[project @ 2005-05-23 10:17:22 by simonpj]

Fix what "standard class" means

	MERGE to STABLE

The Report's definition of defaulting (Section 4.3.4) defines a "standard class" to be
one defined by the Prelude or a standard library.  GHC was omitting the "..or a standard
library" part; and it even omitted the Prelude classes Monad and Functor.
This commit fixes the bug by adding

	Random, RandomGen,
	Monad, MonadPlus, Functor

to the classes defined as "standard".

diff --git a/ghc/compiler/prelude/PrelNames.lhs b/ghc/compiler/prelude/PrelNames.lhs
index 78104f1..13b862a 100644 (file)
--- a/ghc/compiler/prelude/PrelNames.lhs
+++ b/ghc/compiler/prelude/PrelNames.lhs
@@ -196,6 +196,9 @@ basicKnownKeyNames
        -- Splittable class
        splittableClassName, splitName,
 
+       -- Other classes
+       randomClassName, randomGenClassName, monadPlusClassName,
+
        -- Booleans
        andName, orName
        
@@ -257,9 +260,11 @@ lEX                = mkModule "Text.Read.Lex"
 mAIN           = mkModule "Main"
 pREL_INT       = mkModule "GHC.Int"
 pREL_WORD      = mkModule "GHC.Word"
+mONAD          = mkModule "Control.Monad"
 mONAD_FIX      = mkModule "Control.Monad.Fix"
 aRROW          = mkModule "Control.Arrow"
 aDDR           = mkModule "Addr"
+rANDOM         = mkModule "System.Random"
 
 gLA_EXTS       = mkModule "GHC.Exts"
 rOOT_MAIN      = mkModule ":Main"              -- Root module for initialisation 
@@ -614,12 +619,17 @@ monadFixClassName  = clsQual mONAD_FIX FSLIT("MonadFix") monadFixClassKey
 mfixName          = methName monadFixClassName FSLIT("mfix") mfixIdKey
 
 -- Arrow notation
-arrAName          = varQual aRROW FSLIT("arr") arrAIdKey
-composeAName      = varQual aRROW FSLIT(">>>") composeAIdKey
-firstAName        = varQual aRROW FSLIT("first")       firstAIdKey
-appAName          = varQual aRROW FSLIT("app") appAIdKey
-choiceAName       = varQual aRROW FSLIT("|||") choiceAIdKey
-loopAName         = varQual aRROW FSLIT("loop")        loopAIdKey
+arrAName          = varQual aRROW FSLIT("arr")   arrAIdKey
+composeAName      = varQual aRROW FSLIT(">>>")   composeAIdKey
+firstAName        = varQual aRROW FSLIT("first") firstAIdKey
+appAName          = varQual aRROW FSLIT("app")   appAIdKey
+choiceAName       = varQual aRROW FSLIT("|||")   choiceAIdKey
+loopAName         = varQual aRROW FSLIT("loop")  loopAIdKey
+
+-- Other classes, needed for type defaulting
+monadPlusClassName  = clsQual mONAD FSLIT("MonadPlus")  monadPlusClassKey
+randomClassName     = clsQual rANDOM FSLIT("Random")    randomClassKey
+randomGenClassName  = clsQual rANDOM FSLIT("RandomGen") randomGenClassKey
 
 -- dotnet interop
 objectTyConName            = tcQual   dOTNET FSLIT("Object") objectTyConKey
@@ -697,6 +707,10 @@ typeable7ClassKey  = mkPreludeClassUnique 27
 
 monadFixClassKey       = mkPreludeClassUnique 28
 splittableClassKey     = mkPreludeClassUnique 29
+
+monadPlusClassKey      = mkPreludeClassUnique 30
+randomClassKey         = mkPreludeClassUnique 31
+randomGenClassKey      = mkPreludeClassUnique 32
 \end{code}
 
 %************************************************************************
@@ -1021,7 +1035,12 @@ needsDataDeclCtxtClassKeys = -- see comments in TcDeriv
        [ readClassKey
        ]
 
+-- The "standard classes" are used in defaulting (Haskell 98 report 4.3.4),
+-- and are: "classes defined in the Prelude or a standard library"
 standardClassKeys = derivableClassKeys ++ numericClassKeys
+                 ++ [randomClassKey, randomGenClassKey,
+                     functorClassKey, 
+                     monadClassKey, monadPlusClassKey]
 
 noDictClassKeys = [] -- ToDo: remove?
 \end{code}