Enum created with `@alias` breaks when unioned with table

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Linux

What is the issue affecting?

Type Checking

Expected Behaviour

it should allow either the enum or a table

Actual Behaviour

Cannot assign `integer` to parameter ``BAR`|`FOO`|any[]`.
- `integer` cannot match ``BAR`|`FOO`|any[]`
- Type `integer` cannot match `any[]`
- Type `number` cannot match `any[]`

Reproduction steps

FOO = 1
BAR = 2

--- @alias WAT `FOO` | `BAR`
--- @param a WAT | any[]
local function aa(a) end

aa(FOO)

Additional Notes

Bonus: If you change the type to WAT | WAT[] the error message is

Cannot assign `integer` to parameter ``BAR`|`BAR`|`FOO`[]|`FOO``.
- `integer` cannot match ``BAR`|`BAR`|`FOO`[]|`FOO``
- Type `integer` cannot match ``BAR`|`FOO`[]`
- Type `number` cannot match ``BAR`|`FOO`[]`

which looks very visually confusing

Log File

No response

Reproduce the reported Lua code in the Visual Studio Code extension and inspect the type-checking path for aliases combined with unions and tables. Done means aa(FOO) is accepted for WAT | any[], and the resulting type diagnostics are no longer confusing for the WAT | WAT[] case.