Support lets

src/compiler/compile/render_dom/index.ts

@@ -455,7 +455,7 @@ export default function dom(
 				${(reactive_declarations.length > 0 || uses_slots) && b`
 				$$self.$$.update = () => {
 					if (${renderer.dirty(['$$scope'], true)}) {
-						#update_$$slots($$scope, $$self.$$.dirty)
+						#update_$$slots($$scope)
 					}
 
 					${reactive_declarations}

src/runtime/internal/slots.ts

@@ -1,5 +1,5 @@
 import { onDestroy } from './lifecycle';
-import { assign } from './utils'
+import { assign, noop } from './utils';
 
 export function create_slot(definition, ctx, $$scope, fn) {
 	if (definition) {
@@ -39,28 +39,37 @@ export function get_slot_changes(definition, $$scope, dirty, fn) {
 }
 
 export function create_slots_accessor(slots, scope) {
-	const slot_list = [];
-	function update(scope, dirty) {
-		slot_list.forEach(({ slot, definition }) =>
-			slot.p(
-				get_slot_context(definition, [], scope, null),
-				get_slot_changes(definition, scope, dirty, null)
-			)
-		);
+	const update_list = [];
+	function update(scope) {
+		update_list.forEach(fn => fn(scope));
 	}
 
 	const $$slots = {};
 	for (const key in slots) {
-		$$slots[key] = function () {
-			let definition = slots[key];
-			let slot = create_slot(definition, [], scope, null);
+		$$slots[key] = function (ctx, callback = noop) {
+			const definition = slots[key];
+			const slot = create_slot(definition, null, scope, () => ctx);
+			const content = slot.c();
+
+			function local_update (scope, ctx_fn, dirty_fn) {
+					slot.p(
+						get_slot_context(definition, null, scope, ctx_fn),
+						get_slot_changes(definition, scope, 0, dirty_fn)
+					);
+					callback(content);
+			}
 
 			if (slot.d) onDestroy(slot.d);
-			if (slot.p) slot_list.push({ definition, slot });
+			if (slot.p) update_list.push(local_update);
 
 			return {
-					content: slot.c(),
-					mount: slot.m
+				content,
+				mount: slot.m,
+				update: props => local_update(
+					scope,
+					() => assign(ctx, props),
+					() => Object.keys(props).reduce((o, k) => (o[k] = true, o), {})
+				)
 			};
 		};
 	}

test/runtime/samples/$$slots-let/Child.svelte

@@ -0,0 +1,8 @@
+<script>
+  const slot = $$slots.default({ value: 'foo' })
+  let target
+  $: target && slot.mount(target)
+</script>
+
+<button on:click={e => slot.update({ value: 'bar' })}>Click me</button>
+<div bind:this={target} />

test/runtime/samples/$$slots-let/_config.js

@@ -0,0 +1,18 @@
+export default {
+	async test({ assert, target, window, }) {
+		assert.htmlEqual(target.innerHTML, `
+			<button>Click me</button>
+			<div>foo</div>
+		`);
+
+		const btn = target.querySelector('button');
+		const clickEvent = new window.MouseEvent('click');
+
+		await btn.dispatchEvent(clickEvent);
+
+		assert.htmlEqual(target.innerHTML, `
+			<button>Click me</button>
+			<div>bar</div>
+		`);
+	}
+};

test/runtime/samples/$$slots-let/main.svelte

@@ -0,0 +1,7 @@
+<script>
+  import Child from './Child.svelte'
+</script>
+
+<Child let:value>
+  {value}
+</Child>