_symbol: true })}`}
 			function ${this.name}(${this.key ? `${local_key}, ` : ''}ctx) {
 				${this.get_contents(local_key)}
 			}