Language.Haskell.Syntax.Expr

A regular (non-overloaded) record update.

An overloaded record update.

Variable See Note [Located RdrNames]

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.

Variable pointing to record selector See Note [Non-overloaded record field selectors] and Note [Record selectors in the AST]

Overloaded label (Note [Overloaded labels] in GHC.OverloadedLabels) Note [Pragma source text] in GHC.Types.SourceText

Implicit parameter (not in use after typechecking)

Overloaded literals

Simple (non-overloaded) literals

Lambda, Lambda-case, and Lambda-cases

• AnnKeywordId : AnnLam, AnnCase,AnnOpen, AnnClose

• AnnKeywordId : AnnLam, AnnCases,AnnOpen, AnnClose

Application

Visible type application

Explicit type argument; e.g f @Int x y NB: Has wildcards, but no implicit quantification

• AnnKeywordId : GHC.Parser.Annotation.AnnAt,

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

Negation operator. Contains the negated expression and the name of negate

• AnnKeywordId : AnnMinus

• AnnKeywordId : AnnOpen '(', AnnClose ')'

Used for explicit tuples and sections thereof

• AnnKeywordId : AnnOpen, AnnClose

Used for unboxed sum types

• AnnKeywordId : AnnOpen '(#', AnnVbar, AnnClose '#)',

There will be multiple AnnVbar, (1 - alternative) before the expression, (arity - alternative) after it

• AnnKeywordId : AnnCase, AnnOf,AnnOpen '{', AnnClose '}'

• AnnKeywordId : AnnIf, AnnSemi, AnnThen,AnnSemi, AnnElse,

Multi-way if

• AnnKeywordId : AnnIf AnnOpen,AnnClose,

let(rec)

• AnnKeywordId : AnnLet, AnnOpen '{', AnnClose '}',AnnIn

• AnnKeywordId : AnnDo, AnnOpen, AnnSemi, AnnVbar, AnnClose

Syntactic list: [a,b,c,...]

• AnnKeywordId : AnnOpen '[', AnnClose ']'

Record construction

• AnnKeywordId : AnnOpen '{', AnnDotdot,AnnClose '}'

Record update

• AnnKeywordId : AnnOpen '{', AnnDotdot,AnnClose '}' 'GHC.Parser.Annotation.AnnComma, AnnDot, AnnClose '}'

Record field selection e.g z.x.

• AnnKeywordId : AnnDot

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].

Expression with an explicit type signature. e :: type

• AnnKeywordId : AnnDcolon

Arithmetic sequence

• AnnKeywordId : AnnOpen '[', AnnComma,AnnDotdot, AnnClose ']'

• AnnKeywordId : AnnOpen, AnnOpenE,AnnOpenEQ, AnnClose,AnnCloseQ

• AnnKeywordId : AnnOpen, AnnClose

proc notation for Arrows

• AnnKeywordId : AnnProc, AnnRarrow

• AnnKeywordId : AnnStatic,

• AnnKeywordId : AnnOpen, AnnOpen '{-# GENERATED', AnnVal,AnnVal, AnnColon,AnnVal, AnnMinus, AnnVal,AnnColon, AnnVal, AnnClose '#-}'

The argument

The argument is missing, but this is its type

Extension point; see Note [Trees That Grow] in Language.Haskell.Syntax.Extension

`p -> e`

`case pi -> ei `

`cases psi -> ei`

• AnnKeywordId : Annlarrowtail, Annrarrowtail,AnnLarrowtail, AnnRarrowtail

• AnnKeywordId : AnnOpenB '(|', AnnCloseB '|)'

Lambda-case

• AnnKeywordId : AnnLam, AnnCase,AnnOpen '{', AnnClose '}'

• AnnKeywordId : AnnLam, AnnCases,AnnOpen '{', AnnClose '}'

• AnnKeywordId : AnnOpen '(', AnnClose ')'

• AnnKeywordId : AnnCase, AnnOf,AnnOpen '{', AnnClose '}'

• AnnKeywordId : AnnIf, AnnSemi, AnnThen,AnnSemi, AnnElse,

• AnnKeywordId : AnnLet, AnnOpen '{', AnnClose '}',AnnIn

• AnnKeywordId : AnnDo, AnnOpen, AnnSemi, AnnVbar, AnnClose

First order arrow application -<

Higher order arrow application -<<

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

• AnnKeywordId : AnnLet AnnOpen '{',AnnClose '}',

• AnnKeywordId : AnnRec

A pattern matching on an argument of a function binding

Patterns and guards in a case alternative

Patterns and guards in @, case and cases@

Guards of a multi-way if alternative

A pattern match inside arrow notation

A pattern binding eg [y] <- e = e

Guards of pattern bindings, e.g., (Just b) | Just _ <- x = e | otherwise = e'

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

Pattern of a do-stmt, list comprehension, pattern guard, etc

A Template Haskell pattern splice

A Template Haskell pattern quotation [p| (a,b) |]

A pattern synonym declaration

An irrefutable pattern

Context for HsDo (do-notation and comprehensions)

Pattern guard for specified thing

A branch of a parallel stmt

A branch of a transform stmt

do-notation in an arrow-command context

A proc expression

A case alternative inside arrow notation

A , case or cases alternative inside arrow notation

ModuleName.

do { ... }

ModuleName.

mdo { ... } ie recursive do-expression

A command-line Stmt in GHCi pat <- rhs