[commit: ghc] wip/impredicativity: Add printing of error messages involving InstanceOf constraints (3dc731c)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : wip/impredicativity
Link       : http://ghc.haskell.org/trac/ghc/changeset/3dc731c6c34156994e1d2cbfff791ec6052cfd94/ghc

>---------------------------------------------------------------

commit 3dc731c6c34156994e1d2cbfff791ec6052cfd94
Author: Alejandro Serrano <trupill at gmail.com>
Date:   Wed Jun 24 13:38:32 2015 +0200

    Add printing of error messages involving InstanceOf constraints


>---------------------------------------------------------------

3dc731c6c34156994e1d2cbfff791ec6052cfd94
 compiler/typecheck/TcErrors.hs   | 19 +++++++++++++++++--
 compiler/typecheck/TcSimplify.hs |  1 +
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/compiler/typecheck/TcErrors.hs b/compiler/typecheck/TcErrors.hs
index 36b7947..655bc60 100644
--- a/compiler/typecheck/TcErrors.hs
+++ b/compiler/typecheck/TcErrors.hs
@@ -348,13 +348,14 @@ reportWanteds ctxt (WC { wc_simple = simples, wc_insol = insols, wc_impl = impli
 
                 , ("Implicit params", is_ip,       False, mkGroupReporter mkIPErr)
                 , ("Irreds",          is_irred,    False, mkGroupReporter mkIrredErr)
-                , ("Dicts",           is_dict,     False, mkGroupReporter mkDictErr) ]
+                , ("Dicts",           is_dict,     False, mkGroupReporter mkDictErr)
+                , ("Instantiation",   is_instanceof, False, mkGroupReporter mkInstanceOfErr) ]
 
     (&&&) :: (Ct->PredTree->Bool) -> (Ct->PredTree->Bool) -> (Ct->PredTree->Bool)
     (&&&) p1 p2 ct pred = p1 ct pred && p2 ct pred
 
     is_skol_eq, is_hole, is_dict,
-      is_equality, is_ip, is_irred :: Ct -> PredTree -> Bool
+      is_equality, is_ip, is_irred, is_instanceof :: Ct -> PredTree -> Bool
 
     utterly_wrong _ (EqPred NomEq ty1 ty2) = isRigid ty1 && isRigid ty2
     utterly_wrong _ _                      = False
@@ -378,6 +379,9 @@ reportWanteds ctxt (WC { wc_simple = simples, wc_insol = insols, wc_impl = impli
     is_irred _ (IrredPred {}) = True
     is_irred _ _              = False
 
+    is_instanceof _ (InstanceOfPred {}) = True
+    is_instanceof _ _                   = False
+
 
 -- isRigidEqPred :: PredTree -> Bool
 -- isRigidEqPred (EqPred NomEq ty1 ty2) = isRigid ty1 && isRigid ty2
@@ -1725,3 +1729,14 @@ solverDepthErrorTcS loc ty
       , text "(any upper bound you could choose might fail unpredictably with"
       , text " minor updates to GHC, so disabling the check is recommended if"
       , text " you're sure that type checking should terminate)" ]
+
+{-
+************************************************************************
+*                                                                      *
+                 Instantiation errors
+*                                                                      *
+************************************************************************
+-}
+
+mkInstanceOfErr :: ReportErrCtxt -> [Ct] -> TcM ErrMsg
+mkInstanceOfErr = mkIrredErr  -- temporal way to show
diff --git a/compiler/typecheck/TcSimplify.hs b/compiler/typecheck/TcSimplify.hs
index cef26dc..94b5e2f 100644
--- a/compiler/typecheck/TcSimplify.hs
+++ b/compiler/typecheck/TcSimplify.hs
@@ -1696,6 +1696,7 @@ findDefaultableGroups :: ([Type], (Bool,Bool))
                       -> TcS [(TyVar, [Ct])]
 findDefaultableGroups info wanteds
   = do { simples <- approximateWC wanteds
+       ; traceTcS "findDefaultableGroups" (ppr simples)
        ; return (findDefaultableGroups_ info simples) }
 
 findDefaultableGroups_