From 03d035acba60b56222d1d34baeab0dd0f6d374e5 Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Thu, 27 Mar 2025 16:29:29 -0700
Subject: [PATCH] init

---
 .changeset/pink-lamps-leave.md                |  5 +++
 .../3-transform/client/visitors/ClassBody.js  | 35 ++++++-------------
 2 files changed, 16 insertions(+), 24 deletions(-)
 create mode 100644 .changeset/pink-lamps-leave.md

diff --git a/.changeset/pink-lamps-leave.md b/.changeset/pink-lamps-leave.md
new file mode 100644
index 000000000000..7ca9d8736229
--- /dev/null
+++ b/.changeset/pink-lamps-leave.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: add setters to `$derived` class properties
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/ClassBody.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/ClassBody.js
index 5787b590a8f9..24c20d7f947f 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/ClassBody.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/ClassBody.js
@@ -142,30 +142,17 @@ export function ClassBody(node, context) {
 					// get foo() { return this.#foo; }
 					body.push(b.method('get', definition.key, [], [b.return(b.call('$.get', member))]));
 
-					if (field.kind === 'state' || field.kind === 'raw_state') {
-						// set foo(value) { this.#foo = value; }
-						const value = b.id('value');
-
-						body.push(
-							b.method(
-								'set',
-								definition.key,
-								[value],
-								[b.stmt(b.call('$.set', member, value, field.kind === 'state' && b.true))]
-							)
-						);
-					}
-
-					if (dev && (field.kind === 'derived' || field.kind === 'derived_by')) {
-						body.push(
-							b.method(
-								'set',
-								definition.key,
-								[b.id('_')],
-								[b.throw_error(`Cannot update a derived property ('${name}')`)]
-							)
-						);
-					}
+					// set foo(value) { this.#foo = value; }
+					const val = b.id('value');
+
+					body.push(
+						b.method(
+							'set',
+							definition.key,
+							[val],
+							[b.stmt(b.call('$.set', member, val, field.kind === 'state' && b.true))]
+						)
+					);
 				}
 				continue;
 			}