this post was submitted on 28 Mar 2024
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Rust
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Without static type annotations you can only make best effort guesses that are sometimes right. Better than nothing but not remotely the same as actual static types. The LSP you linked works best when you use static type annotations.
Also I would really recommend Pylance over that if you can - it's much better but is also closed source unfortunately.
Why would it just be best effort? To find references for a specific thing, it still would parse an AST, find the current scope, see it's imported from some module, find other imports of the module, etc.
Where is the definition of x? What is the type of x? If you can't identify it, neither can the LSP.
This kind of thing actually happens when implementing interfaces, inheritance, etc. Thus, LSPs in dynamic languages are best effort both theoretically and in practice.
Tbf this example can be deducted as
string | int
just fine.The real problem is when you start using runtime reflection, like
getattr(obj, "x")