GHC.Types.Error

ghc-9.4.0.20220501: The GHC API

Safe Haskell | Safe-Inferred
Language | Haskell2010

GHC.Types.Error

Contents

- Messages
- Classifying Messages
- Hints and refactoring actions
- Rendering Messages
- Queries

Synopsis

- data Messages e
- mkMessages :: Bag (MsgEnvelope e) -> Messages e
- getMessages :: Messages e -> Bag (MsgEnvelope e)
- emptyMessages :: Messages e
- isEmptyMessages :: Messages e -> Bool
- singleMessage :: MsgEnvelope e -> Messages e
- addMessage :: MsgEnvelope e -> Messages e -> Messages e
- unionMessages :: Messages e -> Messages e -> Messages e
- unionManyMessages :: Foldable f => f (Messages e) -> Messages e
- data MsgEnvelope e = MsgEnvelope {
  - errMsgSpan :: SrcSpan
  - errMsgContext :: PrintUnqualified
  - errMsgDiagnostic :: e
  - errMsgSeverity :: Severity
  }
- data MessageClass
  - = MCOutput
  - | MCFatal
  - | MCInteractive
  - | MCDump
  - | MCInfo
  - | MCDiagnostic Severity DiagnosticReason
- data Severity
  - = SevIgnore
  - | SevWarning
  - | SevError
- class Diagnostic a where
  - diagnosticMessage :: a -> DecoratedSDoc
  - diagnosticReason :: a -> DiagnosticReason
  - diagnosticHints :: a -> [GhcHint]
- data DiagnosticMessage = DiagnosticMessage {
  - diagMessage :: !DecoratedSDoc
  - diagReason :: !DiagnosticReason
  - diagHints :: [GhcHint]
  }
- data DiagnosticReason
  - = WarningWithoutFlag
  - | WarningWithFlag !WarningFlag
  - | ErrorWithoutFlag
- data DiagnosticHint = DiagnosticHint !SDoc
- mkPlainDiagnostic :: DiagnosticReason -> [GhcHint] -> SDoc -> DiagnosticMessage
- mkPlainError :: [GhcHint] -> SDoc -> DiagnosticMessage
- mkDecoratedDiagnostic :: DiagnosticReason -> [GhcHint] -> [SDoc] -> DiagnosticMessage
- mkDecoratedError :: [GhcHint] -> [SDoc] -> DiagnosticMessage
- data GhcHint
  - = forall a.(Outputable a, Typeable a) => UnknownHint a
  - | SuggestExtension !LanguageExtensionHint
  - | SuggestMissingDo
  - | SuggestLetInDo
  - | SuggestAddSignatureCabalFile !ModuleName
  - | SuggestSignatureInstantiations !ModuleName [InstantiationSuggestion]
  - | SuggestUseSpaces
  - | SuggestUseWhitespaceAfter !OperatorWhitespaceSymbol
  - | SuggestUseWhitespaceAround !String !OperatorWhitespaceOccurrence
  - | SuggestParentheses
  - | SuggestIncreaseMaxPmCheckModels
  - | SuggestAddTypeSignatures AvailableBindings
  - | SuggestBindToWildcard !(LHsExpr GhcTc)
  - | SuggestAddInlineOrNoInlinePragma !Var !Activation
  - | SuggestAddPhaseToCompetingRule !RuleName
  - | SuggestAddToHSigExportList !Name !(Maybe Module)
  - | SuggestIncreaseSimplifierIterations
  - | SuggestUseTypeFromDataKind (Maybe RdrName)
  - | SuggestQualifiedAfterModuleName
  - | SuggestThQuotationSyntax
  - | SuggestRoles [Role]
  - | SuggestQualifyStarOperator
  - | SuggestTypeSignatureForm
  - | SuggestFixOrphanInstance
  - | SuggestAddStandaloneDerivation
  - | SuggestFillInWildcardConstraint
  - | SuggestRenameForall
  - | SuggestAppropriateTHTick NameSpace
  - | SuggestDumpSlices
  - | SuggestAddTick UntickedPromotedThing
  - | SuggestMoveToDeclarationSite SDoc RdrName
  - | SuggestSimilarNames RdrName (NonEmpty SimilarName)
  - | RemindFieldSelectorSuppressed {
    - suppressed_selector :: RdrName
    - suppressed_parents :: [Name]
    }
  - | ImportSuggestion ImportSuggestion
  - | SuggestImportingDataCon
  - | SuggestPlacePragmaInHeader
- data AvailableBindings
  - = NamedBindings (NonEmpty Name)
  - | UnnamedBinding
- data LanguageExtensionHint
  - = SuggestSingleExtension !SDoc !Extension
  - | SuggestAnyExtension !SDoc [Extension]
  - | SuggestExtensions !SDoc [Extension]
  - | SuggestExtensionInOrderTo !SDoc !Extension
- suggestExtension :: Extension -> GhcHint
- suggestExtensionWithInfo :: SDoc -> Extension -> GhcHint
- suggestExtensions :: [Extension] -> GhcHint
- suggestExtensionsWithInfo :: SDoc -> [Extension] -> GhcHint
- suggestAnyExtension :: [Extension] -> GhcHint
- suggestAnyExtensionWithInfo :: SDoc -> [Extension] -> GhcHint
- useExtensionInOrderTo :: SDoc -> Extension -> GhcHint
- noHints :: [GhcHint]
- data SDoc
- data DecoratedSDoc
- mkDecorated :: [SDoc] -> DecoratedSDoc
- mkSimpleDecorated :: SDoc -> DecoratedSDoc
- unionDecoratedSDoc :: DecoratedSDoc -> DecoratedSDoc -> DecoratedSDoc
- mapDecoratedSDoc :: (SDoc -> SDoc) -> DecoratedSDoc -> DecoratedSDoc
- pprMessageBag :: Bag SDoc -> SDoc
- mkLocMessage :: MessageClass -> SrcSpan -> SDoc -> SDoc
- mkLocMessageAnn :: Maybe String -> MessageClass -> SrcSpan -> SDoc -> SDoc
- getCaretDiagnostic :: MessageClass -> SrcSpan -> IO SDoc
- isIntrinsicErrorMessage :: Diagnostic e => MsgEnvelope e -> Bool
- isExtrinsicErrorMessage :: MsgEnvelope e -> Bool
- isWarningMessage :: Diagnostic e => MsgEnvelope e -> Bool
- getErrorMessages :: Diagnostic e => Messages e -> Bag (MsgEnvelope e)
- getWarningMessages :: Diagnostic e => Messages e -> Bag (MsgEnvelope e)
- partitionMessages :: Diagnostic e => Messages e -> (Messages e, Messages e)
- errorsFound :: Diagnostic e => Messages e -> Bool
- errorsOrFatalWarningsFound :: Messages e -> Bool

