[project @ 1999-01-28 16:37:41 by simonpj]

[ghc-hetmet.git] / ghc / compiler / basicTypes / OccName.lhs

diff --git a/ghc/compiler/basicTypes/OccName.lhs b/ghc/compiler/basicTypes/OccName.lhs
index cba9b4f..834134f 100644 (file)
--- a/ghc/compiler/basicTypes/OccName.lhs
+++ b/ghc/compiler/basicTypes/OccName.lhs
@@ -394,13 +394,12 @@ mk_deriv occ_sp sys_prefix str = mkSysOcc occ_sp (encode sys_prefix ++ str)
 \end{code}
 
 \begin{code}
-mkDictOcc, mkWorkerOcc, mkMethodOcc, mkDefaultMethodOcc,
+mkDictOcc, mkWorkerOcc, mkDefaultMethodOcc,
           mkClassTyConOcc, mkClassDataConOcc, mkSpecOcc
    :: OccName -> OccName
 
 -- These derived variables have a prefix that no Haskell value could have
 mkWorkerOcc        = mk_simple_deriv varName  "$w"
-mkMethodOcc       = mk_simple_deriv varName  "$m"
 mkDefaultMethodOcc = mk_simple_deriv varName  "$dm"
 mkClassTyConOcc    = mk_simple_deriv tcName   ":T"     -- The : prefix makes sure it classifies
 mkClassDataConOcc  = mk_simple_deriv dataName ":D"     -- as a tycon/datacon
@@ -437,6 +436,31 @@ mkDFunOcc cls_occ tycon_occ index
               | otherwise  = show index
 \end{code}
 
+We used to add a '$m' to indicate a method, but that gives rise to bad
+error messages from the type checker when we print the function name or pattern
+of an instance-decl binding.  Why? Because the binding is zapped
+to use the method name in place of the selector name.
+(See TcClassDcl.tcMethodBind)
+
+The way it is now, -ddump-xx output may look confusing, but
+you can always say -dppr-debug to get the uniques.
+
+However, we *do* have to zap the first character to be lower case,
+because overloaded constructors (blarg) generate methods too.
+And convert to VarName space
+
+e.g. a call to constructor MkFoo where
+       data (Ord a) => Foo a = MkFoo a
+
+If this is necessary, we do it by prefixing '$m'.  These 
+guys never show up in error messages.  What a hack.
+
+\begin{code}
+mkMethodOcc :: OccName -> OccName
+mkMethodOcc occ@(OccName VarName fs) = occ
+mkMethodOcc occ                             = mk_simple_deriv varName "$m"
+\end{code}
+
 
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