    {-# LANGUAGE ConstraintKinds #-}
    {-# LANGUAGE DataKinds #-}
    {-# LANGUAGE DeriveDataTypeable #-}
    {-# LANGUAGE ExistentialQuantification #-}
    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE FlexibleInstances #-}
    {-# LANGUAGE GADTs #-}
    {-# LANGUAGE ScopedTypeVariables #-}
    {-# LANGUAGE TypeFamilyDependencies #-}
    {-# LANGUAGE UndecidableInstances #-} -- Wrinkle in Note [Trees That Grow]
                                          -- in module Language.Haskell.Syntax.Extension

    {-
    (c) The University of Glasgow 2006
    (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
    -}

    -- See Note [Language.Haskell.Syntax.* Hierarchy] for why not GHC.Hs.*

    -- | Abstract Haskell syntax for expressions.
    module Language.Haskell.Syntax.Expr where

    import Language.Haskell.Syntax.Basic
    import Language.Haskell.Syntax.Decls
    import Language.Haskell.Syntax.Pat
    import Language.Haskell.Syntax.Lit
    import Language.Haskell.Syntax.Extension
    import Language.Haskell.Syntax.Type
    import Language.Haskell.Syntax.Binds

    -- others:
    import GHC.Types.Fixity (LexicalFixity(Infix), Fixity)
    import GHC.Types.SourceText (StringLiteral, SourceText)

    import GHC.Unit.Module (ModuleName)
    import GHC.Data.FastString (FastString)

    -- libraries:
    import Data.Data hiding (Fixity(..))
    import Data.Bool
    import Data.Eq
    import Data.Maybe
    import Data.List.NonEmpty ( NonEmpty )
    import GHC.Types.Name.Reader

    {- Note [RecordDotSyntax field updates]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The extensions @OverloadedRecordDot@ @OverloadedRecordUpdate@ together
    enable record updates like @a{foo.bar.baz = 1}@. Introducing this
    syntax slightly complicates parsing. This note explains how it's done.

    In the event a record is being constructed or updated, it's this
    production that's in play:
    @
    aexp1 -> aexp1 '{' fbinds '}' {
      ...
      mkHsRecordPV ... $1 (snd $3)
    }
    @
    @fbinds@ is a list of field bindings. @mkHsRecordPV@ is a function of
    the @DisambECP b@ typeclass, see Note [Ambiguous syntactic
    categories].

    The "normal" rules for an @fbind@ are:
    @
    fbind
            : qvar '=' texp
            | qvar
    @
    These rules compute values of @LHsRecField GhcPs (Located b)@. They
    apply in the context of record construction, record updates, record
    patterns and record expressions. That is, @b@ ranges over @HsExpr
    GhcPs@, @HsPat GhcPs@ and @HsCmd GhcPs@.

    When @OverloadedRecordDot@ and @OverloadedRecordUpdate@ are both
    enabled, two additional @fbind@ rules are admitted:
    @
            | field TIGHT_INFIX_PROJ fieldToUpdate '=' texp
            | field TIGHT_INFIX_PROJ fieldToUpdate
    @

    These rules only make sense when parsing record update expressions
    (that is, patterns and commands cannot be parsed by these rules and
    neither record constructions).

    The results of these new rules cannot be represented by @LHsRecField
    GhcPs (LHsExpr GhcPs)@ values as the type is defined today. We
    minimize modifying existing code by having these new rules calculate
    @LHsRecProj GhcPs (LHsExpr GhcPs)@ ("record projection") values
    instead:
    @
    newtype FieldLabelStrings = FieldLabelStrings [XRec p (DotFieldOcc p)]
    type RecProj arg = HsFieldBind FieldLabelStrings arg
    type LHsRecProj p arg = XRec p (RecProj arg)
    @

    The @fbind@ rule is then given the type @fbind :: { forall b.
    DisambECP b => PV (Fbind b) }@ accommodating both alternatives:
    @
    type Fbind b = Either
                      (LHsRecField GhcPs (LocatedA b))
                      ( LHsRecProj GhcPs (LocatedA b))
    @

    In @data HsExpr p@, the @RecordUpd@ constuctor indicates regular
    updates vs. projection updates by means of the @rupd_flds@ member
    type, an @Either@ instance:
    @
      | RecordUpd
          { rupd_ext  :: XRecordUpd p
          , rupd_expr :: LHsExpr p
          , rupd_flds :: Either [LHsRecUpdField p] [LHsRecUpdProj p]
          }
    @
    Here,
    @
    type RecUpdProj p = RecProj p (LHsExpr p)
    type LHsRecUpdProj p = XRec p (RecUpdProj p)
    @
    and @Left@ values indicating regular record update, @Right@ values
    updates desugared to @setField@s.

    If @OverloadedRecordUpdate@ is enabled, any updates parsed as
    @LHsRecField GhcPs@ values are converted to @LHsRecUpdProj GhcPs@
    values (see function @mkRdrRecordUpd@ in 'GHC.Parser.PostProcess').
    -}

    -- | RecordDotSyntax field updates

    type LFieldLabelStrings p = XRec p (FieldLabelStrings p)

    newtype FieldLabelStrings p =
      FieldLabelStrings [XRec p (DotFieldOcc p)]

    -- Field projection updates (e.g. @foo.bar.baz = 1@). See Note
    -- [RecordDotSyntax field updates].
    type RecProj p arg = HsFieldBind (LFieldLabelStrings p) arg

    -- The phantom type parameter @p@ is for symmetry with @LHsRecField p
    -- arg@ in the definition of @data Fbind@ (see GHC.Parser.Process).
    type LHsRecProj p arg = XRec p (RecProj p arg)

    -- These two synonyms are used in the definition of syntax @RecordUpd@
    -- below.
    type RecUpdProj p = RecProj p (LHsExpr p)
    type LHsRecUpdProj p = XRec p (RecUpdProj p)

    -- | Haskell Record Update Fields.
    data LHsRecUpdFields p where
      -- | A regular (non-overloaded) record update.
      RegularRecUpdFields
        :: { forall p. LHsRecUpdFields p -> XLHsRecUpdLabels p
    xRecUpdFields :: XLHsRecUpdLabels p
           , forall p. LHsRecUpdFields p -> [LHsRecUpdField p p]
    recUpdFields  :: [LHsRecUpdField p p] }
        -> LHsRecUpdFields p
      -- | An overloaded record update.
      OverloadedRecUpdFields
        :: { forall p. LHsRecUpdFields p -> XLHsOLRecUpdLabels p
    xOLRecUpdFields :: XLHsOLRecUpdLabels p
           , forall p. LHsRecUpdFields p -> [LHsRecUpdProj p]
    olRecUpdFields  :: [LHsRecUpdProj p] }
        -> LHsRecUpdFields p

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Expressions proper}
    *                                                                      *
    ************************************************************************
    -}

    -- * Expressions proper

    -- | Located Haskell Expression
    type LHsExpr p = XRec p (HsExpr p)
      -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma' when
      --   in a list

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

    -------------------------
    {- Note [NoSyntaxExpr]
    ~~~~~~~~~~~~~~~~~~~~~~
    Syntax expressions can be missing (NoSyntaxExprRn or NoSyntaxExprTc)
    for several reasons:

     1. As described in Note [Rebindable if]

     2. In order to suppress "not in scope: xyz" messages when a bit of
        rebindable syntax does not apply. For example, when using an irrefutable
        pattern in a BindStmt, we don't need a `fail` operator.

     3. Rebindable syntax might just not make sense. For example, a BodyStmt
        contains the syntax for `guard`, but that's used only in monad comprehensions.
        If we had more of a whiz-bang type system, we might be able to rule this
        case out statically.
    -}

    -- | Syntax Expression
    --
    -- SyntaxExpr is represents the function used in interpreting rebindable
    -- syntax. In the parser, we have no information to supply; in the renamer,
    -- we have the name of the function (but see
    -- Note [Monad fail : Rebindable syntax, overloaded strings] for a wrinkle)
    -- and in the type-checker we have a more elaborate structure 'SyntaxExprTc'.
    --
    -- In some contexts, rebindable syntax is not implemented, and so we have
    -- constructors to represent that possibility in both the renamer and
    -- typechecker instantiations.
    --
    -- E.g. @(>>=)@ is filled in before the renamer by the appropriate 'Name' for
    --      @(>>=)@, and then instantiated by the type checker with its type args
    --      etc
    type family SyntaxExpr p

    {-
    Note [Record selectors in the AST]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Here is how record selectors are expressed in GHC's AST:

    Example data type
      data T = MkT { size :: Int }

    Record selectors:
                          |    GhcPs     |   GhcRn              |    GhcTc            |
    ----------------------------------------------------------------------------------|
    size (assuming one    | HsVar        | HsRecSel             | HsRecSel            |
         'size' in scope) |              |                      |                     |
    ----------------------|--------------|----------------------|---------------------|
    .size (assuming       | HsProjection | getField @"size"     | getField @"size"    |
     OverloadedRecordDot) |              |                      |                     |
    ----------------------|--------------|----------------------|---------------------|
    e.size (assuming      | HsGetField   | getField @"size" e   | getField @"size" e  |
     OverloadedRecordDot) |              |                      |                     |

    NB 1: DuplicateRecordFields makes no difference to the first row of
    this table, except that if 'size' is a field of more than one data
    type, then a naked use of the record selector 'size' may well be
    ambiguous. You have to use a qualified name. And there is no way to do
    this if both data types are declared in the same module.

    NB 2: The notation getField @"size" e is short for
    HsApp (HsAppType (HsVar "getField") (HsWC (HsTyLit (HsStrTy "size")) [])) e.
    We track the original parsed syntax via ExpandedThingRn.

    -}

    {-
    Note [Non-overloaded record field selectors]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Consider
        data T = MkT { x,y :: Int }
        f r x = x + y r

    This parses with HsVar for x, y, r on the RHS of f. Later, the renamer
    recognises that y in the RHS of f is really a record selector, and
    changes it to a HsRecSel. In contrast x is locally bound, shadowing
    the record selector, and stays as an HsVar.

