revert

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

@@ -15,7 +15,7 @@ import {
 import { equals, safe_equals } from './equality.js';
 import * as e from '../errors.js';
 import { destroy_effect } from './effects.js';
-import { inspect_effects, old_values, set_inspect_effects } from './sources.js';
+import { inspect_effects, set_inspect_effects } from './sources.js';
 import { get_stack } from '../dev/tracing.js';
 import { tracing_mode_flag } from '../../flags/index.js';
 import { component_context } from '../context.js';
@@ -175,27 +175,6 @@ export function update_derived(derived) {
 	var value = execute_derived(derived);
 
 	if (!derived.equals(value)) {
-		// store old value before updating
-		// so that user_effect teardown functions
-		// can access the previous value.
-		// this is needed because derived updates happen early during
-		// effects dependency resolution (before cleanup),
-		// unlike direct state/derived updates, and this
-		// can happen also during template_effect execution
-		// that also happens before user_effect teardown.
-		//
-		// store old value only if not inside a teardown function
-		// because we only need to save the old values before
-		// the cleanup is triggered othewise accessing
-		// a derived during cleanup will return the incorrect
-		// value in case the derived wasn't in the deps of the effect,
-		// or the teardown was executed because the component was
-		// destroyed.
-		if (!is_destroying_effect) {
-			var old_value = derived.v;
-			old_values.set(derived, old_value);
-		}
-
 		derived.v = value;
 		derived.wv = increment_write_version();
 	}