allow event handlers to come from destructured var declarations - fixes #2149

src/compile/nodes/EventHandler.ts

@@ -32,7 +32,7 @@ export default class EventHandler extends Node {
 				if (node && node.type === 'VariableDeclaration') {
 					// for `const handleClick = () => {...}`, we want the [arrow] function expression node
 					const declarator = node.declarations.find(d => d.id.name === info.expression.name);
-					node = declarator.init;
+					node = declarator && declarator.init;
 				}
 
 				if (node && /Function/.test(node.type) && node.params.length === 0) {

test/runtime/samples/event-handler-destructured/_config.js

@@ -0,0 +1,15 @@
+export default {
+	html: `
+		<button>clicked: false</button>
+	`,
+
+	async test({ assert, component, target, window }) {
+		const button = target.querySelector('button');
+		const event = new window.MouseEvent('click');
+
+		await button.dispatchEvent(event);
+		assert.htmlEqual(target.innerHTML, `
+			<button>clicked: true</button>
+		`);
+	}
+};

test/runtime/samples/event-handler-destructured/main.svelte

@@ -0,0 +1,16 @@
+<script>
+	function get_handlers() {
+		return {
+			handle_click: () => {
+				clicked = true;
+			}
+		};
+	}
+
+	let clicked = false;
+	const { handle_click } = get_handlers();
+</script>
+
+<button on:click={handle_click}>
+	clicked: {clicked}
+</button>