    The renamer adds the Name of the record selector into the XCFieldOcc
    extension field, The typechecker keeps HsRecSel as HsRecSel, and
    transforms the record-selector Name to an Id.
    -}

    -- | A Haskell expression.
    data HsExpr p
      = HsVar     (XVar p)
                  (LIdP p) -- ^ Variable
                           -- See Note [Located RdrNames]

      | HsUnboundVar (XUnboundVar p)
                     RdrName     -- ^ Unbound variable; also used for "holes"
                                 --   (_ or _x).
                                 -- Turned from HsVar to HsUnboundVar by the
                                 --   renamer, when it finds an out-of-scope
                                 --   variable or hole.
                                 -- The (XUnboundVar p) field becomes an HoleExprRef
                                 --   after typechecking; this is where the
                                 --   erroring expression will be written after
                                 --   solving. See Note [Holes] in GHC.Tc.Types.Constraint.

      | HsRecSel  (XRecSel p)
                  (FieldOcc p) -- ^ Variable pointing to record selector
                               -- See Note [Non-overloaded record field selectors] and
                               -- Note [Record selectors in the AST]

      | HsOverLabel (XOverLabel p) SourceText FastString
         -- ^ Overloaded label (Note [Overloaded labels] in GHC.OverloadedLabels)
         -- Note [Pragma source text] in GHC.Types.SourceText

      | HsIPVar   (XIPVar p)
                  HsIPName   -- ^ Implicit parameter (not in use after typechecking)
      | HsOverLit (XOverLitE p)
                  (HsOverLit p)  -- ^ Overloaded literals

      | HsLit     (XLitE p)
                  (HsLit p)      -- ^ Simple (non-overloaded) literals

      -- | Lambda, Lambda-case, and Lambda-cases
      --
      -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam',
      --           'GHC.Parser.Annotation.AnnCase','GHC.Parser.Annotation.AnnOpen',
      --           'GHC.Parser.Annotation.AnnClose'
      -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam',
      --           'GHC.Parser.Annotation.AnnCases','GHC.Parser.Annotation.AnnOpen',
      --           'GHC.Parser.Annotation.AnnClose'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsLam     (XLam p)
                  HsLamVariant -- ^ Tells whether this is for lambda, \case, or \cases
                  (MatchGroup p (LHsExpr p))
                           -- ^ LamSingle: one match of arity >= 1
                           --   LamCase: many arity-1 matches
                           --   LamCases: many matches of uniform arity >= 1
           --
           -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam',
           --       'GHC.Parser.Annotation.AnnRarrow',

           -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      | HsApp     (XApp p) (LHsExpr p) (LHsExpr p) -- ^ Application

      | HsAppType (XAppTypeE p) -- After typechecking: the type argument
                  (LHsExpr p)
                  (LHsWcType (NoGhcTc p))  -- ^ Visible type application
           --
           -- Explicit type argument; e.g  f @Int x y
           -- NB: Has wildcards, but no implicit quantification
           --
           -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnAt',

      -- | Operator applications:
      -- NB Bracketed ops such as (+) come out as Vars.

      -- NB Sadly, we need an expr for the operator in an OpApp/Section since
      -- the renamer may turn a HsVar into HsRecSel or HsUnboundVar

      | OpApp       (XOpApp p)
                    (LHsExpr p)       -- left operand
                    (LHsExpr p)       -- operator
                    (LHsExpr p)       -- right operand

      -- | Negation operator. Contains the negated expression and the name
      -- of 'negate'
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnMinus'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | NegApp      (XNegApp p)
                    (LHsExpr p)
                    (SyntaxExpr p)

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@,
      --             'GHC.Parser.Annotation.AnnClose' @')'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsPar       (XPar p)
                    (LHsExpr p)  -- ^ Parenthesised expr; see Note [Parens in HsSyn]

      | SectionL    (XSectionL p)
                    (LHsExpr p)    -- operand; see Note [Sections in HsSyn]
                    (LHsExpr p)    -- operator
      | SectionR    (XSectionR p)
                    (LHsExpr p)    -- operator; see Note [Sections in HsSyn]
                    (LHsExpr p)    -- operand

      -- | Used for explicit tuples and sections thereof
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen',
      --         'GHC.Parser.Annotation.AnnClose'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      -- Note [ExplicitTuple]
      | ExplicitTuple
            (XExplicitTuple p)
            [HsTupArg p]
            Boxity

      -- | Used for unboxed sum types
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'(#'@,
      --          'GHC.Parser.Annotation.AnnVbar', 'GHC.Parser.Annotation.AnnClose' @'#)'@,
      --
      --  There will be multiple 'GHC.Parser.Annotation.AnnVbar', (1 - alternative) before
      --  the expression, (arity - alternative) after it
      | ExplicitSum
              (XExplicitSum p)
              ConTag   --  Alternative (one-based)
              SumWidth --  Sum arity
              (LHsExpr p)

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnCase',
      --       'GHC.Parser.Annotation.AnnOf','GHC.Parser.Annotation.AnnOpen' @'{'@,
      --       'GHC.Parser.Annotation.AnnClose' @'}'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsCase      (XCase p)
                    (LHsExpr p)
                    (MatchGroup p (LHsExpr p))

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnIf',
      --       'GHC.Parser.Annotation.AnnSemi',
      --       'GHC.Parser.Annotation.AnnThen','GHC.Parser.Annotation.AnnSemi',
      --       'GHC.Parser.Annotation.AnnElse',

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsIf        (XIf p)        -- GhcPs: this is a Bool; False <=> do not use
                                   --  rebindable syntax
                    (LHsExpr p)    --  predicate
                    (LHsExpr p)    --  then part
                    (LHsExpr p)    --  else part

      -- | Multi-way if
      --
      -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnIf'
      --       'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose',

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsMultiIf   (XMultiIf p) [LGRHS p (LHsExpr p)]

      -- | let(rec)
      --
      -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLet',
      --       'GHC.Parser.Annotation.AnnOpen' @'{'@,
      --       'GHC.Parser.Annotation.AnnClose' @'}'@,'GHC.Parser.Annotation.AnnIn'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsLet       (XLet p)
                    (HsLocalBinds p)
                    (LHsExpr  p)

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDo',
      --             'GHC.Parser.Annotation.AnnOpen', 'GHC.Parser.Annotation.AnnSemi',
      --             'GHC.Parser.Annotation.AnnVbar',
      --             'GHC.Parser.Annotation.AnnClose'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsDo        (XDo p)                  -- Type of the whole expression
                    HsDoFlavour
                    (XRec p [ExprLStmt p])   -- "do":one or more stmts

      -- | Syntactic list: [a,b,c,...]
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'['@,
      --              'GHC.Parser.Annotation.AnnClose' @']'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      -- See Note [Empty lists]
      | ExplicitList
                    (XExplicitList p)  -- Gives type of components of list
                    [LHsExpr p]

      -- | Record construction
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'{'@,
      --         'GHC.Parser.Annotation.AnnDotdot','GHC.Parser.Annotation.AnnClose' @'}'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | RecordCon
          { forall p. HsExpr p -> XRecordCon p
    rcon_ext  :: XRecordCon p
          , forall p. HsExpr p -> XRec p (ConLikeP p)
    rcon_con  :: XRec p (ConLikeP p)  -- The constructor
          , forall p. HsExpr p -> HsRecordBinds p
    rcon_flds :: HsRecordBinds p }    -- The fields

      -- | Record update
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'{'@,
      --         'GHC.Parser.Annotation.AnnDotdot','GHC.Parser.Annotation.AnnClose' @'}'@
      --         'GHC.Parser.Annotation.AnnComma, 'GHC.Parser.Annotation.AnnDot',
      --         'GHC.Parser.Annotation.AnnClose' @'}'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | RecordUpd
          { forall p. HsExpr p -> XRecordUpd p
    rupd_ext  :: XRecordUpd p
          , forall p. HsExpr p -> LHsExpr p
    rupd_expr :: LHsExpr p
          , forall p. HsExpr p -> LHsRecUpdFields p
    rupd_flds :: LHsRecUpdFields p
          }
      -- For a type family, the arg types are of the *instance* tycon,
      -- not the family tycon

      -- | Record field selection e.g @z.x@.
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDot'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      -- This case only arises when the OverloadedRecordDot langauge
      -- extension is enabled. See Note [Record selectors in the AST].
      | HsGetField {
            forall p. HsExpr p -> XGetField p
    gf_ext :: XGetField p
          , forall p. HsExpr p -> LHsExpr p
    gf_expr :: LHsExpr p
          , forall p. HsExpr p -> XRec p (DotFieldOcc p)
    gf_field :: XRec p (DotFieldOcc p)
          }

      -- | Record field selector. e.g. @(.x)@ or @(.x.y)@
      --
      -- This case only arises when the OverloadedRecordDot langauge
      -- extensions is enabled. See Note [Record selectors in the AST].

      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpenP'
      --         'GHC.Parser.Annotation.AnnDot', 'GHC.Parser.Annotation.AnnCloseP'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsProjection {
            forall p. HsExpr p -> XProjection p
    proj_ext :: XProjection p
          , forall p. HsExpr p -> NonEmpty (XRec p (DotFieldOcc p))
    proj_flds :: NonEmpty (XRec p (DotFieldOcc p))
          }

      -- | Expression with an explicit type signature. @e :: type@
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDcolon'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | ExprWithTySig
                    (XExprWithTySig p)

                    (LHsExpr p)
                    (LHsSigWcType (NoGhcTc p))

      -- | Arithmetic sequence
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'['@,
      --              'GHC.Parser.Annotation.AnnComma','GHC.Parser.Annotation.AnnDotdot',
      --              'GHC.Parser.Annotation.AnnClose' @']'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | ArithSeq
                    (XArithSeq p)
                    (Maybe (SyntaxExpr p))
                                      -- For OverloadedLists, the fromList witness
                    (ArithSeqInfo p)

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      -----------------------------------------------------------
      -- MetaHaskell Extensions

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen',
      --         'GHC.Parser.Annotation.AnnOpenE','GHC.Parser.Annotation.AnnOpenEQ',
      --         'GHC.Parser.Annotation.AnnClose','GHC.Parser.Annotation.AnnCloseQ'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsTypedBracket   (XTypedBracket p)   (LHsExpr p)
      | HsUntypedBracket (XUntypedBracket p) (HsQuote p)

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen',
      --         'GHC.Parser.Annotation.AnnClose'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsTypedSplice    (XTypedSplice p)   (LHsExpr p) -- `$$z` or `$$(f 4)`
      | HsUntypedSplice  (XUntypedSplice p) (HsUntypedSplice p)

      -----------------------------------------------------------
      -- Arrow notation extension

      -- | @proc@ notation for Arrows
      --
      --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnProc',
      --          'GHC.Parser.Annotation.AnnRarrow'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsProc      (XProc p)
                    (LPat p)               -- arrow abstraction, proc
                    (LHsCmdTop p)          -- body of the abstraction
                                           -- always has an empty stack

      ---------------------------------------
      -- static pointers extension
      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnStatic',

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsStatic (XStatic p) -- Free variables of the body, and type after typechecking
                 (LHsExpr p)        -- Body

      ---------------------------------------
      -- Expressions annotated with pragmas, written as {-# ... #-}
      | HsPragE (XPragE p) (HsPragE p) (LHsExpr p)

      -- Embed the syntax of types into expressions.
      -- Used with RequiredTypeArguments, e.g. fn (type (Int -> Bool))
      | HsEmbTy   (XEmbTy p)
                  (LHsWcType (NoGhcTc p))

      | XExpr       !(XXExpr p)
      -- Note [Trees That Grow] in Language.Haskell.Syntax.Extension for the
      -- general idea, and Note [Rebindable syntax and XXExprGhcRn] in GHC.Hs.Expr
      -- for an example of how we use it.

