Remove ErrDoc and MsgDoc

This commit boldly removes the ErrDoc and the MsgDoc from the codebase.
The former was introduced with the only purpose of classifying errors
according to their importance, but a similar result can be obtained just
by having a simple [SDoc], and placing bullets after each of them.

On top of that I have taken the perhaps controversial decision to also
banish MsgDoc, as it was merely a type alias over an SDoc and as such it wasn't
offering any extra type safety. Granted, it was perhaps making type
signatures slightly more "focused", but at the expense of cognitive
burden: if it's really just an SDoc, let's call it with its proper name.

1 files changed, 12 insertions, 12 deletions

diff --git a/compiler/GHC/Tc/Module.hs b/compiler/GHC/Tc/Module.hs
index 746b5c71ea..bdcc85ef64 100644
--- a/compiler/GHC/Tc/Module.hs
+++ b/compiler/GHC/Tc/Module.hs
@@ -188,7 +188,7 @@ tcRnModule :: HscEnv
            -> ModSummary
            -> Bool              -- True <=> save renamed syntax
            -> HsParsedModule
-           -> IO (Messages ErrDoc, Maybe TcGblEnv)
+           -> IO (Messages [SDoc], Maybe TcGblEnv)
 
 tcRnModule hsc_env mod_sum save_rn_syntax
    parsedModule@HsParsedModule {hpm_module= L loc this_module}
@@ -1986,7 +1986,7 @@ this Note.
 *********************************************************
 -}
 
-runTcInteractive :: HscEnv -> TcRn a -> IO (Messages ErrDoc, Maybe a)
+runTcInteractive :: HscEnv -> TcRn a -> IO (Messages [SDoc], Maybe a)
 -- Initialise the tcg_inst_env with instances from all home modules.
 -- This mimics the more selective call to hptInstances in tcRnImports
 runTcInteractive hsc_env thing_inside
@@ -2102,7 +2102,7 @@ We don't bother with the tcl_th_bndrs environment either.
 -- The returned TypecheckedHsExpr is of type IO [ () ], a list of the bound
 -- values, coerced to ().
 tcRnStmt :: HscEnv -> GhciLStmt GhcPs
-         -> IO (Messages ErrDoc, Maybe ([Id], LHsExpr GhcTc, FixityEnv))
+         -> IO (Messages [SDoc], Maybe ([Id], LHsExpr GhcTc, FixityEnv))
 tcRnStmt hsc_env rdr_stmt
   = runTcInteractive hsc_env $ do {
 
@@ -2482,7 +2482,7 @@ getGhciStepIO = do
 
     return (noLoc $ ExprWithTySig noExtField (nlHsVar ghciStepIoMName) stepTy)
 
-isGHCiMonad :: HscEnv -> String -> IO (Messages ErrDoc, Maybe Name)
+isGHCiMonad :: HscEnv -> String -> IO (Messages [SDoc], Maybe Name)
 isGHCiMonad hsc_env ty
   = runTcInteractive hsc_env $ do
         rdrEnv <- getGlobalRdrEnv
@@ -2509,7 +2509,7 @@ data TcRnExprMode = TM_Inst     -- ^ Instantiate inferred quantifiers only (:typ
 tcRnExpr :: HscEnv
          -> TcRnExprMode
          -> LHsExpr GhcPs
-         -> IO (Messages ErrDoc, Maybe Type)
+         -> IO (Messages [SDoc], Maybe Type)
 tcRnExpr hsc_env mode rdr_expr
   = runTcInteractive hsc_env $
     do {
@@ -2578,7 +2578,7 @@ has a special case for application chains.
 --------------------------
 tcRnImportDecls :: HscEnv
                 -> [LImportDecl GhcPs]
-                -> IO (Messages ErrDoc, Maybe GlobalRdrEnv)
+                -> IO (Messages [SDoc], Maybe GlobalRdrEnv)
 -- Find the new chunk of GlobalRdrEnv created by this list of import
 -- decls.  In contract tcRnImports *extends* the TcGblEnv.
 tcRnImportDecls hsc_env import_decls
@@ -2594,7 +2594,7 @@ tcRnType :: HscEnv
          -> ZonkFlexi
          -> Bool        -- Normalise the returned type
          -> LHsType GhcPs
-         -> IO (Messages ErrDoc, Maybe (Type, Kind))
+         -> IO (Messages [SDoc], Maybe (Type, Kind))
 tcRnType hsc_env flexi normalise rdr_type
   = runTcInteractive hsc_env $
     setXOptM LangExt.PolyKinds $   -- See Note [Kind-generalise in tcRnType]
@@ -2728,7 +2728,7 @@ tcRnDeclsi exists to allow class, data, and other declarations in GHCi.
 
 tcRnDeclsi :: HscEnv
            -> [LHsDecl GhcPs]
-           -> IO (Messages ErrDoc, Maybe TcGblEnv)
+           -> IO (Messages [SDoc], Maybe TcGblEnv)
 tcRnDeclsi hsc_env local_decls
   = runTcInteractive hsc_env $
     tcRnSrcDecls False local_decls Nothing
@@ -2753,13 +2753,13 @@ externaliseAndTidyId this_mod id
 -- a package module with an interface on disk.  If neither of these is
 -- true, then the result will be an error indicating the interface
 -- could not be found.
-getModuleInterface :: HscEnv -> Module -> IO (Messages ErrDoc, Maybe ModIface)
+getModuleInterface :: HscEnv -> Module -> IO (Messages [SDoc], Maybe ModIface)
 getModuleInterface hsc_env mod
   = runTcInteractive hsc_env $
     loadModuleInterface (text "getModuleInterface") mod
 
 tcRnLookupRdrName :: HscEnv -> Located RdrName
-                  -> IO (Messages ErrDoc, Maybe [Name])
+                  -> IO (Messages [SDoc], Maybe [Name])
 -- ^ Find all the Names that this RdrName could mean, in GHCi
 tcRnLookupRdrName hsc_env (L loc rdr_name)
   = runTcInteractive hsc_env $
@@ -2773,7 +2773,7 @@ tcRnLookupRdrName hsc_env (L loc rdr_name)
        ; when (null names) (addErrTc (text "Not in scope:" <+> quotes (ppr rdr_name)))
        ; return names }
 
-tcRnLookupName :: HscEnv -> Name -> IO (Messages ErrDoc, Maybe TyThing)
+tcRnLookupName :: HscEnv -> Name -> IO (Messages [SDoc], Maybe TyThing)
 tcRnLookupName hsc_env name
   = runTcInteractive hsc_env $
     tcRnLookupName' name
@@ -2792,7 +2792,7 @@ tcRnLookupName' name = do
 
 tcRnGetInfo :: HscEnv
             -> Name
-            -> IO ( Messages ErrDoc
+            -> IO ( Messages [SDoc]
                   , Maybe (TyThing, Fixity, [ClsInst], [FamInst], SDoc))
 
 -- Used to implement :info in GHCi