From e7fddba11a7ac5dd5a3906c54269320cfc936bff Mon Sep 17 00:00:00 2001
From: "S. Elliott Johnson" <sejohnson@torchcloudconsulting.com>
Date: Mon, 24 Mar 2025 17:34:41 -0700
Subject: [PATCH 01/12] typescript

---
 apps/svelte.dev/vite.config.ts                |  2 +-
 packages/editor/package.json                  |  3 +-
 packages/editor/src/lib/Workspace.svelte.ts   |  4 ++
 .../editor/src/lib/compile-worker/worker.ts   |  4 +-
 packages/repl/package.json                    |  4 +-
 .../src/lib/Output/console/Console.svelte     |  2 +-
 .../repl/src/lib/workers/bundler/index.ts     |  7 +-
 .../bundler/plugins/typescript-strip-types.ts | 21 ++++++
 packages/typestript/.gitignore                |  1 +
 packages/typestript/package.json              | 31 +++++++++
 packages/typestript/src/index.ts              | 66 +++++++++++++++++++
 packages/typestript/tsconfig.json             | 20 ++++++
 pnpm-lock.yaml                                | 52 +++++++++++++--
 13 files changed, 206 insertions(+), 11 deletions(-)
 create mode 100644 packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts
 create mode 100644 packages/typestript/.gitignore
 create mode 100644 packages/typestript/package.json
 create mode 100644 packages/typestript/src/index.ts
 create mode 100644 packages/typestript/tsconfig.json

diff --git a/apps/svelte.dev/vite.config.ts b/apps/svelte.dev/vite.config.ts
index e1d4ffc832..c9d89e455d 100644
--- a/apps/svelte.dev/vite.config.ts
+++ b/apps/svelte.dev/vite.config.ts
@@ -71,7 +71,7 @@ const config: UserConfig = {
 		}
 	},
 	optimizeDeps: {
-		exclude: ['@sveltejs/site-kit', '@sveltejs/repl', '@rollup/browser']
+		exclude: ['@sveltejs/site-kit', '@sveltejs/repl', '@rollup/browser', 'typestript']
 	},
 	ssr: {
 		noExternal: ['@sveltejs/site-kit', '@sveltejs/repl'],
diff --git a/packages/editor/package.json b/packages/editor/package.json
index 17651a37c3..ea3eabf6e1 100644
--- a/packages/editor/package.json
+++ b/packages/editor/package.json
@@ -64,6 +64,7 @@
 	"dependencies": {
 		"@lezer/highlight": "^1.2.1",
 		"esm-env": "^1.0.0",
-		"tarparser": "^0.0.4"
+		"tarparser": "^0.0.4",
+		"typestript": "workspace:*"
 	}
 }
diff --git a/packages/editor/src/lib/Workspace.svelte.ts b/packages/editor/src/lib/Workspace.svelte.ts
index 17e1e2f65b..eb97bda861 100644
--- a/packages/editor/src/lib/Workspace.svelte.ts
+++ b/packages/editor/src/lib/Workspace.svelte.ts
@@ -577,6 +577,10 @@ export class Workspace {
 				extensions.push(javascript());
 				break;
 
+			case 'ts':
+				extensions.push(javascript({ typescript: true }));
+				break;
+
 			case 'html':
 				extensions.push(html());
 				break;
diff --git a/packages/editor/src/lib/compile-worker/worker.ts b/packages/editor/src/lib/compile-worker/worker.ts
index c00ed75e9f..f3861cac30 100644
--- a/packages/editor/src/lib/compile-worker/worker.ts
+++ b/packages/editor/src/lib/compile-worker/worker.ts
@@ -3,6 +3,7 @@ import { parseTar } from 'tarparser';
 import type { CompileResult } from 'svelte/compiler';
 import type { ExposedCompilerOptions, File } from '../Workspace.svelte';
 import type { FileDescription } from 'tarparser';
+import { stripTypes } from 'typestript';
 
 // hack for magic-string and Svelte 4 compiler
 // do not put this into a separate module and import it, would be treeshaken in prod
@@ -139,7 +140,8 @@ addEventListener('message', async (event) => {
 				compilerOptions.experimental = { async: true };
 			}
 
-			result = svelte.compileModule(file.contents, compilerOptions);
+			const { content } = stripTypes(file.contents);
+			result = svelte.compileModule(content, compilerOptions);
 		}
 
