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{-# LANGUAGE DataKinds #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE DeriveDataTypeable #-}
-- | Bits of concrete syntax (tokens, layout).
module Language.Haskell.Syntax.Concrete
( LHsToken, LHsUniToken,
HsToken(HsTok),
HsUniToken(HsNormalTok, HsUnicodeTok),
LayoutInfo(ExplicitBraces, VirtualBraces, NoLayoutInfo)
) where
import GHC.Prelude
import GHC.TypeLits (Symbol, KnownSymbol)
import Data.Data
import Language.Haskell.Syntax.Extension
type LHsToken tok p = XRec p (HsToken tok)
type LHsUniToken tok utok p = XRec p (HsUniToken tok utok)
-- | A token stored in the syntax tree. For example, when parsing a
-- let-expression, we store @HsToken "let"@ and @HsToken "in"@.
-- The locations of those tokens can be used to faithfully reproduce
-- (exactprint) the original program text.
data HsToken (tok :: Symbol) = HsTok
-- | With @UnicodeSyntax@, there might be multiple ways to write the same
-- token. For example an arrow could be either @->@ or @→@. This choice must be
-- recorded in order to exactprint such tokens, so instead of @HsToken "->"@ we
-- introduce @HsUniToken "->" "→"@.
--
-- See also @IsUnicodeSyntax@ in @GHC.Parser.Annotation@; we do not use here to
-- avoid a dependency.
data HsUniToken (tok :: Symbol) (utok :: Symbol) = HsNormalTok | HsUnicodeTok
deriving instance KnownSymbol tok => Data (HsToken tok)
deriving instance (KnownSymbol tok, KnownSymbol utok) => Data (HsUniToken tok utok)
-- | Layout information for declarations.
data LayoutInfo pass =
-- | Explicit braces written by the user.
--
-- @
-- class C a where { foo :: a; bar :: a }
-- @
ExplicitBraces !(LHsToken "{" pass) !(LHsToken "}" pass)
|
-- | Virtual braces inserted by the layout algorithm.
--
-- @
-- class C a where
-- foo :: a
-- bar :: a
-- @
VirtualBraces
!Int -- ^ Layout column (indentation level, begins at 1)
|
-- | Empty or compiler-generated blocks do not have layout information
-- associated with them.
NoLayoutInfo
|
