Convert interface file loading errors into proper diagnostics

This patch converts all the errors to do with loading interface files
into proper structured diagnostics.

* DriverMessage: Sometimes in the driver we attempt to load an interface
  file so we embed the IfaceMessage into the DriverMessage.
* TcRnMessage: Most the time we are loading interface files during
  typechecking, so we embed the IfaceMessage

This patch also removes the TcRnInterfaceLookupError constructor which
is superceded by the IfaceMessage, which is now structured compared to
just storing an SDoc before.

1 files changed, 7 insertions, 3 deletions

diff --git a/ghc/Main.hs b/ghc/Main.hs
index ae862a7014..ef3de102c0 100644
--- a/ghc/Main.hs
+++ b/ghc/Main.hs
@@ -79,12 +79,13 @@ import GHC.Iface.Load
 import GHC.Iface.Recomp.Binary ( fingerprintBinMem )
 
 import GHC.Tc.Utils.Monad      ( initIfaceCheck )
-import System.FilePath
+import GHC.Iface.Errors.Ppr
 
 -- Standard Haskell libraries
 import System.IO
 import System.Environment
 import System.Exit
+import System.FilePath
 import Control.Monad
 import Control.Monad.Trans.Class
 import Control.Monad.Trans.Except (throwE, runExceptT)
@@ -1100,8 +1101,11 @@ abiHash strs = do
          r <- findImportedModule hsc_env modname NoPkgQual
          case r of
            Found _ m -> return m
-           _error    -> throwGhcException $ CmdLineError $ showSDoc dflags $
-                          cannotFindModule hsc_env modname r
+           _error    ->
+            let opts   = initIfaceMessageOpts dflags
+                err_txt = missingInterfaceErrorDiagnostic opts
+                        $ cannotFindModule hsc_env modname r
+            in throwGhcException . CmdLineError $ showSDoc dflags err_txt
 
   mods <- mapM find_it strs