X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcRnTypes.lhs;h=eb1cd0427111f1af107c0e4c3a5f65231bed1566;hp=1e03afd5a383bba6f30d3c10acdb3ceb26471b3a;hb=3f1b316d7035c55cd712cd39a9981339bcef2e8c;hpb=deda0c55629600e886f47a5e90bad67953df1ad8

diff --git a/compiler/typecheck/TcRnTypes.lhs b/compiler/typecheck/TcRnTypes.lhs
index 1e03afd..eb1cd04 100644
--- a/compiler/typecheck/TcRnTypes.lhs
+++ b/compiler/typecheck/TcRnTypes.lhs
@@ -1,4 +1,4 @@
-%
+
 % (c) The University of Glasgow 2006
 % (c) The GRASP Project, Glasgow University, 1992-2002
 %
@@ -152,7 +152,7 @@ data TcGblEnv
 		-- (Ids defined in this module start in the local envt, 
 		--  though they move to the global envt during zonking)
 
-	tcg_type_env_var :: TcRef TypeEnv,	
+	tcg_type_env_var :: TcRef TypeEnv,
 		-- Used only to initialise the interface-file
 		-- typechecker in initIfaceTcRn, so that it can see stuff
 		-- bound in this module when dealing with hi-boot recursions
@@ -369,7 +369,7 @@ type ThLevel = Int
 	-- Incremented when going inside a bracket,
 	-- decremented when going inside a splice
 	-- NB: ThLevel is one greater than the 'n' in Fig 2 of the
-	--     original "Template meta-programmign for Haskell" paper
+	--     original "Template meta-programming for Haskell" paper
 
 impLevel, topLevel :: ThLevel
 topLevel = 1	-- Things defined at top level of this module
@@ -661,7 +661,7 @@ data Inst
 				    -- Includes coercion variables
 				    --   mentioned in tci_reft
 	tci_reft   :: Refinement,
-	tci_given  :: [Inst],	    -- Only Dicts
+	tci_given  :: [Inst],	    -- Only Dicts and EqInsts
 				    --   (no Methods, LitInsts, ImplicInsts)
 	tci_wanted :: [Inst],	    -- Only Dicts and ImplicInsts
 				    --   (no Methods or LitInsts)
@@ -715,23 +715,22 @@ data Inst
 
   | EqInst {			  -- delayed unification of the form 
 				  --  	co :: ty1 ~ ty2
-	tci_left  :: TcType,      -- ty1
-	tci_right :: TcType,      -- ty2
+	tci_left  :: TcType,      -- ty1    -- both types are...
+	tci_right :: TcType,      -- ty2    -- ...free of boxes
 	tci_co    :: Either    	  -- co
-			TcTyVar	  --	a wanted equation, with a hole, to be 
-				  --      filled with a witness for the equality
-                                  --        for equation generated by the 
-                                  --        unifier, 'ty1' is the actual and
-                                  --        'ty2' the expected type
-			Coercion, --    a given equation, with a coercion
-				  --	  witnessing the equality
-				  --         a coercion that originates from a
-				  --         signature or a GADT is a CoVar, but
-                                  --         after normalisation of coercions,
-				  --         they can be arbitrary Coercions 
-                                  --         involving constructors and 
-                                  --         pseudo-constructors like sym and 
-                                  --         trans.
+			TcTyVar	  --  - a wanted equation, with a hole, to be 
+				  --    filled with a witness for the equality;
+                                  --    for equation arising from deferring
+                                  --    unification, 'ty1' is the actual and
+                                  --    'ty2' the expected type
+			Coercion, --  - a given equation, with a coercion
+				  --	witnessing the equality;
+				  --    a coercion that originates from a
+				  --    signature or a GADT is a CoVar, but
+                                  --    after normalisation of coercions, they
+				  --    can be arbitrary Coercions involving
+                                  --    constructors and pseudo-constructors 
+                                  --    like sym and trans.
 	tci_loc   :: InstLoc,
 
 	tci_name  :: Name	-- Debugging help only: this makes it easier to