add global `resolved_promise`

src/runtime/internal/constants.ts

@@ -0,0 +1 @@
+export const resolved_promise = Promise.resolve();

src/runtime/internal/scheduler.ts

@@ -1,5 +1,6 @@
 import { run_all } from './utils';
 import { current_component, set_current_component } from './lifecycle';
+import { resolved_promise } from './constants';
 
 export const dirty_components = [];
 export const intros = { enabled: false };
@@ -8,7 +9,6 @@ export const binding_callbacks = [];
 const render_callbacks = [];
 const flush_callbacks = [];
 
-const resolved_promise = Promise.resolve();
 let update_scheduled = false;
 
 export function schedule_update() {

src/runtime/internal/transitions.ts

@@ -6,6 +6,7 @@ import { custom_event } from './dom';
 import { add_render_callback } from './scheduler';
 import { TransitionConfig } from '../transition';
 import { Fragment } from './Component';
+import { resolved_promise } from './constants';
 
 let promise: Promise<void> | null;
 type INTRO = 1;
@@ -27,7 +28,7 @@ interface Outro {
 
 function wait() {
 	if (!promise) {
-		promise = Promise.resolve();
+		promise = resolved_promise;
 		promise.then(() => {
 			promise = null;
 		});

src/runtime/motion/spring.ts

@@ -1,6 +1,7 @@
 import { Readable, writable } from 'svelte/store';
 import { loop, now, Task } from 'svelte/internal';
 import { is_date } from './utils';
+import { resolved_promise } from 'svelte/internal/constants';
 
 interface TickContext<T> {
 	inv_mass: number;
@@ -89,7 +90,7 @@ export function spring<T=any>(value?: T, opts: SpringOpts = {}): Spring<T> {
 			last_time = now();
 			last_value = new_value;
 			store.set(value = target_value);
-			return Promise.resolve();
+			return resolved_promise;
 		} else if (opts.soft) {
 			const rate = opts.soft === true ? .5 : +opts.soft;
 			inv_mass_recovery_rate = 1 / (rate * 60);

src/runtime/motion/tweened.ts

@@ -2,6 +2,7 @@ import { Readable, writable } from 'svelte/store';
 import { assign, loop, now, Task } from 'svelte/internal';
 import { linear } from 'svelte/easing';
 import { is_date } from './utils';
+import { resolved_promise } from 'svelte/internal/constants';
 
 function get_interpolator(a, b) {
 	if (a === b || a !== a) return () => a;
@@ -78,7 +79,7 @@ export function tweened<T>(value?: T, defaults: Options<T> = {}): Tweened<T> {
 	function set(new_value: T, opts?: Options<T>) {
 		if (value == null) {
 			store.set(value = new_value);
-			return Promise.resolve();
+			return resolved_promise;
 		}
 
 		target_value = new_value;
@@ -100,7 +101,7 @@ export function tweened<T>(value?: T, defaults: Options<T> = {}): Tweened<T> {
 			}
 
 			store.set(value = target_value);
-			return Promise.resolve();
+			return resolved_promise;
 		}
 
 		const start = now() + delay;