fix: generalize lang="ts" hint to all template expression contexts

Instead of only hinting on snippet params, detect TypeScript syntax
across all expression sites: acorn_error catches colon annotations
that make acorn fail, read_expression catches as/satisfies/!/: that
acorn silently skips over.

packages/svelte/src/compiler/phases/1-parse/index.js

@@ -177,11 +177,17 @@ export class Parser {
 
 	/**
 	 * @param {any} err
-	 * @param {string} [suffix]
 	 * @returns {never}
 	 */
-	acorn_error(err, suffix = '') {
+	acorn_error(err) {
-		e.js_parse_error(err.pos, err.message.replace(regex_position_indicator, '') + suffix);
+		const message = err.message.replace(regex_position_indicator, '');
+
+		const hint =
+			!this.ts && typeof err.pos === 'number' && this.template[err.pos] === ':'
+				? ` (did you forget to add \`lang="ts"\`?)`
+				: '';
+
+		e.js_parse_error(err.pos, message + hint);
 	}
 
 	/**

packages/svelte/src/compiler/phases/1-parse/read/expression.js

@@ -33,14 +33,19 @@ export function get_loose_identifier(parser, opening_token) {
  * @returns {Expression}
  */
 export default function read_expression(parser, opening_token, disallow_loose) {
+	/** @type {Expression | undefined} */
+	let node;
+
 	try {
 		let comment_index = parser.root.comments.length;
 
-		const node = parse_expression_at(
+		node = /** @type {Expression} */ (
-			parser.template,
+			parse_expression_at(
-			parser.root.comments,
+				parser.template,
-			parser.ts,
+				parser.root.comments,
-			parser.index
+				parser.ts,
+				parser.index
+			)
 		);
 
 		let num_parens = 0;
@@ -76,8 +81,6 @@ export default function read_expression(parser, opening_token, disallow_loose) {
 		}
 
 		parser.index = index;
-
-		return /** @type {Expression} */ (node);
 	} catch (err) {
 		// If we are in an each loop we need the error to be thrown in cases like
 		// `as { y = z }` so we still throw and handle the error there
@@ -90,4 +93,22 @@ export default function read_expression(parser, opening_token, disallow_loose) {
 
 		parser.acorn_error(err);
 	}
+
+	if (!parser.ts) {
+		let j = parser.index;
+		while (j < parser.template.length && regex_whitespace.test(parser.template[j])) j++;
+
+		const remaining = parser.template.slice(j);
+
+		if (
+			remaining[0] === ':' ||
+			/^satisfies[\s(]/.test(remaining) ||
+			(remaining[0] === '!' && remaining[1] !== '=') ||
+			(/^as[\s(]/.test(remaining) && !disallow_loose)
+		) {
+			e.js_parse_error(j, `Unexpected token (did you forget to add \`lang="ts"\`?)`);
+		}
+	}
+
+	return node;
 }

packages/svelte/src/compiler/phases/1-parse/state/tag.js

@@ -403,11 +403,7 @@ function open(parser) {
 					)
 				);
 			} catch (/** @type {any} */ err) {
-				const suffix =
+				parser.acorn_error(err);
-					!parser.ts && parser.template[err.pos] === ':'
-						? ` (did you forget to add \`lang="ts"\`?)`
-						: '';
-				parser.acorn_error(err, suffix);
 			}
 		} else {
 			function_expression = { params: [] };

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-as/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'js_parse_error',
+		message: 'Unexpected token (did you forget to add `lang="ts"`?)',
+		position: [3, 3]
+	}
+});

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-as/main.svelte

@@ -0,0 +1 @@
+{x as number}

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-attribute/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'js_parse_error',
+		message: 'Unexpected token (did you forget to add `lang="ts"`?)',
+		position: [14, 14]
+	}
+});

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-attribute/main.svelte

@@ -0,0 +1 @@
+<div class={x as Foo} />

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-colon/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'js_parse_error',
+		message: 'Unexpected token (did you forget to add `lang="ts"`?)',
+		position: [2, 2]
+	}
+});

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-colon/main.svelte

@@ -0,0 +1 @@
+{x: number}

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-non-null/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'js_parse_error',
+		message: 'Unexpected token (did you forget to add `lang="ts"`?)',
+		position: [2, 2]
+	}
+});

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-non-null/main.svelte

@@ -0,0 +1 @@
+{x!}

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-satisfies/_config.js

@@ -0,0 +1,9 @@
+import { test } from '../../test';
+
+export default test({
+	error: {
+		code: 'js_parse_error',
+		message: 'Unexpected token (did you forget to add `lang="ts"`?)',
+		position: [3, 3]
+	}
+});

packages/svelte/tests/compiler-errors/samples/ts-annotation-no-lang-satisfies/main.svelte

@@ -0,0 +1 @@
+{x satisfies Foo}