    -- ---------------------------------------------------------------------

    data DotFieldOcc p
      = DotFieldOcc
        { forall p. DotFieldOcc p -> XCDotFieldOcc p
    dfoExt   :: XCDotFieldOcc p
        , forall p. DotFieldOcc p -> XRec p FieldLabelString
    dfoLabel :: XRec p FieldLabelString
        }
      | XDotFieldOcc !(XXDotFieldOcc p)

    -- ---------------------------------------------------------------------

    -- | A pragma, written as {-# ... #-}, that may appear within an expression.
    data HsPragE p
      = HsPragSCC   (XSCC p)
                    StringLiteral         -- "set cost centre" SCC pragma

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen',
      --       'GHC.Parser.Annotation.AnnOpen' @'{-\# GENERATED'@,
      --       'GHC.Parser.Annotation.AnnVal','GHC.Parser.Annotation.AnnVal',
      --       'GHC.Parser.Annotation.AnnColon','GHC.Parser.Annotation.AnnVal',
      --       'GHC.Parser.Annotation.AnnMinus',
      --       'GHC.Parser.Annotation.AnnVal','GHC.Parser.Annotation.AnnColon',
      --       'GHC.Parser.Annotation.AnnVal',
      --       'GHC.Parser.Annotation.AnnClose' @'\#-}'@

      | XHsPragE !(XXPragE p)

    -- | Located Haskell Tuple Argument
    --
    -- 'HsTupArg' is used for tuple sections
    -- @(,a,)@ is represented by
    -- @ExplicitTuple [Missing ty1, Present a, Missing ty3]@
    -- Which in turn stands for @(\x:ty1 \y:ty2. (x,a,y))@
    type LHsTupArg id = XRec id (HsTupArg id)
    -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnComma'

    -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

    -- | Haskell Tuple Argument
    data HsTupArg id
      = Present (XPresent id) (LHsExpr id)     -- ^ The argument
      | Missing (XMissing id)    -- ^ The argument is missing, but this is its type
      | XTupArg !(XXTupArg id)   -- ^ Extension point; see Note [Trees That Grow]
                                 -- in Language.Haskell.Syntax.Extension

    -- | Which kind of lambda case are we dealing with?
    data HsLamVariant
      = LamSingle  -- ^ `\p -> e`
      | LamCase    -- ^ `\case pi -> ei `
      | LamCases   -- ^ `\cases psi -> ei`
      deriving (Typeable HsLamVariant
    Typeable HsLamVariant =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> HsLamVariant -> c HsLamVariant)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c HsLamVariant)
    -> (HsLamVariant -> Constr)
    -> (HsLamVariant -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c HsLamVariant))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e))
        -> Maybe (c HsLamVariant))
    -> ((forall b. Data b => b -> b) -> HsLamVariant -> HsLamVariant)
    -> (forall r r'.
        (r -> r' -> r)
        -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r)
    -> (forall r r'.
        (r' -> r -> r)
        -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r)
    -> (forall u. (forall d. Data d => d -> u) -> HsLamVariant -> [u])
    -> (forall u.
        Int -> (forall d. Data d => d -> u) -> HsLamVariant -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant)
    -> Data HsLamVariant
    HsLamVariant -> Constr
    HsLamVariant -> DataType
    (forall b. Data b => b -> b) -> HsLamVariant -> HsLamVariant
    forall a.
    Typeable a =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> a -> c a)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c a)
    -> (a -> Constr)
    -> (a -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c a))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a))
    -> ((forall b. Data b => b -> b) -> a -> a)
    -> (forall r r'.
        (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall r r'.
        (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall u. (forall d. Data d => d -> u) -> a -> [u])
    -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> Data a
    forall u. Int -> (forall d. Data d => d -> u) -> HsLamVariant -> u
    forall u. (forall d. Data d => d -> u) -> HsLamVariant -> [u]
    forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r
    forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r
    forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsLamVariant
    forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsLamVariant -> c HsLamVariant
    forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsLamVariant)
    forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsLamVariant)
    $cgfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsLamVariant -> c HsLamVariant
    gfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsLamVariant -> c HsLamVariant
    $cgunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsLamVariant
    gunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsLamVariant
    $ctoConstr :: HsLamVariant -> Constr
    toConstr :: HsLamVariant -> Constr
    $cdataTypeOf :: HsLamVariant -> DataType
    dataTypeOf :: HsLamVariant -> DataType
    $cdataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsLamVariant)
    dataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsLamVariant)
    $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsLamVariant)
    dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsLamVariant)
    $cgmapT :: (forall b. Data b => b -> b) -> HsLamVariant -> HsLamVariant
    gmapT :: (forall b. Data b => b -> b) -> HsLamVariant -> HsLamVariant
    $cgmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r
    gmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r
    $cgmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r
    gmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsLamVariant -> r
    $cgmapQ :: forall u. (forall d. Data d => d -> u) -> HsLamVariant -> [u]
    gmapQ :: forall u. (forall d. Data d => d -> u) -> HsLamVariant -> [u]
    $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsLamVariant -> u
    gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsLamVariant -> u
    $cgmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    gmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    $cgmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    gmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    $cgmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    gmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsLamVariant -> m HsLamVariant
    Data, HsLamVariant -> HsLamVariant -> Bool
    (HsLamVariant -> HsLamVariant -> Bool)
    -> (HsLamVariant -> HsLamVariant -> Bool) -> Eq HsLamVariant
    forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
    $c== :: HsLamVariant -> HsLamVariant -> Bool
    == :: HsLamVariant -> HsLamVariant -> Bool
    $c/= :: HsLamVariant -> HsLamVariant -> Bool
    /= :: HsLamVariant -> HsLamVariant -> Bool
    Eq)

    {-
    Note [Parens in HsSyn]
    ~~~~~~~~~~~~~~~~~~~~~~
    HsPar (and ParPat in patterns, HsParTy in types) is used as follows

      * HsPar is required; the pretty printer does not add parens.

      * HsPars are respected when rearranging operator fixities.
        So   a * (b + c)  means what it says (where the parens are an HsPar)

      * For ParPat and HsParTy the pretty printer does add parens but this should be
        a no-op for ParsedSource, based on the pretty printer round trip feature
        introduced in
        https://phabricator.haskell.org/rGHC499e43824bda967546ebf95ee33ec1f84a114a7c

      * ParPat and HsParTy are pretty printed as '( .. )' regardless of whether or
        not they are strictly necessary. This should be addressed when #13238 is
        completed, to be treated the same as HsPar.

    Note [Sections in HsSyn]
    ~~~~~~~~~~~~~~~~~~~~~~~~
    Sections should always appear wrapped in an HsPar, thus
             HsPar (SectionR ...)
    The parser parses sections in a wider variety of situations
    (See Note [Parsing sections]), but the renamer checks for those
    parens.  This invariant makes pretty-printing easier; we don't need
    a special case for adding the parens round sections.

    Note [Rebindable if]
    ~~~~~~~~~~~~~~~~~~~~
    The rebindable syntax for 'if' is a bit special, because when
    rebindable syntax is *off* we do not want to treat
       (if c then t else e)
    as if it was an application (ifThenElse c t e).  Why not?
    Because we allow an 'if' to return *unboxed* results, thus
      if blah then 3# else 4#
    whereas that would not be possible using a all to a polymorphic function
    (because you can't call a polymorphic function at an unboxed type).

    So we use NoSyntaxExpr to mean "use the old built-in typing rule".

    A further complication is that, in the `deriving` code, we never want
    to use rebindable syntax. So, even in GhcPs, we want to denote whether
    to use rebindable syntax or not. This is done via the type instance
    for XIf GhcPs.

    Note [Record Update HsWrapper]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    There is a wrapper in RecordUpd which is used for the *required*
    constraints for pattern synonyms. This wrapper is created in the
    typechecking and is then directly used in the desugaring without
    modification.

    For example, if we have the record pattern synonym P,
      pattern P :: (Show a) => a -> Maybe a
      pattern P{x} = Just x

      foo = (Just True) { x = False }
    then `foo` desugars to something like
      foo = case Just True of
              P x -> P False
    hence we need to provide the correct dictionaries to P's matcher on
    the RHS so that we can build the expression.

    Note [Located RdrNames]
    ~~~~~~~~~~~~~~~~~~~~~~~
    A number of syntax elements have seemingly redundant locations
    attached to them.  This is deliberate, to allow transformations making
    use of the exact print annotations to easily correlate a Located Name
    in the RenamedSource with a Located RdrName in the ParsedSource.

    There are unfortunately enough differences between the ParsedSource
    and the RenamedSource that the exact print annotations cannot be used
    directly with RenamedSource, so this allows a simple mapping to be
    used based on the location.

    Note [ExplicitTuple]
    ~~~~~~~~~~~~~~~~~~~~
    An ExplicitTuple is never just a data constructor like (,,,).
    That is, the `[LHsTupArg p]` argument of `ExplicitTuple` has at least
    one `Present` member (and is thus never empty).

    A tuple data constructor like () or (,,,) is parsed as an `HsVar`, not an
    `ExplicitTuple`, and stays that way. This is important for two reasons:

      1. We don't need -XTupleSections for (,,,)
      2. The type variables in (,,,) can be instantiated with visible type application.
         That is,

           (,,)     :: forall a b c. a -> b -> c -> (a,b,c)
           (True,,) :: forall {b} {c}. b -> c -> (Bool,b,c)

         Note that the tuple section has *inferred* arguments, while the data
         constructor has *specified* ones.
         (See Note [Required, Specified, and Inferred for types] in GHC.Tc.TyCl
         for background.)

    Sadly, the grammar for this is actually ambiguous, and it's only thanks to the
    preference of a shift in a shift/reduce conflict that the parser works as this
    Note details. Search for a reference to this Note in GHC.Parser for further
    explanation.

    Note [Empty lists]
    ~~~~~~~~~~~~~~~~~~
    An empty list could be considered either a data constructor (stored with
    HsVar) or an ExplicitList. This Note describes how empty lists flow through the
    various phases and why.

    Parsing
    -------
    An empty list is parsed by the sysdcon nonterminal. It thus comes to life via
    HsVar nilDataCon (defined in GHC.Builtin.Types). A freshly-parsed (HsExpr GhcPs) empty list
    is never a ExplicitList.

