Change isUnliftedTyCon to marshalablePrimTyCon (#20401)

isUnliftedTyCon was used in three places: Ticky, Template Haskell
and FFI checks.

It was straightforward to remove it from Ticky and Template Haskell.

It is now used in FFI only and renamed to marshalablePrimTyCon.

Previously, it was fetching information from a field
in PrimTyCon called is_unlifted. Instead, I've changed the code
to compute liftedness based on the kind.

isFFITy and legalFFITyCon are removed. They were only referred from
an old comment that I removed.

There were three functions to define a PrimTyCon, but the only difference
was that they were setting is_unlifted to True or False.
Everything is now done in mkPrimTyCon.

I also added missing integer types in Ticky.hs, I think it was an oversight.

Fixes #20401

1 files changed, 17 insertions, 21 deletions

diff --git a/compiler/GHC/Tc/Utils/TcType.hs b/compiler/GHC/Tc/Utils/TcType.hs
index b79a4152e1..a4dfead21b 100644
--- a/compiler/GHC/Tc/Utils/TcType.hs
+++ b/compiler/GHC/Tc/Utils/TcType.hs
@@ -118,7 +118,6 @@ module GHC.Tc.Utils.TcType (
   isFFIPrimArgumentTy, -- :: DynFlags -> Type -> Bool
   isFFIPrimResultTy,   -- :: DynFlags -> Type -> Bool
   isFFILabelTy,        -- :: Type -> Bool
-  isFFITy,             -- :: Type -> Bool
   isFunPtrTy,          -- :: Type -> Bool
   tcSplitIOType_maybe, -- :: Type -> Maybe Type
 
@@ -228,7 +227,7 @@ import GHC.Data.List.SetOps ( getNth, findDupsEq )
 import GHC.Utils.Outputable
 import GHC.Utils.Panic
 import GHC.Utils.Panic.Plain
-import GHC.Utils.Error( Validity'(..), Validity, isValid )
+import GHC.Utils.Error( Validity'(..), Validity )
 import qualified GHC.LanguageExtensions as LangExt
 
 import Data.List  ( mapAccumL )
@@ -2200,10 +2199,6 @@ tcSplitIOType_maybe ty
         _ ->
             Nothing
 
-isFFITy :: Type -> Bool
--- True for any TyCon that can possibly be an arg or result of an FFI call
-isFFITy ty = isValid (checkRepTyCon legalFFITyCon ty)
-
 isFFIArgumentTy :: DynFlags -> Safety -> Type -> Validity
 -- Checks for valid argument type for a 'foreign import'
 isFFIArgumentTy dflags safety ty
@@ -2332,17 +2327,19 @@ legalOutgoingTyCon :: DynFlags -> Safety -> TyCon -> Validity
 legalOutgoingTyCon dflags _ tc
   = marshalableTyCon dflags tc
 
-legalFFITyCon :: TyCon -> Validity
--- True for any TyCon that can possibly be an arg or result of an FFI call
-legalFFITyCon tc
-  | isUnliftedTyCon tc = IsValid
-  | tc == unitTyCon    = IsValid
-  | otherwise          = boxedMarshalableTyCon tc
+-- Check for marshalability of a primitive type.
+-- We exclude lifted types such as RealWorld and TYPE.
+-- They can technically appear in types, e.g.
+-- f :: RealWorld -> TYPE LiftedRep -> RealWorld
+-- f x _ = x
+-- but there are no values of type RealWorld or TYPE LiftedRep,
+-- so it doesn't make sense to use them in FFI.
+marshalablePrimTyCon :: TyCon -> Bool
+marshalablePrimTyCon tc = isPrimTyCon tc && not (isLiftedTypeKind (tyConResKind tc))
 
 marshalableTyCon :: DynFlags -> TyCon -> Validity
 marshalableTyCon dflags tc
-  | isUnliftedTyCon tc
-  , not (isUnboxedTupleTyCon tc || isUnboxedSumTyCon tc)
+  | marshalablePrimTyCon tc
   , not (null (tyConPrimRep tc)) -- Note [Marshalling void]
   = validIfUnliftedFFITypes dflags
   | otherwise
@@ -2366,11 +2363,8 @@ boxedMarshalableTyCon tc
 
 legalFIPrimArgTyCon :: DynFlags -> TyCon -> Validity
 -- Check args of 'foreign import prim', only allow simple unlifted types.
--- Strictly speaking it is unnecessary to ban unboxed tuples and sums here since
--- currently they're of the wrong kind to use in function args anyway.
 legalFIPrimArgTyCon dflags tc
-  | isUnliftedTyCon tc
-  , not (isUnboxedTupleTyCon tc || isUnboxedSumTyCon tc)
+  | marshalablePrimTyCon tc
   = validIfUnliftedFFITypes dflags
   | otherwise
   = NotValid unlifted_only
@@ -2379,9 +2373,11 @@ legalFIPrimResultTyCon :: DynFlags -> TyCon -> Validity
 -- Check result type of 'foreign import prim'. Allow simple unlifted
 -- types and also unboxed tuple and sum result types.
 legalFIPrimResultTyCon dflags tc
-  | isUnliftedTyCon tc
-  , isUnboxedTupleTyCon tc || isUnboxedSumTyCon tc
-     || not (null (tyConPrimRep tc))   -- Note [Marshalling void]
+  | marshalablePrimTyCon tc
+  , not (null (tyConPrimRep tc))   -- Note [Marshalling void]
+  = validIfUnliftedFFITypes dflags
+
+  | isUnboxedTupleTyCon tc || isUnboxedSumTyCon tc
   = validIfUnliftedFFITypes dflags
 
   | otherwise