[commit: ghc] wip/rae-new-coercible: Finished removing inert_repr_eqs (2945111)

[git at git.haskell.org]

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

On branch  : wip/rae-new-coercible
Link       : http://ghc.haskell.org/trac/ghc/changeset/2945111811cc9bbc98ff573b2fdad9c27d780e79/ghc

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

commit 2945111811cc9bbc98ff573b2fdad9c27d780e79
Author: Richard Eisenberg <eir at cis.upenn.edu>
Date:   Sun Dec 7 11:31:15 2014 -0500

    Finished removing inert_repr_eqs


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

2945111811cc9bbc98ff573b2fdad9c27d780e79
 compiler/typecheck/TcInteract.lhs                  |  8 +++---
 compiler/typecheck/TcSMonad.lhs                    |  4 +--
 testsuite/tests/deriving/should_fail/T7148.stderr  | 30 +++++++++++++---------
 testsuite/tests/deriving/should_fail/T7148a.stderr | 19 ++++++++------
 4 files changed, 36 insertions(+), 25 deletions(-)

diff --git a/compiler/typecheck/TcInteract.lhs b/compiler/typecheck/TcInteract.lhs
index be60594..c95ebe2 100644
--- a/compiler/typecheck/TcInteract.lhs
+++ b/compiler/typecheck/TcInteract.lhs
@@ -43,6 +43,7 @@ import Pair (Pair(..))
 import Unique( hasKey )
 import FastString ( sLit )
 import DynFlags
+import Data.List ( find )
 import Util
 \end{code}
 
@@ -688,9 +689,10 @@ lookupFlattenTyVar :: TyVarEnv EqualCtList -> TcTyVar -> TcType
 -- ^ Look up a flatten-tyvar in the inert nominal TyVarEqs;
 -- this is used only when dealing with a CFunEqCan
 lookupFlattenTyVar inert_eqs ftv
-  = case lookupVarEnv inert_eqs ftv of
-      Just (CTyEqCan { cc_rhs = rhs } : _) -> rhs
-      _                                    -> mkTyVarTy ftv
+    -- TODO (RAE): This is fishy. Why only return one equality?
+  = case lookupVarEnv inert_eqs ftv >>= find ((== NomEq) . ctEqRel) of
+      Just (CTyEqCan { cc_rhs = rhs }) -> rhs
+      _                                -> mkTyVarTy ftv
 
 reactFunEq :: CtEvidence -> TcTyVar    -- From this  :: F tys ~ fsk1
            -> CtEvidence -> TcTyVar    -- Solve this :: F tys ~ fsk2
diff --git a/compiler/typecheck/TcSMonad.lhs b/compiler/typecheck/TcSMonad.lhs
index 3675082..0135893 100644
--- a/compiler/typecheck/TcSMonad.lhs
+++ b/compiler/typecheck/TcSMonad.lhs
@@ -592,7 +592,7 @@ getUnsolvedInerts :: TcS ( Bag Implication
                          , Cts     -- Insoluble
                          , Cts )   -- All others
 getUnsolvedInerts
- = do { IC { inert_eqs = tv_eqs
+ = do { IC { inert_eqs    = tv_eqs
            , inert_funeqs = fun_eqs
            , inert_irreds = irreds, inert_dicts = idicts
            , inert_insols = insols } <- getInertCans
@@ -748,7 +748,7 @@ removeInertCt is ct =
       is { inert_funeqs = delFunEq (inert_funeqs is) tf tys }
 
     CTyEqCan  { cc_tyvar = x,  cc_rhs    = ty } ->
-      is { inert_eqs      = delTyEq (inert_eqs is) x ty }
+      is { inert_eqs    = delTyEq (inert_eqs is) x ty }
 
     CIrredEvCan {}   -> panic "removeInertCt: CIrredEvCan"
     CNonCanonical {} -> panic "removeInertCt: CNonCanonical"
diff --git a/testsuite/tests/deriving/should_fail/T7148.stderr b/testsuite/tests/deriving/should_fail/T7148.stderr
index 4edb968..ba3a88b 100644
--- a/testsuite/tests/deriving/should_fail/T7148.stderr
+++ b/testsuite/tests/deriving/should_fail/T7148.stderr
@@ -1,14 +1,20 @@
 
-T7148a.hs:19:50:
-    Couldn't match representation of type ‘b’ with that of ‘Result a b’
-      ‘b’ is a rigid type variable bound by
-          the type forall b1. Proxy b1 -> a -> Result a b1 at T7148a.hs:19:50
-    arising from the coercion of the method ‘coerce’
-      from type ‘forall b. Proxy b -> a -> Result a b’
-        to type ‘forall b.
-                 Proxy b -> IS_NO_LONGER a -> Result (IS_NO_LONGER a) b’
+T7148.hs:27:40:
+    Occurs check: cannot construct the infinite type: b ~ Tagged a b
+    arising from the coercion of the method ‘iso2’
+      from type ‘forall b. SameType b () -> SameType b b’
+        to type ‘forall b. SameType b () -> SameType b (Tagged a b)’
     Relevant role signatures:
-      type role IS_NO_LONGER representational
-      type role Result nominal nominal
-      type role Proxy phantom
-    When deriving the instance for (Convert (IS_NO_LONGER a))
+      type role Tagged phantom representational
+      type role SameType nominal nominal
+    When deriving the instance for (IsoUnit (Tagged a b))
+
+T7148.hs:27:40:
+    Occurs check: cannot construct the infinite type: b ~ Tagged a b
+    arising from the coercion of the method ‘iso1’
+      from type ‘forall b. SameType () b -> SameType b b’
+        to type ‘forall b. SameType () b -> SameType (Tagged a b) b’
+    Relevant role signatures:
+      type role Tagged phantom representational
+      type role SameType nominal nominal
+    When deriving the instance for (IsoUnit (Tagged a b))
diff --git a/testsuite/tests/deriving/should_fail/T7148a.stderr b/testsuite/tests/deriving/should_fail/T7148a.stderr
index 5f865d1..4edb968 100644
--- a/testsuite/tests/deriving/should_fail/T7148a.stderr
+++ b/testsuite/tests/deriving/should_fail/T7148a.stderr
@@ -1,11 +1,14 @@
 
 T7148a.hs:19:50:
-    Could not coerce from ‘Result a b’ to ‘b’
-      because ‘Result a b’ and ‘b’ are different types.
-      arising from the coercion of the method ‘coerce’ from type
-                   ‘forall b. Proxy b -> a -> Result a b’ to type
-                   ‘forall b. Proxy b -> IS_NO_LONGER a -> Result (IS_NO_LONGER a) b’
-    Possible fix:
-      use a standalone 'deriving instance' declaration,
-        so you can specify the instance context yourself
+    Couldn't match representation of type ‘b’ with that of ‘Result a b’
+      ‘b’ is a rigid type variable bound by
+          the type forall b1. Proxy b1 -> a -> Result a b1 at T7148a.hs:19:50
+    arising from the coercion of the method ‘coerce’
+      from type ‘forall b. Proxy b -> a -> Result a b’
+        to type ‘forall b.
+                 Proxy b -> IS_NO_LONGER a -> Result (IS_NO_LONGER a) b’
+    Relevant role signatures:
+      type role IS_NO_LONGER representational
+      type role Result nominal nominal
+      type role Proxy phantom
     When deriving the instance for (Convert (IS_NO_LONGER a))