The runIO function lets you run an I/O computation in the Q monad. Take care: you are guaranteed the ordering of calls to runIO within a single Q computation, but not about the order in which splices are run.

Note: for various murky reasons, stdout and stderr handles are not necesarily flushed when the compiler finishes running, so you should flush them yourself.

addDependentFile :: FilePath -> Q () Source

Record external files that runIO is using (dependent upon). The compiler can then recognize that it should re-compile the file using this TH when the external file changes. Note that ghc -M will still not know about these dependencies - it does not execute TH. Expects an absolute file path.

isInstance :: Name -> [Type] -> Q Bool Source

reifyInstances :: Name -> [Type] -> Q [Dec]Source

classInstances looks up instaces of a class

Names

data Name Source

For global names (NameG ) we need a totally unique name, so we must include the name-space of the thing

For unique-numbered things (NameU ), we've got a unique reference anyway, so no need for name space

For dynamically bound thing (NameS ) we probably want them to in a context-dependent way, so again we don't want the name space. For example:

 let v = mkName "T" in [| data $v = $v |]

Here we use the same Name for both type constructor and data constructor

NameL and NameG are bound *outside* the TH syntax tree either globally (NameG) or locally (NameL). Ex:

 f x = $(h [| (map, x) |])

The map will be a NameG, and x wil be a NameL

These Names should never appear in a binding position in a TH syntax tree

Constructors

Name OccName NameFlavour

Instances

Eq Name

Data Name

Ord Name

Show Name

Typeable Name

Ppr Name

mkName :: String -> Name Source

The string can have a . , thus Foo.baz, giving a dynamically-bound qualified name, in which case we want to generate a NameQ

Parse the string to see if it has a . in it so we know whether to generate a qualified or unqualified name It's a bit tricky because we need to parse

 Foo.Baz.x as Qual Foo.Baz x

So we parse it from back to front

newName :: String -> Q Name Source

nameBase :: Name -> String Source

Base, unqualified name.

nameModule :: Name -> Maybe String Source

showName :: Name -> String Source

showName' :: NameIs -> Name -> String Source

data NameIs Source

Constructors

Alone

Applied

Infix

The algebraic data types

Note [Unresolved infix] ~~~~~~~~~~~~~~~~~~~~~~~

When implementing antiquotation for quasiquoters, one often wants to parse strings into expressions:

 parse :: String -> Maybe 'Exp'

But how should we parse a + b * c? If we don't know the fixities of + and *, we don't know whether to parse it as a + (b * c) or (a + b) * c.

In cases like this, use UInfixE or UInfixP , which stand for "unresolved infix expression" and "unresolved infix pattern". When the compiler is given a splice containing a tree of UInfixE applications such as

 UInfixE
 (UInfixE e1 op1 e2)
 op2
 (UInfixE e3 op3 e4)

it will look up and the fixities of the relevant operators and reassociate the tree as necessary.

trees will not be reassociated across ParensE or ParensP , which are of use for parsing expressions like

 (a + b * c) + d * e

InfixE and InfixP expressions are never reassociated.
The UInfixE constructor doesn't support sections. Sections such as (a *) have no ambiguity, so InfixE suffices. For longer sections such as (a + b * c -), use an InfixE constructor for the outer-most section, and use UInfixE constructors for all other operators:

 InfixE
 Just (UInfixE ...a + b * c...)
 op
 Nothing

Sections such as (a + b +) and ((a + b) +) should be rendered into Exp s differently:

 (+ a + b) ---> InfixE Nothing + (Just $ UInfixE a + b)
 -- will result in a fixity error if (+) is left-infix
 (+ (a + b)) ---> InfixE Nothing + (Just $ ParensE $ UInfixE a + b)
 -- no fixity errors

Quoted expressions such as

 [| a * b + c |] :: Q Exp
 [p| a : b : c |] :: Q Pat

will never contain UInfixE , UInfixP , ParensE , or ParensP constructors.

data Dec Source

Constructors

FunD Name [Clause]

{ f p1 p2 = b where decs }

ValD Pat Body [Dec]

{ p = b where decs }

DataD Cxt Name [TyVarBndr] [Con] [Name]

{ data Cxt x => T x = A x | B (T x)
 deriving (Z,W)}

NewtypeD Cxt Name [TyVarBndr] Con [Name]

{ newtype Cxt x => T x = A (B x)
 deriving (Z,W)}

TySynD Name [TyVarBndr] Type

{ type T x = (x,x) }

ClassD Cxt Name [TyVarBndr] [FunDep] [Dec]

{ class Eq a => Ord a where ds }

InstanceD Cxt Type [Dec]

{ instance Show w => Show [w]
 where ds }

SigD Name Type

{ length :: [a] -> Int }

ForeignD Foreign

PragmaD Pragma

{ {--} }

FamilyD FamFlavour Name [TyVarBndr] (Maybe Kind)

{ type family T a b c :: * }

DataInstD Cxt Name [Type] [Con] [Name]

{ data instance Cxt x => T [x] = A x 
 | B (T x)
 deriving (Z,W)}

NewtypeInstD Cxt Name [Type] Con [Name]

{ newtype instance Cxt x => T [x] = A (B x)
 deriving (Z,W)}

TySynInstD Name [Type] Type

{ type instance T (Maybe x) = (x,x) }

Instances

Eq Dec

Data Dec

Show Dec

Typeable Dec

Ppr Dec

data Exp Source

The CompE constructor represents a list comprehension, and takes a [Stmt ]. The result expression of the comprehension is the *last* of these, and should be a NoBindS .

