From a0be1aaf6d98fcf8767a72b9f850581026d817ac Mon Sep 17 00:00:00 2001
From: Jeremiasz Major <jrh.mjr@gmail.com>
Date: Mon, 29 Apr 2024 16:49:38 +0200
Subject: [PATCH] require whitespace after `@const` tag

---
 .changeset/six-boats-shave.md                            | 5 +++++
 packages/svelte/src/compiler/phases/1-parse/state/tag.js | 2 +-
 .../samples/const-tag-whitespace/_config.js              | 9 +++++++++
 .../samples/const-tag-whitespace/main.svelte             | 3 +++
 4 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/six-boats-shave.md
 create mode 100644 packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/_config.js
 create mode 100644 packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/main.svelte

diff --git a/.changeset/six-boats-shave.md b/.changeset/six-boats-shave.md
new file mode 100644
index 000000000000..6dc8c9628f97
--- /dev/null
+++ b/.changeset/six-boats-shave.md
@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: require whitespace after `@const` tag
diff --git a/packages/svelte/src/compiler/phases/1-parse/state/tag.js b/packages/svelte/src/compiler/phases/1-parse/state/tag.js
index bf6adccccfcf..a41c5d09a012 100644
--- a/packages/svelte/src/compiler/phases/1-parse/state/tag.js
+++ b/packages/svelte/src/compiler/phases/1-parse/state/tag.js
@@ -543,7 +543,7 @@ function special(parser) {
 	}
 
 	if (parser.eat('const')) {
-		parser.allow_whitespace();
+		parser.require_whitespace();
 
 		const id = read_pattern(parser);
 		parser.allow_whitespace();
diff --git a/packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/_config.js b/packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/_config.js
new file mode 100644
index 000000000000..45c6e5da4d45
--- /dev/null
+++ b/packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/_config.js
@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'expected_whitespace',
+		message: 'Expected whitespace',
+		position: [19, 19]
+	}
+});
diff --git a/packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/main.svelte b/packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/main.svelte
new file mode 100644
index 000000000000..9794dd92276f
--- /dev/null
+++ b/packages/svelte/tests/compiler-errors/samples/const-tag-whitespace/main.svelte
@@ -0,0 +1,3 @@
+{#if true}
+	{@constfoo = 'bar'}
+{/if}