Refactor -dynamic-too handling

1) Don't modify DynFlags (too much) for -dynamic-too: now when we
   generate dynamic outputs for "-dynamic-too", we only set "dynamicNow"
   boolean field in DynFlags instead of modifying several other fields.
   These fields now have accessors that take dynamicNow into account.

2) Use DynamicTooState ADT to represent -dynamic-too state. It's much
   clearer than the undocumented "DynamicTooConditional" that was used
   before.

As a result, we can finally remove the hscs_iface_dflags field in
HscRecomp. There was a comment on this field saying:

   "FIXME (osa): I don't understand why this is necessary, but I spent
   almost two days trying to figure this out and I couldn't .. perhaps
   someone who understands this code better will remove this later."

I don't fully understand the details, but it was needed because of the
changes made to the DynFlags for -dynamic-too.

There is still something very dubious in GHC.Iface.Recomp: we have to
disable the "dynamicNow" flag at some point for some Backpack's "heinous
hack" to continue to work. It may be because interfaces for indefinite
units are always non-dynamic, or because we mix and match dynamic and
non-dynamic interfaces (#9176), or something else, who knows?

1 files changed, 9 insertions, 4 deletions

diff --git a/compiler/GHC/Tc/Utils/Monad.hs b/compiler/GHC/Tc/Utils/Monad.hs
index de3c4aeb01..6b66c32ccc 100644
--- a/compiler/GHC/Tc/Utils/Monad.hs
+++ b/compiler/GHC/Tc/Utils/Monad.hs
@@ -28,7 +28,7 @@ module GHC.Tc.Utils.Monad(
   whenDOptM, whenGOptM, whenWOptM,
   whenXOptM, unlessXOptM,
   getGhcMode,
-  withDoDynamicToo,
+  withDynamicNow, withoutDynamicNow,
   getEpsVar,
   getEps,
   updateEps, updateEps_,
@@ -546,10 +546,15 @@ unlessXOptM flag thing_inside = do b <- xoptM flag
 getGhcMode :: TcRnIf gbl lcl GhcMode
 getGhcMode = do { env <- getTopEnv; return (ghcMode (hsc_dflags env)) }
 
-withDoDynamicToo :: TcRnIf gbl lcl a -> TcRnIf gbl lcl a
-withDoDynamicToo =
+withDynamicNow :: TcRnIf gbl lcl a -> TcRnIf gbl lcl a
+withDynamicNow =
   updTopEnv (\top@(HscEnv { hsc_dflags = dflags }) ->
-              top { hsc_dflags = dynamicTooMkDynamicDynFlags dflags })
+              top { hsc_dflags = setDynamicNow dflags })
+
+withoutDynamicNow :: TcRnIf gbl lcl a -> TcRnIf gbl lcl a
+withoutDynamicNow =
+  updTopEnv (\top@(HscEnv { hsc_dflags = dflags }) ->
+              top { hsc_dflags = dflags { dynamicNow = False} })
 
 getEpsVar :: TcRnIf gbl lcl (TcRef ExternalPackageState)
 getEpsVar = do { env <- getTopEnv; return (hsc_EPS env) }