[project @ 2000-05-14 07:16:50 by lewie]

Wobble.  Fine tuning tcSimplifyAndCheck a bit further (wrt implicit params).
The key is that a method that doesn't constrain a local tyvar, but does has
implicit params, needs to be reduced further.

diff --git a/ghc/compiler/typecheck/Inst.lhs b/ghc/compiler/typecheck/Inst.lhs
index 55a1a4f..f00e8a1 100644 (file)
--- a/ghc/compiler/typecheck/Inst.lhs
+++ b/ghc/compiler/typecheck/Inst.lhs
@@ -25,7 +25,8 @@ module Inst (
 
        lookupInst, lookupSimpleInst, LookupInstResult(..),
 
-       isDict, isClassDict, isTyVarDict, isStdClassTyVarDict, isMethodFor, notFunDep,
+       isDict, isClassDict, isMethod,
+       isTyVarDict, isStdClassTyVarDict, isMethodFor, notFunDep,
        instBindingRequired, instCanBeGeneralised,
 
        zonkInst, zonkInsts, zonkFunDeps, zonkTvFunDeps,
@@ -302,10 +303,14 @@ Predicates
 \begin{code}
 isDict :: Inst -> Bool
 isDict (Dict _ _ _) = True
-isDict other         = False
+isDict other       = False
 isClassDict :: Inst -> Bool
 isClassDict (Dict _ (Class _ _) _) = True
-isClassDict other            = False
+isClassDict other                 = False
+
+isMethod :: Inst -> Bool
+isMethod (Method _ _ _ _ _ _) = True
+isMethod other               = False
 
 isMethodFor :: TcIdSet -> Inst -> Bool
 isMethodFor ids (Method uniq id tys _ _ loc) 
@@ -574,10 +579,10 @@ pprInst (Dict u pred loc) = pprPred pred <+> show_uniq u
 
 pprInst m@(Method u id tys theta tau loc)
   = hsep [ppr id, ptext SLIT("at"), 
-         brackets (interppSP tys),
+         brackets (interppSP tys) {- ,
          ppr theta, ppr tau,
          show_uniq u,
-         ppr (instToId m)]
+         ppr (instToId m) -}]
 
 pprInst (FunDep clas fds loc)
   = hsep [ppr clas, ppr fds]

diff --git a/ghc/compiler/typecheck/TcSimplify.lhs b/ghc/compiler/typecheck/TcSimplify.lhs
index 08b2211..9eb4db8 100644 (file)
--- a/ghc/compiler/typecheck/TcSimplify.lhs
+++ b/ghc/compiler/typecheck/TcSimplify.lhs
@@ -132,7 +132,7 @@ import TcHsSyn              ( TcExpr, TcId,
 import TcMonad
 import Inst            ( lookupInst, lookupSimpleInst, LookupInstResult(..),
                          tyVarsOfInst, tyVarsOfInsts,
-                         isDict, isClassDict, isStdClassTyVarDict,
+                         isDict, isClassDict, isMethod, isStdClassTyVarDict,
                          isMethodFor, notFunDep,
                          instToId, instBindingRequired, instCanBeGeneralised,
                          newDictFromOld,
@@ -299,6 +299,7 @@ tcSimplifyAndCheck str local_tvs given_lie wanted_lie
     try_me inst 
       -- Does not constrain a local tyvar
       | isEmptyVarSet (tyVarsOfInst inst `intersectVarSet` local_tvs)
+        && (not (isMethod inst) || null (getIPs inst))
       = Free
 
       -- When checking against a given signature we always reduce