 		postMessage({
diff --git a/packages/repl/package.json b/packages/repl/package.json
index 5ab688c8e7..f3cc26dc66 100644
--- a/packages/repl/package.json
+++ b/packages/repl/package.json
@@ -52,6 +52,7 @@
 		"@sveltejs/package": "^2.0.0",
 		"@sveltejs/vite-plugin-svelte": "4.0.0",
 		"@types/estree": "^1.0.5",
+		"magic-string": "^0.30.11",
 		"prettier": "^3.3.2",
 		"prettier-plugin-svelte": "^3.3.2",
 		"publint": "^0.2.12",
@@ -87,6 +88,7 @@
 		"resolve.exports": "^2.0.2",
 		"svelte": "5.23.0",
 		"tarparser": "^0.0.4",
-		"zimmerframe": "^1.1.2"
+		"zimmerframe": "^1.1.2",
+		"typestript": "workspace:*"
 	}
 }
diff --git a/packages/repl/src/lib/Output/console/Console.svelte b/packages/repl/src/lib/Output/console/Console.svelte
index cc9471eb29..4c27f3ecec 100644
--- a/packages/repl/src/lib/Output/console/Console.svelte
+++ b/packages/repl/src/lib/Output/console/Console.svelte
@@ -1,4 +1,4 @@
-<script module>
+<script module lang="ts">
 	export type Log = {
 		command: 'info' | 'warn' | 'error' | 'table' | 'group' | 'clear' | 'unclonable';
 		action?: 'console';
diff --git a/packages/repl/src/lib/workers/bundler/index.ts b/packages/repl/src/lib/workers/bundler/index.ts
index 6b2f7b26d5..88bf2c61a2 100644
--- a/packages/repl/src/lib/workers/bundler/index.ts
+++ b/packages/repl/src/lib/workers/bundler/index.ts
@@ -4,6 +4,7 @@ import { sleep } from '../../utils';
 import { rollup } from '@rollup/browser';
 import { DEV } from 'esm-env';
 import * as resolve from 'resolve.exports';
+import typescriptStripTypes from './plugins/typescript-strip-types';
 import commonjs from './plugins/commonjs';
 import glsl from './plugins/glsl';
 import json from './plugins/json';
@@ -282,6 +283,7 @@ async function get_bundle(
 				return importee;
 			if (local_files_lookup.has(importee + '.js')) return importee + '.js';
 			if (local_files_lookup.has(importee + '.json')) return importee + '.json';
+			if (local_files_lookup.has(importee + '.ts')) return importee + '.ts';
 
 			// remove trailing slash
 			if (importee.endsWith('/')) importee = importee.slice(0, -1);
@@ -412,7 +414,7 @@ async function get_bundle(
 
 			self.postMessage({ type: 'status', uid, message: `bundling ${id}` });
 
-			if (!/\.(svelte|js)$/.test(id)) return null;
+			if (!/\.(svelte|js|ts)$/.test(id)) return null;
 
 			const name = id.split('/').pop()?.split('.')[0];
 
