Refactor tuple constraints

Make tuple constraints be handled by a perfectly ordinary
type class, with the component constraints being the
superclasses:
    class (c1, c2) => (c2, c2)

This change was provoked by

  #10359  inability to re-use a given tuple
          constraint as a whole

  #9858   confusion between term tuples
          and constraint tuples

but it's generally a very nice simplification. We get rid of
 -  In Type, the TuplePred constructor of PredTree,
    and all the code that dealt with TuplePreds
 -  In TcEvidence, the constructors EvTupleMk, EvTupleSel

See Note [How tuples work] in TysWiredIn.

Of course, nothing is ever entirely simple. This one
proved quite fiddly.

- I did quite a bit of renaming, which makes this patch
  touch a lot of modules. In partiuclar tupleCon -> tupleDataCon.

- I made constraint tuples known-key rather than wired-in.
  This is different to boxed/unboxed tuples, but it proved
  awkward to have all the superclass selectors wired-in.
  Easier just to use the standard mechanims.

- While I was fiddling with known-key names, I split the TH Name
  definitions out of DsMeta into a new module THNames.  That meant
  that the known-key names can all be gathered in PrelInfo, without
  causing module loops.

- I found that the parser was parsing an import item like
      T( .. )
  as a *data constructor* T, and then using setRdrNameSpace to
  fix it.  Stupid!  So I changed the parser to parse a *type
  constructor* T, which means less use of setRdrNameSpace.

  I also improved setRdrNameSpace to behave better on Exact Names.
  Largely on priciple; I don't think it matters a lot.

- When compiling a data type declaration for a wired-in thing like
  tuples (,), or lists, we don't really need to look at the
  declaration.  We have the wired-in thing!  And not doing so avoids
  having to line up the uniques for data constructor workers etc.
  See Note [Declarations for wired-in things]

- I found that FunDeps.oclose wasn't taking superclasses into
  account; easily fixed.

- Some error message refactoring for invalid constraints in TcValidity

- Haddock needs to absorb the change too; so there is a submodule update

3 files changed, 7 insertions, 6 deletions

diff --git a/compiler/coreSyn/CoreLint.hs b/compiler/coreSyn/CoreLint.hs
index ec0bb5e225..13285a5b3c 100644
--- a/compiler/coreSyn/CoreLint.hs
+++ b/compiler/coreSyn/CoreLint.hs
@@ -1570,7 +1570,7 @@ lookupIdInScope id
 
 
 oneTupleDataConId :: Id -- Should not happen
-oneTupleDataConId = dataConWorkId (tupleCon BoxedTuple 1)
+oneTupleDataConId = dataConWorkId (tupleDataCon Boxed 1)
 
 checkBndrIdInScope :: Var -> Var -> LintM ()
 checkBndrIdInScope binder id
diff --git a/compiler/coreSyn/MkCore.hs b/compiler/coreSyn/MkCore.hs
index 6905641f56..3b76aef36d 100644
--- a/compiler/coreSyn/MkCore.hs
+++ b/compiler/coreSyn/MkCore.hs
@@ -379,7 +379,7 @@ mkCoreVarTupTy ids = mkBoxedTupleTy (map idType ids)
 mkCoreTup :: [CoreExpr] -> CoreExpr
 mkCoreTup []  = Var unitDataConId
 mkCoreTup [c] = c
-mkCoreTup cs  = mkConApp (tupleCon BoxedTuple (length cs))
+mkCoreTup cs  = mkConApp (tupleDataCon Boxed (length cs))
                          (map (Type . exprType) cs ++ cs)
 
 -- | Build a big tuple holding the specified variables
@@ -484,7 +484,7 @@ mkSmallTupleSelector [var] should_be_the_same_var _ scrut
 mkSmallTupleSelector vars the_var scrut_var scrut
   = ASSERT( notNull vars )
     Case scrut scrut_var (idType the_var)
-         [(DataAlt (tupleCon BoxedTuple (length vars)), vars, Var the_var)]
+         [(DataAlt (tupleDataCon Boxed (length vars)), vars, Var the_var)]
 
 -- | A generalization of 'mkTupleSelector', allowing the body
 -- of the case to be an arbitrary expression.
@@ -537,7 +537,8 @@ mkSmallTupleCase [var] body _scrut_var scrut
   = bindNonRec var scrut body
 mkSmallTupleCase vars body scrut_var scrut
 -- One branch no refinement?
-  = Case scrut scrut_var (exprType body) [(DataAlt (tupleCon BoxedTuple (length vars)), vars, body)]
+  = Case scrut scrut_var (exprType body)
+         [(DataAlt (tupleDataCon Boxed (length vars)), vars, body)]
 
 {-
 ************************************************************************
diff --git a/compiler/coreSyn/PprCore.hs b/compiler/coreSyn/PprCore.hs
index 24abf1828a..ecea85021c 100644
--- a/compiler/coreSyn/PprCore.hs
+++ b/compiler/coreSyn/PprCore.hs
@@ -131,7 +131,7 @@ ppr_expr add_par expr@(App {})
     let
         pp_args     = sep (map pprArg args)
         val_args    = dropWhile isTypeArg args   -- Drop the type arguments for tuples
-        pp_tup_args = sep (punctuate comma (map pprCoreExpr val_args))
+        pp_tup_args = pprWithCommas pprCoreExpr val_args
     in
     case fun of
         Var f -> case isDataConWorkId_maybe f of
@@ -230,7 +230,7 @@ pprCoreAlt (con, args, rhs)
 ppr_case_pat :: OutputableBndr a => AltCon -> [a] -> SDoc
 ppr_case_pat (DataAlt dc) args
   | Just sort <- tyConTuple_maybe tc
-  = tupleParens sort (hsep (punctuate comma (map ppr_bndr args)))
+  = tupleParens sort (pprWithCommas ppr_bndr args)
   where
     ppr_bndr = pprBndr CaseBind
     tc = dataConTyCon dc