Zubin pushed to branch wip/no-try-lookup at Glasgow Haskell Compiler / GHC

Commits:

• efe1efed
  by Zubin Duggal at 2025-07-29T17:00:40+05:30

  In commit "Don't cache solved [W] HasCallStack constraints" (256ac29c8df4f17a1d50ea243408d506ebf395d6),
  we attempt to use `tryM` to avoid errors when looking up certain known-key names like CallStack while
  compiling ghc-prim and ghc-internal.
  
  Unfortunately, `tryM` doesn't catch module lookup errors. This manifests as a failure to build ghc-prim
  in `--make` mode on the GHC 9.10 branch.
  
  Instead, we explicitly avoid doing lookups when we are compiling ghc-prim or ghc-internal instead of
  relying on catching the exception.
  
  (cherry picked from commit 7492d00749488b628139d5c3bd5fa4b33cc2e4ad)
  

1 changed file:

• compiler/GHC/Tc/Solver/Monad.hs

Changes:

     -- See Note [Using isCallStackTy in mightMentionIP].

     is_tyConTy :: (Type -> Bool) -> Name -> TcS (Type -> Bool)

     is_tyConTy is_eq tc_name

-      = do { (mb_tc, _) <- wrapTcS $ TcM.tryTc $ TcM.tcLookupTyCon tc_name

+      = do {  mb_tc <- wrapTcS $ do

+                mod <- tcg_mod <$> TcM.getGblEnv

+                if moduleUnit mod `elem` [primUnit, ghcInternalUnit, bignumUnit]

+                then return Nothing

+                else Just <$> TcM.tcLookupTyCon tc_name

            ; case mb_tc of

               Just tc ->

                 return $ \ ty -> not (typesAreApart ty (mkTyConTy tc))