@@ -462,7 +464,7 @@ async function get_bundle(
 					$$_styles.push($$__style);
 				`.replace(/\t/g, '');
 				}
-			} else if (id.endsWith('.svelte.js')) {
+			} else if (/\.svelte\.(js|ts)$/.test(id)) {
 				const compilerOptions: any = {
 					filename: name + '.js',
 					generate: 'client',
@@ -507,6 +509,7 @@ async function get_bundle(
 		bundle = await rollup({
 			input: './__entry.js',
 			plugins: [
+				typescriptStripTypes,
 				repl_plugin,
 				commonjs,
 				json,
diff --git a/packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts b/packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts
new file mode 100644
index 0000000000..726bc3080e
--- /dev/null
+++ b/packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts
@@ -0,0 +1,21 @@
+import type { Plugin } from '@rollup/browser';
+import { stripTypes } from 'typestript';
+
+const plugin: Plugin = {
+	name: 'typescript-strip-types',
+	transform: (code, id) => {
+		const match = id.endsWith('.ts');
+		if (!match) return;
+
+		const { content, sourceMap } = stripTypes(code);
+
+		console.log(content);
+
+		return {
+			code: content,
+			map: sourceMap
+		};
+	}
+};
+
+export default plugin;
diff --git a/packages/typestript/.gitignore b/packages/typestript/.gitignore
new file mode 100644
index 0000000000..53c37a1660
--- /dev/null
+++ b/packages/typestript/.gitignore
@@ -0,0 +1 @@
+dist
\ No newline at end of file
diff --git a/packages/typestript/package.json b/packages/typestript/package.json
new file mode 100644
index 0000000000..107a2a542d
--- /dev/null
+++ b/packages/typestript/package.json
@@ -0,0 +1,31 @@
+{
+	"name": "typestript",
+	"private": true,
+	"scripts": {
+		"build": "tsc",
+		"lint": "prettier --check .",
+		"format": "prettier --write ."
+	},
+	"exports": {
+		".": "./dist/index.js"
+	},
+	"files": [
+		"dist",
+		"!dist/**/*.test.*",
+		"!dist/**/*.spec.*",
+    "src",
+    "!src/**/*.test.*",
+    "!src/**/*.spec.*"
+	],
+	"type": "module",
+	"dependencies": {
+		"@sveltejs/acorn-typescript": "^1.0.5",
+		"acorn": "^8.11.3",
+		"magic-string": "^0.30.11",
+		"zimmerframe": "^1.1.2"
+	},
+	"devDependencies": {
+		"@typescript-eslint/types": "^8.28.0",
+		"typescript": "^5.8.2"
+	}
+}
diff --git a/packages/typestript/src/index.ts b/packages/typestript/src/index.ts
new file mode 100644
index 0000000000..d2d3d7d092
--- /dev/null
+++ b/packages/typestript/src/index.ts
@@ -0,0 +1,66 @@
+import * as acorn from 'acorn';
+import { tsPlugin } from '@sveltejs/acorn-typescript';
+import { walk } from 'zimmerframe';
+import type { TSESTree } from '@typescript-eslint/types';
+import MagicString, { SourceMap } from 'magic-string';
+
+const TSParser = acorn.Parser.extend(tsPlugin());
+
+export function stripTypes(content: string): { content: string; sourceMap: SourceMap } {
+	console.log(content);
+
+	const ast = TSParser.parse(content, {
+		sourceType: 'module',
+		ecmaVersion: 13,
+		locations: true
+	});
+
+	const s = new MagicString(content);
+
+	walk(ast as unknown as TSESTree.Node, null, {
+		_: (node, context) => {
+			console.log(node.type);
+			if (node.type.startsWith('TS') && node.type !== 'TSAsExpression') {
+				const { start, end } = node as unknown as { start: number; end: number };
+				s.overwrite(start, end, ' '.repeat(end - start));
+			} else {
+				context.next();
+			}
+		},
+		TSAsExpression: (node) => {
+			const { end: start } = node.expression as unknown as { end: number; start: number };
+			const { end } = node.typeAnnotation as unknown as { start: number; end: number };
+			s.overwrite(start, end, ' '.repeat(end - start));
+		},
+		ImportDeclaration: (node, context) => {
+			if (
+				node.importKind === 'type' ||
+				node.specifiers.every(
+					(specifier) => specifier.type === 'ImportSpecifier' && specifier.importKind === 'type'
+				)
+			) {
+				const { start, end } = node as unknown as { start: number; end: number };
+				s.overwrite(start, end, ' '.repeat(end - start));
+			} else {
+				context.next();
+			}
+		},
+		ImportSpecifier: (node, context) => {
+			if (node.importKind === 'type') {
+				const { start, end } = node as unknown as { start: number; end: number };
+				s.overwrite(start, end, ' '.repeat(end - start));
+			} else {
+				context.next();
+			}
+		}
+	});
+
+	console.log(s.toString());
+
+	return {
+		content: s.toString(),
+		sourceMap: s.generateMap({
+			hires: true
+		})
+	};
+}
diff --git a/packages/typestript/tsconfig.json b/packages/typestript/tsconfig.json
new file mode 100644
index 0000000000..7c74640aaa
--- /dev/null
+++ b/packages/typestript/tsconfig.json
@@ -0,0 +1,20 @@
+{
+	"compilerOptions": {
+    "outDir": "dist",
+		"allowJs": true,
+		"checkJs": true,
+    "verbatimModuleSyntax": true,
+		"isolatedModules": true,
+		"lib": [
+			"esnext",
+			"DOM",
+			"DOM.Iterable"
+		],
+		"moduleResolution": "bundler",
+		"module": "esnext",
+		"target": "esnext",
+    "declaration": true,
+    "declarationMap": true,
+	},
+  "include": ["src/**/*.ts"],
+}
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index d68dce3e53..f73e649910 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -219,6 +219,9 @@ importers:
       tarparser:
         specifier: ^0.0.4
         version: 0.0.4
+      typestript:
+        specifier: workspace:*
+        version: link:../typestript
     devDependencies:
       '@codemirror/autocomplete':
         specifier: ^6.9.0
@@ -379,6 +382,9 @@ importers:
       tarparser:
         specifier: ^0.0.4
         version: 0.0.4
+      typestript:
+        specifier: workspace:*
+        version: link:../typestript
       zimmerframe:
         specifier: ^1.1.2
         version: 1.1.2
@@ -401,6 +407,9 @@ importers:
       '@types/estree':
         specifier: ^1.0.5
         version: 1.0.6
+      magic-string:
+        specifier: ^0.30.11
+        version: 0.30.12
       prettier:
         specifier: ^3.3.2
         version: 3.3.2
@@ -520,6 +529,28 @@ importers:
         specifier: ^5.4.3
         version: 5.4.11(@types/node@20.14.2)(lightningcss@1.25.1)
 
+  packages/typestript:
+    dependencies:
+      '@sveltejs/acorn-typescript':
+        specifier: ^1.0.5
+        version: 1.0.5(acorn@8.14.1)
+      acorn:
+        specifier: ^8.11.3
+        version: 8.14.1
+      magic-string:
+        specifier: ^0.30.11
+        version: 0.30.12
+      zimmerframe:
+        specifier: ^1.1.2
+        version: 1.1.2
+    devDependencies:
+      '@typescript-eslint/types':
+        specifier: ^8.28.0
+        version: 8.28.0
+      typescript:
+        specifier: ^5.8.2
+        version: 5.8.2
+
 packages:
 
   '@ampproject/remapping@2.3.0':
@@ -1737,6 +1768,10 @@ packages:
   '@types/ws@8.5.10':
     resolution: {integrity: sha512-vmQSUcfalpIq0R9q7uTo2lXs6eGIpt9wtnLdMv9LVpIjCA/+ufZRozlVoVelIYixx1ugCBKDhn89vnsEGOCx9A==}
 
