Add GhcMessage and ancillary types

This commit adds GhcMessage and ancillary (PsMessage, TcRnMessage, ..)
types.
These types will be expanded to represent more errors generated
by different subsystems within GHC. Right now, they are underused,
but more will come in the glorious future.

See
https://gitlab.haskell.org/ghc/ghc/-/wikis/Errors-as-(structured)-values
for a design overview.

Along the way, lots of other things had to happen:

* Adds Semigroup and Monoid instance for Bag

* Fixes #19746 by parsing OPTIONS_GHC pragmas into Located Strings.
  See GHC.Parser.Header.toArgs (moved from GHC.Utils.Misc, where it
  didn't belong anyway).

* Addresses (but does not completely fix) #19709, now reporting
  desugarer warnings and errors appropriately for TH splices.
  Not done: reporting type-checker warnings for TH splices.

* Some small refactoring around Safe Haskell inference, in order
  to keep separate classes of messages separate.

* Some small refactoring around initDsTc, in order to keep separate
  classes of messages separate.

* Separate out the generation of messages (that is, the construction
  of the text block) from the wrapping of messages (that is, assigning
  a SrcSpan). This is more modular than the previous design, which
  mixed the two.

Close #19746.

This was a collaborative effort by Alfredo di Napoli and
Richard Eisenberg, with a key assist on #19746 by Iavor
Diatchki.

Metric Increase:
    MultiLayerModules

1 files changed, 10 insertions, 10 deletions

diff --git a/compiler/GHC/Driver/Monad.hs b/compiler/GHC/Driver/Monad.hs
index 1a42d8402f..2fa3c51cc1 100644
--- a/compiler/GHC/Driver/Monad.hs
+++ b/compiler/GHC/Driver/Monad.hs
@@ -27,8 +27,8 @@ module GHC.Driver.Monad (
         putMsgM,
         withTimingM,
 
-        -- ** Warnings
-        logWarnings, printException,
+        -- ** Diagnostics
+        logDiagnostics, printException,
         WarnErrLogger, defaultWarnErrLogger
   ) where
 
@@ -36,7 +36,8 @@ import GHC.Prelude
 
 import GHC.Driver.Session
 import GHC.Driver.Env
-import GHC.Driver.Errors ( printOrThrowDiagnostics, printBagOfErrors )
+import GHC.Driver.Errors ( printOrThrowDiagnostics, printMessages )
+import GHC.Driver.Errors.Types
 
 import GHC.Utils.Monad
 import GHC.Utils.Exception
@@ -141,10 +142,10 @@ withTimingM doc force action = do
     withTiming logger dflags doc force action
 
 -- -----------------------------------------------------------------------------
--- | A monad that allows logging of warnings.
+-- | A monad that allows logging of diagnostics.
 
-logWarnings :: GhcMonad m => WarningMessages -> m ()
-logWarnings warns = do
+logDiagnostics :: GhcMonad m => Messages GhcMessage -> m ()
+logDiagnostics warns = do
   dflags <- getSessionDynFlags
   logger <- getLogger
   liftIO $ printOrThrowDiagnostics logger dflags warns
@@ -240,13 +241,13 @@ instance ExceptionMonad m => GhcMonad (GhcT m) where
   setSession s' = GhcT $ \(Session r) -> liftIO $ writeIORef r s'
 
 
--- | Print the error message and all warnings.  Useful inside exception
---   handlers.  Clears warnings after printing.
+-- | Print the all diagnostics in a 'SourceError'.  Useful inside exception
+--   handlers.
 printException :: GhcMonad m => SourceError -> m ()
 printException err = do
   dflags <- getSessionDynFlags
   logger <- getLogger
-  liftIO $ printBagOfErrors logger dflags (srcErrorMessages err)
+  liftIO $ printMessages logger dflags (srcErrorMessages err)
 
 -- | A function called to log warnings and errors.
 type WarnErrLogger = forall m. GhcMonad m => Maybe SourceError -> m ()
@@ -254,4 +255,3 @@ type WarnErrLogger = forall m. GhcMonad m => Maybe SourceError -> m ()
 defaultWarnErrLogger :: WarnErrLogger
 defaultWarnErrLogger Nothing  = return ()
 defaultWarnErrLogger (Just e) = printException e
-