Copyright	© 2015–2017 Megaparsec contributors
License	FreeBSD
Maintainer	Mark Karpov <markkarpov@opmbx.org>
Stability	experimental
Portability	portable
Safe Haskell	None
Language	Haskell2010

Text.Megaparsec.Error

Description

Parse errors. Current version of Megaparsec supports well-typed errors instead of String-based ones. This gives a lot of flexibility in describing what exactly went wrong as well as a way to return arbitrary data in case of failure.

Synopsis

Documentation

data ErrorItem t Source #

Data type that is used to represent “unexpected/expected” items in parse error. The data type is parametrized over token type t.

Since: 5.0.0

Constructors

Tokens (NonEmpty t)	Non-empty stream of tokens
Label (NonEmpty Char)	Label (cannot be empty)
EndOfInput	End of input

Instances

Eq t => Eq (ErrorItem t) Source #
Methods (==) :: ErrorItem t -> ErrorItem t -> Bool # (/=) :: ErrorItem t -> ErrorItem t -> Bool #
Data t => Data (ErrorItem t) Source #
Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ErrorItem t -> c (ErrorItem t) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (ErrorItem t) # toConstr :: ErrorItem t -> Constr # dataTypeOf :: ErrorItem t -> DataType # dataCast1 :: Typeable (* -> ) t => (forall d. Data d => c (t d)) -> Maybe (c (ErrorItem t)) # dataCast2 :: Typeable ( -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (ErrorItem t)) # gmapT :: (forall b. Data b => b -> b) -> ErrorItem t -> ErrorItem t # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ErrorItem t -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ErrorItem t -> r # gmapQ :: (forall d. Data d => d -> u) -> ErrorItem t -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> ErrorItem t -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> ErrorItem t -> m (ErrorItem t) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ErrorItem t -> m (ErrorItem t) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ErrorItem t -> m (ErrorItem t) #
Ord t => Ord (ErrorItem t) Source #
Methods compare :: ErrorItem t -> ErrorItem t -> Ordering # (<) :: ErrorItem t -> ErrorItem t -> Bool # (<=) :: ErrorItem t -> ErrorItem t -> Bool # (>) :: ErrorItem t -> ErrorItem t -> Bool # (>=) :: ErrorItem t -> ErrorItem t -> Bool # max :: ErrorItem t -> ErrorItem t -> ErrorItem t # min :: ErrorItem t -> ErrorItem t -> ErrorItem t #
Read t => Read (ErrorItem t) Source #
Methods readsPrec :: Int -> ReadS (ErrorItem t) # readList :: ReadS [ErrorItem t] # readPrec :: ReadPrec (ErrorItem t) # readListPrec :: ReadPrec [ErrorItem t] #
Show t => Show (ErrorItem t) Source #
Methods showsPrec :: Int -> ErrorItem t -> ShowS # show :: ErrorItem t -> String # showList :: [ErrorItem t] -> ShowS #
Generic (ErrorItem t) Source #
Associated Types type Rep (ErrorItem t) :: * -> * # Methods from :: ErrorItem t -> Rep (ErrorItem t) x # to :: Rep (ErrorItem t) x -> ErrorItem t #
Arbitrary t => Arbitrary (ErrorItem t) Source #
Methods arbitrary :: Gen (ErrorItem t) # shrink :: ErrorItem t -> [ErrorItem t] #
NFData t => NFData (ErrorItem t) Source #
Methods rnf :: ErrorItem t -> () #
(Ord t, ShowToken t) => ShowErrorComponent (ErrorItem t) Source #
Methods showErrorComponent :: ErrorItem t -> String Source #
type Rep (ErrorItem t) Source #
type Rep (ErrorItem t) = D1 (MetaData "ErrorItem" "Text.Megaparsec.Error" "megaparsec-5.3.0-JgUNKthlpeP7bNz0nJXbfN" False) ((:+:) (C1 (MetaCons "Tokens" PrefixI False) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (NonEmpty t)))) ((:+:) (C1 (MetaCons "Label" PrefixI False) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (NonEmpty Char)))) (C1 (MetaCons "EndOfInput" PrefixI False) U1)))

class Ord e => ErrorComponent e where Source #

The type class defines how to represent information about various exceptional situations. Data types that are used as custom data component in ParseError must be instances of this type class.

Since: 5.0.0

Minimal complete definition

representFail, representIndentation

Methods

representFail :: String -> e Source #

Represent the message passed to fail in parser monad.

Since: 5.0.0

representIndentation :: Ordering -> Pos -> Pos -> e Source #

Represent information about incorrect indentation.