+  '@typescript-eslint/types@8.28.0':
+    resolution: {integrity: sha512-bn4WS1bkKEjx7HqiwG2JNB3YJdC1q6Ue7GyGlwPHyt0TnVq6TtD/hiOdTZt71sq0s7UzqBFXD8t8o2e63tXgwA==}
+    engines: {node: ^18.18.0 || ^20.9.0 || >=21.1.0}
+
   '@typescript/vfs@1.6.0':
     resolution: {integrity: sha512-hvJUjNVeBMp77qPINuUvYXj4FyWeeMMKZkxEATEU3hqBAQ7qdTBCUFT7Sp0Zu0faeEtFf+ldXxMEDr/bk73ISg==}
     peerDependencies:
@@ -3167,6 +3202,11 @@ packages:
     engines: {node: '>=14.17'}
     hasBin: true
 
+  typescript@5.8.2:
+    resolution: {integrity: sha512-aJn6wq13/afZp/jT9QZmwEjDqqvSGp1VT5GVg+f/t6/oVyrgXM6BY1h9BRh/O5p3PlUPAe+WuiEZOmb/49RqoQ==}
+    engines: {node: '>=14.17'}
+    hasBin: true
+
   ultrahtml@1.5.3:
     resolution: {integrity: sha512-GykOvZwgDWZlTQMtp5jrD4BVL+gNn2NVlVafjcFUJ7taY20tqYdwdoWBFy6GBJsNTZe1GkGPkSl5knQAjtgceg==}
 
@@ -4642,6 +4682,8 @@ snapshots:
     dependencies:
       '@types/node': 20.14.2
 
+  '@typescript-eslint/types@8.28.0': {}
+
   '@typescript/vfs@1.6.0(typescript@5.5.4)':
     dependencies:
       debug: 4.4.0
@@ -4659,8 +4701,8 @@ snapshots:
     dependencies:
       '@mapbox/node-pre-gyp': 2.0.0-rc.0
       '@rollup/pluginutils': 5.1.3(rollup@4.21.2)
-      acorn: 8.14.0
-      acorn-import-attributes: 1.9.5(acorn@8.14.0)
+      acorn: 8.14.1
+      acorn-import-attributes: 1.9.5(acorn@8.14.1)
       async-sema: 3.1.1
       bindings: 1.5.0
       estree-walker: 2.0.2
@@ -4723,9 +4765,9 @@ snapshots:
 
   abbrev@2.0.0: {}
 
-  acorn-import-attributes@1.9.5(acorn@8.14.0):
+  acorn-import-attributes@1.9.5(acorn@8.14.1):
     dependencies:
-      acorn: 8.14.0
+      acorn: 8.14.1
 
   acorn@8.14.0: {}
 
@@ -6040,6 +6082,8 @@ snapshots:
 
   typescript@5.5.4: {}
 
+  typescript@5.8.2: {}
+
   ultrahtml@1.5.3: {}
 
   undici-types@5.26.5: {}

From 8264097856e12d6a30d65739b263ea539ddba94b Mon Sep 17 00:00:00 2001
From: "S. Elliott Johnson" <sejohnson@torchcloudconsulting.com>
Date: Mon, 24 Mar 2025 17:42:14 -0700
Subject: [PATCH 02/12] checkpoint

---
 packages/typestript/package.json |  1 +
 packages/typestript/src/index.ts | 28 ++++++++++++++++++++++++----
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/packages/typestript/package.json b/packages/typestript/package.json
index 107a2a542d..ca0fed554e 100644
--- a/packages/typestript/package.json
+++ b/packages/typestript/package.json
@@ -2,6 +2,7 @@
 	"name": "typestript",
 	"private": true,
 	"scripts": {
+		"dev": "tsc --watch",
 		"build": "tsc",
 		"lint": "prettier --check .",
 		"format": "prettier --write ."
diff --git a/packages/typestript/src/index.ts b/packages/typestript/src/index.ts
index d2d3d7d092..e396376558 100644
--- a/packages/typestript/src/index.ts
+++ b/packages/typestript/src/index.ts
@@ -20,7 +20,10 @@ export function stripTypes(content: string): { content: string; sourceMap: Sourc
 	walk(ast as unknown as TSESTree.Node, null, {
 		_: (node, context) => {
 			console.log(node.type);
-			if (node.type.startsWith('TS') && node.type !== 'TSAsExpression') {
+			if (
+				node.type.startsWith('TS') &&
+				!['TSAsExpression', 'TSSatisfiesExpression', 'TSNonNullExpression'].includes(node.type)
+			) {
 				const { start, end } = node as unknown as { start: number; end: number };
 				s.overwrite(start, end, ' '.repeat(end - start));
 			} else {
@@ -28,9 +31,14 @@ export function stripTypes(content: string): { content: string; sourceMap: Sourc
 			}
 		},
 		TSAsExpression: (node) => {
-			const { end: start } = node.expression as unknown as { end: number; start: number };
-			const { end } = node.typeAnnotation as unknown as { start: number; end: number };
-			s.overwrite(start, end, ' '.repeat(end - start));
+			handleTypeExpression(node, s);
+		},
+		TSSatisfiesExpression: (node) => {
+			handleTypeExpression(node, s);
+		},
+		TSNonNullExpression: (node) => {
+			const { end } = node as unknown as { start: number; end: number };
+			s.overwrite(end - 1, end, ' ');
 		},
 		ImportDeclaration: (node, context) => {
 			if (
@@ -64,3 +72,15 @@ export function stripTypes(content: string): { content: string; sourceMap: Sourc
 		})
 	};
 }
+
+function handleTypeExpression(
+	node: {
+		expression: unknown;
+		typeAnnotation: unknown;
+	},
+	s: { overwrite: (start: number, end: number, content: string) => void }
+) {
+	const { end: start } = node.expression as unknown as { end: number; start: number };
+	const { end } = node.typeAnnotation as unknown as { start: number; end: number };
+	s.overwrite(start, end, ' '.repeat(end - start));
+}