# Messages

data Messages e Source #

A collection of messages emitted by GHC during error reporting. A diagnostic message is typically a warning or an error. See Note [Messages].

INVARIANT: All the messages in this collection must be relevant, i.e. their `Severity` should not be `SevIgnore`. The smart constructor `mkMessages` will filter out any message which `Severity` is `SevIgnore`.

#### Instances

Instances details

Foldable Messages Source # |
Instance details Defined in GHC.Types.Error Methods fold :: Monoid m => Messages m -> m Source # foldMap :: Monoid m => (a -> m) -> Messages a -> m Source # foldMap' :: Monoid m => (a -> m) -> Messages a -> m Source # foldr :: (a -> b -> b) -> b -> Messages a -> b Source # foldr' :: (a -> b -> b) -> b -> Messages a -> b Source # foldl :: (b -> a -> b) -> b -> Messages a -> b Source # foldl' :: (b -> a -> b) -> b -> Messages a -> b Source # foldr1 :: (a -> a -> a) -> Messages a -> a Source # foldl1 :: (a -> a -> a) -> Messages a -> a Source # toList :: Messages a -> [a] Source # null :: Messages a -> Bool Source # length :: Messages a -> Int Source # elem :: Eq a => a -> Messages a -> Bool Source # maximum :: Ord a => Messages a -> a Source # minimum :: Ord a => Messages a -> a Source # sum :: Num a => Messages a -> a Source # product :: Num a => Messages a -> a Source #
Traversable Messages Source # |
Instance details Defined in GHC.Types.Error Methods traverse :: Applicative f => (a -> f b) -> Messages a -> f (Messages b) Source # sequenceA :: Applicative f => Messages (f a) -> f (Messages a) Source # mapM :: Monad m => (a -> m b) -> Messages a -> m (Messages b) Source # sequence :: Monad m => Messages (m a) -> m (Messages a) Source #
Functor Messages Source # |
Instance details Defined in GHC.Types.Error Methods fmap :: (a -> b) -> Messages a -> Messages b Source # (<$) :: a -> Messages b -> Messages a Source #
Monoid (Messages e) Source # |
Instance details Defined in GHC.Types.Error Methods mempty :: Messages e Source # mappend :: Messages e -> Messages e -> Messages e Source # mconcat :: [Messages e] -> Messages e Source #
Semigroup (Messages e) Source # |
Instance details Defined in GHC.Types.Error Methods (<>) :: Messages e -> Messages e -> Messages e Source # sconcat :: NonEmpty (Messages e) -> Messages e Source # stimes :: Integral b => b -> Messages e -> Messages e Source #
Diagnostic e => Outputable (Messages e) Source # |
Instance details Defined in GHC.Types.Error Methods ppr :: Messages e -> SDoc Source #

