X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fiface%2FLoadIface.lhs;h=5d75259a7b802a62d719875a06512b8fc316b799;hb=49d454d8f8f0e1a83369ec12f8aafc1dcf80aea9;hp=fce5c1d00cca27bd7304a016d2790212a565a5bb;hpb=311b1cdfc9b1c311cc53482c461c18cba8885b2a;p=ghc-hetmet.git

diff --git a/compiler/iface/LoadIface.lhs b/compiler/iface/LoadIface.lhs
index fce5c1d..5d75259 100644
--- a/compiler/iface/LoadIface.lhs
+++ b/compiler/iface/LoadIface.lhs
@@ -238,9 +238,12 @@ loadInterface doc_str mod from
 	; new_eps_fam_insts <- mapM tcIfaceFamInst (mi_fam_insts iface)
 	; new_eps_rules     <- tcIfaceRules ignore_prags (mi_rules iface)
 
-	; let {	final_iface = iface {	mi_decls = panic "No mi_decls in PIT",
-					mi_insts = panic "No mi_insts in PIT",
-					mi_rules = panic "No mi_rules in PIT" } }
+	; let {	final_iface = iface {	
+			        mi_decls     = panic "No mi_decls in PIT",
+				mi_insts     = panic "No mi_insts in PIT",
+				mi_fam_insts = panic "No mi_fam_insts in PIT",
+				mi_rules     = panic "No mi_rules in PIT"
+                              } }
 
 	; updateEps_  $ \ eps -> 
 	    eps { 
@@ -252,6 +255,15 @@ loadInterface doc_str mod from
 						   new_eps_insts,
 	      eps_fam_inst_env = extendFamInstEnvList (eps_fam_inst_env eps)
 						      new_eps_fam_insts,
+              eps_mod_fam_inst_env
+			       = let
+				   fam_inst_env = 
+				     extendFamInstEnvList emptyFamInstEnv
+							  new_eps_fam_insts
+				 in
+				 extendModuleEnv (eps_mod_fam_inst_env eps)
+						 mod
+						 fam_inst_env,
 	      eps_stats        = addEpsInStats (eps_stats eps) 
 					       (length new_eps_decls)
 	      (length new_eps_insts) (length new_eps_rules) }
@@ -311,7 +323,27 @@ loadDecl ignore_prags mod (_version, decl)
 	; thing <- forkM doc $ do { bumpDeclStats main_name
 				  ; tcIfaceDecl ignore_prags decl }
 
-	-- Populate the type environment with the implicitTyThings too
+	-- Populate the type environment with the implicitTyThings too.
+	-- 
+	-- Note [Tricky iface loop]
+	-- ~~~~~~~~~~~~~~~~~~~~~~~~
+	-- The delicate point here is that 'mini-env' should be
+	-- buildable from 'thing' without demanding any of the things 'forkM'd 
+	-- by tcIfaceDecl.  For example
+	--	class C a where { data T a; op :: T a -> Int }
+	-- We return the bindings
+	--	[("C", <cls>), ("T", lookup env "T"), ("op", lookup env "op")]
+	-- The call (lookup env "T") must return the tycon T without first demanding
+	-- op; because getting the latter will look up T, hence loop.
+	--
+	-- Of course, there is no reason in principle why (lookup env "T") should demand
+	-- anything do to with op, but take care: 
+	--	(a) implicitTyThings, and 
+	--	(b) getOccName of all the things returned by implicitThings, 
+	-- must not depend on any of the nested type-checks
+	-- 
+	-- All a bit too finely-balanced for my liking.
+
 	; let mini_env = mkOccEnv [(getOccName t, t) | t <- implicitTyThings thing]
 	      lookup n = case lookupOccEnv mini_env (getOccName n) of
 			   Just thing -> thing
@@ -456,6 +488,8 @@ initExternalPackageState
       eps_fam_inst_env = emptyFamInstEnv,
       eps_rule_base    = mkRuleBase builtinRules,
 	-- Initialise the EPS rule pool with the built-in rules
+      eps_mod_fam_inst_env
+                       = emptyModuleEnv,
       eps_stats = EpsStats { n_ifaces_in = 0, n_decls_in = 0, n_decls_out = 0
 			   , n_insts_in = 0, n_insts_out = 0
 			   , n_rules_in = length builtinRules, n_rules_out = 0 }
@@ -504,7 +538,7 @@ ifaceStats eps
     	 hsep [ int (n_rules_out stats), text "rule decls imported, out of",  
     	        int (n_rules_in stats), text "read"]
 	]
-\end{code}    
+\end{code}
 
 
 %************************************************************************
@@ -541,6 +575,7 @@ pprModIface iface
 	, pprFixities (mi_fixities iface)
 	, vcat (map pprIfaceDecl (mi_decls iface))
 	, vcat (map ppr (mi_insts iface))
+	, vcat (map ppr (mi_fam_insts iface))
 	, vcat (map ppr (mi_rules iface))
 	, pprDeprecs (mi_deprecs iface)
 	]