From b91ab291894a02ead656e2d00fcea17fb0998e24 Mon Sep 17 00:00:00 2001
From: "S. Elliott Johnson" <sejohnson@torchcloudconsulting.com>
Date: Mon, 24 Mar 2025 17:53:13 -0700
Subject: [PATCH 03/12] final not final

---
 packages/typestript/src/index.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/typestript/src/index.ts b/packages/typestript/src/index.ts
index e396376558..f516c323b4 100644
--- a/packages/typestript/src/index.ts
+++ b/packages/typestript/src/index.ts
@@ -36,9 +36,10 @@ export function stripTypes(content: string): { content: string; sourceMap: Sourc
 		TSSatisfiesExpression: (node) => {
 			handleTypeExpression(node, s);
 		},
-		TSNonNullExpression: (node) => {
+		TSNonNullExpression: (node, context) => {
 			const { end } = node as unknown as { start: number; end: number };
 			s.overwrite(end - 1, end, ' ');
+			context.next();
 		},
 		ImportDeclaration: (node, context) => {
 			if (

From 43075673d2d90330ad6ffdff85ee44f4d9f2b77c Mon Sep 17 00:00:00 2001
From: "S. Elliott Johnson" <sejohnson@torchcloudconsulting.com>
Date: Mon, 24 Mar 2025 17:55:11 -0700
Subject: [PATCH 04/12] nasty fix

---
 apps/svelte.dev/package.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/apps/svelte.dev/package.json b/apps/svelte.dev/package.json
index 5efe141419..30adac684d 100644
--- a/apps/svelte.dev/package.json
+++ b/apps/svelte.dev/package.json
@@ -6,7 +6,7 @@
 	"type": "module",
 	"scripts": {
 		"dev": "node scripts/update.js && node scripts/create-tutorial-zip/index.js && vite dev",
-		"build": "node scripts/update.js && node scripts/create-tutorial-zip/index.js && vite build",
+		"build": "pnpm -F typestript build && node scripts/update.js && node scripts/create-tutorial-zip/index.js && vite build",
 		"update": "node scripts/update.js --force=true && node scripts/create-tutorial-zip/index.js --force=true",
 		"preview": "vite preview",
 		"start": "node build",

From c531861e1389f609cc9af4f7cf8357c9d4c38ea2 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:17:35 -0400
Subject: [PATCH 05/12] convert to JSDoc

---
 .../bundler/plugins/typescript-strip-types.ts | 11 ++-
 .../repl/src/lib/workers/compiler/index.ts    |  4 +-
 packages/typestript/package.json              | 12 ++--
 .../typestript/src/{index.ts => index.js}     | 68 +++++++++----------
 4 files changed, 45 insertions(+), 50 deletions(-)
 rename packages/typestript/src/{index.ts => index.js} (50%)

diff --git a/packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts b/packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts
index 726bc3080e..7499203829 100644
--- a/packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts
+++ b/packages/repl/src/lib/workers/bundler/plugins/typescript-strip-types.ts
@@ -4,16 +4,13 @@ import { stripTypes } from 'typestript';
 const plugin: Plugin = {
 	name: 'typescript-strip-types',
 	transform: (code, id) => {
-		const match = id.endsWith('.ts');
-		if (!match) return;
+		if (!id.endsWith('.ts')) return;
 
-		const { content, sourceMap } = stripTypes(code);
-
-		console.log(content);
+		const s = stripTypes(code);
 
 		return {
-			code: content,
-			map: sourceMap
+			code: s.toString(),
+			map: s.generateMap({ hires: true })
 		};
 	}
 };
diff --git a/packages/repl/src/lib/workers/compiler/index.ts b/packages/repl/src/lib/workers/compiler/index.ts
index 45c04dccda..8ca8e8f85f 100644
--- a/packages/repl/src/lib/workers/compiler/index.ts
+++ b/packages/repl/src/lib/workers/compiler/index.ts
@@ -81,8 +81,8 @@ addEventListener('message', async (event) => {
 				compilerOptions.experimental = { async: true };
 			}
 
