believe it or not this is faster. it also looks cooler

packages/svelte/src/internal/client/reactivity/deriveds.js

@@ -9,7 +9,7 @@ import {
 	set_signal_status
 } from '../runtime.js';
 import { push_reference } from './effects.js';
-import { default_equals, safe_equal } from './equality.js';
+import { default_equals, safe_equals } from './equality.js';
 
 /**
  * @template V
@@ -56,7 +56,7 @@ export function derived(fn) {
 /*#__NO_SIDE_EFFECTS__*/
 export function derived_safe_equal(fn) {
 	const signal = derived(fn);
-	signal.eq = safe_equal;
+	signal.eq = safe_equals;
 	return signal;
 }
 

packages/svelte/src/internal/client/reactivity/equality.js

@@ -1,10 +1,6 @@
-/**
- * @param {unknown} a
- * @param {unknown} b
- * @returns {boolean}
- */
-export function default_equals(a, b) {
-	return a === b;
+/** @type {import('#client').Equals} */
+export function default_equals(value) {
+	return value === this.v;
 }
 
 /**
@@ -20,11 +16,7 @@ export function safe_not_equal(a, b) {
 		: a !== b || (a !== null && typeof a === 'object') || typeof a === 'function';
 }
 
-/**
- * @param {unknown} a
- * @param {unknown} b
- * @returns {boolean}
- */
-export function safe_equal(a, b) {
-	return !safe_not_equal(a, b);
+/** @type {import('#client').Equals} */
+export function safe_equals(value) {
+	return !safe_not_equal(value, this.v);
 }

packages/svelte/src/internal/client/reactivity/sources.js

@@ -18,7 +18,7 @@ import {
 	set_signal_status,
 	untrack
 } from '../runtime.js';
-import { default_equals, safe_equal } from './equality.js';
+import { default_equals, safe_equals } from './equality.js';
 import { CLEAN, DERIVED, DIRTY, MANAGED, SOURCE } from '../constants.js';
 
 /**
@@ -52,7 +52,7 @@ export function source(value) {
 /*#__NO_SIDE_EFFECTS__*/
 export function mutable_source(initial_value) {
 	const s = source(initial_value);
-	s.eq = safe_equal;
+	s.eq = safe_equals;
 
 	// bind the signal to the component context, in case we need to
 	// track updates to trigger beforeUpdate/afterUpdate callbacks
@@ -109,7 +109,7 @@ export function set(signal, value) {
 					: '')
 		);
 	}
-	if ((signal.f & SOURCE) !== 0 && !signal.eq(value, signal.v)) {
+	if ((signal.f & SOURCE) !== 0 && !signal.eq(value)) {
 		signal.v = value;
 		// Increment write version so that unowned signals can properly track dirtyness
 		signal.w++;

packages/svelte/src/internal/client/reactivity/types.d.ts

@@ -1,4 +1,4 @@
-import type { Block, ComponentContext, EqualsFunctions } from '#client';
+import type { Block, ComponentContext, Equals } from '#client';
 import type { EFFECT, PRE_EFFECT, RENDER_EFFECT } from '../constants';
 
 export type EffectType = typeof EFFECT | typeof PRE_EFFECT | typeof RENDER_EFFECT;
@@ -7,7 +7,7 @@ export interface Source<V = unknown> {
 	/** Signals that read from this signal */
 	reactions: null | Reaction[];
 	/** Equality function */
-	eq: EqualsFunctions;
+	eq: Equals;
 	/** Flags bitmask */
 	f: number;
 	/** The latest value for this signal */

packages/svelte/src/internal/client/render.js

@@ -75,7 +75,7 @@ import {
 import { run } from '../common.js';
 import { bind_transition, trigger_transitions } from './transitions.js';
 import { mutable_source, source, set } from './reactivity/sources.js';
-import { safe_equal, safe_not_equal } from './reactivity/equality.js';
+import { safe_equals, safe_not_equal } from './reactivity/equality.js';
 import { STATE_SYMBOL } from './constants.js';
 
 /** @type {Set<string>} */
@@ -2829,7 +2829,7 @@ export function prop(props, key, flags, initial) {
 		return (inner_current_value.v = parent_value);
 	});
 
-	if (!immutable) current_value.eq = safe_equal;
+	if (!immutable) current_value.eq = safe_equals;
 
 	return function (/** @type {V} */ value, mutation = false) {
 		var current = get(current_value);

packages/svelte/src/internal/client/runtime.js

@@ -693,7 +693,7 @@ function update_derived(signal, force_schedule) {
 			? MAYBE_DIRTY
 			: CLEAN;
 	set_signal_status(signal, status);
-	if (!signal.eq(value, signal.v)) {
+	if (!signal.eq(value)) {
 		signal.v = value;
 		mark_reactions(signal, DIRTY, force_schedule);
 

packages/svelte/src/internal/client/types.d.ts

@@ -57,7 +57,7 @@ export type ComponentContext = {
 	};
 };
 
-export type EqualsFunctions<T = any> = (a: T, v: T) => boolean;
+export type Equals = (this: Value, value: unknown) => boolean;
 
 export type BlockType =
 	| typeof ROOT_BLOCK