    Renaming
    --------
    If -XOverloadedLists is enabled, we must type-check the empty list as if it
    were a call to fromListN. (This is true regardless of the setting of
    -XRebindableSyntax.) This is very easy if the empty list is an ExplicitList,
    but an annoying special case if it's an HsVar. So the renamer changes a
    HsVar nilDataCon to an ExplicitList [], but only if -XOverloadedLists is on.
    (Why not always? Read on, dear friend.) This happens in the HsVar case of rnExpr.

    Type-checking
    -------------
    We want to accept an expression like [] @Int. To do this, we must infer that
    [] :: forall a. [a]. This is easy if [] is a HsVar with the right DataCon inside.
    However, the type-checking for explicit lists works differently: [x,y,z] is never
    polymorphic. Instead, we unify the types of x, y, and z together, and use the
    unified type as the argument to the cons and nil constructors. Thus, treating
    [] as an empty ExplicitList in the type-checker would prevent [] @Int from working.

    However, if -XOverloadedLists is on, then [] @Int really shouldn't be allowed:
    it's just like fromListN 0 [] @Int. Since
      fromListN :: forall list. IsList list => Int -> [Item list] -> list
    that expression really should be rejected. Thus, the renamer's behaviour is
    exactly what we want: treat [] as a datacon when -XNoOverloadedLists, and as
    an empty ExplicitList when -XOverloadedLists.

    See also #13680, which requested [] @Int to work.
    -}

    {-
    HsSyn records exactly where the user put parens, with HsPar.
    So generally speaking we print without adding any parens.
    However, some code is internally generated, and in some places
    parens are absolutely required; so for these places we use
    pprParendLExpr (but don't print double parens of course).

    For operator applications we don't add parens, because the operator
    fixities should do the job, except in debug mode (-dppr-debug) so we
    can see the structure of the parse tree.
    -}

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Commands (in arrow abstractions)}
    *                                                                      *
    ************************************************************************

    We re-use HsExpr to represent these.
    -}

    -- | Located Haskell Command (for arrow syntax)
    type LHsCmd id = XRec id (HsCmd id)

    -- | Haskell Command (e.g. a "statement" in an Arrow proc block)
    data HsCmd id
      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.Annlarrowtail',
      --          'GHC.Parser.Annotation.Annrarrowtail','GHC.Parser.Annotation.AnnLarrowtail',
      --          'GHC.Parser.Annotation.AnnRarrowtail'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      = HsCmdArrApp          -- Arrow tail, or arrow application (f -< arg)
            (XCmdArrApp id)  -- type of the arrow expressions f,
                             -- of the form a t t', where arg :: t
            (LHsExpr id)     -- arrow expression, f
            (LHsExpr id)     -- input expression, arg
            HsArrAppType     -- higher-order (-<<) or first-order (-<)
            Bool             -- True => right-to-left (f -< arg)
                             -- False => left-to-right (arg >- f)

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpenB' @'(|'@,
      --         'GHC.Parser.Annotation.AnnCloseB' @'|)'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsCmdArrForm         -- Command formation,  (| e cmd1 .. cmdn |)
            (XCmdArrForm id)
            (LHsExpr id)     -- The operator.
                             -- After type-checking, a type abstraction to be
                             -- applied to the type of the local environment tuple
            LexicalFixity    -- Whether the operator appeared prefix or infix when
                             -- parsed.
            (Maybe Fixity)   -- fixity (filled in by the renamer), for forms that
                             -- were converted from OpApp's by the renamer
            [LHsCmdTop id]   -- argument commands

      | HsCmdApp    (XCmdApp id)
                    (LHsCmd id)
                    (LHsExpr id)

      -- | Lambda-case
      --
      -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam',
      --     'GHC.Parser.Annotation.AnnCase','GHC.Parser.Annotation.AnnOpen' @'{'@,
      --     'GHC.Parser.Annotation.AnnClose' @'}'@
      -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLam',
      --     'GHC.Parser.Annotation.AnnCases','GHC.Parser.Annotation.AnnOpen' @'{'@,
      --     'GHC.Parser.Annotation.AnnClose' @'}'@

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | HsCmdLam (XCmdLamCase id) HsLamVariant
                 (MatchGroup id (LHsCmd id)) -- bodies are HsCmd's

      | HsCmdPar    (XCmdPar id)
                    (LHsCmd id)                     -- parenthesised command
        -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnOpen' @'('@,
        --             'GHC.Parser.Annotation.AnnClose' @')'@

        -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      | HsCmdCase   (XCmdCase id)
                    (LHsExpr id)
                    (MatchGroup id (LHsCmd id))     -- bodies are HsCmd's
        -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnCase',
        --       'GHC.Parser.Annotation.AnnOf','GHC.Parser.Annotation.AnnOpen' @'{'@,
        --       'GHC.Parser.Annotation.AnnClose' @'}'@

        -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      | HsCmdIf     (XCmdIf id)
                    (SyntaxExpr id)         -- cond function
                    (LHsExpr id)            -- predicate
                    (LHsCmd id)             -- then part
                    (LHsCmd id)             -- else part
        -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnIf',
        --       'GHC.Parser.Annotation.AnnSemi',
        --       'GHC.Parser.Annotation.AnnThen','GHC.Parser.Annotation.AnnSemi',
        --       'GHC.Parser.Annotation.AnnElse',

        -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      | HsCmdLet    (XCmdLet id)
                    (HsLocalBinds id)      -- let(rec)
                    (LHsCmd  id)
        -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLet',
        --       'GHC.Parser.Annotation.AnnOpen' @'{'@,
        --       'GHC.Parser.Annotation.AnnClose' @'}'@,'GHC.Parser.Annotation.AnnIn'

        -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      | HsCmdDo     (XCmdDo id)                     -- Type of the whole expression
                    (XRec id [CmdLStmt id])
        -- ^ - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnDo',
        --             'GHC.Parser.Annotation.AnnOpen', 'GHC.Parser.Annotation.AnnSemi',
        --             'GHC.Parser.Annotation.AnnVbar',
        --             'GHC.Parser.Annotation.AnnClose'

        -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation

      | XCmd        !(XXCmd id)     -- Extension point; see Note [Trees That Grow]
                                    -- in Language.Haskell.Syntax.Extension

    -- | Haskell arrow application type.
    data HsArrAppType
      -- | First order arrow application '-<'
      = HsHigherOrderApp
      -- | Higher order arrow application '-<<'
      | HsFirstOrderApp
        deriving Typeable HsArrAppType
    Typeable HsArrAppType =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> HsArrAppType -> c HsArrAppType)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c HsArrAppType)
    -> (HsArrAppType -> Constr)
    -> (HsArrAppType -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c HsArrAppType))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e))
        -> Maybe (c HsArrAppType))
    -> ((forall b. Data b => b -> b) -> HsArrAppType -> HsArrAppType)
    -> (forall r r'.
        (r -> r' -> r)
        -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r)
    -> (forall r r'.
        (r' -> r -> r)
        -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r)
    -> (forall u. (forall d. Data d => d -> u) -> HsArrAppType -> [u])
    -> (forall u.
        Int -> (forall d. Data d => d -> u) -> HsArrAppType -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType)
    -> Data HsArrAppType
    HsArrAppType -> Constr
    HsArrAppType -> DataType
    (forall b. Data b => b -> b) -> HsArrAppType -> HsArrAppType
    forall a.
    Typeable a =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> a -> c a)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c a)
    -> (a -> Constr)
    -> (a -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c a))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a))
    -> ((forall b. Data b => b -> b) -> a -> a)
    -> (forall r r'.
        (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall r r'.
        (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall u. (forall d. Data d => d -> u) -> a -> [u])
    -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> Data a
    forall u. Int -> (forall d. Data d => d -> u) -> HsArrAppType -> u
    forall u. (forall d. Data d => d -> u) -> HsArrAppType -> [u]
    forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r
    forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r
    forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsArrAppType
    forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsArrAppType -> c HsArrAppType
    forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsArrAppType)
    forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsArrAppType)
    $cgfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsArrAppType -> c HsArrAppType
    gfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsArrAppType -> c HsArrAppType
    $cgunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsArrAppType
    gunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsArrAppType
    $ctoConstr :: HsArrAppType -> Constr
    toConstr :: HsArrAppType -> Constr
    $cdataTypeOf :: HsArrAppType -> DataType
    dataTypeOf :: HsArrAppType -> DataType
    $cdataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsArrAppType)
    dataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsArrAppType)
    $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsArrAppType)
    dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsArrAppType)
    $cgmapT :: (forall b. Data b => b -> b) -> HsArrAppType -> HsArrAppType
    gmapT :: (forall b. Data b => b -> b) -> HsArrAppType -> HsArrAppType
    $cgmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r
    gmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r
    $cgmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r
    gmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsArrAppType -> r
    $cgmapQ :: forall u. (forall d. Data d => d -> u) -> HsArrAppType -> [u]
    gmapQ :: forall u. (forall d. Data d => d -> u) -> HsArrAppType -> [u]
    $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsArrAppType -> u
    gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsArrAppType -> u
    $cgmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    gmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    $cgmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    gmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    $cgmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    gmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsArrAppType -> m HsArrAppType
    Data

    {- | Top-level command, introducing a new arrow.
    This may occur inside a proc (where the stack is empty) or as an
    argument of a command-forming operator.
    -}

    -- | Located Haskell Top-level Command
    type LHsCmdTop p = XRec p (HsCmdTop p)

    -- | Haskell Top-level Command
    data HsCmdTop p
      = HsCmdTop (XCmdTop p)
                 (LHsCmd p)
      | XCmdTop !(XXCmdTop p)        -- Extension point; see Note [Trees That Grow]
                                     -- in Language.Haskell.Syntax.Extension

    -----------------------

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Record binds}
    *                                                                      *
    ************************************************************************
    -}

    -- | Haskell Record Bindings
    type HsRecordBinds p = HsRecFields p (LHsExpr p)

    {-
    ************************************************************************
    *                                                                      *
    \subsection{@Match@, @GRHSs@, and @GRHS@ datatypes}
    *                                                                      *
    ************************************************************************

    @Match@es are sets of pattern bindings and right hand sides for
    functions, patterns or case branches. For example, if a function @g@
    is defined as:
    \begin{verbatim}
    g (x,y) = y
    g ((x:ys),y) = y+1,
    \end{verbatim}
    then \tr{g} has two @Match@es: @(x,y) = y@ and @((x:ys),y) = y+1@.

