Using a union of string literals as a table key doesn't force use of the keys

How are you using the lua-language-server?

NeoVim

Which OS are you using?

Linux

What is the issue affecting?

Type Checking

Expected Behaviour

---@alias SomeUnion
--- | 'a'
--- | 'b'

---@type table<SomeUnion, number>
local a

should work roughly like

---@class (exact) SomeUnion
---@field a number
---@field b number
local a

Actual Behaviour

Reproduction steps

---@alias SomeUnion
--- | 'a'
--- | 'b'

---@type table<SomeUnion, number>
local a = {
  c = "should be invalid"
}

Additional Notes

No response

Log File

No response

Start by reproducing the reported type-checking example in the issue and trace the language server's handling of table keys whose type is a string-literal union. Done means the c key in the reproduction is reported invalid while the a and b keys remain valid.