disable loop protection inside generators (#4716)

src/compiler/compile/Component.ts

@@ -714,8 +714,14 @@ export default class Component {
 		};
 		let scope_updated = false;
 
+		let generator_count = 0;
+
 		walk(content, {
 			enter(node: Node, parent, prop, index) {
+				if ((node.type === 'FunctionDeclaration' || node.type === 'FunctionExpression') && node.generator === true) {
+					generator_count++;
+				}
+
 				if (map.has(node)) {
 					scope = map.get(node);
 				}
@@ -742,8 +748,12 @@ export default class Component {
 			},
 
 			leave(node: Node) {
+				if ((node.type === 'FunctionDeclaration' || node.type === 'FunctionExpression') && node.generator === true) {
+					generator_count--;
+				}
+
 				// do it on leave, to prevent infinite loop
-				if (component.compile_options.dev && component.compile_options.loopGuardTimeout > 0) {
+				if (component.compile_options.dev && component.compile_options.loopGuardTimeout > 0 && generator_count <= 0) {
 					const to_replace_for_loop_protect = component.loop_protect(node, scope, component.compile_options.loopGuardTimeout);
 					if (to_replace_for_loop_protect) {
 						this.replace(to_replace_for_loop_protect);

test/runtime/samples/loop-protect-generator-opt-out/_config.js

@@ -0,0 +1,6 @@
+export default {
+	compileOptions: {
+		dev: true,
+		loopGuardTimeout: 1,
+	},
+};

test/runtime/samples/loop-protect-generator-opt-out/main.svelte

@@ -0,0 +1,14 @@
+<script>
+	const it = gen();
+	it.next();
+
+	setTimeout(() => {
+		it.next();
+	}, 20)
+
+	function* gen() {
+		while (true) {
+			yield;
+		}
+	}
+</script>