[project @ 1997-09-05 16:23:41 by simonpj]

[ghc-hetmet.git] / ghc / compiler / prelude / PrelInfo.lhs

diff --git a/ghc/compiler/prelude/PrelInfo.lhs b/ghc/compiler/prelude/PrelInfo.lhs
index 0dab797..5b84197 100644 (file)
--- a/ghc/compiler/prelude/PrelInfo.lhs
+++ b/ghc/compiler/prelude/PrelInfo.lhs
@@ -494,7 +494,12 @@ deriving_occ_info
                         showParen_RDR, showSpace_RDR, showList___RDR])
     , (readClassKey,   [intTyCon_RDR, numClass_RDR, ordClass_RDR, append_RDR, 
                         lex_RDR, readParen_RDR, readList___RDR])
-    , (ixClassKey,     [intTyCon_RDR, numClass_RDR, and_RDR, map_RDR, enumFromTo_RDR])
+    , (ixClassKey,     [intTyCon_RDR, numClass_RDR, and_RDR, map_RDR, enumFromTo_RDR, 
+                        returnM_RDR, zeroM_RDR])
+                            -- the last two are needed to force returnM, thenM and zeroM
+                            -- in before typechecking the list(monad) comprehension
+                            -- generated for derived Ix instances (range method)
+                            -- of single constructor types.  -- SOF 8/97
     ]
        -- intTyCon: Practically any deriving needs Int, either for index calculations, 
        --              or for taggery.