-			const { content } = stripTypes(file.contents);
-			result = svelte.compileModule(content, compilerOptions);
+			const s = stripTypes(file.contents);
+			result = svelte.compileModule(s.toString(), compilerOptions);
 		}
 
 		postMessage({
diff --git a/packages/typestript/package.json b/packages/typestript/package.json
index ca0fed554e..6c445a5114 100644
--- a/packages/typestript/package.json
+++ b/packages/typestript/package.json
@@ -8,15 +8,13 @@
 		"format": "prettier --write ."
 	},
 	"exports": {
-		".": "./dist/index.js"
+		".": {
+			"types": "./src/index.js",
+			"default": "./src/index.js"
+		}
 	},
 	"files": [
-		"dist",
-		"!dist/**/*.test.*",
-		"!dist/**/*.spec.*",
-    "src",
-    "!src/**/*.test.*",
-    "!src/**/*.spec.*"
+		"src"
 	],
 	"type": "module",
 	"dependencies": {
diff --git a/packages/typestript/src/index.ts b/packages/typestript/src/index.js
similarity index 50%
rename from packages/typestript/src/index.ts
rename to packages/typestript/src/index.js
index f516c323b4..25a71d6e0d 100644
--- a/packages/typestript/src/index.ts
+++ b/packages/typestript/src/index.js
@@ -1,44 +1,46 @@
+/** @import { TSESTree } from '@typescript-eslint/types' */
 import * as acorn from 'acorn';
 import { tsPlugin } from '@sveltejs/acorn-typescript';
 import { walk } from 'zimmerframe';
-import type { TSESTree } from '@typescript-eslint/types';
-import MagicString, { SourceMap } from 'magic-string';
+import MagicString from 'magic-string';
 
 const TSParser = acorn.Parser.extend(tsPlugin());
 
-export function stripTypes(content: string): { content: string; sourceMap: SourceMap } {
-	console.log(content);
-
-	const ast = TSParser.parse(content, {
-		sourceType: 'module',
-		ecmaVersion: 13,
-		locations: true
-	});
+/**
+ * @param {string} content
+ * @returns {MagicString}
+ */
+export function stripTypes(content) {
+	const ast = /** @type {unknown} */ (
+		TSParser.parse(content, {
+			sourceType: 'module',
+			ecmaVersion: 13,
+			locations: true
+		})
+	);
 
 	const s = new MagicString(content);
 
-	walk(ast as unknown as TSESTree.Node, null, {
+	walk(/** @type {TSESTree.Node & { start: number, end: number }} */ (ast), null, {
 		_: (node, context) => {
-			console.log(node.type);
 			if (
 				node.type.startsWith('TS') &&
 				!['TSAsExpression', 'TSSatisfiesExpression', 'TSNonNullExpression'].includes(node.type)
 			) {
-				const { start, end } = node as unknown as { start: number; end: number };
+				const { start, end } = node;
 				s.overwrite(start, end, ' '.repeat(end - start));
 			} else {
 				context.next();
 			}
 		},
 		TSAsExpression: (node) => {
-			handleTypeExpression(node, s);
+			handle_type_expression(node, s);
 		},
 		TSSatisfiesExpression: (node) => {
-			handleTypeExpression(node, s);
+			handle_type_expression(node, s);
 		},
 		TSNonNullExpression: (node, context) => {
-			const { end } = node as unknown as { start: number; end: number };
-			s.overwrite(end - 1, end, ' ');
+			s.overwrite(node.end - 1, node.end, ' ');
 			context.next();
 		},
 		ImportDeclaration: (node, context) => {
@@ -48,7 +50,7 @@ export function stripTypes(content: string): { content: string; sourceMap: Sourc
 					(specifier) => specifier.type === 'ImportSpecifier' && specifier.importKind === 'type'
 				)
 			) {
-				const { start, end } = node as unknown as { start: number; end: number };
+				const { start, end } = node;
 				s.overwrite(start, end, ' '.repeat(end - start));
 			} else {
 				context.next();
@@ -56,7 +58,7 @@ export function stripTypes(content: string): { content: string; sourceMap: Sourc
 		},
 		ImportSpecifier: (node, context) => {
 			if (node.importKind === 'type') {
-				const { start, end } = node as unknown as { start: number; end: number };
+				const { start, end } = node;
 				s.overwrite(start, end, ' '.repeat(end - start));
 			} else {
 				context.next();
@@ -64,24 +66,22 @@ export function stripTypes(content: string): { content: string; sourceMap: Sourc
 		}
 	});
 
+	console.log(content);
 	console.log(s.toString());
 
-	return {
-		content: s.toString(),
-		sourceMap: s.generateMap({
-			hires: true
-		})
-	};
+	return s;
 }
 
-function handleTypeExpression(
-	node: {
-		expression: unknown;
-		typeAnnotation: unknown;
-	},
-	s: { overwrite: (start: number, end: number, content: string) => void }
-) {
-	const { end: start } = node.expression as unknown as { end: number; start: number };
-	const { end } = node.typeAnnotation as unknown as { start: number; end: number };
+/**
+ * @param {TSESTree.Node} node
+ * @param {MagicString} s
+ */
+function handle_type_expression(node, s) {
+	// @ts-ignore
+	const start = node.expression.end;
+
+	// @ts-ignore
+	const end = node.typeAnnotation.end;
+
 	s.overwrite(start, end, ' '.repeat(end - start));
 }

From 3aa5de1032c29c3f8435884b79de351909d58993 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:20:52 -0400
Subject: [PATCH 06/12] tidy up