mkMessages :: Bag (MsgEnvelope e) -> Messages e Source #

getMessages :: Messages e -> Bag (MsgEnvelope e) Source #

emptyMessages :: Messages e Source #

isEmptyMessages :: Messages e -> Bool Source #

singleMessage :: MsgEnvelope e -> Messages e Source #

addMessage :: MsgEnvelope e -> Messages e -> Messages e Source #

Adds a `Message` to the input collection of messages. See Note [Discarding Messages].

unionMessages :: Messages e -> Messages e -> Messages e Source #

Joins two collections of messages together. See Note [Discarding Messages].

unionManyMessages :: Foldable f => f (Messages e) -> Messages e Source #

Joins many `Messages`s together

data MsgEnvelope e Source #

An envelope for GHC's facts about a running program, parameterised over the domain-specific (i.e. parsing, typecheck-renaming, etc) diagnostics.

To say things differently, GHC emits diagnostics about the running program, each of which is wrapped into a `MsgEnvelope` that carries specific information like where the error happened, etc. Finally, multiple `MsgEnvelope`s are aggregated into `Messages` that are returned to the user.

Constructors

MsgEnvelope |
Fields errMsgSpan :: SrcSpan The SrcSpan is used for sorting errors into line-number order errMsgContext :: PrintUnqualified errMsgDiagnostic :: e errMsgSeverity :: Severity

#### Instances

Instances details

Foldable MsgEnvelope Source # |
Instance details Defined in GHC.Types.Error Methods fold :: Monoid m => MsgEnvelope m -> m Source # foldMap :: Monoid m => (a -> m) -> MsgEnvelope a -> m Source # foldMap' :: Monoid m => (a -> m) -> MsgEnvelope a -> m Source # foldr :: (a -> b -> b) -> b -> MsgEnvelope a -> b Source # foldr' :: (a -> b -> b) -> b -> MsgEnvelope a -> b Source # foldl :: (b -> a -> b) -> b -> MsgEnvelope a -> b Source # foldl' :: (b -> a -> b) -> b -> MsgEnvelope a -> b Source # foldr1 :: (a -> a -> a) -> MsgEnvelope a -> a Source # foldl1 :: (a -> a -> a) -> MsgEnvelope a -> a Source # toList :: MsgEnvelope a -> [a] Source # null :: MsgEnvelope a -> Bool Source # length :: MsgEnvelope a -> Int Source # elem :: Eq a => a -> MsgEnvelope a -> Bool Source # maximum :: Ord a => MsgEnvelope a -> a Source # minimum :: Ord a => MsgEnvelope a -> a Source # sum :: Num a => MsgEnvelope a -> a Source # product :: Num a => MsgEnvelope a -> a Source #
Traversable MsgEnvelope Source # |
Instance details Defined in GHC.Types.Error Methods traverse :: Applicative f => (a -> f b) -> MsgEnvelope a -> f (MsgEnvelope b) Source # sequenceA :: Applicative f => MsgEnvelope (f a) -> f (MsgEnvelope a) Source # mapM :: Monad m => (a -> m b) -> MsgEnvelope a -> m (MsgEnvelope b) Source # sequence :: Monad m => MsgEnvelope (m a) -> m (MsgEnvelope a) Source #
Functor MsgEnvelope Source # |
Instance details Defined in GHC.Types.Error Methods fmap :: (a -> b) -> MsgEnvelope a -> MsgEnvelope b Source # (<$) :: a -> MsgEnvelope b -> MsgEnvelope a Source #
Show (MsgEnvelope DiagnosticMessage) Source # |
Instance details Defined in GHC.Types.Error Methods showsPrec :: Int -> MsgEnvelope DiagnosticMessage -> ShowS Source # show :: MsgEnvelope DiagnosticMessage -> String Source # showList :: [MsgEnvelope DiagnosticMessage] -> ShowS Source #

# Classifying Messages

data MessageClass Source #

The class for a diagnostic message. The main purpose is to classify a message within GHC, to distinguish it from a debug/dump message vs a proper diagnostic, for which we include a `DiagnosticReason`.

Constructors

MCOutput |
MCFatal |
MCInteractive |
MCDump | Log message intended for compiler developers No file/line/column stuff
MCInfo | Log messages intended for end users. No file/line/column stuff.
MCDiagnostic Severity DiagnosticReason | 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 instead. Use this constructor directly only if you need to construct and manipulate diagnostic messages directly, for example inside `Error`. In all the other circumstances, especially when emitting compiler diagnostics, use the smart constructor.

