GHC master fails to build with alex 3.5.1.0

Summary

Upgrading to Alex 3.5.1.0 makes compilation of GHC on master fail because of 7dfdf3d9 (cc @hsyl20)

compiler/GHC/Parser/Lexer.x:2871:20: error: [GHC-88464]
    Data constructor not in scope: C# :: t0 -> Char
    Suggested fixes:
      • Perhaps use one of these:
          ‘GHC.Exts.C#’ (imported from GHC.Exts),
          ‘GHC.Exts.D#’ (imported from GHC.Exts),
          ‘GHC.Exts.F#’ (imported from GHC.Exts)
      • Add ‘C#’ to the import list in the import of ‘GHC.Exts’
        (at _build/stage0/compiler/build/GHC/Parser/Lexer.hs:100:1-202).
     |
2871 |
     |                    ^^

compiler/GHC/Parser/Lexer.x:2871:24: error: [GHC-88464]
    Variable not in scope: chr# :: Int# -> t0
    Suggested fixes:
      • Perhaps use one of these:
          ‘GHC.Exts.chr#’ (imported from GHC.Exts),
          ‘chr’ (imported from Data.Char)
      • Add ‘chr#’ to the import list in the import of ‘GHC.Exts’
        (at _build/stage0/compiler/build/GHC/Parser/Lexer.hs:100:1-202).
     |
2871 |
     |                        ^^^^

Steps to reproduce

Try building master with alex 3.5.1.0

Environment

• GHC version used: 9.8.2, alex 3.5.1.0

Solution

It seems to be sufficient to qualify the names with GHC.Exts