Basic string concat type inference is missing

[stylpe]

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Windows

What is the issue affecting?

Type Checking, Hover

Expected Behaviour

Two string vars or a string var and a string literal being concatenated should get the result inferred to also be a string.

Actual Behaviour

It infers unknown.

Reproduction steps

Additional Notes

I'm guessing #680 maybe took away too much? It seems reasonable to infer string as the result type when both the sources are also pure strings (or possibly other basic types too). And maybe there are also other operators where this is the case.

I'd say it doesn't need to be a goal to support every weird corner case like if one variable is ´string|CustomType´ or accounting for metatable shenanigans, but the straightforward basic cases should be supported.

Log File

No response