ensure hoisting doesnt mess up source maps

packages/svelte/src/compiler/phases/3-transform/client/utils.js

@@ -288,7 +288,8 @@ function get_hoistable_params(node, context) {
 				params.push(b.id(binding.node.name.slice(1)));
 				params.push(b.id(binding.node.name));
 			} else {
-				params.push(binding.node);
+				// create a copy to remove start/end tags which would mess up source maps
+				params.push(b.id(binding.node.name));
 			}
 		}
 	}

playgrounds/sandbox/run.js

@@ -35,6 +35,7 @@ for (const generate of ['client', 'server']) {
 		const source = fs.readFileSync(input, 'utf-8');
 
 		const output_js = `${cwd}/output/${generate}/${file}.js`;
+		const output_map = `${cwd}/output/${generate}/${file}.js.map`;
 		const output_css = `${cwd}/output/${generate}/${file}.css`;
 
 		mkdirp(path.dirname(output_js));
@@ -54,7 +55,11 @@ for (const generate of ['client', 'server']) {
 			runes: argv.runes
 		});
 
-		fs.writeFileSync(output_js, compiled.js.code);
+		fs.writeFileSync(
+			output_js,
+			compiled.js.code + '\n//# sourceMappingURL=' + path.basename(output_map)
+		);
+		fs.writeFileSync(output_map, compiled.js.map.toString());
 		if (compiled.css) {
 			fs.writeFileSync(output_css, compiled.css.code);
 		}