---
 apps/svelte.dev/package.json     | 2 +-
 packages/typestript/package.json | 5 +----
 2 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/apps/svelte.dev/package.json b/apps/svelte.dev/package.json
index 9cb32856c8..2cfa8e1336 100644
--- a/apps/svelte.dev/package.json
+++ b/apps/svelte.dev/package.json
@@ -6,7 +6,7 @@
 	"type": "module",
 	"scripts": {
 		"dev": "node scripts/update.js && node scripts/create-tutorial-zip/index.js && vite dev",
-		"build": "pnpm -F typestript build && node scripts/update.js && node scripts/create-tutorial-zip/index.js && vite build",
+		"build": "node scripts/update.js && node scripts/create-tutorial-zip/index.js && vite build",
 		"update": "node scripts/update.js --force=true && node scripts/create-tutorial-zip/index.js --force=true",
 		"preview": "vite preview",
 		"start": "node build",
diff --git a/packages/typestript/package.json b/packages/typestript/package.json
index 6c445a5114..cf91f81a4c 100644
--- a/packages/typestript/package.json
+++ b/packages/typestript/package.json
@@ -2,8 +2,6 @@
 	"name": "typestript",
 	"private": true,
 	"scripts": {
-		"dev": "tsc --watch",
-		"build": "tsc",
 		"lint": "prettier --check .",
 		"format": "prettier --write ."
 	},
@@ -24,7 +22,6 @@
 		"zimmerframe": "^1.1.2"
 	},
 	"devDependencies": {
-		"@typescript-eslint/types": "^8.28.0",
-		"typescript": "^5.8.2"
+		"@typescript-eslint/types": "^8.28.0"
 	}
 }

From a0a7509cfd5a2362cd3cc0d915f5ca349d728511 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:26:39 -0400
Subject: [PATCH 07/12] only strip types from .ts files

---
 packages/repl/src/lib/workers/compiler/index.ts | 6 +++---
 packages/typestript/src/index.js                | 3 ---
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/packages/repl/src/lib/workers/compiler/index.ts b/packages/repl/src/lib/workers/compiler/index.ts
index 8ca8e8f85f..46c22edf00 100644
--- a/packages/repl/src/lib/workers/compiler/index.ts
+++ b/packages/repl/src/lib/workers/compiler/index.ts
@@ -22,7 +22,7 @@ addEventListener('message', async (event) => {
 
 	const { can_use_experimental_async, svelte } = (cache[version] ??= await load_svelte(version));
 
-	if (!file.name.endsWith('.svelte') && !svelte.compileModule) {
+	if (!file.name.endsWith('.svelte') && !file.name.includes('.svelte.') && !svelte.compileModule) {
 		// .svelte.js file compiled with Svelte 3/4 compiler
 		postMessage({
 			id,
@@ -81,8 +81,8 @@ addEventListener('message', async (event) => {
 				compilerOptions.experimental = { async: true };
 			}
 
-			const s = stripTypes(file.contents);
-			result = svelte.compileModule(s.toString(), compilerOptions);
+			const code = file.name.endsWith('.ts') ? stripTypes(file.contents).toString() : file.contents;
+			result = svelte.compileModule(code, compilerOptions);
 		}
 
 		postMessage({
diff --git a/packages/typestript/src/index.js b/packages/typestript/src/index.js
index 25a71d6e0d..272fcd27f5 100644
--- a/packages/typestript/src/index.js
+++ b/packages/typestript/src/index.js
@@ -66,9 +66,6 @@ export function stripTypes(content) {
 		}
 	});
 
-	console.log(content);
-	console.log(s.toString());
-
 	return s;
 }
 

From 310d553e98f4a40230e8baf5340608a2161ca08c Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:27:52 -0400
Subject: [PATCH 08/12] only attempt to migrate .svelte files

---
 packages/repl/src/lib/workers/compiler/index.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/repl/src/lib/workers/compiler/index.ts b/packages/repl/src/lib/workers/compiler/index.ts
index 46c22edf00..7c13626a97 100644
--- a/packages/repl/src/lib/workers/compiler/index.ts
+++ b/packages/repl/src/lib/workers/compiler/index.ts
@@ -38,7 +38,7 @@ addEventListener('message', async (event) => {
 
 	let migration = null;
 
-	if (svelte.migrate) {
+	if (file.name.endsWith('.svelte') && svelte.migrate) {
 		try {
 			migration = svelte.migrate(file.contents, { filename: file.name });
 		} catch (e) {

From 419f2e70c2106ec6a736ba57c11c8a74af74ab74 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:31:45 -0400
Subject: [PATCH 09/12] add prettier

---
 packages/typestript/package.json |  3 ++-
 pnpm-lock.yaml                   | 13 +++----------
 2 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/packages/typestript/package.json b/packages/typestript/package.json
index cf91f81a4c..fe56c2ebd0 100644
--- a/packages/typestript/package.json
+++ b/packages/typestript/package.json
@@ -22,6 +22,7 @@
 		"zimmerframe": "^1.1.2"
 	},
 	"devDependencies": {
-		"@typescript-eslint/types": "^8.28.0"
+		"@typescript-eslint/types": "^8.28.0",
+		"prettier": "^3.3.2"
 	}
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 7052ed9349..67b24c894e 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -459,9 +459,9 @@ importers:
       '@typescript-eslint/types':
         specifier: ^8.28.0
         version: 8.28.0
-      typescript:
-        specifier: ^5.8.2
-        version: 5.8.2
+      prettier:
+        specifier: ^3.3.2
+        version: 3.3.2
 
 packages:
 
