Simon Jakobi pushed to branch wip/sjakobi/deprecated-flags-2016 at Glasgow Haskell Compiler / GHC

Commits:

• b3ba3621
  by Simon Jakobi at 2026-10-12T16:07:54+02:00

  Make T2464 actually test #ifdef'd pragmas
  
  The test guarded a LANGUAGE EmptyDataDecls pragma behind #if, but
  EmptyDataDecls is on by default since Haskell2010, so the module
  compiled even when the guarded pragma was ignored. Guard MagicHash
  instead, which is unlikely to be included in a future default language.
  
  Also restore the check that warnings from file-header pragmas are
  emitted only once, even though the pragmas are parsed both before and
  after CPP. The -fffi deprecation warning used to serve as that canary.
  Use an unrecognised warning flag instead, which will not go away.
  
  Assisted-by: Claude Fable 5.1
  

2 changed files:

• testsuite/tests/driver/T2464.hs
• + testsuite/tests/driver/T2464.stderr

Changes:

 {-# LANGUAGE CPP #-}

 {-# OPTIONS_GHC -DTEST #-}

+{-# OPTIONS_GHC -Wno-such-warning #-} -- warned about exactly once

 #if defined(TEST)

-{-# LANGUAGE EmptyDataDecls #-}

+{-# LANGUAGE MagicHash #-}

 #endif

 module Test2464 where

-data T

+

+import GHC.Exts

+

+f :: Int# -> Int#

+f x = x +# 1#

+

+T2464.hs:3:17: warning: [GHC-93741] [-Wunrecognised-warning-flags (in -Wdefault)]

+    unrecognised warning flag: -Wno-such-warning