propagate changes through slots with props (sveltejs#4091)

src/compiler/compile/render_dom/wrappers/InlineComponent/index.ts

@@ -182,11 +182,9 @@ export default class InlineComponentWrapper extends Wrapper {
 			});
 		});
 
-		const non_let_dependencies = Array.from(fragment_dependencies).filter(name => !this.node.scope.is_let(name));
-
 		const dynamic_attributes = this.node.attributes.filter(a => a.get_dependencies().length > 0);
 
-		if (!uses_spread && (dynamic_attributes.length > 0 || this.node.bindings.length > 0 || non_let_dependencies.length > 0)) {
+		if (!uses_spread && (dynamic_attributes.length > 0 || this.node.bindings.length > 0 || fragment_dependencies.size > 0)) {
 			updates.push(b`const ${name_changes} = {};`);
 		}
 
@@ -266,9 +264,9 @@ export default class InlineComponentWrapper extends Wrapper {
 			}
 		}
 
-		if (non_let_dependencies.length > 0) {
+		if (fragment_dependencies.size > 0) {
 			updates.push(b`
-				if (${renderer.dirty(non_let_dependencies)}) {
+				if (${renderer.dirty(Array.from(fragment_dependencies))}) {
 					${name_changes}.$$scope = { dirty: #dirty, ctx: #ctx };
 				}`);
 		}

test/runtime/samples/component-slot-let-in-slot/Inner.svelte

@@ -0,0 +1 @@
+<slot/>

test/runtime/samples/component-slot-let-in-slot/Outer.svelte

@@ -0,0 +1,5 @@
+<script>
+	export let prop
+</script>
+
+<slot value={prop} />

test/runtime/samples/component-slot-let-in-slot/_config.js

@@ -0,0 +1,12 @@
+export default {
+	props: {
+		prop: 'a',
+	},
+
+	html: 'a',
+
+	test({ assert, component, target }) {
+		component.prop = 'b';
+		assert.htmlEqual( target.innerHTML, 'b' );
+	}
+};

test/runtime/samples/component-slot-let-in-slot/main.svelte

@@ -0,0 +1,10 @@
+<script>
+	import Outer from './Outer.svelte'
+	import Inner from './Inner.svelte'
+
+	export let prop
+</script>
+
+<Outer {prop} let:value>
+	<Inner>{value}</Inner>
+</Outer>