X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Fmain%2FHscTypes.lhs;h=1d3f4dcc7cac5d95a6c2750ea90082d19f7cefd8;hb=5e0453cad41cb0f004c1680b392d79651053a1d4;hp=76e28be6d488dca9dcc85cba788d710574d8c554;hpb=1246293616fc45787ecaed13aa31a2555510f7e3;p=ghc-hetmet.git

diff --git a/compiler/main/HscTypes.lhs b/compiler/main/HscTypes.lhs
index 76e28be..1d3f4dc 100644
--- 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'.
@@ -1982,8 +1992,14 @@ data Linkable = LM {
 					-- (i.e. when the bytecodes were produced,
 					--	 or the mod date on the files)
   linkableModule   :: Module,           -- ^ The linkable module itself
-  linkableUnlinked :: [Unlinked]        -- ^ Those files and chunks of code we have
-                                        -- yet to link
+  linkableUnlinked :: [Unlinked]
+    -- ^ Those files and chunks of code we have yet to link.
+    --
+    -- INVARIANT: A valid linkable always has at least one 'Unlinked' item.
+    -- If this list is empty, the Linkable represents a fake linkable, which
+    -- is generated in HscNothing mode to avoid recompiling modules.
+    --
+    -- XXX: Do items get removed from this list when they get linked?
  }
 
 isObjectLinkable :: Linkable -> Bool