Feature request: Opaque/nominal types

The problem

It often happens that library functions return objects the type of which is an implementation detail. For example an identifier may be an integer but could suddenly be changed to a string, and the client code shouldn't fail because of that.

Safely typing such an identifier in LLS is currently impossible:

• typing it as integer depends on a potentially unstable implementation detail
• typing it as any is unsound

In other words, structural typing fails when the structure isn't stable or known.

Feature request

An annotations that declares a completely opaque/nominal type. It could be --@opaque typename, --@alias typename without any arguments, or anything else. Values belonging of such a type cannot be inspected in any way and can only be passed around. Values of different opaque types cannot be mixed up (so this is stronger than unknown in typescript)

未指定任何文件、测试或入口点。首先定位别名和未知类型的注解与类型检查代码，然后追踪值是如何被检查或混合的。完成的标准是 language server 支持只能传递的不同不透明类型，并为所请求的行为提供覆盖。