`@overload` return union unexpected behaviour

How are you using the lua-language-server?

NeoVim

Which OS are you using?

Windows

What is the issue affecting?

Type Checking, Diagnostics/Syntax Checking

Expected Behaviour

Type of r1 = EA|0
Not warning: probably nil

Actual Behaviour

Type of r1 = integer|EA|0
Warning: probably nil

Reproduction steps

1. Create file test.lua
2. Fill

---@enum EA
local EA = {
  a = 1,
  b = 2,
}
local ab = 0
---@overload fun(): 0
---@overload fun(): EA, [string]
local function fua()
  if ab == 0 then
    return 0
  else
    return EA[ab] or EA.a, { "aa" }
  end
end

local r1, r2 = fua()

if r1 == 0 then
  print(0)
else
  print(r2[1])
end

4. See type of r1
5. See Need check nil at line 22

Additional Notes

Maybe duplicate of #1456

Log File

Log file

Start by reproducing the report in test.lua with the supplied @overload example and inspect the inferred types and diagnostic at line 22. Done means r1 is inferred as EA|0 and the nil warning is no longer reported for the shown control flow.