use `is_function` everywhere

src/compiler/utils/clone.ts

@@ -1,3 +1,5 @@
+import { is_function} from '../../runtime/internal/utils';
+
 // adapted from klona v2.0.4 - https://github.com/lukeed/klona
 // (c) Luke Edwards, under MIT License
 
@@ -22,7 +24,7 @@ export function clone(val) {
 					enumerable: true,
 					writable: true
 				});
-			} else if (typeof val[k] !== 'function') { // MODIFICATION: skip functions
+			} else if (!is_function(val[k])) { // MODIFICATION: skip functions
 				out[k] = (tmp = val[k]) && typeof tmp === 'object' ? clone(tmp) : tmp;
 			}
 		}

src/runtime/internal/Component.ts

@@ -177,7 +177,7 @@ export function init(component, options, instance, create_fragment, not_equal, p
 }
 
 export let SvelteElement;
-if (typeof HTMLElement === 'function') {
+if (is_function(HTMLElement)) {
 	SvelteElement = class extends HTMLElement {
 		$$: T$$;
 		$$set?: ($$props: any) => void;

src/runtime/internal/dev.ts

@@ -1,6 +1,7 @@
 import { custom_event, append, append_hydration, insert, insert_hydration, detach, listen, attr } from './dom';
 import { SvelteComponent } from './Component';
 import { is_void } from '../../shared/utils/names';
+import { is_function } from './utils';
 
 export function dispatch_dev<T=any>(type: string, detail?: T) {
 	document.dispatchEvent(custom_event(type, { version: '__VERSION__', ...detail }, { bubbles: true }));
@@ -93,7 +94,7 @@ export function set_data_dev(text, data) {
 export function validate_each_argument(arg) {
 	if (typeof arg !== 'string' && !(arg && typeof arg === 'object' && 'length' in arg)) {
 		let msg = '{#each} only iterates over array-like objects.';
-		if (typeof Symbol === 'function' && arg && Symbol.iterator in arg) {
+		if (is_function(Symbol) && arg && Symbol.iterator in arg) {
 			msg += ' You can use a spread to convert this iterable into an array.';
 		}
 		throw new Error(msg);

src/runtime/internal/utils.ts

@@ -11,7 +11,7 @@ export function assign<T, S>(tar: T, src: S): T & S {
 }
 
 export function is_promise<T = any>(value: any): value is PromiseLike<T> {
-	return value && typeof value === 'object' && typeof value.then === 'function';
+	return value && typeof value === 'object' && is_function(value.then);
 }
 
 export function add_location(element, file, line, column, char) {
@@ -33,7 +33,7 @@ export function is_function(thing: any): thing is Function {
 }
 
 export function safe_not_equal(a, b) {
-	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || typeof a === 'function');
+	return a != a ? b == b : a !== b || ((a && typeof a === 'object') || is_function(a));
 }
 
 let src_url_equal_anchor;
@@ -55,7 +55,7 @@ export function is_empty(obj) {
 }
 
 export function validate_store(store, name) {
-	if (store != null && typeof store.subscribe !== 'function') {
+	if (store != null && !is_function(store.subscribe)) {
 		throw new Error(`'${name}' is not a store with a 'subscribe' method`);
 	}
 }

src/runtime/motion/tweened.ts

@@ -1,5 +1,5 @@
 import { Readable, writable } from 'svelte/store';
-import { assign, loop, now, Task } from 'svelte/internal';
+import { assign, loop, now, Task, is_function } from 'svelte/internal';
 import { linear } from 'svelte/easing';
 import { is_date } from './utils';
 import { resolved_promise } from 'svelte/internal/constants';
@@ -112,7 +112,7 @@ export function tweened<T>(value?: T, defaults: Options<T> = {}): Tweened<T> {
 
 			if (!started) {
 				fn = interpolate(value, new_value);
-				if (typeof duration === 'function') duration = duration(value, new_value);
+				if (is_function(duration)) duration = duration(value, new_value);
 				started = true;
 			}
 

src/runtime/transition/index.ts

@@ -190,7 +190,7 @@ export function draw(node: SVGElement & { getTotalLength(): number }, {
 		} else {
 			duration = len / speed;
 		}
-	} else if (typeof duration === 'function') {
+	} else if (is_function(duration)) {
 		duration = duration(len);
 	}