Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : ghc-axioms
http://hackage.haskell.org/trac/ghc/changeset/b8178f165b7b49950ead1636cab67e9cbe23fc21 >--------------------------------------------------------------- commit b8178f165b7b49950ead1636cab67e9cbe23fc21 Author: Simon Peyton Jones <[email protected]> Date: Thu Dec 29 16:13:28 2011 +0000 Tidy up lookupPromotedOcc and add -XPolyKinds suggestion >--------------------------------------------------------------- compiler/rename/RnEnv.lhs | 74 +++++++++++++++++++++++++++----------------- 1 files changed, 45 insertions(+), 29 deletions(-) diff --git a/compiler/rename/RnEnv.lhs b/compiler/rename/RnEnv.lhs index c919e46..e7bd0d2 100644 --- a/compiler/rename/RnEnv.lhs +++ b/compiler/rename/RnEnv.lhs @@ -453,32 +453,45 @@ lookupOccRn rdr_name = do -- lookupPromotedOccRn looks up an optionally promoted RdrName. lookupPromotedOccRn :: RdrName -> RnM Name --- see Note [Demotion] in OccName -lookupPromotedOccRn rdr_name = do { - -- 1. lookup the name - opt_name <- lookupOccRn_maybe rdr_name - ; case opt_name of - -- 1.a. we found it! - Just name -> return name - -- 1.b. we did not find it -> 2 - Nothing -> do { - ; -- 2. maybe it was implicitly promoted - case demoteRdrName rdr_name of - -- 2.a it was not in a promoted namespace - Nothing -> err - -- 2.b let's try every thing again -> 3 - Just demoted_rdr_name -> do { - ; poly_kinds <- xoptM Opt_PolyKinds - -- 3. lookup again - ; opt_demoted_name <- lookupOccRn_maybe demoted_rdr_name ; - ; case opt_demoted_name of - -- 3.a. it was implicitly promoted, but confirm that we can promote - -- JPM: We could try to suggest turning on PolyKinds here - Just demoted_name -> if poly_kinds then return demoted_name else err - -- 3.b. use rdr_name to have a correct error message - Nothing -> err } } } - where err = unboundName WL_Any rdr_name +-- see Note [Demotion] +lookupPromotedOccRn rdr_name + = do { mb_name <- lookupOccRn_maybe rdr_name + ; case mb_name of { + Just name -> return name ; + Nothing -> + + do { -- Maybe it's the name of a *data* constructor + poly_kinds <- xoptM Opt_PolyKinds + ; mb_demoted_name <- case demoteRdrName rdr_name of + Just demoted_rdr -> lookupOccRn_maybe demoted_rdr + Nothing -> return Nothing + ; case mb_demoted_name of + Nothing -> unboundName WL_Any rdr_name + Just demoted_name + | poly_kinds -> return demoted_name + | otherwise -> unboundNameX WL_Any rdr_name suggest_pk }}} + where + suggest_pk = ptext (sLit "A data constructor of that name is in scope; did you mean -XPolyKinds?") +\end{code} + +Note [Demotion] +~~~~~~~~~~~~~~~ +When the user writes: + data Nat = Zero | Succ Nat + foo :: f Zero -> Int + +'Zero' in the type signature of 'foo' is parsed as: + HsTyVar ("Zero", TcClsName) +When the renamer hits this occurence of 'Zero' it's going to realise +that it's not in scope. But because it is renaming a type, it knows +that 'Zero' might be a promoted data constructor, so it will demote +its namespace to DataName and do a second lookup. + +The final result (after the renamer) will be: + HsTyVar ("Zero", DataName) + +\begin{code} -- lookupOccRn looks up an occurrence of a RdrName lookupOccRn_maybe :: RdrName -> RnM (Maybe Name) lookupOccRn_maybe rdr_name @@ -1119,13 +1132,16 @@ data WhereLooking = WL_Any -- Any binding | WL_LocalTop -- Any top-level binding in this module unboundName :: WhereLooking -> RdrName -> RnM Name -unboundName where_look rdr_name +unboundName wl rdr = unboundNameX wl rdr empty + +unboundNameX :: WhereLooking -> RdrName -> SDoc -> RnM Name +unboundNameX where_look rdr_name extra = do { show_helpful_errors <- doptM Opt_HelpfulErrors - ; let err = unknownNameErr rdr_name + ; let err = unknownNameErr rdr_name $$ extra ; if not show_helpful_errors then addErr err - else do { extra_err <- unknownNameSuggestErr where_look rdr_name - ; addErr (err $$ extra_err) } + else do { suggestions <- unknownNameSuggestErr where_look rdr_name + ; addErr (err $$ suggestions) } ; env <- getGlobalRdrEnv; ; traceRn (vcat [unknownNameErr rdr_name, _______________________________________________ Cvs-ghc mailing list [email protected] http://www.haskell.org/mailman/listinfo/cvs-ghc