#### Instances

Instances details

Show MessageClass Source # |
Instance details Defined in GHC.Types.Error Methods showsPrec :: Int -> MessageClass -> ShowS Source # show :: MessageClass -> String Source # showList :: [MessageClass] -> ShowS Source #
ToJson MessageClass Source # |
Instance details Defined in GHC.Types.Error Methods json :: MessageClass -> JsonDoc Source #
Eq MessageClass Source # |
Instance details Defined in GHC.Types.Error Methods (==) :: MessageClass -> MessageClass -> Bool # (/=) :: MessageClass -> MessageClass -> Bool #

data Severity Source #

Used to describe warnings and errors o The message has a file/line/column heading, plus "warning:" or "error:", added by mkLocMessage o With `SevIgnore` the message is suppressed o Output is intended for end users

Constructors

SevIgnore | Ignore this message, for example in case of suppression of warnings users don't want to see. See Note [Suppressing Messages]
SevWarning |
SevError |

#### Instances

Instances details

Show Severity Source # |
Instance details Defined in GHC.Types.Error Methods showsPrec :: Int -> Severity -> ShowS Source # show :: Severity -> String Source # showList :: [Severity] -> ShowS Source #
ToJson Severity Source # |
Instance details Defined in GHC.Types.Error Methods json :: Severity -> JsonDoc Source #
Outputable Severity Source # |
Instance details Defined in GHC.Types.Error Methods ppr :: Severity -> SDoc Source #
Eq Severity Source # |
Instance details Defined in GHC.Types.Error Methods (==) :: Severity -> Severity -> Bool # (/=) :: Severity -> Severity -> Bool #

class Diagnostic a where Source #

A class identifying a diagnostic. Dictionary.com defines a diagnostic as:

"a message output by a computer diagnosing an error in a computer program, computer system, or component device".

A `Diagnostic` carries the actual description of the message (which, in GHC's case, it can be an error or a warning) and the reason why such message was generated in the first place. See also Note [Rendering Messages].

Methods

diagnosticMessage :: a -> DecoratedSDoc Source #

diagnosticReason :: a -> DiagnosticReason Source #

diagnosticHints :: a -> [GhcHint] Source #

#### Instances

Instances details

Diagnostic DriverMessage Source # |
Instance details Defined in GHC.Driver.Errors.Ppr Methods diagnosticMessage :: DriverMessage -> DecoratedSDoc Source # diagnosticReason :: DriverMessage -> DiagnosticReason Source # diagnosticHints :: DriverMessage -> [GhcHint] Source #
Diagnostic GhcMessage Source # |
Instance details Defined in GHC.Driver.Errors.Ppr Methods diagnosticMessage :: GhcMessage -> DecoratedSDoc Source # diagnosticReason :: GhcMessage -> DiagnosticReason Source # diagnosticHints :: GhcMessage -> [GhcHint] Source #
Diagnostic DsMessage Source # |
Instance details Defined in GHC.HsToCore.Errors.Ppr Methods diagnosticMessage :: DsMessage -> DecoratedSDoc Source # diagnosticReason :: DsMessage -> DiagnosticReason Source # diagnosticHints :: DsMessage -> [GhcHint] Source #
Diagnostic PsMessage Source # |
Instance details Defined in GHC.Parser.Errors.Ppr Methods diagnosticMessage :: PsMessage -> DecoratedSDoc Source # diagnosticReason :: PsMessage -> DiagnosticReason Source # diagnosticHints :: PsMessage -> [GhcHint] Source #
Diagnostic TcRnMessage Source # |
Instance details Defined in GHC.Tc.Errors.Ppr Methods diagnosticMessage :: TcRnMessage -> DecoratedSDoc Source # diagnosticReason :: TcRnMessage -> DiagnosticReason Source # diagnosticHints :: TcRnMessage -> [GhcHint] Source #
Diagnostic DiagnosticMessage Source # |
Instance details Defined in GHC.Types.Error Methods diagnosticMessage :: DiagnosticMessage -> DecoratedSDoc Source # diagnosticReason :: DiagnosticMessage -> DiagnosticReason Source # diagnosticHints :: DiagnosticMessage -> [GhcHint] Source #

data DiagnosticMessage Source #

A generic `Diagnostic` message, without any further classification or provenance: By looking at a `DiagnosticMessage` we don't know neither where it was generated nor how to intepret its payload (as it's just a structured document). All we can do is to print it out and look at its `DiagnosticReason`.