    It is always the case that each element of an @[Match]@ list has the
    same number of @pats@s inside it.  This corresponds to saying that
    a function defined by pattern matching must have the same number of
    patterns in each equation.
    -}

    data MatchGroup p body
      = MG { forall p body. MatchGroup p body -> XMG p body
    mg_ext     :: XMG p body -- Post-typechecker, types of args and result, and origin
           , forall p body. MatchGroup p body -> XRec p [LMatch p body]
    mg_alts    :: XRec p [LMatch p body] } -- The alternatives
         -- The type is the type of the entire group
         --      t1 -> ... -> tn -> tr
         -- where there are n patterns
      | XMatchGroup !(XXMatchGroup p body)

    -- | Located Match
    type LMatch id body = XRec id (Match id body)
    -- ^ May have 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnSemi' when in a
    --   list

    -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
    data Match p body
      = Match {
            forall p body. Match p body -> XCMatch p body
    m_ext   :: XCMatch p body,
            forall p body. Match p body -> HsMatchContext (LIdP (NoGhcTc p))
    m_ctxt  :: HsMatchContext (LIdP (NoGhcTc p)), -- See Note [m_ctxt in Match]
            forall p body. Match p body -> [LPat p]
    m_pats  :: [LPat p],                          -- The patterns
            forall p body. Match p body -> GRHSs p body
    m_grhss :: (GRHSs p body)
      }
      | XMatch !(XXMatch p body)

    {-
    Note [m_ctxt in Match]
    ~~~~~~~~~~~~~~~~~~~~~~
    A Match can occur in a number of contexts, such as a FunBind, HsCase, HsLam and
    so on.

    In order to simplify tooling processing and pretty print output, the provenance
    is captured in an HsMatchContext.

    This is particularly important for the exact print annotations for a
    multi-equation FunBind.

    The parser initially creates a FunBind with a single Match in it for
    every function definition it sees.

    These are then grouped together by getMonoBind into a single FunBind,
    where all the Matches are combined.

    In the process, all the original FunBind fun_id's bar one are
    discarded, including the locations.

    This causes a problem for source to source conversions via exact print
    annotations, so the original fun_ids and infix flags are preserved in
    the Match, when it originates from a FunBind.

    Example infix function definition requiring individual exact print
    annotations

        (&&&  ) [] [] =  []
        xs    &&&   [] =  xs
        (  &&&  ) [] ys =  ys
    -}

    isInfixMatch :: Match id body -> Bool
    isInfixMatch :: forall id body. Match id body -> Bool
    isInfixMatch Match id body
    match = case Match id body -> HsMatchContext (LIdP (NoGhcTc id))
    forall p body. Match p body -> HsMatchContext (LIdP (NoGhcTc p))
    m_ctxt Match id body
    match of
      FunRhs {mc_fixity :: forall fn. HsMatchContext fn -> LexicalFixity
    mc_fixity = LexicalFixity
    Infix} -> Bool
    True
      HsMatchContext (LIdP (NoGhcTc id))
    _                          -> Bool
    False

    -- | Guarded Right-Hand Sides
    --
    -- GRHSs are used both for pattern bindings and for Matches
    --
    --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnVbar',
    --        'GHC.Parser.Annotation.AnnEqual','GHC.Parser.Annotation.AnnWhere',
    --        'GHC.Parser.Annotation.AnnOpen','GHC.Parser.Annotation.AnnClose'
    --        'GHC.Parser.Annotation.AnnRarrow','GHC.Parser.Annotation.AnnSemi'

    -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
    data GRHSs p body
      = GRHSs {
          forall p body. GRHSs p body -> XCGRHSs p body
    grhssExt :: XCGRHSs p body,
          forall p body. GRHSs p body -> [LGRHS p body]
    grhssGRHSs :: [LGRHS p body],     -- ^ Guarded RHSs
          forall p body. GRHSs p body -> HsLocalBinds p
    grhssLocalBinds :: HsLocalBinds p -- ^ The where clause
        }
      | XGRHSs !(XXGRHSs p body)

    -- | Located Guarded Right-Hand Side
    type LGRHS id body = XRec id (GRHS id body)

    -- | Guarded Right Hand Side.
    data GRHS p body = GRHS (XCGRHS p body)
                            [GuardLStmt p] -- Guards
                            body           -- Right hand side
                      | XGRHS !(XXGRHS p body)

    -- We know the list must have at least one @Match@ in it.

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Do stmts and list comprehensions}
    *                                                                      *
    ************************************************************************
    -}

    -- | Located @do@ block Statement
    type LStmt id body = XRec id (StmtLR id id body)

    -- | Located Statement with separate Left and Right id's
    type LStmtLR idL idR body = XRec idL (StmtLR idL idR body)

    -- | @do@ block Statement
    type Stmt id body = StmtLR id id body

    -- | Command Located Statement
    type CmdLStmt   id = LStmt id (LHsCmd  id)

    -- | Command Statement
    type CmdStmt    id = Stmt  id (LHsCmd  id)

    -- | Expression Located Statement
    type ExprLStmt  id = LStmt id (LHsExpr id)

    -- | Expression Statement
    type ExprStmt   id = Stmt  id (LHsExpr id)

    -- | Guard Located Statement
    type GuardLStmt id = LStmt id (LHsExpr id)

    -- | Guard Statement
    type GuardStmt  id = Stmt  id (LHsExpr id)

    -- | Ghci Located Statement
    type GhciLStmt  id = LStmt id (LHsExpr id)

    -- | Ghci Statement
    type GhciStmt   id = Stmt  id (LHsExpr id)

    -- The SyntaxExprs in here are used *only* for do-notation and monad
    -- comprehensions, which have rebindable syntax. Otherwise they are unused.
    -- | Exact print annotations when in qualifier lists or guards
    --  - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnVbar',
    --         'GHC.Parser.Annotation.AnnComma','GHC.Parser.Annotation.AnnThen',
    --         'GHC.Parser.Annotation.AnnBy','GHC.Parser.Annotation.AnnBy',
    --         'GHC.Parser.Annotation.AnnGroup','GHC.Parser.Annotation.AnnUsing'

    -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
    data StmtLR idL idR body -- body should always be (LHs**** idR)
      = LastStmt  -- Always the last Stmt in ListComp, MonadComp,
                  -- and (after the renamer, see GHC.Rename.Expr.checkLastStmt) DoExpr, MDoExpr
                  -- Not used for GhciStmtCtxt, PatGuard, which scope over other stuff
              (XLastStmt idL idR body)
              body
              (Maybe Bool)  -- Whether return was stripped
                -- Just True <=> return with a dollar was stripped by ApplicativeDo
                -- Just False <=> return without a dollar was stripped by ApplicativeDo
                -- Nothing <=> Nothing was stripped
              (SyntaxExpr idR)   -- The return operator
                -- The return operator is used only for MonadComp
                -- For ListComp we use the baked-in 'return'
                -- For DoExpr, MDoExpr, we don't apply a 'return' at all
                -- See Note [Monad Comprehensions]
                -- - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLarrow'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | BindStmt (XBindStmt idL idR body)
                 -- ^ Post renaming has optional fail and bind / (>>=) operator.
                 -- Post typechecking, also has multiplicity of the argument
                 -- and the result type of the function passed to bind;
                 -- that is, (P, S) in (>>=) :: Q -> (R % P -> S) -> T
                 -- See Note [The type of bind in Stmts]
                 (LPat idL)
                 body

      -- | 'ApplicativeStmt' represents an applicative expression built with
      -- '<$>' and '<*>'.  It is generated by the renamer, and is desugared into the
      -- appropriate applicative expression by the desugarer, but it is intended
      -- to be invisible in error messages.
      --
      -- For full details, see Note [ApplicativeDo] in "GHC.Rename.Expr"
      --
      | ApplicativeStmt
                 (XApplicativeStmt idL idR body) -- Post typecheck, Type of the body
                 [ ( SyntaxExpr idR
                   , ApplicativeArg idL) ]
                          -- [(<$>, e1), (<*>, e2), ..., (<*>, en)]
                 (Maybe (SyntaxExpr idR))  -- 'join', if necessary

      | BodyStmt (XBodyStmt idL idR body) -- Post typecheck, element type
                                          -- of the RHS (used for arrows)
                 body              -- See Note [BodyStmt]
                 (SyntaxExpr idR)  -- The (>>) operator
                 (SyntaxExpr idR)  -- The `guard` operator; used only in MonadComp
                                   -- See notes [Monad Comprehensions]

      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnLet'
      --          'GHC.Parser.Annotation.AnnOpen' @'{'@,'GHC.Parser.Annotation.AnnClose' @'}'@,

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | LetStmt  (XLetStmt idL idR body) (HsLocalBindsLR idL idR)

      -- ParStmts only occur in a list/monad comprehension
      | ParStmt  (XParStmt idL idR body)    -- Post typecheck,
                                            -- S in (>>=) :: Q -> (R -> S) -> T
                 [ParStmtBlock idL idR]
                 (HsExpr idR)               -- Polymorphic `mzip` for monad comprehensions
                 (SyntaxExpr idR)           -- The `>>=` operator
                                            -- See notes [Monad Comprehensions]
                -- After renaming, the ids are the binders
                -- bound by the stmts and used after them

      | TransStmt {
          forall idL idR body. StmtLR idL idR body -> XTransStmt idL idR body
    trS_ext   :: XTransStmt idL idR body, -- Post typecheck,
                                                -- R in (>>=) :: Q -> (R -> S) -> T
          forall idL idR body. StmtLR idL idR body -> TransForm
    trS_form  :: TransForm,
          forall idL idR body. StmtLR idL idR body -> [ExprLStmt idL]
    trS_stmts :: [ExprLStmt idL],   -- Stmts to the *left* of the 'group'
                                          -- which generates the tuples to be grouped

          forall idL idR body. StmtLR idL idR body -> [(IdP idR, IdP idR)]
    trS_bndrs :: [(IdP idR, IdP idR)], -- See Note [TransStmt binder map]

          forall idL idR body. StmtLR idL idR body -> LHsExpr idR
    trS_using :: LHsExpr idR,
          forall idL idR body. StmtLR idL idR body -> Maybe (LHsExpr idR)
    trS_by :: Maybe (LHsExpr idR),  -- "by e" (optional)
            -- Invariant: if trS_form = GroupBy, then grp_by = Just e

          forall idL idR body. StmtLR idL idR body -> SyntaxExpr idR
    trS_ret :: SyntaxExpr idR,      -- The monomorphic 'return' function for
                                          -- the inner monad comprehensions
          forall idL idR body. StmtLR idL idR body -> SyntaxExpr idR
    trS_bind :: SyntaxExpr idR,     -- The '(>>=)' operator
          forall idL idR body. StmtLR idL idR body -> HsExpr idR
    trS_fmap :: HsExpr idR          -- The polymorphic 'fmap' function for desugaring
                                          -- Only for 'group' forms
                                          -- Just a simple HsExpr, because it's
                                          -- too polymorphic for tcSyntaxOp
        }                                 -- See Note [Monad Comprehensions]

