fix: improve `each_key_without_as` error

.changeset/three-wasps-work.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: improve `each_key_without_as` error

packages/svelte/src/compiler/phases/2-analyze/visitors/EachBlock.js

@@ -1,3 +1,4 @@
+/** @import { Expression } from 'estree' */
 /** @import { AST, Binding } from '#compiler' */
 /** @import { Context } from '../types' */
 /** @import { Scope } from '../../scope' */
@@ -29,7 +30,7 @@ export function EachBlock(node, context) {
 	}
 
 	if (node.metadata.keyed && !node.context) {
-		e.each_key_without_as(node);
+		e.each_key_without_as(/** @type {Expression} */ (node.key));
 	}
 
 	// evaluate expression in parent scope