Constructors

DiagnosticMessage |
Fields diagMessage :: !DecoratedSDoc diagReason :: !DiagnosticReason diagHints :: [GhcHint]

#### Instances

Instances details

Diagnostic DiagnosticMessage Source # |
Instance details Defined in GHC.Types.Error Methods diagnosticMessage :: DiagnosticMessage -> DecoratedSDoc Source # diagnosticReason :: DiagnosticMessage -> DiagnosticReason Source # diagnosticHints :: DiagnosticMessage -> [GhcHint] Source #
Show (MsgEnvelope DiagnosticMessage) Source # |
Instance details Defined in GHC.Types.Error Methods showsPrec :: Int -> MsgEnvelope DiagnosticMessage -> ShowS Source # show :: MsgEnvelope DiagnosticMessage -> String Source # showList :: [MsgEnvelope DiagnosticMessage] -> ShowS Source #

data DiagnosticReason Source #

The reason why a `Diagnostic` was emitted in the first place. Diagnostic messages are born within GHC with a very precise reason, which can be completely statically-computed (i.e. this is an error or a warning no matter what), or influenced by the specific state of the `DynFlags` at the moment of the creation of a new `Diagnostic`. For example, a parsing error is always going to be an error, whereas a 'WarningWithoutFlag Opt_WarnUnusedImports' might turn into an error due to '-Werror' or '-Werror=warn-unused-imports'. Interpreting a `DiagnosticReason` together with its associated `Severity` gives us the full picture.

Constructors

WarningWithoutFlag | Born as a warning.
WarningWithFlag !WarningFlag | Warning was enabled with the flag.
ErrorWithoutFlag | Born as an error.

#### Instances

Instances details

Show DiagnosticReason Source # |
Instance details Defined in GHC.Types.Error Methods showsPrec :: Int -> DiagnosticReason -> ShowS Source # show :: DiagnosticReason -> String Source # showList :: [DiagnosticReason] -> ShowS Source #
Outputable DiagnosticReason Source # |
Instance details Defined in GHC.Types.Error Methods ppr :: DiagnosticReason -> SDoc Source #
Eq DiagnosticReason Source # |
Instance details Defined in GHC.Types.Error Methods (==) :: DiagnosticReason -> DiagnosticReason -> Bool # (/=) :: DiagnosticReason -> DiagnosticReason -> Bool #

data DiagnosticHint Source #

A generic `Hint` message, to be used with `DiagnosticMessage`.

Constructors

DiagnosticHint !SDoc |

#### Instances

Instances details

Outputable DiagnosticHint Source # |
Instance details Defined in GHC.Types.Error Methods ppr :: DiagnosticHint -> SDoc Source #

mkPlainDiagnostic :: DiagnosticReason -> [GhcHint] -> SDoc -> DiagnosticMessage Source #

mkPlainError :: [GhcHint] -> SDoc -> DiagnosticMessage Source #

Create an error `DiagnosticMessage` holding just a single `SDoc`

mkDecoratedDiagnostic :: DiagnosticReason -> [GhcHint] -> [SDoc] -> DiagnosticMessage Source #

Create a `DiagnosticMessage` from a list of bulleted SDocs and a `DiagnosticReason`

mkDecoratedError :: [GhcHint] -> [SDoc] -> DiagnosticMessage Source #

Create an error `DiagnosticMessage` from a list of bulleted SDocs

# Hints and refactoring actions

data GhcHint Source #

A type for hints emitted by GHC. A hint suggests a possible way to deal with a particular warning or error.