      -- Recursive statement (see Note [How RecStmt works] below)
      -- | - 'GHC.Parser.Annotation.AnnKeywordId' : 'GHC.Parser.Annotation.AnnRec'

      -- For details on above see Note [exact print annotations] in GHC.Parser.Annotation
      | RecStmt
         { forall idL idR body. StmtLR idL idR body -> XRecStmt idL idR body
    recS_ext :: XRecStmt idL idR body
         , forall idL idR body.
    StmtLR idL idR body -> XRec idR [LStmtLR idL idR body]
    recS_stmts :: XRec idR [LStmtLR idL idR body]
         -- Assume XRec is the same for idL and idR, pick one arbitrarily

            -- The next two fields are only valid after renaming
         , forall idL idR body. StmtLR idL idR body -> [IdP idR]
    recS_later_ids :: [IdP idR]
                             -- The ids are a subset of the variables bound by the
                             -- stmts that are used in stmts that follow the RecStmt

         , forall idL idR body. StmtLR idL idR body -> [IdP idR]
    recS_rec_ids :: [IdP idR]
                             -- Ditto, but these variables are the "recursive" ones,
                             -- that are used before they are bound in the stmts of
                             -- the RecStmt.
            -- An Id can be in both groups
            -- Both sets of Ids are (now) treated monomorphically
            -- See Note [How RecStmt works] for why they are separate

            -- Rebindable syntax
         , forall idL idR body. StmtLR idL idR body -> SyntaxExpr idR
    recS_bind_fn :: SyntaxExpr idR -- The bind function
         , forall idL idR body. StmtLR idL idR body -> SyntaxExpr idR
    recS_ret_fn  :: SyntaxExpr idR -- The return function
         , forall idL idR body. StmtLR idL idR body -> SyntaxExpr idR
    recS_mfix_fn :: SyntaxExpr idR -- The mfix function
          }
      | XStmtLR !(XXStmtLR idL idR body)

    data TransForm   -- The 'f' below is the 'using' function, 'e' is the by function
      = ThenForm     -- then f               or    then f by e             (depending on trS_by)
      | GroupForm    -- then group using f   or    then group by e using f (depending on trS_by)
      deriving Typeable TransForm
    Typeable TransForm =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> TransForm -> c TransForm)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c TransForm)
    -> (TransForm -> Constr)
    -> (TransForm -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c TransForm))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c TransForm))
    -> ((forall b. Data b => b -> b) -> TransForm -> TransForm)
    -> (forall r r'.
        (r -> r' -> r)
        -> r -> (forall d. Data d => d -> r') -> TransForm -> r)
    -> (forall r r'.
        (r' -> r -> r)
        -> r -> (forall d. Data d => d -> r') -> TransForm -> r)
    -> (forall u. (forall d. Data d => d -> u) -> TransForm -> [u])
    -> (forall u.
        Int -> (forall d. Data d => d -> u) -> TransForm -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> TransForm -> m TransForm)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> TransForm -> m TransForm)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> TransForm -> m TransForm)
    -> Data TransForm
    TransForm -> Constr
    TransForm -> DataType
    (forall b. Data b => b -> b) -> TransForm -> TransForm
    forall a.
    Typeable a =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> a -> c a)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c a)
    -> (a -> Constr)
    -> (a -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c a))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a))
    -> ((forall b. Data b => b -> b) -> a -> a)
    -> (forall r r'.
        (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall r r'.
        (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall u. (forall d. Data d => d -> u) -> a -> [u])
    -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> Data a
    forall u. Int -> (forall d. Data d => d -> u) -> TransForm -> u
    forall u. (forall d. Data d => d -> u) -> TransForm -> [u]
    forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> TransForm -> r
    forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> TransForm -> r
    forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c TransForm
    forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> TransForm -> c TransForm
    forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c TransForm)
    forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c TransForm)
    $cgfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> TransForm -> c TransForm
    gfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> TransForm -> c TransForm
    $cgunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c TransForm
    gunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c TransForm
    $ctoConstr :: TransForm -> Constr
    toConstr :: TransForm -> Constr
    $cdataTypeOf :: TransForm -> DataType
    dataTypeOf :: TransForm -> DataType
    $cdataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c TransForm)
    dataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c TransForm)
    $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c TransForm)
    dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c TransForm)
    $cgmapT :: (forall b. Data b => b -> b) -> TransForm -> TransForm
    gmapT :: (forall b. Data b => b -> b) -> TransForm -> TransForm
    $cgmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> TransForm -> r
    gmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> TransForm -> r
    $cgmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> TransForm -> r
    gmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> TransForm -> r
    $cgmapQ :: forall u. (forall d. Data d => d -> u) -> TransForm -> [u]
    gmapQ :: forall u. (forall d. Data d => d -> u) -> TransForm -> [u]
    $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> TransForm -> u
    gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> TransForm -> u
    $cgmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    gmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    $cgmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    gmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    $cgmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    gmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> TransForm -> m TransForm
    Data

    -- | Parenthesised Statement Block
    data ParStmtBlock idL idR
      = ParStmtBlock
            (XParStmtBlock idL idR)
            [ExprLStmt idL]
            [IdP idR]          -- The variables to be returned
            (SyntaxExpr idR)   -- The return operator
      | XParStmtBlock !(XXParStmtBlock idL idR)

    -- | The fail operator
    --
    -- This is used for `.. <-` "bind statements" in do notation, including
    -- non-monadic "binds" in applicative.
    --
    -- The fail operator is 'Just expr' if it potentially fail monadically. if the
    -- pattern match cannot fail, or shouldn't fail monadically (regular incomplete
    -- pattern exception), it is 'Nothing'.
    --
    -- See Note [Monad fail : Rebindable syntax, overloaded strings] for the type of
    -- expression in the 'Just' case, and why it is so.
    --
    -- See Note [Failing pattern matches in Stmts] for which contexts for
    -- '@BindStmt@'s should use the monadic fail and which shouldn't.
    type FailOperator id = Maybe (SyntaxExpr id)

    -- | Applicative Argument
    data ApplicativeArg idL
      = ApplicativeArgOne      -- A single statement (BindStmt or BodyStmt)
        { forall idL. ApplicativeArg idL -> XApplicativeArgOne idL
    xarg_app_arg_one  :: XApplicativeArgOne idL
          -- ^ The fail operator, after renaming
          --
          -- The fail operator is needed if this is a BindStmt
          -- where the pattern can fail. E.g.:
          -- (Just a) <- stmt
          -- The fail operator will be invoked if the pattern
          -- match fails.
          -- It is also used for guards in MonadComprehensions.
          -- The fail operator is Nothing
          -- if the pattern match can't fail
        , forall idL. ApplicativeArg idL -> LPat idL
    app_arg_pattern   :: LPat idL -- WildPat if it was a BodyStmt (see below)
        , forall idL. ApplicativeArg idL -> LHsExpr idL
    arg_expr          :: LHsExpr idL
        , forall idL. ApplicativeArg idL -> Bool
    is_body_stmt      :: Bool
          -- ^ True <=> was a BodyStmt,
          -- False <=> was a BindStmt.
          -- See Note [Applicative BodyStmt]
        }
      | ApplicativeArgMany     -- do { stmts; return vars }
        { forall idL. ApplicativeArg idL -> XApplicativeArgMany idL
    xarg_app_arg_many :: XApplicativeArgMany idL
        , forall idL. ApplicativeArg idL -> [ExprLStmt idL]
    app_stmts         :: [ExprLStmt idL] -- stmts
        , forall idL. ApplicativeArg idL -> HsExpr idL
    final_expr        :: HsExpr idL    -- return (v1,..,vn), or just (v1,..,vn)
        , forall idL. ApplicativeArg idL -> LPat idL
    bv_pattern        :: LPat idL      -- (v1,...,vn)
        , forall idL. ApplicativeArg idL -> HsDoFlavour
    stmt_context      :: HsDoFlavour
          -- ^ context of the do expression, used in pprArg
        }
      | XApplicativeArg !(XXApplicativeArg idL)

    {-
    Note [The type of bind in Stmts]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Some Stmts, notably BindStmt, keep the (>>=) bind operator.
    We do NOT assume that it has type
        (>>=) :: m a -> (a -> m b) -> m b
    In some cases (see #303, #1537) it might have a more
    exotic type, such as
        (>>=) :: m i j a -> (a -> m j k b) -> m i k b
    So we must be careful not to make assumptions about the type.
    In particular, the monad may not be uniform throughout.

    Note [TransStmt binder map]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The [(idR,idR)] in a TransStmt behaves as follows:

      * Before renaming: []

      * After renaming:
              [ (x27,x27), ..., (z35,z35) ]
        These are the variables
           bound by the stmts to the left of the 'group'
           and used either in the 'by' clause,
                    or     in the stmts following the 'group'
        Each item is a pair of identical variables.

      * After typechecking:
              [ (x27:Int, x27:[Int]), ..., (z35:Bool, z35:[Bool]) ]
        Each pair has the same unique, but different *types*.

    Note [BodyStmt]
    ~~~~~~~~~~~~~~~
    BodyStmts are a bit tricky, because what they mean
    depends on the context.  Consider the following contexts:

            A do expression of type (m res_ty)
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            * BodyStmt E any_ty:   do { ....; E; ... }
                    E :: m any_ty
              Translation: E >> ...

            A list comprehensions of type [elt_ty]
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            * BodyStmt E Bool:   [ .. | .... E ]
                            [ .. | ..., E, ... ]
                            [ .. | .... | ..., E | ... ]
                    E :: Bool
              Translation: if E then fail else ...

            A guard list, guarding a RHS of type rhs_ty
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            * BodyStmt E BooParStmtBlockl:   f x | ..., E, ... = ...rhs...
                    E :: Bool
              Translation: if E then fail else ...

            A monad comprehension of type (m res_ty)
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            * BodyStmt E Bool:   [ .. | .... E ]
                    E :: Bool
              Translation: guard E >> ...

    Array comprehensions are handled like list comprehensions.

