Equality constraint solver is now externally pure

[ghc-hetmet.git] / compiler / typecheck / TcRnMonad.lhs

diff --git a/compiler/typecheck/TcRnMonad.lhs b/compiler/typecheck/TcRnMonad.lhs
index 6df6e28..ca11d17 100644 (file)
--- a/compiler/typecheck/TcRnMonad.lhs
+++ b/compiler/typecheck/TcRnMonad.lhs
@@ -9,6 +9,8 @@ module TcRnMonad(
        module IOEnv
   ) where
 
+#include "HsVersions.h"
+
 import TcRnTypes       -- Re-export all
 import IOEnv           -- Re-export all
 
@@ -123,7 +125,9 @@ initTc hsc_env hsc_src keep_rn_syntax mod do_this
                tcl_arrow_ctxt = NoArrowCtxt,
                tcl_env        = emptyNameEnv,
                tcl_tyvars     = tvs_var,
-               tcl_lie        = panic "initTc:LIE"     -- LIE only valid inside a getLIE
+               tcl_lie        = panic "initTc:LIE", -- only valid inside getLIE
+               tcl_tybinds    = panic "initTc:tybinds" 
+                                               -- only valid inside a getTyBinds
             } ;
        } ;
    
@@ -823,7 +827,7 @@ debugTc thing
  | otherwise = return ()
 \end{code}
 
- %************************************************************************
+%************************************************************************
 %*                                                                     *
             Type constraints (the so-called LIE)
 %*                                                                     *
@@ -881,6 +885,44 @@ setLclTypeEnv lcl_env thing_inside
 
 %************************************************************************
 %*                                                                     *
+            Meta type variable bindings
+%*                                                                     *
+%************************************************************************
+
+\begin{code}
+getTcTyVarBindsVar :: TcM (TcRef TcTyVarBinds)
+getTcTyVarBindsVar = do { env <- getLclEnv; return (tcl_tybinds env) }
+
+getTcTyVarBinds :: TcM a -> TcM (a, TcTyVarBinds)
+getTcTyVarBinds thing_inside
+  = do { tybinds_var <- newMutVar emptyBag
+       ; res <- updLclEnv (\ env -> env { tcl_tybinds = tybinds_var }) 
+                         thing_inside
+       ; tybinds <- readMutVar tybinds_var
+       ; return (res, tybinds) 
+       }
+
+bindMetaTyVar :: TcTyVar -> TcType -> TcM ()
+bindMetaTyVar tv ty
+  = do { ASSERTM2( do { details <- readMutVar (metaTvRef tv)
+                      ; return (isFlexi details) }, ppr tv )
+       ; tybinds_var <- getTcTyVarBindsVar
+       ; tybinds <- readMutVar tybinds_var
+       ; writeMutVar tybinds_var (tybinds `snocBag` TcTyVarBind tv ty) 
+       }
+
+getTcTyVarBindsRelation :: TcM [(TcTyVar, TcTyVarSet)]
+getTcTyVarBindsRelation
+  = do { tybinds_var <- getTcTyVarBindsVar
+       ; tybinds <- readMutVar tybinds_var
+       ; return $ map freeTvs (bagToList tybinds)
+       }
+  where
+    freeTvs (TcTyVarBind tv ty) = (tv, tyVarsOfType ty)
+\end{code}
+
+%************************************************************************
+%*                                                                     *
             Template Haskell context
 %*                                                                     *
 %************************************************************************