Missing "need-check-nil" on self fields

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, Diagnostics/Syntax Checking

Expected Behaviour

I expect both methods to report the "need check nil" diagnostic:

---@class Y
---@field z string

---@class X
---@field y Y?
local X = {}

function X:no_warning()
    print(self.y.z) -- no diagnostics
end

function X:warning()
    local y = self.y
    print(y.z) -- need-check-nil
end

Actual Behaviour

The potential problem is only reported when using a local variable.

Reproduction steps

Try the code above. and note how only the first method (no_warning) works without any diagnostics.

Additional Notes

No response

Log File

No response

Reproduce the issue in the Visual Studio Code extension using the Lua snippet in the report, and compare diagnostics for self.y.z with the local-variable case y.z. Trace the type-checking or diagnostic entry point responsible for nil checking; done means both methods report the need-check-nil diagnostic without changing the example's types.