Constructors

forall a.(Outputable a, Typeable a) => UnknownHint a | An "unknown" hint. This type constructor allows arbitrary -- hints to be embedded. The typical use case would be GHC plugins -- willing to emit hints alongside their custom diagnostics.
SuggestExtension !LanguageExtensionHint | Suggests adding a particular language extension. GHC will do its best trying to guess when the user is using the syntax of a particular language extension without having the relevant extension enabled. Example: If the user uses the keyword "mdo" (and we are in a monadic block), but the relevant extension is not enabled, GHC will emit a 'SuggestExtension RecursiveDo'. Test case(s): parsershould_failT12429, parsershould_failT8501c, parsershould_failT18251e, ... (and many more)
SuggestMissingDo | Suggests that a monadic code block is probably missing a "do" keyword. Example: main = putStrLn "hello" putStrLn "world" Test case(s): parsershould_failT8501a, parsershould_failreadFail007, parsershould_failInfixAppPatErr, parsershould_failT984
SuggestLetInDo | Suggests that a "let" expression is needed in a "do" block. Test cases: None (that explicitly test this particular hint is emitted).
SuggestAddSignatureCabalFile !ModuleName | Suggests to add an ".hsig" signature file to the Cabal manifest. Triggered by: `DriverUnexpectedSignature`, if Cabal is being used. Example: See comment of `DriverUnexpectedSignature`. Test case(s): driver/T12955
SuggestSignatureInstantiations !ModuleName [InstantiationSuggestion] | Suggests to explicitly list the instantiations for the signatures in the GHC invocation command. Triggered by: `DriverUnexpectedSignature`, if Cabal is not being used. Example: See comment of `DriverUnexpectedSignature`. Test case(s): driver/T12955
SuggestUseSpaces | Suggests to use spaces instead of tabs. Triggered by: `PsWarnTab`. Examples: None Test Case(s): None
SuggestUseWhitespaceAfter !OperatorWhitespaceSymbol | Suggests adding a whitespace after the given symbol. Examples: None Test Case(s): parsershould_compileT18834a.hs
SuggestUseWhitespaceAround !String !OperatorWhitespaceOccurrence | Suggests adding a whitespace around the given operator symbol, as it might be repurposed as special syntax by a future language extension. The second parameter is how such operator occurred, if in a prefix, suffix or tight infix position. Triggered by: `PsWarnOperatorWhitespace`. Example: h a b = a+b -- not OK, no spaces around `+`. Test Case(s): parsershould_compileT18834b.hs
SuggestParentheses | Suggests wrapping an expression in parentheses Examples: None Test Case(s): None
SuggestIncreaseMaxPmCheckModels | Suggests to increase the -fmax-pmcheck-models limit for the pattern match checker. Triggered by: `DsMaxPmCheckModelsReached` Test case(s): pmcheckshould_compileTooManyDeltas pmcheckshould_compileTooManyDeltas pmcheckshould_compileT11822
SuggestAddTypeSignatures AvailableBindings | Suggests adding a type signature, typically to resolve ambiguity or help GHC inferring types.
SuggestBindToWildcard !(LHsExpr GhcTc) | Suggests to explicitly discard the result of a monadic action by binding the result to the '_' wilcard. Example: main = do _ <- getCurrentTime
SuggestAddInlineOrNoInlinePragma !Var !Activation |
SuggestAddPhaseToCompetingRule !RuleName |
SuggestAddToHSigExportList !Name !(Maybe Module) | Suggests adding an identifier to the export list of a signature.
SuggestIncreaseSimplifierIterations | Suggests increasing the limit for the number of iterations in the simplifier.
SuggestUseTypeFromDataKind (Maybe RdrName) | Suggests to explicitly import `Type` from the `Kind` module, because using "*" to mean `Type` relies on the StarIsType extension, which will become deprecated in the future. Triggered by: `PsWarnStarIsType` Example: None Test case(s): wcompat-warnings/WCompatWarningsOn.hs
SuggestQualifiedAfterModuleName | Suggests placing the `qualified` keyword after the module name. Triggered by: `PsWarnImportPreQualified` Example: None Test case(s): module/mod184.hs
SuggestThQuotationSyntax | Suggests using TemplateHaskell quotation syntax. Triggered by: `PsErrEmptyDoubleQuotes` only if TemplateHaskell is enabled. Example: None Test case(s): parsershould_failT13450TH.hs
SuggestRoles [Role] | Suggests alternative roles in case we found an illegal one. Triggered by: `PsErrIllegalRoleName` Example: None Test case(s): rolesshould_failRoles7.hs
SuggestQualifyStarOperator | Suggests qualifying the `*` operator in modules where StarIsType is enabled. Triggered by: `PsWarnStarBinder` Test case(s): warningsshould_compileStarBinder.hs
SuggestTypeSignatureForm | Suggests that a type signature should have form variable :: type in order to be accepted by GHC. Triggered by: `PsErrInvalidTypeSignature` Test case(s): parsershould_failT3811
SuggestFixOrphanInstance | Suggests to move an orphan instance or to newtype-wrap it. Triggered by: `TcRnOrphanInstance` Test cases(s): warningsshould_compileT9178 typecheckshould_compileT4912
SuggestAddStandaloneDerivation | Suggests to use a standalone deriving declaration when GHC can't derive a typeclass instance in a trivial way. Triggered by: `DerivBadErrConstructor` Test cases(s): typecheckshould_failtcfail086
SuggestFillInWildcardConstraint | Suggests the user to fill in the wildcard constraint to disambiguate which constraint that is. Example: deriving instance _ => Eq (Foo f a) Triggered by: `DerivBadErrConstructor` Test cases(s): partial-sigsshould_failT13324_fail2
SuggestRenameForall | Suggests to use an identifier other than `forall` Triggered by: `TcRnForallIdentifier`
SuggestAppropriateTHTick NameSpace | Suggests to use the appropriate Template Haskell tick: a single tick for a term-level `NameSpace`, or a double tick for a type-level `NameSpace`. Triggered by: `TcRnIncorrectNameSpace`.
SuggestDumpSlices | Suggests enabling -ddump-splices to help debug an issue when a `Name` is not in scope or is used in multiple different namespaces (e.g. both as a data constructor and a type constructor). Concomitant with `NoExactName` or `SameName` errors, see e.g. "GHC.Rename.Env.lookupExactOcc_either". Test cases: T5971, T7241, T13937.
SuggestAddTick UntickedPromotedThing | Suggests adding a tick to refer to something which has been promoted to the type level, e.g. a data constructor. Test cases: T9778, T19984.
SuggestMoveToDeclarationSite | Something is split off from its corresponding declaration. For example, a datatype is given a role declaration in a different module. Test cases: T495, T8485, T2713, T5533.
Fields SDoc fixity declaration, role annotation, type signature, ... RdrName the `RdrName` for the declaration site
SuggestSimilarNames RdrName (NonEmpty SimilarName) | Suggest a similar name that the user might have meant, e.g. suggest `traverse` when the user has written `travrese`. Test case: mod73.
RemindFieldSelectorSuppressed | Remind the user that the field selector has been suppressed because of -XNoFieldSelectors. Test cases: NFSSuppressed, records-nofieldselectors.
Fields suppressed_selector :: RdrName suppressed_parents :: [Name]
ImportSuggestion ImportSuggestion | Suggest importing from a module, removing a `hiding` clause, or explain to the user that we couldn't find a module with the given `ModuleName`. Test cases: mod28, mod36, mod87, mod114, ...
SuggestImportingDataCon | Suggest importing a data constructor to bring it into scope Triggered by: `TcRnTypeCannotBeMarshaled` Test cases: ccfail004
SuggestPlacePragmaInHeader |

