Fix lookup of fixity signatures for type operators (#6027)

Extend name lookup for fixity declaration to the TcClsName namespace for
all reader names, instead of only those in DataName.

compiler/rename/RnEnv.lhs

@@ -19,7 +19,7 @@ module RnEnv (
         lookupTypeOccRn, lookupKindOccRn, 
         lookupGlobalOccRn, lookupGlobalOccRn_maybe,
 
-	HsSigCtxt(..), lookupLocalDataTcNames, lookupSigOccRn,
+	HsSigCtxt(..), lookupLocalTcNames, lookupSigOccRn,
 
 	lookupFixityRn, lookupTyFixityRn, 
 	lookupInstDeclBndr, lookupSubBndrOcc, lookupFamInstName,
@@ -927,30 +927,32 @@ lookupBindGroupOcc ctxt what rdr_name
 
 
 ---------------
-lookupLocalDataTcNames :: NameSet -> SDoc -> RdrName -> RnM [Name]
--- GHC extension: look up both the tycon and data con 
--- for con-like things.  Used for top-level fixity signatures
--- Complain if neither is in scope
-lookupLocalDataTcNames bndr_set what rdr_name
+lookupLocalTcNames :: NameSet -> SDoc -> RdrName -> RnM [Name]
+-- GHC extension: look up both the tycon and data con or variable.
+-- Used for top-level fixity signatures. Complain if neither is in scope.
+-- See Note [Fixity signature lookup]
+lookupLocalTcNames bndr_set what rdr_name
   | Just n <- isExact_maybe rdr_name	
 	-- Special case for (:), which doesn't get into the GlobalRdrEnv
   = do { n' <- lookupExactOcc n; return [n'] }	-- For this we don't need to try the tycon too
   | otherwise
-  = do	{ mb_gres <- mapM (lookupBindGroupOcc (LocalBindCtxt bndr_set) what)
-			  (dataTcOccs rdr_name)
-	; let (errs, names) = splitEithers mb_gres
-	; when (null names) (addErr (head errs))	-- Bleat about one only
-	; return names }
+  = do { mb_gres <- mapM lookup (dataTcOccs rdr_name)
+       ; let (errs, names) = splitEithers mb_gres
+       ; when (null names) $ addErr (head errs) -- Bleat about one only
+       ; return names }
+  where
+    lookup = lookupBindGroupOcc (LocalBindCtxt bndr_set) what
 
 dataTcOccs :: RdrName -> [RdrName]
--- If the input is a data constructor, return both it and a type
--- constructor.  This is useful when we aren't sure which we are
--- looking at.
+-- Return both the given name and the same name promoted to the TcClsName
+-- namespace.  This is useful when we aren't sure which we are looking at.
 dataTcOccs rdr_name
-  | isDataOcc occ 	      = [rdr_name, rdr_name_tc]
-  | otherwise 	  	      = [rdr_name]
-  where    
-    occ 	= rdrNameOcc rdr_name
+  | isDataOcc occ || isVarOcc occ
+  = [rdr_name, rdr_name_tc]
+  | otherwise
+  = [rdr_name]
+  where
+    occ = rdrNameOcc rdr_name
     rdr_name_tc = setRdrNameSpace rdr_name tcName
 \end{code}
 
@@ -961,6 +963,26 @@ dataTcOccs rdr_name
 %*							*
 %*********************************************************
 
+Note [Fixity signature lookup]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+A fixity declaration like
+
+    infixr 2 ?
+
+can refer to a value-level operator, e.g.:
+
+    (?) :: String -> String -> String
+
+or a type-level operator, like:
+
+    data (?) a b = A a | B b
+
+so we extend the lookup of the reader name '?' to the TcClsName namespace, as
+well as the original namespace.
+
+The extended lookup is also used in other places, like resolution of
+deprecation declarations, and lookup of names in GHCi.
+
 \begin{code}
 --------------------------------
 type FastStringEnv a = UniqFM a		-- Keyed by FastString

compiler/rename/RnSource.lhs

@@ -269,7 +269,7 @@ rnSrcFixityDecls bndr_set fix_decls
     rn_decl (L loc (FixitySig (L name_loc rdr_name) fixity))
       = setSrcSpan name_loc $
                     -- this lookup will fail if the definition isn't local
-        do names <- lookupLocalDataTcNames bndr_set what rdr_name
+        do names <- lookupLocalTcNames bndr_set what rdr_name
            return [ L loc (FixitySig (L name_loc name) fixity)
                   | name <- names ]
     what = ptext (sLit "fixity signature")
@@ -304,7 +304,7 @@ rnSrcWarnDecls bndr_set decls
  where
    rn_deprec (Warning rdr_name txt)
        -- ensures that the names are defined locally
-     = do { names <- lookupLocalDataTcNames bndr_set what rdr_name
+     = do { names <- lookupLocalTcNames bndr_set what rdr_name
           ; return [(nameOccName name, txt) | name <- names] }
    
    what = ptext (sLit "deprecation")