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
-------------------------

3 files changed, 40 insertions, 4 deletions

diff --git a/compiler/GHC/Builtin/Names.hs b/compiler/GHC/Builtin/Names.hs
index 22b2cf6b9c..5f02b8e42b 100644
--- a/compiler/GHC/Builtin/Names.hs
+++ b/compiler/GHC/Builtin/Names.hs
@@ -1860,7 +1860,8 @@ statePrimTyConKey, stableNamePrimTyConKey, stableNameTyConKey,
     typeConKey, threadIdPrimTyConKey, bcoPrimTyConKey, ptrTyConKey,
     funPtrTyConKey, tVarPrimTyConKey, eqPrimTyConKey,
     eqReprPrimTyConKey, eqPhantPrimTyConKey,
-    compactPrimTyConKey, stackSnapshotPrimTyConKey :: Unique
+    compactPrimTyConKey, stackSnapshotPrimTyConKey,
+    concretePrimTyConKey :: Unique
 statePrimTyConKey                       = mkPreludeTyConUnique 50
 stableNamePrimTyConKey                  = mkPreludeTyConUnique 51
 stableNameTyConKey                      = mkPreludeTyConUnique 52
@@ -1889,6 +1890,7 @@ funPtrTyConKey                          = mkPreludeTyConUnique 78
 tVarPrimTyConKey                        = mkPreludeTyConUnique 79
 compactPrimTyConKey                     = mkPreludeTyConUnique 80
 stackSnapshotPrimTyConKey               = mkPreludeTyConUnique 81
+concretePrimTyConKey                    = mkPreludeTyConUnique 82
 
 eitherTyConKey :: Unique
 eitherTyConKey                          = mkPreludeTyConUnique 84
@@ -2228,7 +2230,6 @@ integerIPDataConKey       = mkPreludeDataConUnique 122
 naturalNSDataConKey       = mkPreludeDataConUnique 123
 naturalNBDataConKey       = mkPreludeDataConUnique 124
 
-
 ---------------- Template Haskell -------------------
 --      GHC.Builtin.Names.TH: USES DataUniques 200-250
 -----------------------------------------------------
diff --git a/compiler/GHC/Builtin/PrimOps.hs b/compiler/GHC/Builtin/PrimOps.hs
index 9bfed53382..40f5e65605 100644
--- a/compiler/GHC/Builtin/PrimOps.hs
+++ b/compiler/GHC/Builtin/PrimOps.hs
@@ -692,7 +692,7 @@ significantly simpler since otherwise we would need to define a calling
 convention for curried applications that can accommodate representation
 polymorphism.
 
-To ensure saturation, CorePrep eta expands expand all primop applications as
+To ensure saturation, CorePrep eta expands all primop applications as
 described in Note [Eta expansion of hasNoBinding things in CorePrep] in
 GHC.Core.Prep.
 
diff --git a/compiler/GHC/Builtin/Types/Prim.hs b/compiler/GHC/Builtin/Types/Prim.hs
index 9ba6d87927..32ceb36a2d 100644
--- a/compiler/GHC/Builtin/Types/Prim.hs
+++ b/compiler/GHC/Builtin/Types/Prim.hs
@@ -102,6 +102,8 @@ module GHC.Builtin.Types.Prim(
         eqPhantPrimTyCon,       -- ty1 ~P# ty2  (at role Phantom)
         equalityTyCon,
 
+        concretePrimTyCon,
+
         -- * SIMD
 #include "primop-vector-tys-exports.hs-incl"
   ) where
@@ -164,6 +166,7 @@ unexposedPrimTyCons
   = [ eqPrimTyCon
     , eqReprPrimTyCon
     , eqPhantPrimTyCon
+    , concretePrimTyCon
     ]
 
 -- | Primitive 'TyCon's that are defined in, and exported from, GHC.Prim.
@@ -227,7 +230,19 @@ mkBuiltInPrimTc fs unique tycon
                   BuiltInSyntax
 
