From b6575cc29daab783fa5d745c978fe65413be1eb5 Mon Sep 17 00:00:00 2001
From: Simon Holthausen <simon.holthausen@vercel.com>
Date: Fri, 10 May 2024 15:43:52 +0200
Subject: [PATCH] fix: don't warn on writes to `$state`

fixes #10905
---
 .changeset/calm-buses-clap.md                             | 5 +++++
 packages/svelte/src/compiler/phases/2-analyze/index.js    | 8 +++++++-
 .../validator/samples/static-state-reference/input.svelte | 5 +++++
 3 files changed, 17 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/calm-buses-clap.md

diff --git a/.changeset/calm-buses-clap.md b/.changeset/calm-buses-clap.md
new file mode 100644
index 0000000000..409949443d
--- /dev/null
+++ b/.changeset/calm-buses-clap.md
@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: don't warn on writes to `$state`
diff --git a/packages/svelte/src/compiler/phases/2-analyze/index.js b/packages/svelte/src/compiler/phases/2-analyze/index.js
index e4d6f6a4db..cf05dfbf53 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/index.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/index.js
@@ -1242,6 +1242,7 @@ const common_visitors = {
 			if (
 				context.state.analysis.runes &&
 				node !== binding.node &&
+				context.state.function_depth === binding.scope.function_depth &&
 				// If we have $state that can be proxied or frozen and isn't re-assigned, then that means
 				// it's likely not using a primitive value and thus this warning isn't that helpful.
 				((binding.kind === 'state' &&
@@ -1252,7 +1253,12 @@ const common_visitors = {
 							!should_proxy_or_freeze(binding.initial.arguments[0], context.state.scope)))) ||
 					binding.kind === 'frozen_state' ||
 					binding.kind === 'derived') &&
-				context.state.function_depth === binding.scope.function_depth
+				// We're only concerned with reads here
+				parent.type !== 'AssignmentExpression' &&
+				parent.type !== 'UpdateExpression' &&
+				(parent.type !== 'MemberExpression' ||
+					(context.path.at(-2)?.type !== 'AssignmentExpression' &&
+						context.path.at(-2)?.type !== 'UpdateExpression'))
 			) {
 				w.state_referenced_locally(node);
 			}
diff --git a/packages/svelte/tests/validator/samples/static-state-reference/input.svelte b/packages/svelte/tests/validator/samples/static-state-reference/input.svelte
index 2971960a14..72590de4f4 100644
--- a/packages/svelte/tests/validator/samples/static-state-reference/input.svelte
+++ b/packages/svelte/tests/validator/samples/static-state-reference/input.svelte
@@ -6,6 +6,11 @@
 	console.log(obj);
 	console.log(count);
 	console.log(doubled);
+	// these are ok because they're writes
+	count++;
+	count = 1;
+	obj.a++;
+	obj.a = 1;
 </script>
 
 <button onclick={() => count += 1}>