partial fix

Author: Rich-Harris

packages/svelte/src/compiler/phases/3-transform/client/visitors/AwaitExpression.js

@@ -3,15 +3,18 @@
 /** @import { Context } from '../types' */
 import { dev } from '../../../../state.js';
 import * as b from '../../../../utils/builders.js';
+import { get_rune } from '../../../scope.js';
 
 /**
  * @param {AwaitExpression} node
  * @param {Context} context
  */
 export function AwaitExpression(node, context) {
-	const tla = context.state.is_instance && context.state.scope.function_depth === 1;
-
-	const save = tla || !is_last_evaluated_expression(context.path, node);
+	const save =
+		// preserve context if this is a top-level await in `<script>`
+		(context.state.is_instance && context.state.scope.function_depth === 1) ||
+		// or if this is a derived/template expression
+		(is_reactive_expression(context) && !is_last_evaluated_expression(context.path, node));
 
 	if (dev || save) {
 		const expression = /** @type {Expression} */ (context.visit(node.argument));
@@ -22,11 +25,40 @@ export function AwaitExpression(node, context) {
 }
 
 /**
- *
+ * @param {Context} context
+ */
+function is_reactive_expression(context) {
+	let i = context.path.length;
+
+	while (i--) {
+		const parent = context.path[i];
+
+		if (
+			parent.type === 'ArrowFunctionExpression' ||
+			parent.type === 'FunctionExpression' ||
+			parent.type === 'FunctionDeclaration'
+		) {
+			return false;
+		}
+
+		if (parent.type === 'CallExpression' && get_rune(parent, context.state.scope) === '$derived') {
+			return true;
+		}
+
+		// @ts-expect-error we could probably use a neater/more robust mechanism
+		if (parent.metadata) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+/**
  * @param {AST.SvelteNode[]} path
  * @param {Expression | SpreadElement | Property} node
  */
-export function is_last_evaluated_expression(path, node) {
+function is_last_evaluated_expression(path, node) {
 	let i = path.length;
 
 	while (i--) {