 
-charPrimTyConName, intPrimTyConName, int8PrimTyConName, int16PrimTyConName, int32PrimTyConName, int64PrimTyConName, wordPrimTyConName, word32PrimTyConName, word8PrimTyConName, word16PrimTyConName, word64PrimTyConName, addrPrimTyConName, floatPrimTyConName, doublePrimTyConName, statePrimTyConName, proxyPrimTyConName, realWorldTyConName, arrayPrimTyConName, arrayArrayPrimTyConName, smallArrayPrimTyConName, byteArrayPrimTyConName, mutableArrayPrimTyConName, mutableByteArrayPrimTyConName, mutableArrayArrayPrimTyConName, smallMutableArrayPrimTyConName, mutVarPrimTyConName, mVarPrimTyConName, ioPortPrimTyConName, tVarPrimTyConName, stablePtrPrimTyConName, stableNamePrimTyConName, compactPrimTyConName, bcoPrimTyConName, weakPrimTyConName, threadIdPrimTyConName, eqPrimTyConName, eqReprPrimTyConName, eqPhantPrimTyConName, stackSnapshotPrimTyConName :: Name
+charPrimTyConName, intPrimTyConName, int8PrimTyConName, int16PrimTyConName, int32PrimTyConName, int64PrimTyConName,
+  wordPrimTyConName, word32PrimTyConName, word8PrimTyConName, word16PrimTyConName, word64PrimTyConName,
+  addrPrimTyConName, floatPrimTyConName, doublePrimTyConName,
+  statePrimTyConName, proxyPrimTyConName, realWorldTyConName,
+  arrayPrimTyConName, arrayArrayPrimTyConName, smallArrayPrimTyConName, byteArrayPrimTyConName,
+  mutableArrayPrimTyConName, mutableByteArrayPrimTyConName, mutableArrayArrayPrimTyConName,
+  smallMutableArrayPrimTyConName, mutVarPrimTyConName, mVarPrimTyConName,
+  ioPortPrimTyConName, tVarPrimTyConName, stablePtrPrimTyConName,
+  stableNamePrimTyConName, compactPrimTyConName, bcoPrimTyConName,
+  weakPrimTyConName, threadIdPrimTyConName,
+  eqPrimTyConName, eqReprPrimTyConName, eqPhantPrimTyConName,
+  stackSnapshotPrimTyConName,
+  concretePrimTyConName :: Name
 charPrimTyConName             = mkPrimTc (fsLit "Char#") charPrimTyConKey charPrimTyCon
 intPrimTyConName              = mkPrimTc (fsLit "Int#") intPrimTyConKey  intPrimTyCon
 int8PrimTyConName             = mkPrimTc (fsLit "Int8#") int8PrimTyConKey int8PrimTyCon
@@ -267,6 +282,7 @@ stackSnapshotPrimTyConName    = mkPrimTc (fsLit "StackSnapshot#") stackSnapshotP
 bcoPrimTyConName              = mkPrimTc (fsLit "BCO") bcoPrimTyConKey bcoPrimTyCon
 weakPrimTyConName             = mkPrimTc (fsLit "Weak#") weakPrimTyConKey weakPrimTyCon
 threadIdPrimTyConName         = mkPrimTc (fsLit "ThreadId#") threadIdPrimTyConKey threadIdPrimTyCon
+concretePrimTyConName         = mkPrimTc (fsLit "Concrete#") concretePrimTyConKey concretePrimTyCon
 
 {-
 ************************************************************************
@@ -1028,6 +1044,25 @@ equalityTyCon Phantom          = eqPhantPrimTyCon
 
 {- *********************************************************************
 *                                                                      *
+                 The Concrete mechanism
+*                                                                      *
+********************************************************************* -}
+
+-- See Note [The Concrete mechanism] in GHC.Tc.Utils.Concrete.
+
+-- type Concrete# :: forall k. k -> TYPE (TupleRep '[])
+
+concretePrimTyCon :: TyCon
+concretePrimTyCon =
+  mkPrimTyCon concretePrimTyConName binders res_kind roles
+    where
+      -- Kind :: forall k. k -> TYPE (TupleRep '[])
+      binders = mkTemplateTyConBinders [liftedTypeKind] (\[k] -> [k])
+      res_kind = unboxedTupleKind []
+      roles   = [Nominal, Nominal]
+
+{- *********************************************************************
+*                                                                      *
              The primitive array types
 *                                                                      *
 ********************************************************************* -}