Major clean-up of HscMain.

[ghc-hetmet.git] / compiler / main / HscTypes.lhs

diff --git a/compiler/main/HscTypes.lhs b/compiler/main/HscTypes.lhs
index 76e28be..0d83a92 100644 (file)
--- a/compiler/main/HscTypes.lhs
+++ b/compiler/main/HscTypes.lhs
@@ -18,7 +18,7 @@ module HscTypes (
         handleFlagWarnings,
 
        -- * Sessions and compilation state
-       Session(..), withSession, modifySession,
+       Session(..), withSession, modifySession, withTempSession,
         HscEnv(..), hscEPS,
        FinderCache, FindResult(..), ModLocationCache,
        Target(..), TargetId(..), pprTarget, pprTargetId,
@@ -293,6 +293,16 @@ modifySession :: GhcMonad m => (HscEnv -> HscEnv) -> m ()
 modifySession f = do h <- getSession
                      setSession $! f h
 
+withSavedSession :: GhcMonad m => m a -> m a
+withSavedSession m = do
+  saved_session <- getSession
+  m `gfinally` setSession saved_session
+
+-- | Call an action with a temporarily modified Session.
+withTempSession :: GhcMonad m => (HscEnv -> HscEnv) -> m a -> m a
+withTempSession f m =
+  withSavedSession $ modifySession f >> m
+
 -- | A minimal implementation of a 'GhcMonad'.  If you need a custom monad,
 -- e.g., to maintain additional state consider wrapping this monad or using
 -- 'GhcT'.