#### Instances

Instances details

Outputable GhcHint Source # |
Instance details Defined in GHC.Types.Hint.Ppr Methods ppr :: GhcHint -> SDoc Source #

data AvailableBindings Source #

The bindings we have available in scope when suggesting an explicit type signature.

Constructors

NamedBindings (NonEmpty Name) |
UnnamedBinding | An unknown binding (i.e. too complicated to turn into a `Name`)

data LanguageExtensionHint Source #

Constructors

SuggestSingleExtension !SDoc !Extension | Suggest to enable the input extension. This is the hint that GHC emits if this is not a "known" fix, i.e. this is GHC giving its best guess on what extension might be necessary to make a certain program compile. For example, GHC might suggests to enable `BlockArguments` when the user simply formatted incorrectly the input program, so GHC here is trying to be as helpful as possible. If the input `SDoc` is not empty, it will contain some extra information about the why the extension is required, but it's totally irrelevant/redundant for IDEs and other tools.
SuggestAnyExtension !SDoc [Extension] | Suggest to enable the input extensions. The list is to be intended as disjuctive i.e. the user is suggested to enable any of the extensions listed. If the input `SDoc` is not empty, it will contain some extra information about the why the extensions are required, but it's totally irrelevant/redundant for IDEs and other tools.
SuggestExtensions !SDoc [Extension] | Suggest to enable the input extensions. The list is to be intended as conjunctive i.e. the user is suggested to enable all the extensions listed. If the input `SDoc` is not empty, it will contain some extra information about the why the extensions are required, but it's totally irrelevant/redundant for IDEs and other tools.
SuggestExtensionInOrderTo !SDoc !Extension | Suggest to enable the input extension in order to fix a certain problem. This is the suggestion that GHC emits when is more-or-less clear "what's going on". For example, if both `DeriveAnyClass` and `GeneralizedNewtypeDeriving` are turned on, the right thing to do is to enabled `DerivingStrategies`, so in contrast to `SuggestSingleExtension` GHC will be a bit more "imperative" (i.e. "Use X Y Z in order to ... "). If the input `SDoc` is not empty, it will contain some extra information about the why the extensions are required, but it's totally irrelevant/redundant for IDEs and other tools.

suggestExtension :: Extension -> GhcHint Source #

Suggests a single extension without extra user info.

suggestExtensionWithInfo :: SDoc -> Extension -> GhcHint Source #

Like `suggestExtension` but allows supplying extra info for the user.

suggestExtensions :: [Extension] -> GhcHint Source #

Suggests to enable every extension in the list.

suggestExtensionsWithInfo :: SDoc -> [Extension] -> GhcHint Source #

Like `suggestExtensions` but allows supplying extra info for the user.

suggestAnyExtension :: [Extension] -> GhcHint Source #

Suggests to enable any extension in the list.

suggestAnyExtensionWithInfo :: SDoc -> [Extension] -> GhcHint Source #

Like `suggestAnyExtension` but allows supplying extra info for the user.

useExtensionInOrderTo :: SDoc -> Extension -> GhcHint Source #

noHints :: [GhcHint] Source #

Helper function to use when no hints can be provided. Currently this function can be used to construct plain `DiagnosticMessage` and add hints to them, but once #18516 will be fully executed, the main usage of this function would be in the implementation of the `diagnosticHints` typeclass method, to report the fact that a particular `Diagnostic` has no hints.

