Deal more correctly with orphan instances

[ghc-hetmet.git] / compiler / rename / RnNames.lhs

diff --git a/compiler/rename/RnNames.lhs b/compiler/rename/RnNames.lhs
index ccdf18b..0c09827 100644 (file)
--- a/compiler/rename/RnNames.lhs
+++ b/compiler/rename/RnNames.lhs
@@ -22,7 +22,7 @@ import HsSyn          ( IE(..), ieName, ImportDecl(..), LImportDecl,
 import RnEnv
 import RnHsDoc          ( rnHsDoc )
 import IfaceEnv                ( ifaceExportNames )
-import LoadIface       ( loadSrcInterface )
+import LoadIface       ( loadSrcInterface, loadSysInterface )
 import TcRnMonad hiding (LIE)
 
 import PrelNames
@@ -143,7 +143,7 @@ rnImportDecl this_mod (L loc (ImportDecl loc_imp_mod_name want_boot
     let
        imp_mod    = mi_module iface
        deprecs    = mi_deprecs iface
-       is_orph    = mi_orphan iface 
+       orph_iface = mi_orphan iface 
        has_finsts = mi_finsts iface 
        deps       = mi_deps iface
 
@@ -186,9 +186,9 @@ rnImportDecl this_mod (L loc (ImportDecl loc_imp_mod_name want_boot
     let
        -- Compute new transitive dependencies
 
-       orphans | is_orph   = ASSERT( not (imp_mod `elem` dep_orphs deps) )
-                             imp_mod : dep_orphs deps
-               | otherwise = dep_orphs deps
+       orphans | orph_iface = ASSERT( not (imp_mod `elem` dep_orphs deps) )
+                              imp_mod : dep_orphs deps
+               | otherwise  = dep_orphs deps
 
        finsts | has_finsts = ASSERT( not (imp_mod `elem` dep_finsts deps) )
                              imp_mod : dep_finsts deps
@@ -949,18 +949,34 @@ lookupImpDeprec dflags hpt pit gre
                      case gre_par gre of       
                        ParentIs p -> mi_dep_fn iface p -- its parent*, is deprec'd
                        NoParent   -> Nothing
-       Nothing    
-         | isWiredInName name -> Nothing
-               -- We have not necessarily loaded the .hi file for a 
-               -- wired-in name (yet), although we *could*.
-               -- And we never deprecate them
-
-        | otherwise -> pprPanic "lookupDeprec" (ppr name)      
-               -- By now all the interfaces should have been loaded
+
+       Nothing -> Nothing      -- See Note [Used names with interface not loaded]
   where
        name = gre_name gre
 \end{code}
 
+Note [Used names with interface not loaded]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+By now all the interfaces should have been loaded,
+because reportDeprecations happens after typechecking.
+However, it's still (just) possible to to find a used 
+Name whose interface hasn't been loaded:
+
+a) It might be a WiredInName; in that case we may not load 
+   its interface (although we could).
+
+b) It might be GHC.Real.fromRational, or GHC.Num.fromInteger
+   These are seen as "used" by the renamer (if -fno-implicit-prelude) 
+   is on), but the typechecker may discard their uses 
+   if in fact the in-scope fromRational is GHC.Read.fromRational,
+   (see tcPat.tcOverloadedLit), and the typechecker sees that the type 
+   is fixed, say, to GHC.Base.Float (see Inst.lookupSimpleInst).
+   In that obscure case it won't force the interface in.
+
+In both cases we simply don't permit deprecations; 
+this is, after all, wired-in stuff.
+
+
 %*********************************************************
 %*                                                      *
                Unused names
@@ -1201,7 +1217,7 @@ printMinimalImports :: FiniteMap ModuleName AvailEnv      -- Minimal imports
 printMinimalImports imps
  = ifOptM Opt_D_dump_minimal_imports $ do {
 
-   mod_ies  <-  mappM to_ies (fmToList imps) ;
+   mod_ies  <-  initIfaceTcRn $ mappM to_ies (fmToList imps) ;
    this_mod <- getModule ;
    rdr_env  <- getGlobalRdrEnv ;
    ioToTcRn (do { h <- openFile (mkFilename this_mod) WriteMode ;
@@ -1222,7 +1238,7 @@ printMinimalImports imps
     to_ies (mod, avail_env) = do ies <- mapM to_ie (availEnvElts avail_env)
                                  returnM (mod, ies)
 
-    to_ie :: AvailInfo -> RnM (IE Name)
+    to_ie :: AvailInfo -> IfG (IE Name)
        -- The main trick here is that if we're importing all the constructors
        -- we want to say "T(..)", but if we're importing only a subset we want
        -- to say "T(A,B,C)".  So we have to find out what the module exports.
@@ -1230,9 +1246,9 @@ printMinimalImports imps
     to_ie (AvailTC n [m]) = ASSERT( n==m ) 
                            returnM (IEThingAbs n)
     to_ie (AvailTC n ns)  
-       = loadSrcInterface doc n_mod False                      `thenM` \ iface ->
+       = loadSysInterface doc n_mod                    `thenM` \ iface ->
          case [xs | (m,as) <- mi_exports iface,
-                    moduleName m == n_mod,
+                    m == n_mod,
                     AvailTC x xs <- as, 
                     x == nameOccName n] of
              [xs] | all_used xs -> returnM (IEThingAll n)
@@ -1242,7 +1258,7 @@ printMinimalImports imps
        where
          all_used avail_occs = all (`elem` map nameOccName ns) avail_occs
          doc = text "Compute minimal imports from" <+> ppr n
-         n_mod = moduleName (nameModule n)
+         n_mod = nameModule n
 \end{code}