Weird handling of exports named main in 8.10-rc1

Testing the new 8.10 release candidate:

We need 2 modules:

-- M1.hs
module M1 (main) where
main :: IO ()
main = pure () -- seem crucial that it's called main

-- M2.hs
module M2 (M2.main) where
import M1
main :: IO ()
main = putStrLn "test"

GHC 8.10-rc1:

$ ghc -c M1.hs

$ ghc -c M2.hs

M2.hs:1:1: error:
    Ambiguous occurrence ‘main’
    It could refer to
       either ‘M1.main’, imported from ‘M1’ at M2.hs:2:1-9
           or ‘M2.main’, defined at M2.hs:4:1
  |
1 | module M2 (M2.main) where
  | ^

GHC 8.8.2:

$ ghc -c M1.hs
$ ghc -c M2.hs
# no output, success

This also happens in --make mode.

This does not happen if the identifier is not named main.