Since: 5.0.0

Instances

ErrorComponent () Source #
Methods representFail :: String -> () Source # representIndentation :: Ordering -> Pos -> Pos -> () Source #
ErrorComponent Dec Source #
Methods representFail :: String -> Dec Source # representIndentation :: Ordering -> Pos -> Pos -> Dec Source #

data Dec Source #

“Default error component”. This is our instance of ErrorComponent provided out-of-box.

Since: 5.0.0

Constructors

DecFail String	`fail` has been used in parser monad
DecIndentation Ordering Pos Pos	Incorrect indentation error: desired ordering between reference level and actual level, reference indentation level, actual indentation level

Instances

Eq Dec Source #
Methods (==) :: Dec -> Dec -> Bool # (/=) :: Dec -> Dec -> Bool #
Data Dec Source #
Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Dec -> c Dec # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Dec # toConstr :: Dec -> Constr # dataTypeOf :: Dec -> DataType # dataCast1 :: Typeable (* -> ) t => (forall d. Data d => c (t d)) -> Maybe (c Dec) # dataCast2 :: Typeable ( -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Dec) # gmapT :: (forall b. Data b => b -> b) -> Dec -> Dec # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Dec -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Dec -> r # gmapQ :: (forall d. Data d => d -> u) -> Dec -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Dec -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Dec -> m Dec # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Dec -> m Dec # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Dec -> m Dec #
Ord Dec Source #
Methods compare :: Dec -> Dec -> Ordering # (<) :: Dec -> Dec -> Bool # (<=) :: Dec -> Dec -> Bool # (>) :: Dec -> Dec -> Bool # (>=) :: Dec -> Dec -> Bool # max :: Dec -> Dec -> Dec # min :: Dec -> Dec -> Dec #
Read Dec Source #
Methods readsPrec :: Int -> ReadS Dec # readList :: ReadS [Dec] # readPrec :: ReadPrec Dec # readListPrec :: ReadPrec [Dec] #
Show Dec Source #
Methods showsPrec :: Int -> Dec -> ShowS # show :: Dec -> String # showList :: [Dec] -> ShowS #
Arbitrary Dec Source #
Methods arbitrary :: Gen Dec # shrink :: Dec -> [Dec] #
NFData Dec Source #
Methods rnf :: Dec -> () #
ShowErrorComponent Dec Source #
Methods showErrorComponent :: Dec -> String Source #
ErrorComponent Dec Source #
Methods representFail :: String -> Dec Source # representIndentation :: Ordering -> Pos -> Pos -> Dec Source #

data ParseError t e Source #

The data type ParseError represents parse errors. It provides the stack of source positions, set of expected and unexpected tokens as well as set of custom associated data. The data type is parametrized over token type t and custom data e.

Note that the stack of source positions contains current position as its head, and the rest of positions allows to track full sequence of include files with topmost source file at the end of the list.

Semigroup (or Monoid) instance of the data type allows to merge parse errors from different branches of parsing. When merging two ParseErrors, longest match is preferred; if positions are the same, custom data sets and collections of message items are combined.

Constructors

ParseError
Fields errorPos :: NonEmpty SourcePos Stack of source positions errorUnexpected :: Set (ErrorItem t) Unexpected items errorExpected :: Set (ErrorItem t) Expected items errorCustom :: Set e Associated data, if any