    Note [How RecStmt works]
    ~~~~~~~~~~~~~~~~~~~~~~~~
    Example:
       HsDo [ BindStmt x ex

            , RecStmt { recS_rec_ids   = [a, c]
                      , recS_stmts     = [ BindStmt b (return (a,c))
                                         , LetStmt a = ...b...
                                         , BindStmt c ec ]
                      , recS_later_ids = [a, b]

            , return (a b) ]

    Here, the RecStmt binds a,b,c; but
      - Only a,b are used in the stmts *following* the RecStmt,
      - Only a,c are used in the stmts *inside* the RecStmt
            *before* their bindings

    Why do we need *both* rec_ids and later_ids?  For monads they could be
    combined into a single set of variables, but not for arrows.  That
    follows from the types of the respective feedback operators:

            mfix :: MonadFix m => (a -> m a) -> m a
            loop :: ArrowLoop a => a (b,d) (c,d) -> a b c

    * For mfix, the 'a' covers the union of the later_ids and the rec_ids
    * For 'loop', 'c' is the later_ids and 'd' is the rec_ids

    Note [Typing a RecStmt]
    ~~~~~~~~~~~~~~~~~~~~~~~
    A (RecStmt stmts) types as if you had written

      (v1,..,vn, _, ..., _) <- mfix (\~(_, ..., _, r1, ..., rm) ->
                                     do { stmts
                                        ; return (v1,..vn, r1, ..., rm) })

    where v1..vn are the later_ids
          r1..rm are the rec_ids

    Note [Monad Comprehensions]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Monad comprehensions require separate functions like 'return' and
    '>>=' for desugaring. These functions are stored in the statements
    used in monad comprehensions. For example, the 'return' of the 'LastStmt'
    expression is used to lift the body of the monad comprehension:

      [ body | stmts ]
       =>
      stmts >>= \bndrs -> return body

    In transform and grouping statements ('then ..' and 'then group ..') the
    'return' function is required for nested monad comprehensions, for example:

      [ body | stmts, then f, rest ]
       =>
      f [ env | stmts ] >>= \bndrs -> [ body | rest ]

    BodyStmts require the 'Control.Monad.guard' function for boolean
    expressions:

      [ body | exp, stmts ]
       =>
      guard exp >> [ body | stmts ]

    Parallel statements require the 'Control.Monad.Zip.mzip' function:

      [ body | stmts1 | stmts2 | .. ]
       =>
      mzip stmts1 (mzip stmts2 (..)) >>= \(bndrs1, (bndrs2, ..)) -> return body

    In any other context than 'MonadComp', the fields for most of these
    'SyntaxExpr's stay bottom.

    Note [Applicative BodyStmt]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    (#12143) For the purposes of ApplicativeDo, we treat any BodyStmt
    as if it was a BindStmt with a wildcard pattern.  For example,

      do
        x <- A
        B
        return x

    is transformed as if it were

      do
        x <- A
        _ <- B
        return x

    so it transforms to

      (\(x,_) -> x) <$> A <*> B

    But we have to remember when we treat a BodyStmt like a BindStmt,
    because in error messages we want to emit the original syntax the user
    wrote, not our internal representation.  So ApplicativeArgOne has a
    Bool flag that is True when the original statement was a BodyStmt, so
    that we can pretty-print it correctly.
    -}

    {-
    ************************************************************************
    *                                                                      *
                    Template Haskell quotation brackets
    *                                                                      *
    ************************************************************************
    -}

    {-
    Note [Quasi-quote overview]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
    The "quasi-quote" extension is described by Geoff Mainland's paper
    "Why it's nice to be quoted: quasiquoting for Haskell" (Haskell
    Workshop 2007).

    Briefly, one writes
            [p| stuff |]
    and the arbitrary string "stuff" gets parsed by the parser 'p', whose type
    should be Language.Haskell.TH.Quote.QuasiQuoter.  'p' must be defined in
    another module, because we are going to run it here.  It's a bit like an
    /untyped/ TH splice where the parser is applied the "stuff" as a string, thus:
         $(p "stuff")

    Notice that it's an /untyped/ TH splice: it can occur in patterns and types, as well
    as in expressions; and it runs in the renamer.
    -}

    -- | Haskell Splice
    data HsUntypedSplice id
       = HsUntypedSpliceExpr --  $z  or $(f 4)
            (XUntypedSpliceExpr id)
            (LHsExpr id)

       | HsQuasiQuote            -- See Note [Quasi-quote overview]
            (XQuasiQuote id)
            (IdP id)             -- The quoter (the bit between `[` and `|`)
            (XRec id FastString) -- The enclosed string

       | XUntypedSplice !(XXUntypedSplice id) -- Extension point; see Note [Trees That Grow]
                                              -- in Language.Haskell.Syntax.Extension

    -- | Haskell (Untyped) Quote = Expr + Pat + Type + Var
    data HsQuote p
      = ExpBr  (XExpBr p)   (LHsExpr p)   -- [|  expr  |]
      | PatBr  (XPatBr p)   (LPat p)      -- [p| pat   |]
      | DecBrL (XDecBrL p)  [LHsDecl p]   -- [d| decls |]; result of parser
      | DecBrG (XDecBrG p)  (HsGroup p)   -- [d| decls |]; result of renamer
      | TypBr  (XTypBr p)   (LHsType p)   -- [t| type  |]
      | VarBr  (XVarBr p)   Bool (LIdP p) -- True: 'x, False: ''T
      | XQuote !(XXQuote p) -- Extension point; see Note [Trees That Grow]
                            -- in Language.Haskell.Syntax.Extension

    {-
    ************************************************************************
    *                                                                      *
    \subsection{Enumerations and list comprehensions}
    *                                                                      *
    ************************************************************************
    -}

    -- | Arithmetic Sequence Information
    data ArithSeqInfo id
      = From            (LHsExpr id)
      | FromThen        (LHsExpr id)
                        (LHsExpr id)
      | FromTo          (LHsExpr id)
                        (LHsExpr id)
      | FromThenTo      (LHsExpr id)
                        (LHsExpr id)
                        (LHsExpr id)
    -- AZ: Should ArithSeqInfo have a TTG extension?

    {-
    ************************************************************************
    *                                                                      *
    \subsection{HsMatchCtxt}
    *                                                                      *
    ************************************************************************
    -}

    -- | Haskell Match Context
    --
    -- Context of a pattern match. This is more subtle than it would seem. See
    -- Note [FunBind vs PatBind].
    data HsMatchContext fn
      = FunRhs
        -- ^ A pattern matching on an argument of a
        -- function binding
          { forall fn. HsMatchContext fn -> fn
    mc_fun        :: fn    -- ^ function binder of @f@
                                   -- See Note [mc_fun field of FunRhs]
                                   -- See #20415 for a long discussion about this field
          , forall fn. HsMatchContext fn -> LexicalFixity
    mc_fixity     :: LexicalFixity -- ^ fixing of @f@
          , forall fn. HsMatchContext fn -> SrcStrictness
    mc_strictness :: SrcStrictness -- ^ was @f@ banged?
                                           -- See Note [FunBind vs PatBind]
          }
      | CaseAlt                     -- ^Patterns and guards in a case alternative
      | LamAlt HsLamVariant         -- ^Patterns and guards in @\@, @\case@ and @\cases@
      | IfAlt                       -- ^Guards of a multi-way if alternative
      | ArrowMatchCtxt              -- ^A pattern match inside arrow notation
          HsArrowMatchContext
      | PatBindRhs                  -- ^A pattern binding  eg [y] <- e = e
      | PatBindGuards               -- ^Guards of pattern bindings, e.g.,
                                    --    (Just b) | Just _ <- x = e
                                    --             | otherwise   = e'

      | RecUpd                      -- ^Record update [used only in GHC.HsToCore.Expr to
                                    --    tell matchWrapper what sort of
                                    --    runtime error message to generate]

      | StmtCtxt (HsStmtContext fn)  -- ^Pattern of a do-stmt, list comprehension,
                                     --  pattern guard, etc

      | ThPatSplice            -- ^A Template Haskell pattern splice
      | ThPatQuote             -- ^A Template Haskell pattern quotation [p| (a,b) |]
      | PatSyn                 -- ^A pattern synonym declaration
      | LazyPatCtx             -- ^An irrefutable pattern

    {- Note [mc_fun field of FunRhs]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    HsMatchContext is parameterised over `fn`, the function binder stored in `FunRhs`.
    This makes pretty printing easy.

    In the use of `HsMatchContext` in `Match`, it is parameterised thus:
        data Match p body = Match { m_ctxt  :: HsMatchContext (LIdP (NoGhcTc p)), ... }
    So in a Match, the mc_fun field `FunRhs` will be a `RdrName` in pass `GhcPs`, a `Name`
    in `GhcRn`, and (importantly) still a `Name` in `GhcTc` -- not an `Id`.
    See Note [NoGhcTc] in GHC.Hs.Extension.

    * Why a `Name` in the typechecker phase?  Because:
      * A `Name` is all we need, as it turns out.
      * Using an `Id` involves knot-tying in the monad, which led to #22695.

    * Why a /located/ name?  Because we want to record the location of the Id
      on the LHS of /this/ match.  See Note [m_ctxt in Match].  Example:
        (&&&) [] [] = []
        xs  &&&  [] = xs
      The two occurrences of `&&&` have different locations.

    * Why parameterise `HsMatchContext` over `fn` rather than over the pass `p`?
      Because during typechecking (specifically GHC.Tc.Gen.Match.tcMatch) we need to convert
         HsMatchContext (LIdP (NoGhcTc GhcRn)) --> HsMatchContext (LIdP (NoGhcTc GhcTc))
      With this parameterisation it's easy; if it was parametersed over `p` we'd  need
      a recursive traversal of the HsMatchContext.