# Rendering Messages

data SDoc Source #

Represents a pretty-printable document.

To display an `SDoc`, use `printSDoc`, `printSDocLn`, `bufLeftRenderSDoc`, or `renderWithContext`. Avoid calling `runSDoc` directly as it breaks the abstraction layer.

#### Instances

Instances details

IsString SDoc Source # |
Instance details Defined in GHC.Utils.Outputable Methods fromString :: String -> SDoc Source #
Show SDoc Source # |
Instance details Defined in GHC.CmmToAsm.AArch64.Regs Methods showsPrec :: Int -> SDoc -> ShowS Source # show :: SDoc -> String Source # showList :: [SDoc] -> ShowS Source #
Outputable SDoc Source # |
Instance details Defined in GHC.Utils.Outputable Methods ppr :: SDoc -> SDoc Source #
Eq SDoc Source # |
Instance details Defined in GHC.CmmToAsm.AArch64.Regs Methods (==) :: SDoc -> SDoc -> Bool # (/=) :: SDoc -> SDoc -> Bool #
OutputableP env SDoc Source # |
Instance details Defined in GHC.Utils.Outputable Methods pdoc :: env -> SDoc -> SDoc Source #

data DecoratedSDoc Source #

A `DecoratedSDoc` is isomorphic to a '[SDoc]' but it carries the invariant that the input '[SDoc]' needs to be rendered decorated into its final form, where the typical case would be adding bullets between each elements of the list. The type of decoration depends on the formatting function used, but in practice GHC uses the `formatBulleted`.

mkDecorated :: [SDoc] -> DecoratedSDoc Source #

Creates a new `DecoratedSDoc` out of a list of `SDoc`.

mkSimpleDecorated :: SDoc -> DecoratedSDoc Source #

Creates a new `DecoratedSDoc` out of a single `SDoc`

unionDecoratedSDoc :: DecoratedSDoc -> DecoratedSDoc -> DecoratedSDoc Source #

Joins two `DecoratedSDoc` together. The resulting `DecoratedSDoc` will have a number of entries which is the sum of the lengths of the input.

mapDecoratedSDoc :: (SDoc -> SDoc) -> DecoratedSDoc -> DecoratedSDoc Source #

Apply a transformation function to all elements of a `DecoratedSDoc`.

pprMessageBag :: Bag SDoc -> SDoc Source #

mkLocMessage :: MessageClass -> SrcSpan -> SDoc -> SDoc Source #

Make an unannotated error message with location info.

mkLocMessageAnn Source #

Arguments

:: Maybe String | optional annotation
-> MessageClass | What kind of message?
-> SrcSpan | location
-> SDoc | message
-> SDoc |

Make a possibly annotated error message with location info.

getCaretDiagnostic :: MessageClass -> SrcSpan -> IO SDoc Source #

# Queries

isIntrinsicErrorMessage :: Diagnostic e => MsgEnvelope e -> Bool Source #

Returns `True` if this is, intrinsically, a failure. See Note [Intrinsic And Extrinsic Failures].

isExtrinsicErrorMessage :: MsgEnvelope e -> Bool Source #

Returns `True` if the envelope contains a message that will stop compilation: either an intrinsic error or a fatal (-Werror) warning

isWarningMessage :: Diagnostic e => MsgEnvelope e -> Bool Source #

getErrorMessages :: Diagnostic e => Messages e -> Bag (MsgEnvelope e) Source #

getWarningMessages :: Diagnostic e => Messages e -> Bag (MsgEnvelope e) Source #

partitionMessages :: Diagnostic e => Messages e -> (Messages e, Messages e) Source #

Partitions the `Messages` and returns a tuple which first element are the warnings, and the second the errors.

errorsFound :: Diagnostic e => Messages e -> Bool Source #

Are there any hard errors here? -Werror warnings are not detected. If you want to check for -Werror warnings, use `errorsOrFatalWarningsFound`.

errorsOrFatalWarningsFound :: Messages e -> Bool Source #

Are there any errors or -Werror warnings here?