[project @ 2002-02-07 12:51:47 by simonpj]

--------------------------------------------------
	Slurp in a few more instance decls with ghc --make
	--------------------------------------------------

ghc --make wasn't slurping in quite enough instance decls.
The relevant comment is in RnIfaces; the new part is marked.
George Russel's Uniform showed this up.

We slurp in an instance decl from the gated instance pool iff

	all its gates are either in the gates of the module,
	or are a previously-loaded tycon or class.

The latter constraint is because there might have been an instance
decl slurped in during an earlier compilation, like this:

	instance Foo a => Baz (Maybe a) where ...

In the module being compiled we might need (Baz (Maybe T)), where T
is defined in this module, and hence we need (Foo T).  So @Foo@ becomes
a gate.  But there's no way to 'see' that.

NEW:  More generally, types might be involved as well:
NEW:  	instance Foo2 T a => Baz2 a where ...
NEW:
NEW: Now we must treat T as a gate too, as well as Foo.  So the solution
NEW: we adopt is:
NEW:
NEW: 	we simply treat all previously-loaded
NEW: 	tycons and classes as gates.
NEW:
NEW: This gloss only affects ghc --make and ghc --interactive.

diff --git a/ghc/compiler/rename/RnIfaces.lhs b/ghc/compiler/rename/RnIfaces.lhs
index 5e63dde..81479de 100644 (file)
--- a/ghc/compiler/rename/RnIfaces.lhs
+++ b/ghc/compiler/rename/RnIfaces.lhs
@@ -55,7 +55,7 @@ import Module         ( Module, ModuleEnv,
                        )
 import PrelInfo                ( wiredInThingEnv, hasKey, fractionalClassKey, numClassKey, 
                          integerTyConName, doubleTyConName )
-import Maybes          ( maybeToBool )
+import Maybe           ( isJust )
 import FiniteMap
 import Outputable
 import Bag
@@ -456,7 +456,7 @@ that are mentioned in:
 We slurp in an instance decl from the gated instance pool iff
        
        all its gates are either in the gates of the module, 
-       or are a previously-loaded class.  
+       or are a previously-loaded tycon or class.  
 
 The latter constraint is because there might have been an instance
 decl slurped in during an earlier compilation, like this:
@@ -465,9 +465,19 @@ decl slurped in during an earlier compilation, like this:
 
 In the module being compiled we might need (Baz (Maybe T)), where T
 is defined in this module, and hence we need (Foo T).  So @Foo@ becomes
-a gate.  But there's no way to 'see' that, so 
+a gate.  But there's no way to 'see' that.  More generally, types
+might be involved as well:
+
+       instance Foo2 T a => Baz2 a where ...
+
+Now we must treat T as a gate too, as well as Foo.  So the solution
+we adopt is:
+
+       we simply treat all previously-loaded 
+       tycons and classes as gates.
+
+This gloss only affects ghc --make and ghc --interactive.
 
-       we simply treat all previously-loaded classes as gates.
 
 Consructors and class operations
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -610,10 +620,8 @@ getImportedInstDecls gates
     getIfacesRn                                        `thenRn` \ ifaces ->
     getTypeEnvRn                                       `thenRn` \ lookup ->
     let
-       available n
-         | n `elemNameSet` gates = True
-         | otherwise             = case lookup n of { Just (AClass c) -> True; other -> False }
-               -- See "The gating story" above for the AClass thing
+       available n = n `elemNameSet` gates || isJust (lookup n)
+               -- See "The gating story" above for the isJust thing
 
        (decls, new_insts) = selectGated available (iInsts ifaces)
     in
@@ -642,7 +650,7 @@ getImportedRules
                -- Slurp rules for anything that is slurped, 
                -- either now or previously
        gates              = iSlurp ifaces      
-       available n        = n `elemNameSet` gates || maybeToBool (lookup n)
+       available n        = n `elemNameSet` gates || isJust (lookup n)
        (decls, new_rules) = selectGated available (iRules ifaces)
     in
     if null decls then