    See #20415 for a long discussion.
    -}

    -- | Haskell Statement Context.
    data HsStmtContext fn
      = HsDoStmt HsDoFlavour              -- ^ Context for HsDo (do-notation and comprehensions)
      | PatGuard (HsMatchContext fn)      -- ^ Pattern guard for specified thing
      | ParStmtCtxt (HsStmtContext fn)    -- ^ A branch of a parallel stmt
      | TransStmtCtxt (HsStmtContext fn)  -- ^ A branch of a transform stmt
      | ArrowExpr                         -- ^ do-notation in an arrow-command context

    -- | Haskell arrow match context.
    data HsArrowMatchContext
      = ProcExpr                       -- ^ A proc expression
      | ArrowCaseAlt                   -- ^ A case alternative inside arrow notation
      | ArrowLamAlt HsLamVariant       -- ^ A \, \case or \cases alternative inside arrow notation

    data HsDoFlavour
      = DoExpr (Maybe ModuleName)        -- ^[ModuleName.]do { ... }
      | MDoExpr (Maybe ModuleName)       -- ^[ModuleName.]mdo { ... }  ie recursive do-expression
      | GhciStmtCtxt                     -- ^A command-line Stmt in GHCi pat <- rhs
      | ListComp
      | MonadComp
      deriving (HsDoFlavour -> HsDoFlavour -> Bool
    (HsDoFlavour -> HsDoFlavour -> Bool)
    -> (HsDoFlavour -> HsDoFlavour -> Bool) -> Eq HsDoFlavour
    forall a. (a -> a -> Bool) -> (a -> a -> Bool) -> Eq a
    $c== :: HsDoFlavour -> HsDoFlavour -> Bool
    == :: HsDoFlavour -> HsDoFlavour -> Bool
    $c/= :: HsDoFlavour -> HsDoFlavour -> Bool
    /= :: HsDoFlavour -> HsDoFlavour -> Bool
    Eq, Typeable HsDoFlavour
    Typeable HsDoFlavour =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> HsDoFlavour -> c HsDoFlavour)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c HsDoFlavour)
    -> (HsDoFlavour -> Constr)
    -> (HsDoFlavour -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c HsDoFlavour))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e))
        -> Maybe (c HsDoFlavour))
    -> ((forall b. Data b => b -> b) -> HsDoFlavour -> HsDoFlavour)
    -> (forall r r'.
        (r -> r' -> r)
        -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r)
    -> (forall r r'.
        (r' -> r -> r)
        -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r)
    -> (forall u. (forall d. Data d => d -> u) -> HsDoFlavour -> [u])
    -> (forall u.
        Int -> (forall d. Data d => d -> u) -> HsDoFlavour -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour)
    -> Data HsDoFlavour
    HsDoFlavour -> Constr
    HsDoFlavour -> DataType
    (forall b. Data b => b -> b) -> HsDoFlavour -> HsDoFlavour
    forall a.
    Typeable a =>
    (forall (c :: * -> *).
     (forall d b. Data d => c (d -> b) -> d -> c b)
     -> (forall g. g -> c g) -> a -> c a)
    -> (forall (c :: * -> *).
        (forall b r. Data b => c (b -> r) -> c r)
        -> (forall r. r -> c r) -> Constr -> c a)
    -> (a -> Constr)
    -> (a -> DataType)
    -> (forall (t :: * -> *) (c :: * -> *).
        Typeable t =>
        (forall d. Data d => c (t d)) -> Maybe (c a))
    -> (forall (t :: * -> * -> *) (c :: * -> *).
        Typeable t =>
        (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c a))
    -> ((forall b. Data b => b -> b) -> a -> a)
    -> (forall r r'.
        (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall r r'.
        (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> a -> r)
    -> (forall u. (forall d. Data d => d -> u) -> a -> [u])
    -> (forall u. Int -> (forall d. Data d => d -> u) -> a -> u)
    -> (forall (m :: * -> *).
        Monad m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> (forall (m :: * -> *).
        MonadPlus m =>
        (forall d. Data d => d -> m d) -> a -> m a)
    -> Data a
    forall u. Int -> (forall d. Data d => d -> u) -> HsDoFlavour -> u
    forall u. (forall d. Data d => d -> u) -> HsDoFlavour -> [u]
    forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r
    forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r
    forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsDoFlavour
    forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsDoFlavour -> c HsDoFlavour
    forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsDoFlavour)
    forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsDoFlavour)
    $cgfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsDoFlavour -> c HsDoFlavour
    gfoldl :: forall (c :: * -> *).
    (forall d b. Data d => c (d -> b) -> d -> c b)
    -> (forall g. g -> c g) -> HsDoFlavour -> c HsDoFlavour
    $cgunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsDoFlavour
    gunfold :: forall (c :: * -> *).
    (forall b r. Data b => c (b -> r) -> c r)
    -> (forall r. r -> c r) -> Constr -> c HsDoFlavour
    $ctoConstr :: HsDoFlavour -> Constr
    toConstr :: HsDoFlavour -> Constr
    $cdataTypeOf :: HsDoFlavour -> DataType
    dataTypeOf :: HsDoFlavour -> DataType
    $cdataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsDoFlavour)
    dataCast1 :: forall (t :: * -> *) (c :: * -> *).
    Typeable t =>
    (forall d. Data d => c (t d)) -> Maybe (c HsDoFlavour)
    $cdataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsDoFlavour)
    dataCast2 :: forall (t :: * -> * -> *) (c :: * -> *).
    Typeable t =>
    (forall d e. (Data d, Data e) => c (t d e))
    -> Maybe (c HsDoFlavour)
    $cgmapT :: (forall b. Data b => b -> b) -> HsDoFlavour -> HsDoFlavour
    gmapT :: (forall b. Data b => b -> b) -> HsDoFlavour -> HsDoFlavour
    $cgmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r
    gmapQl :: forall r r'.
    (r -> r' -> r)
    -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r
    $cgmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r
    gmapQr :: forall r r'.
    (r' -> r -> r)
    -> r -> (forall d. Data d => d -> r') -> HsDoFlavour -> r
    $cgmapQ :: forall u. (forall d. Data d => d -> u) -> HsDoFlavour -> [u]
    gmapQ :: forall u. (forall d. Data d => d -> u) -> HsDoFlavour -> [u]
    $cgmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsDoFlavour -> u
    gmapQi :: forall u. Int -> (forall d. Data d => d -> u) -> HsDoFlavour -> u
    $cgmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    gmapM :: forall (m :: * -> *).
    Monad m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    $cgmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    gmapMp :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    $cgmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    gmapMo :: forall (m :: * -> *).
    MonadPlus m =>
    (forall d. Data d => d -> m d) -> HsDoFlavour -> m HsDoFlavour
    Data)

    qualifiedDoModuleName_maybe :: HsStmtContext fn -> Maybe ModuleName
    qualifiedDoModuleName_maybe :: forall fn. HsStmtContext fn -> Maybe ModuleName
    qualifiedDoModuleName_maybe HsStmtContext fn
    ctxt = case HsStmtContext fn
    ctxt of
      HsDoStmt (DoExpr Maybe ModuleName
    m) -> Maybe ModuleName
    m
      HsDoStmt (MDoExpr Maybe ModuleName
    m) -> Maybe ModuleName
    m
      HsStmtContext fn
    _ -> Maybe ModuleName
    forall a. Maybe a
    Nothing

    isPatSynCtxt :: HsMatchContext fn -> Bool
    isPatSynCtxt :: forall fn. HsMatchContext fn -> Bool
    isPatSynCtxt HsMatchContext fn
    ctxt =
      case HsMatchContext fn
    ctxt of
        HsMatchContext fn
    PatSyn -> Bool
    True
        HsMatchContext fn
    _      -> Bool
    False

    isComprehensionContext :: HsStmtContext fn -> Bool
    -- Uses comprehension syntax [ e | quals ]
    isComprehensionContext :: forall fn. HsStmtContext fn -> Bool
    isComprehensionContext (ParStmtCtxt HsStmtContext fn
    c)   = HsStmtContext fn -> Bool
    forall fn. HsStmtContext fn -> Bool
    isComprehensionContext HsStmtContext fn
    c
    isComprehensionContext (TransStmtCtxt HsStmtContext fn
    c) = HsStmtContext fn -> Bool
    forall fn. HsStmtContext fn -> Bool
    isComprehensionContext HsStmtContext fn
    c
    isComprehensionContext HsStmtContext fn
    ArrowExpr = Bool
    False
    isComprehensionContext (PatGuard HsMatchContext fn
    _) = Bool
    False
    isComprehensionContext (HsDoStmt HsDoFlavour
    flavour) = HsDoFlavour -> Bool
    isDoComprehensionContext HsDoFlavour
    flavour

    isDoComprehensionContext :: HsDoFlavour -> Bool
    isDoComprehensionContext :: HsDoFlavour -> Bool
    isDoComprehensionContext HsDoFlavour
    GhciStmtCtxt = Bool
    False
    isDoComprehensionContext (DoExpr Maybe ModuleName
    _) = Bool
    False
    isDoComprehensionContext (MDoExpr Maybe ModuleName
    _) = Bool
    False
    isDoComprehensionContext HsDoFlavour
    ListComp = Bool
    True
    isDoComprehensionContext HsDoFlavour
    MonadComp = Bool
    True

    -- | Is this a monadic context?
    isMonadStmtContext :: HsStmtContext fn -> Bool
    isMonadStmtContext :: forall fn. HsStmtContext fn -> Bool
    isMonadStmtContext (ParStmtCtxt HsStmtContext fn
    ctxt)   = HsStmtContext fn -> Bool
    forall fn. HsStmtContext fn -> Bool
    isMonadStmtContext HsStmtContext fn
    ctxt
    isMonadStmtContext (TransStmtCtxt HsStmtContext fn
    ctxt) = HsStmtContext fn -> Bool
    forall fn. HsStmtContext fn -> Bool
    isMonadStmtContext HsStmtContext fn
    ctxt
    isMonadStmtContext (HsDoStmt HsDoFlavour
    flavour) = HsDoFlavour -> Bool
    isMonadDoStmtContext HsDoFlavour
    flavour
    isMonadStmtContext (PatGuard HsMatchContext fn
    _) = Bool
    False
    isMonadStmtContext HsStmtContext fn
    ArrowExpr = Bool
    False

    isMonadDoStmtContext :: HsDoFlavour -> Bool
    isMonadDoStmtContext :: HsDoFlavour -> Bool
    isMonadDoStmtContext HsDoFlavour
    ListComp     = Bool
    False
    isMonadDoStmtContext HsDoFlavour
    MonadComp    = Bool
    True
    isMonadDoStmtContext DoExpr{}     = Bool
    True
    isMonadDoStmtContext MDoExpr{}    = Bool
    True
    isMonadDoStmtContext HsDoFlavour
    GhciStmtCtxt = Bool
    True

    isMonadCompContext :: HsStmtContext fn -> Bool
    isMonadCompContext :: forall fn. HsStmtContext fn -> Bool
    isMonadCompContext (HsDoStmt HsDoFlavour
    flavour)   = HsDoFlavour -> Bool
    isMonadDoCompContext HsDoFlavour
    flavour
    isMonadCompContext (ParStmtCtxt HsStmtContext fn
    _)   = Bool
    False
    isMonadCompContext (TransStmtCtxt HsStmtContext fn
    _) = Bool
    False
    isMonadCompContext (PatGuard HsMatchContext fn
    _)      = Bool
    False
    isMonadCompContext HsStmtContext fn
    ArrowExpr         = Bool
    False

    isMonadDoCompContext :: HsDoFlavour -> Bool
    isMonadDoCompContext :: HsDoFlavour -> Bool
    isMonadDoCompContext HsDoFlavour
    MonadComp    = Bool
    True
    isMonadDoCompContext HsDoFlavour
    ListComp     = Bool
    False
    isMonadDoCompContext HsDoFlavour
    GhciStmtCtxt = Bool
    False
    isMonadDoCompContext (DoExpr Maybe ModuleName
    _)   = Bool
    False
    isMonadDoCompContext (MDoExpr Maybe ModuleName
    _)  = Bool
    False