From 7e0a81d102180e72ad12b22e9c061bd5ea955b11 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sat, 31 May 2025 15:52:18 -0700
Subject: [PATCH] fix: correctly transform reassignments to class fields in SSR
 mode

---
 .changeset/rude-drinks-relate.md                           | 5 +++++
 .../3-transform/server/visitors/AssignmentExpression.js    | 7 ++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/rude-drinks-relate.md

diff --git a/.changeset/rude-drinks-relate.md b/.changeset/rude-drinks-relate.md
new file mode 100644
index 0000000000..d0eab6ba11
--- /dev/null
+++ b/.changeset/rude-drinks-relate.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: correctly transform reassignments to class fields in SSR mode
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/AssignmentExpression.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/AssignmentExpression.js
index 466682fb82..7a054fcbb4 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/AssignmentExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/AssignmentExpression.js
@@ -24,7 +24,12 @@ export function AssignmentExpression(node, context) {
  * @returns {Expression | null}
  */
 function build_assignment(operator, left, right, context) {
-	if (context.state.analysis.runes && left.type === 'MemberExpression') {
+	if (
+		context.state.analysis.runes &&
+		left.type === 'MemberExpression' &&
+		left.object.type === 'ThisExpression' &&
+		!left.computed
+	) {
 		const name = get_name(left.property);
 		const field = name && context.state.state_fields.get(name);