Load plugins in interactive session

Taken from:
https://gitlab.haskell.org/ghc/ghc/commit/599eaada382d04722219bfc319bde94591be3fb1

Fixes #668

clash-ghc/src-bin-861/Clash/GHCi/UI.hs

@@ -69,6 +69,8 @@ import qualified Lexer
 import StringBuffer
 import Outputable hiding ( printForUser, printForUserPartWay )
 
+import DynamicLoading ( initializePlugins )
+
 -- Other random utilities
 import BasicTypes hiding ( isTopLevel )
 import Digraph
@@ -2834,7 +2836,10 @@ newDynFlags interactive_only minus_opts = do
 
       when (interactive_only && packageFlagsChanged idflags1 idflags0) $ do
           liftIO $ hPutStrLn stderr "cannot set package flags with :seti; use :set"
-      GHC.setInteractiveDynFlags idflags1
+      -- Load any new plugins
+      hsc_env0 <- GHC.getSession
+      idflags2 <- liftIO (initializePlugins hsc_env0 idflags1)
+      GHC.setInteractiveDynFlags idflags2
       installInteractivePrint (interactivePrint idflags1) False
 
       dflags0 <- getDynFlags

clash-ghc/src-bin-861/Clash/Main.hs

@@ -59,6 +59,7 @@ import Util
 import Panic
 import UniqSupply
 import MonadUtils       ( liftIO )
+import DynamicLoading   ( initializePlugins )
 
 -- Imports for --abi-hash
 import LoadIface           ( loadUserInterface )
@@ -298,8 +299,8 @@ main' postLoadMode dflags0 args flagWarnings clashOpts = do
        DoMake                 -> doMake srcs
        DoMkDependHS           -> doMkDependHS (map fst srcs)
        StopBefore p           -> liftIO (oneShot hsc_env p srcs)
-       DoInteractive          -> ghciUI clashOpts srcs Nothing
-       DoEval exprs           -> ghciUI clashOpts srcs $ Just $ reverse exprs
+       DoInteractive          -> ghciUI clashOpts hsc_env dflags6 srcs Nothing
+       DoEval exprs           -> ghciUI clashOpts hsc_env dflags6 srcs $ Just $ reverse exprs
        DoAbiHash              -> abiHash (map fst srcs)
        ShowPackages           -> liftIO $ showPackages dflags6
        DoFrontend f           -> doFrontend f srcs
@@ -310,11 +311,14 @@ main' postLoadMode dflags0 args flagWarnings clashOpts = do
 
   liftIO $ dumpFinalStats dflags6
 
-ghciUI :: IORef ClashOpts -> [(FilePath, Maybe Phase)] -> Maybe [String] -> Ghc ()
+ghciUI :: IORef ClashOpts -> HscEnv -> DynFlags -> [(FilePath, Maybe Phase)] -> Maybe [String] -> Ghc ()
 #if !defined(GHCI)
-ghciUI _ _ _ = throwGhcException (CmdLineError "not built for interactive use")
+ghciUI _ _ _ _ _ = throwGhcException (CmdLineError "not built for interactive use")
 #else
-ghciUI opts  = interactiveUI (defaultGhciSettings opts)
+ghciUI opts hsc_env dflags0 srcs maybe_expr = do
+  dflags1 <- liftIO (initializePlugins hsc_env dflags0)
+  _ <- GHC.setSessionDynFlags dflags1
+  interactiveUI (defaultGhciSettings opts) srcs maybe_expr
 #endif
 
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