Instances

(Eq e, Eq t) => Eq (ParseError t e) Source #
Methods (==) :: ParseError t e -> ParseError t e -> Bool # (/=) :: ParseError t e -> ParseError t e -> Bool #
(Ord e, Ord t, Data e, Data t) => Data (ParseError t e) Source #
Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ParseError t e -> c (ParseError t e) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (ParseError t e) # toConstr :: ParseError t e -> Constr # dataTypeOf :: ParseError t e -> DataType # dataCast1 :: Typeable (* -> ) t => (forall d. Data d => c (t d)) -> Maybe (c (ParseError t e)) # dataCast2 :: Typeable ( -> * -> *) t => (forall d a. (Data d, Data a) => c (t d a)) -> Maybe (c (ParseError t e)) # gmapT :: (forall b. Data b => b -> b) -> ParseError t e -> ParseError t e # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ParseError t e -> r # gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ParseError t e -> r # gmapQ :: (forall d. Data d => d -> u) -> ParseError t e -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> ParseError t e -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> ParseError t e -> m (ParseError t e) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ParseError t e -> m (ParseError t e) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ParseError t e -> m (ParseError t e) #
(Ord e, Ord t, Read e, Read t) => Read (ParseError t e) Source #
Methods readsPrec :: Int -> ReadS (ParseError t e) # readList :: ReadS [ParseError t e] # readPrec :: ReadPrec (ParseError t e) # readListPrec :: ReadPrec [ParseError t e] #
(Show e, Show t) => Show (ParseError t e) Source #
Methods showsPrec :: Int -> ParseError t e -> ShowS # show :: ParseError t e -> String # showList :: [ParseError t e] -> ShowS #
Generic (ParseError t e) Source #
Associated Types type Rep (ParseError t e) :: * -> * # Methods from :: ParseError t e -> Rep (ParseError t e) x # to :: Rep (ParseError t e) x -> ParseError t e #
(Ord t, Ord e) => Semigroup (ParseError t e) Source #
Methods (<>) :: ParseError t e -> ParseError t e -> ParseError t e # sconcat :: NonEmpty (ParseError t e) -> ParseError t e # stimes :: Integral b => b -> ParseError t e -> ParseError t e #
(Ord t, Ord e) => Monoid (ParseError t e) Source #
Methods mempty :: ParseError t e # mappend :: ParseError t e -> ParseError t e -> ParseError t e # mconcat :: [ParseError t e] -> ParseError t e #
(Arbitrary t, Ord t, Arbitrary e, Ord e) => Arbitrary (ParseError t e) Source #
Methods arbitrary :: Gen (ParseError t e) # shrink :: ParseError t e -> [ParseError t e] #
(Show t, Typeable * t, Ord t, ShowToken t, Show e, Typeable * e, ShowErrorComponent e) => Exception (ParseError t e) Source #
Methods toException :: ParseError t e -> SomeException # fromException :: SomeException -> Maybe (ParseError t e) # displayException :: ParseError t e -> String #
(NFData t, NFData e) => NFData (ParseError t e) Source #
Methods rnf :: ParseError t e -> () #
type Rep (ParseError t e) Source #
type Rep (ParseError t e) = D1 (MetaData "ParseError" "Text.Megaparsec.Error" "megaparsec-5.3.0-JgUNKthlpeP7bNz0nJXbfN" False) (C1 (MetaCons "ParseError" PrefixI True) ((::) ((::) (S1 (MetaSel (Just Symbol "errorPos") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (NonEmpty SourcePos))) (S1 (MetaSel (Just Symbol "errorUnexpected") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (Set (ErrorItem t))))) ((:*:) (S1 (MetaSel (Just Symbol "errorExpected") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (Set (ErrorItem t)))) (S1 (MetaSel (Just Symbol "errorCustom") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 (Set e))))))

class ShowToken a where Source #

Type class ShowToken includes methods that allow to pretty-print single token as well as stream of tokens. This is used for rendering of error messages.

Minimal complete definition

showTokens

Methods

showTokens :: NonEmpty a -> String Source #

Pretty-print non-empty stream of tokens. This function is also used to print single tokens (represented as singleton lists).

Since: 5.0.0

Instances

ShowToken Char Source #
Methods showTokens :: NonEmpty Char -> String Source #

class Ord a => ShowErrorComponent a where Source #

The type class defines how to print custom data component of ParseError.

Since: 5.0.0

Minimal complete definition

showErrorComponent

Methods

showErrorComponent :: a -> String Source #

Pretty-print custom data component of ParseError.

Instances

ShowErrorComponent Dec Source #
Methods showErrorComponent :: Dec -> String Source #
(Ord t, ShowToken t) => ShowErrorComponent (ErrorItem t) Source #
Methods showErrorComponent :: ErrorItem t -> String Source #

parseErrorPretty Source #

Arguments

:: (Ord t, ShowToken t, ShowErrorComponent e)
=> ParseError t e	Parse error to render
-> String	Result of rendering

Pretty-print ParseError. The rendered String always ends with a newline.

The function is defined as:

parseErrorPretty e =
  sourcePosStackPretty (errorPos e) ++ ":\n" ++ parseErrorTextPretty e

Since: 5.0.0

sourcePosStackPretty :: NonEmpty SourcePos -> String Source #

Pretty-print stack of source positions.

Since: 5.0.0

parseErrorTextPretty Source #

Arguments

:: (Ord t, ShowToken t, ShowErrorComponent e)
=> ParseError t e	Parse error to render
-> String	Result of rendering

Pretty-print textual part of a ParseError, that is, everything except stack of source positions. The rendered staring always ends with a new line.

Since: 5.1.0