Convert interface file loading errors into proper diagnosticswip/interface-loading-errs

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is superceded by the IfaceMessage, which is now structured compared to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, 5 insertions, 1 deletions

diff --git a/compiler/GHC/Linker/Loader.hs b/compiler/GHC/Linker/Loader.hs
index 7080bb0776..f6caa18a9d 100644
--- a/compiler/GHC/Linker/Loader.hs
+++ b/compiler/GHC/Linker/Loader.hs
@@ -119,6 +119,7 @@ import GHC.Iface.Load
 import GHC.Unit.Home
 import Data.Either
 import Control.Applicative
+import GHC.Iface.Errors.Ppr
 
 uninitialised :: a
 uninitialised = panic "Loader not initialised"
@@ -789,7 +790,10 @@ getLinkDeps hsc_env pls replace_osuf span mods
           mb_iface <- initIfaceCheck (text "getLinkDeps") hsc_env $
                         loadInterface msg mod (ImportByUser NotBoot)
           iface <- case mb_iface of
-                    Maybes.Failed err      -> throwGhcExceptionIO (ProgramError (showSDoc dflags err))
+                    Maybes.Failed err ->
+                      let opts   = initIfaceMessageOpts dflags
+                          err_txt = missingInterfaceErrorDiagnostic opts err
+                      in throwGhcExceptionIO (ProgramError (showSDoc dflags err_txt))
                     Maybes.Succeeded iface -> return iface
 
           when (mi_boot iface == IsBoot) $ link_boot_mod_error mod