Introduce Concrete# for representation polymorphism checks

PHASE 1: we never rewrite Concrete# evidence.

This patch migrates all the representation polymorphism checks to
the typechecker, using a new constraint form

  Concrete# :: forall k. k -> TupleRep '[]

Whenever a type `ty` must be representation-polymorphic
(e.g. it is the type of an argument to a function), we emit a new
`Concrete# ty` Wanted constraint. If this constraint goes
unsolved, we report a representation-polymorphism error to the user.
The 'FRROrigin' datatype keeps track of the context of the
representation-polymorphism check, for more informative error messages.

This paves the way for further improvements, such as
allowing type families in RuntimeReps and improving the soundness
of typed Template Haskell. This is left as future work (PHASE 2).

fixes #17907 #20277 #20330 #20423 #20426

updates haddock submodule

-------------------------
Metric Decrease:
    T5642
-------------------------

1 files changed, 7 insertions, 3 deletions

diff --git a/compiler/GHC/Tc/TyCl/Instance.hs b/compiler/GHC/Tc/TyCl/Instance.hs
index 386c657aba..23c9fd8fff 100644
--- a/compiler/GHC/Tc/TyCl/Instance.hs
+++ b/compiler/GHC/Tc/TyCl/Instance.hs
@@ -750,7 +750,10 @@ tcDataFamInstDecl mb_clsinfo tv_skol_env
               ; rep_tc_name <- newFamInstTyConName lfam_name pats
               ; axiom_name  <- newFamInstAxiomName lfam_name [pats]
               ; tc_rhs <- case new_or_data of
-                     DataType -> return (mkDataTyConRhs data_cons)
+                     DataType -> return $
+                        mkLevPolyDataTyConRhs
+                          (isFixedRuntimeRepKind final_res_kind)
+                          data_cons
                      NewType  -> assert (not (null data_cons)) $
                                  mkNewTyConRhs rep_tc_name rec_rep_tc (head data_cons)
 
@@ -1333,8 +1336,9 @@ addDFunPrags dfun_id sc_meth_ids
  where
    con_app    = mkLams dfun_bndrs $
                 mkApps (Var (dataConWrapId dict_con)) dict_args
-                 -- mkApps is OK because of the checkForLevPoly call in checkValidClass
-                 -- See Note [Representation polymorphism checking] in GHC.HsToCore.Monad
+                -- This application will satisfy the Core invariants
+                -- from Note [Representation polymorphism invariants] in GHC.Core,
+                -- because typeclass method types are never unlifted.
    dict_args  = map Type inst_tys ++
                 [mkVarApps (Var id) dfun_bndrs | id <- sc_meth_ids]