add regression test against #3966

test/runtime/samples/each-block-after-let/Child.svelte

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

test/runtime/samples/each-block-after-let/_config.js

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+export default {
+	html: `
+		<div>a a</div>
+		<div>b</div>
+		<div>a a</div>
+	`
+};

test/runtime/samples/each-block-after-let/main.svelte

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+<script>
+	import Child from './Child.svelte';
+	const value = ['a'];
+</script>
+
+<div>
+	{value[0]}
+	{#each value as n}{n}{/each}
+</div>
+<div>
+	<Child value={['b']} let:value>{value[0]}</Child>
+</div>
+<div>
+	{value[0]}
+	{#each value as n}{n}{/each}
+</div>