@@ -3166,11 +3166,6 @@ packages:
     engines: {node: '>=14.17'}
     hasBin: true
 
-  typescript@5.8.2:
-    resolution: {integrity: sha512-aJn6wq13/afZp/jT9QZmwEjDqqvSGp1VT5GVg+f/t6/oVyrgXM6BY1h9BRh/O5p3PlUPAe+WuiEZOmb/49RqoQ==}
-    engines: {node: '>=14.17'}
-    hasBin: true
-
   ultrahtml@1.5.3:
     resolution: {integrity: sha512-GykOvZwgDWZlTQMtp5jrD4BVL+gNn2NVlVafjcFUJ7taY20tqYdwdoWBFy6GBJsNTZe1GkGPkSl5knQAjtgceg==}
 
@@ -6128,8 +6123,6 @@ snapshots:
 
   typescript@5.5.4: {}
 
-  typescript@5.8.2: {}
-
   ultrahtml@1.5.3: {}
 
   undici-types@5.26.5: {}

From bef6b7394a283b3c80e6e37d99d2e836ba17796e Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:33:55 -0400
Subject: [PATCH 10/12] prettier

---
 packages/typestript/tsconfig.json | 16 ++++++----------
 1 file changed, 6 insertions(+), 10 deletions(-)

diff --git a/packages/typestript/tsconfig.json b/packages/typestript/tsconfig.json
index 7c74640aaa..3b16fea544 100644
--- a/packages/typestript/tsconfig.json
+++ b/packages/typestript/tsconfig.json
@@ -1,20 +1,16 @@
 {
 	"compilerOptions": {
-    "outDir": "dist",
+		"outDir": "dist",
 		"allowJs": true,
 		"checkJs": true,
-    "verbatimModuleSyntax": true,
+		"verbatimModuleSyntax": true,
 		"isolatedModules": true,
-		"lib": [
-			"esnext",
-			"DOM",
-			"DOM.Iterable"
-		],
+		"lib": ["esnext", "DOM", "DOM.Iterable"],
 		"moduleResolution": "bundler",
 		"module": "esnext",
 		"target": "esnext",
-    "declaration": true,
-    "declarationMap": true,
+		"declaration": true,
+		"declarationMap": true
 	},
-  "include": ["src/**/*.ts"],
+	"include": ["src/**/*.ts"]
 }

From 58b6a5de7b51f891cfcddc02be05de811181f90c Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:36:15 -0400
Subject: [PATCH 11/12] snake_case

---
 packages/repl/src/lib/workers/bundler/index.ts | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/repl/src/lib/workers/bundler/index.ts b/packages/repl/src/lib/workers/bundler/index.ts
index 86b95dbf95..79fff0cfea 100644
--- a/packages/repl/src/lib/workers/bundler/index.ts
+++ b/packages/repl/src/lib/workers/bundler/index.ts
@@ -3,7 +3,7 @@ import { walk } from 'zimmerframe';
 import '../patch_window';
 import { rollup } from '@rollup/browser';
 import { DEV } from 'esm-env';
-import typescriptStripTypes from './plugins/typescript-strip-types';
+import strip_types from './plugins/typescript-strip-types';
 import commonjs from './plugins/commonjs';
 import glsl from './plugins/glsl';
 import json from './plugins/json';
@@ -388,7 +388,7 @@ async function get_bundle(
 		input: './__entry.js',
 		cache: previous?.key === key && previous.cache,
 		plugins: [
-			typescriptStripTypes,
+			strip_types,
 			repl_plugin,
 			commonjs,
 			json,

From 34ce6ec4c3d0d559fac8dfd97718886c25667904 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 4 Apr 2025 16:40:39 -0400
Subject: [PATCH 12/12] small drive-by fix

---
 packages/repl/src/lib/workers/bundler/index.ts | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/repl/src/lib/workers/bundler/index.ts b/packages/repl/src/lib/workers/bundler/index.ts
index 79fff0cfea..ed37a38065 100644
--- a/packages/repl/src/lib/workers/bundler/index.ts
+++ b/packages/repl/src/lib/workers/bundler/index.ts
@@ -283,13 +283,13 @@ async function get_bundle(
 
 			if (!/\.(svelte|js|ts)$/.test(id)) return null;
 
-			const name = id.split('/').pop()?.split('.')[0];
+			const filename = id.split('/').pop()!;
 
 			let result: CompileResult;
 
 			if (id.endsWith('.svelte')) {
 				const compilerOptions: any = {
-					filename: name + '.svelte',
+					filename,
 					generate: Number(svelte.VERSION.split('.')[0]) >= 5 ? 'client' : 'dom',
 					dev: true
 				};
@@ -345,7 +345,7 @@ async function get_bundle(
 				}
 			} else if (/\.svelte\.(js|ts)$/.test(id)) {
 				const compilerOptions: any = {
-					filename: name + '.js',
+					filename,
 					generate: 'client',
 					dev: true
 				};