Parser fails when a decorator follows a type-only declaration (Unexpected character '@')

[Chakroun-Anas]

Description

When a decorator appears immediately after a TypeScript-only declaration such as a type or interface, the parser throws a syntax error — even though this is perfectly valid TypeScript syntax.

This seems to happen because the parser doesn’t correctly reset its internal state after handling a type-only declaration, so the next @ token is misinterpreted.

---

Reproduction

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

type User = {
  id: number;
  name: string;
  email: string;
}

@Injectable({
  providedIn: 'root', // makes the service available app-wide
})
export class UserService {
  private apiUrl = 'https://jsonplaceholder.typicode.com/users';

  constructor(private http: HttpClient) {}

  // Fetch all users
  getUsers(): Observable<User[]> {
    return this.http.get<User[]>(this.apiUrl);
  }

  // Fetch a single user by ID
  getUserById(id: number): Observable<User> {
    return this.http.get<User>(`${this.apiUrl}/${id}`);
  }
}

Output

Failed to parse source code: Unexpected character '@' (11:0)

Expected

The code should parse successfully. This is valid TypeScript and compiles fine in the TypeScript compiler and Babel’s TypeScript parser.

Environment

Node: 20.x
"acorn": "^8.15.0",
"@sveltejs/acorn-typescript": "^1.0.6"