don't self-invalidate when updating a source create inside current reaction

Author: Rich-Harris

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

@@ -154,9 +154,7 @@ export function set(source, value, should_proxy = false) {
 		!untracking &&
 		is_runes() &&
 		(active_reaction.f & (DERIVED | BLOCK_EFFECT)) !== 0 &&
-		// If the source was created locally within the current derived, then
-		// we allow the mutation.
-		(derived_sources === null || !derived_sources.includes(source))
+		active_reaction !== source.parent
 	) {
 		e.state_unsafe_mutation();
 	}

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

@@ -367,6 +367,8 @@ function schedule_possible_effect_self_invalidation(signal, effect, root = true)
 
 	for (var i = 0; i < reactions.length; i++) {
 		var reaction = reactions[i];
+		if (signal.parent === reaction) continue;
+
 		if ((reaction.f & DERIVED) !== 0) {
 			schedule_possible_effect_self_invalidation(/** @type {Derived} */ (reaction), effect, false);
 		} else if (effect === reaction) {