ATs are now implicitTyThings

[ghc-hetmet.git] / compiler / typecheck / TcTyClsDecls.lhs

diff --git a/compiler/typecheck/TcTyClsDecls.lhs b/compiler/typecheck/TcTyClsDecls.lhs
index 9065d28..c9dee4b 100644 (file)
--- a/compiler/typecheck/TcTyClsDecls.lhs
+++ b/compiler/typecheck/TcTyClsDecls.lhs
@@ -213,12 +213,20 @@ tcTyAndClassDecls boot_details allDecls
        -- Add the implicit things;
        -- we want them in the environment because 
        -- they may be mentioned in interface files
+       -- NB: All associated types and their implicit things will be added a
+       --     second time here.  This doesn't matter as the definitions are
+       --     the same.
        ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
        ; traceTc ((text "Adding" <+> ppr alg_tyclss) 
                   $$ (text "and" <+> ppr implicit_things))
        ; tcExtendGlobalEnv implicit_things getGblEnv
     }}
   where
+    -- Pull associated types out of class declarations, to tie them into the
+    -- knot above.  
+    -- NB: We put them in the same place in the list as `tcTyClDecl' will
+    --    eventually put the matching `TyThing's.  That's crucial; otherwise,
+    --    the two argument lists of `mkGlobalThings' don't match up.
     addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
     addATs decl                                         = [decl]