Design Meeting Notes, 2026-06-23

isolatedDeclarations and Control Flow Analysis

https://github.com/microsoft/typescript-go/pull/4367

• Want to be able to infer types for trivial expressions in isolatedDeclarations in a function block.
  • Specifically in discussion is if there are no return statements.
• But what happpens when you have a never-returning call? That can cause a never.
• Feels like anything with multiple statements in the body is questionable.
• We could make a special-case for () => {}.
  • Probably enough to just say "just write void".
• Feels bad to say we can't come up with a type for () => {}
  • Why? Feels like it's not a big deal?
  • Well it's even more trivial than a single expression being returned.
  • Sure, but the reason we added trivial expression inference was because people often have bigger structures of objects that are nested. So the triviality was not really about writing small expressions.
• One reason why we didn't do it (we think) is that we don't want to close the door to ourselves on how void vs. undefined is inferred for no-return-expression functions.

Bắt đầu bằng cách đọc phần thảo luận của issue và pull request được liên kết, microsoft/typescript-go#4367. Làm rõ hành vi dự kiến của isolatedDeclarations đối với các thân hàm không có câu lệnh return, bao gồm các lệnh gọi không bao giờ trả về và sự phân biệt giữa void và undefined. Công việc được xem là hoàn tất khi dự án đã thống nhất hành vi và phạm vi triển khai tương ứng.