fix: migration script messing with attributes (#14260)

.changeset/afraid-donuts-whisper.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: migration script messing with attributes

packages/svelte/src/compiler/migrate/index.js

@@ -1309,7 +1309,7 @@ const template = {
 						parent.type === 'RegularElement' ||
 						parent.type === 'SvelteElement' ||
 						parent.type === 'SvelteFragment') &&
-					parent.attributes.some((attr) => (attr.type = 'LetDirective'))
+					parent.attributes.some((attr) => attr.type === 'LetDirective')
 			)
 		) {
 			aliased_slot_name = `${name}_render`;

packages/svelte/tests/migrate/samples/slot-dont-mess-with-attributes/input.svelte

@@ -0,0 +1,5 @@
+<MyComponent
+  variant="outlined"
+>
+  <slot />
+</MyComponent>

packages/svelte/tests/migrate/samples/slot-dont-mess-with-attributes/output.svelte

@@ -0,0 +1,15 @@
+<script>
+  /**
+   * @typedef {Object} Props
+   * @property {import('svelte').Snippet} [children]
+   */
+
+  /** @type {Props} */
+  let { children } = $props();
+</script>
+
+<MyComponent
+  variant="outlined"
+>
+  {@render children?.()}
+</MyComponent>