From ec2bb952b26b389ed8b7300e0214973f46d9e0db Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Thu, 13 Mar 2025 21:34:49 -0700
Subject: [PATCH] replace 'undefined' with 'void 0'

---
 .changeset/curvy-countries-flow.md                           | 5 +++++
 .../3-transform/client/visitors/VariableDeclaration.js       | 2 +-
 .../phases/3-transform/server/visitors/CallExpression.js     | 2 +-
 .../3-transform/server/visitors/VariableDeclaration.js       | 4 ++--
 4 files changed, 9 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/curvy-countries-flow.md

diff --git a/.changeset/curvy-countries-flow.md b/.changeset/curvy-countries-flow.md
new file mode 100644
index 0000000000..6ef8545804
--- /dev/null
+++ b/.changeset/curvy-countries-flow.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: replace `undefined` with `void 0` to avoid edge case
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
index 31e712cdcc..4d55b3c432 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
@@ -117,7 +117,7 @@ export function VariableDeclaration(node, context) {
 
 			const args = /** @type {CallExpression} */ (init).arguments;
 			const value =
-				args.length === 0 ? b.id('undefined') : /** @type {Expression} */ (context.visit(args[0]));
+				args.length === 0 ? b.unary('void', b.literal(0)) : /** @type {Expression} */ (context.visit(args[0]));
 
 			if (rune === '$state' || rune === '$state.raw') {
 				/**
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
index 386c6b6ff3..6793250d1d 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/CallExpression.js
@@ -13,7 +13,7 @@ export function CallExpression(node, context) {
 	const rune = get_rune(node, context.state.scope);
 
 	if (rune === '$host') {
-		return b.id('undefined');
+		return b.unary('void', b.literal(0));
 	}
 
 	if (rune === '$effect.tracking') {
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/VariableDeclaration.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/VariableDeclaration.js
index c4c31d7eb3..78f9dbb8f7 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/VariableDeclaration.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/VariableDeclaration.js
@@ -45,7 +45,7 @@ export function VariableDeclaration(node, context) {
 						) {
 							const right = node.right.arguments.length
 								? /** @type {Expression} */ (context.visit(node.right.arguments[0]))
-								: b.id('undefined');
+								: b.unary('void', b.literal(0));
 							return b.assignment_pattern(node.left, right);
 						}
 					}
@@ -76,7 +76,7 @@ export function VariableDeclaration(node, context) {
 
 			const args = /** @type {CallExpression} */ (init).arguments;
 			const value =
-				args.length === 0 ? b.id('undefined') : /** @type {Expression} */ (context.visit(args[0]));
+				args.length === 0 ? b.unary('void', b.literal(0)) : /** @type {Expression} */ (context.visit(args[0]));
 
 			if (rune === '$derived.by') {
 				declarations.push(