X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=ghc%2Fcompiler%2Ftypecheck%2FTcMType.lhs;h=207411cda5df789c7d6e465fe47cb9743455d284;hb=3a223cd2811d46295048b3a2dab11403ca291b20;hp=3d9f210c8c07cb66c669e52375eed42dd235d838;hpb=221b6b69d68ad9b8de2948b6af40d1c08ffaa0c6;p=ghc-hetmet.git

diff --git a/ghc/compiler/typecheck/TcMType.lhs b/ghc/compiler/typecheck/TcMType.lhs
index 3d9f210..207411c 100644
--- a/ghc/compiler/typecheck/TcMType.lhs
+++ b/ghc/compiler/typecheck/TcMType.lhs
@@ -11,7 +11,7 @@ module TcMType (
 
   --------------------------------
   -- Creating new mutable type variables
-  newTyVar, 
+  newTyVar, newSigTyVar,
   newTyVarTy,		-- Kind -> TcM TcType
   newTyVarTys,		-- Int -> Kind -> TcM [TcType]
   newKindVar, newKindVars, newOpenTypeKind,
@@ -112,6 +112,11 @@ newTyVar kind
   = newUnique 	`thenM` \ uniq ->
     newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("t")) kind VanillaTv
 
+newSigTyVar :: Kind -> TcM TcTyVar
+newSigTyVar kind
+  = newUnique 	`thenM` \ uniq ->
+    newMutTyVar (mkSystemTvNameEncoded uniq FSLIT("s")) kind SigTv
+
 newTyVarTy  :: Kind -> TcM TcType
 newTyVarTy kind
   = newTyVar kind	`thenM` \ tc_tyvar ->
@@ -744,13 +749,25 @@ kindErr kind       = ptext SLIT("Expecting an ordinary type, but found a type of
 %************************************************************************
 
 \begin{code}
+-- Enumerate the contexts in which a "source type", <S>, can occur
+--	Eq a 
+-- or 	?x::Int
+-- or 	r <: {x::Int}
+-- or 	(N a) where N is a newtype
+
 data SourceTyCtxt
   = ClassSCCtxt Name	-- Superclasses of clas
-  | SigmaCtxt		-- Context of a normal for-all type
-  | DataTyCtxt Name	-- Context of a data decl
+			-- 	class <S> => C a where ...
+  | SigmaCtxt		-- Theta part of a normal for-all type
+			--	f :: <S> => a -> a
+  | DataTyCtxt Name	-- Theta part of a data decl
+			--	data <S> => T a = MkT a
   | TypeCtxt 		-- Source type in an ordinary type
+			-- 	f :: N a -> N a
   | InstThetaCtxt	-- Context of an instance decl
+			--	instance <S> => C [a] where ...
   | InstHeadCtxt	-- Head of an instance decl
+			-- 	instance ... => Eq a where ...
 		
 pprSourceTyCtxt (ClassSCCtxt c) = ptext SLIT("the super-classes of class") <+> quotes (ppr c)
 pprSourceTyCtxt SigmaCtxt       = ptext SLIT("the context of a polymorphic type")