Simon Hengel pushed to branch wip/sol/lint-messages at Glasgow Haskell Compiler / GHC Commits: 26bc4e03 by Simon Hengel at 2025-08-07T16:29:09+07:00 Refactoring: Don't misuse `MCDiagnostic` for lint messages `MCDiagnostic` is meant to be used for compiler diagnostics. Any code that creates `MCDiagnostic` directly, without going through `GHC.Driver.Errors.printMessage`, side steps `-fdiagnostics-as-json` (see e.g. !14475, !14492 !14548). To avoid this in the future I want to control more narrowly who creates `MCDiagnostic` (see #24113). Some parts of the compiler use `MCDiagnostic` purely for formatting purposes, without creating any real compiler diagnostics. This change introduces a helper function, `formatDiagnostic`, that can be used in such cases instead of constructing `MCDiagnostic`. - - - - - 4 changed files: - compiler/GHC/Core/Lint.hs - compiler/GHC/Stg/Lint.hs - compiler/GHC/Types/Error.hs - compiler/GHC/Utils/Error.hs Changes: ===================================== compiler/GHC/Core/Lint.hs ===================================== @@ -3418,7 +3418,7 @@ addMsg show_context env msgs msg [] -> noSrcSpan (s:_) -> s !diag_opts = le_diagOpts env - mk_msg msg = mkLocMessage (mkMCDiagnostic diag_opts WarningWithoutFlag Nothing) msg_span + mk_msg msg = mkLintMessage diag_opts msg_span (msg $$ context) addLoc :: LintLocInfo -> LintM a -> LintM a ===================================== compiler/GHC/Stg/Lint.hs ===================================== @@ -107,7 +107,6 @@ import GHC.Core.Type import GHC.Types.Basic ( TopLevelFlag(..), isTopLevel, isMarkedCbv ) import GHC.Types.CostCentre ( isCurrentCCS ) -import GHC.Types.Error ( DiagnosticReason(WarningWithoutFlag) ) import GHC.Types.Id import GHC.Types.Var.Set import GHC.Types.Name ( getSrcLoc, nameIsLocalOrFrom ) @@ -116,7 +115,7 @@ import GHC.Types.SrcLoc import GHC.Utils.Logger import GHC.Utils.Outputable -import GHC.Utils.Error ( mkLocMessage, DiagOpts ) +import GHC.Utils.Error ( DiagOpts ) import qualified GHC.Utils.Error as Err import GHC.Unit.Module ( Module ) @@ -540,7 +539,7 @@ addErr diag_opts errs_so_far msg locs = errs_so_far `snocBag` mk_msg locs where mk_msg (loc:_) = let (l,hdr) = dumpLoc loc - in mkLocMessage (Err.mkMCDiagnostic diag_opts WarningWithoutFlag Nothing) + in Err.mkLintMessage diag_opts l (hdr $$ msg) mk_msg [] = msg ===================================== compiler/GHC/Types/Error.hs ===================================== @@ -72,6 +72,7 @@ module GHC.Types.Error , pprMessageBag , mkLocMessage , mkLocMessageWarningGroups + , formatDiagnostic , getCaretDiagnostic , jsonDiagnostic @@ -495,11 +496,11 @@ data MessageClass -- ^ Diagnostics from the compiler. This constructor is very powerful as -- it allows the construction of a 'MessageClass' with a completely -- arbitrary permutation of 'Severity' and 'DiagnosticReason'. As such, - -- users are encouraged to use the 'mkMCDiagnostic' smart constructor + -- users are encouraged to use higher level primitives -- instead. Use this constructor directly only if you need to construct -- and manipulate diagnostic messages directly, for example inside -- 'GHC.Utils.Error'. In all the other circumstances, /especially/ when - -- emitting compiler diagnostics, use the smart constructor. + -- emitting compiler diagnostics, use higher level primitives. -- -- The @Maybe 'DiagnosticCode'@ field carries a code (if available) for -- this diagnostic. If you are creating a message not tied to any @@ -656,32 +657,51 @@ mkLocMessageWarningGroups -> SrcSpan -- ^ location -> SDoc -- ^ message -> SDoc - -- Always print the location, even if it is unhelpful. Error messages - -- are supposed to be in a standard format, and one without a location - -- would look strange. Better to say explicitly "<no location info>". mkLocMessageWarningGroups show_warn_groups msg_class locn msg - = sdocOption sdocColScheme $ \col_scheme -> - let locn' = sdocOption sdocErrorSpans $ \case - True -> ppr locn - False -> ppr (srcSpanStart locn) - + = case msg_class of + MCDiagnostic severity reason code -> formatDiagnostic show_warn_groups locn severity reason code msg + _ -> sdocOption sdocColScheme $ \col_scheme -> + let msg_colour = getMessageClassColour msg_class col_scheme - col = coloured msg_colour . text msg_title = coloured msg_colour $ case msg_class of - MCDiagnostic SevError _ _ -> text "error" - MCDiagnostic SevWarning _ _ -> text "warning" MCFatal -> text "fatal" _ -> empty + in formatLocMessageWarningGroups locn msg_title empty empty msg + +formatDiagnostic + :: Bool -- ^ Print warning groups? + -> SrcSpan -- ^ location + -> Severity + -> ResolvedDiagnosticReason + -> Maybe DiagnosticCode + -> SDoc -- ^ message + -> SDoc +formatDiagnostic show_warn_groups locn severity reason code msg + = sdocOption sdocColScheme $ \col_scheme -> + let + msg_colour :: Col.PprColour + msg_colour = getSeverityColour severity col_scheme + + col :: String -> SDoc + col = coloured msg_colour . text + + msg_title :: SDoc + msg_title = coloured msg_colour $ + case severity of + SevError -> text "error" + SevWarning -> text "warning" + SevIgnore -> empty + + warning_flag_doc :: SDoc warning_flag_doc = - case msg_class of - MCDiagnostic sev reason _code - | Just msg <- flag_msg sev (resolvedDiagnosticReason reason) - -> brackets msg - _ -> empty + case flag_msg severity (resolvedDiagnosticReason reason) of + Nothing -> empty + Just msg -> brackets msg + ppr_with_hyperlink :: DiagnosticCode -> SDoc ppr_with_hyperlink code = -- this is a bit hacky, but we assume that if the terminal supports colors -- then it should also support links @@ -691,10 +711,11 @@ mkLocMessageWarningGroups show_warn_groups msg_class locn msg then ppr $ LinkedDiagCode code else ppr code + code_doc :: SDoc code_doc = - case msg_class of - MCDiagnostic _ _ (Just code) -> brackets (ppr_with_hyperlink code) - _ -> empty + case code of + Just code -> brackets (ppr_with_hyperlink code) + Nothing -> empty flag_msg :: Severity -> DiagnosticReason -> Maybe SDoc flag_msg SevIgnore _ = Nothing @@ -725,13 +746,35 @@ mkLocMessageWarningGroups show_warn_groups msg_class locn msg vcat [ text "locn:" <+> ppr locn , text "msg:" <+> ppr msg ] + warn_flag_grp :: [WarningGroup] -> SDoc warn_flag_grp groups | show_warn_groups, not (null groups) = text $ "(in " ++ intercalate ", " (map (("-W"++) . warningGroupName) groups) ++ ")" | otherwise = empty + in formatLocMessageWarningGroups locn msg_title code_doc warning_flag_doc msg + +formatLocMessageWarningGroups + :: SrcSpan -- ^ location + -> SDoc -- ^ title + -> SDoc -- ^ diagnostic code + -> SDoc -- ^ warning groups + -> SDoc -- ^ message + -> SDoc +formatLocMessageWarningGroups locn msg_title code_doc warning_flag_doc msg + = sdocOption sdocColScheme $ \col_scheme -> + let + -- Always print the location, even if it is unhelpful. Error messages + -- are supposed to be in a standard format, and one without a location + -- would look strange. Better to say explicitly "<no location info>". + locn' :: SDoc + locn' = sdocOption sdocErrorSpans $ \case + True -> ppr locn + False -> ppr (srcSpanStart locn) + -- Add prefixes, like Foo.hs:34: warning: -- <the warning message> + header :: SDoc header = locn' <> colon <+> msg_title <> colon <+> code_doc <+> warning_flag_doc @@ -741,11 +784,16 @@ mkLocMessageWarningGroups show_warn_groups msg_class locn msg msg) getMessageClassColour :: MessageClass -> Col.Scheme -> Col.PprColour -getMessageClassColour (MCDiagnostic SevError _reason _code) = Col.sError -getMessageClassColour (MCDiagnostic SevWarning _reason _code) = Col.sWarning +getMessageClassColour (MCDiagnostic severity _reason _code) = getSeverityColour severity getMessageClassColour MCFatal = Col.sFatal getMessageClassColour _ = const mempty +getSeverityColour :: Severity -> Col.Scheme -> Col.PprColour +getSeverityColour severity = case severity of + SevError -> Col.sError + SevWarning -> Col.sWarning + SevIgnore -> const mempty + getCaretDiagnostic :: MessageClass -> SrcSpan -> IO SDoc getCaretDiagnostic _ (UnhelpfulSpan _) = pure empty getCaretDiagnostic msg_class (RealSrcSpan span _) = ===================================== compiler/GHC/Utils/Error.hs ===================================== @@ -32,7 +32,7 @@ module GHC.Utils.Error ( emptyMessages, mkDecorated, mkLocMessage, mkMsgEnvelope, mkPlainMsgEnvelope, mkPlainErrorMsgEnvelope, mkErrorMsgEnvelope, - mkMCDiagnostic, diagReasonSeverity, + mkLintMessage, diagReasonSeverity, mkPlainError, mkPlainDiagnostic, @@ -160,12 +160,10 @@ diag_reason_severity opts reason = fmap ResolvedDiagnosticReason $ case reason o ErrorWithoutFlag -> (SevError, reason) --- | Make a 'MessageClass' for a given 'DiagnosticReason', consulting the --- 'DiagOpts'. -mkMCDiagnostic :: DiagOpts -> DiagnosticReason -> Maybe DiagnosticCode -> MessageClass -mkMCDiagnostic opts reason code = MCDiagnostic sev reason' code +mkLintMessage :: DiagOpts -> SrcSpan -> SDoc -> SDoc +mkLintMessage opts span = formatDiagnostic True span severity reason Nothing where - (sev, reason') = diag_reason_severity opts reason + (severity, reason) = diag_reason_severity opts WarningWithoutFlag -- -- Creating MsgEnvelope(s) View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/26bc4e0314283a230450f2684f9c9796... -- View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/26bc4e0314283a230450f2684f9c9796... 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