E.g. translation:

 [ f x | x <- xs ]

 CompE [BindS (VarP x) (VarE xs), NoBindS (AppE (VarE f) (VarE x))]

Constructors

VarE Name

{ x }

ConE Name

data T1 = C1 t1 t2; p = {C1} e1 e2

LitE Lit

{ 5 or c}

AppE Exp Exp

{ f x }

InfixE (Maybe Exp) Exp (Maybe Exp)

{x + y} or {(x+)} or {(+ x)} or {(+)}

It's a bit gruesome to use an Exp as the operator, but how else can we distinguish constructors from non-constructors? Maybe there should be a var-or-con type? Or maybe we should leave it to the String itself?

UInfixE Exp Exp Exp

{x + y}

See Note [Unresolved infix] at Language.Haskell.TH.Syntax

ParensE Exp

{ (e) }

See Note [Unresolved infix] at Language.Haskell.TH.Syntax

LamE [Pat] Exp

{ p1 p2 -> e }

TupE [Exp]

{ (e1,e2) }

UnboxedTupE [Exp]

{ () }

CondE Exp Exp Exp

{ if e1 then e2 else e3 }

LetE [Dec] Exp

{ let x=e1; y=e2 in e3 }

CaseE Exp [Match]

{ case e of m1; m2 }

DoE [Stmt]

{ do { p <- e1; e2 } }

CompE [Stmt]

{ [ (x,y) | x <- xs, y <- ys ] }

ArithSeqE Range

{ [ 1 ,2 .. 10 ] }

ListE [Exp]

{ [1,2,3] }

SigE Exp Type

{ e :: t }

RecConE Name [FieldExp]

{ T { x = y, z = w } }

RecUpdE Exp [FieldExp]

{ (f x) { z = w } }

Instances

Eq Exp

Data Exp

Show Exp

Typeable Exp

Ppr Exp

data Con Source

Constructors

NormalC Name [StrictType]

C Int a

RecC Name [VarStrictType]

C { v :: Int, w :: a }

InfixC StrictType Name StrictType

Int :+ a

ForallC [TyVarBndr] Cxt Con

forall a. Eq a => C [a]

Instances

Eq Con

Data Con

Show Con

Typeable Con

Ppr Con

data Type Source

Constructors

ForallT [TyVarBndr] Cxt Type

forall vars. ctxt -> type

VarT Name

ConT Name

TupleT Int

(,), (,,), etc.

UnboxedTupleT Int

(), (), etc.

ArrowT

->

ListT

[]

AppT Type Type

T a b

SigT Type Kind

t :: k

Instances

Eq Type

Data Type

Show Type

Typeable Type

Ppr Type

data TyVarBndr Source

Constructors

PlainTV Name

KindedTV Name Kind

(a :: k)

Instances

Eq TyVarBndr

data Kind Source

Constructors

StarK

ArrowK Kind Kind

k1 -> k2

Instances

Eq Kind

Data Kind

Show Kind

Typeable Kind

Ppr Kind

type Cxt Source

Arguments

= [Pred]

(Eq a, Ord b)

data Pred Source

Constructors

ClassP Name [Type]

Eq (Int, a)

EqualP Type Type

F a ~ Bool

Instances

Eq Pred

Data Pred

Show Pred

Typeable Pred

Ppr Pred

data Match Source

Constructors

Match Pat Body [Dec]

case e of { pat -> body where decs }

Instances

Eq Match

Data Match

Show Match

Typeable Match

Ppr Match

data Clause Source

Constructors

Clause [Pat] Body [Dec]

f { p1 p2 = body where decs }

Instances

Eq Clause

Data Clause

Show Clause

Typeable Clause

Ppr Clause

data Body Source

Constructors

GuardedB [(Guard, Exp)]

f p { | e1 = e2 | e3 = e4 } where ds

NormalB Exp

f p { = e } where ds

Instances

Eq Body

Data Body

Show Body

Typeable Body

data Guard Source

Constructors

NormalG Exp

PatG [Stmt]

Instances

Eq Guard

Data Guard

Show Guard

Typeable Guard

data Stmt Source

Constructors

BindS Pat Exp

LetS [Dec]

NoBindS Exp

ParS [[Stmt]]

Instances

Eq Stmt

Data Stmt

Show Stmt

Typeable Stmt

Ppr Stmt

data Range Source

Constructors

FromR Exp

FromThenR Exp Exp

FromToR Exp Exp

FromThenToR Exp Exp Exp

Instances

Eq Range

Data Range

Show Range

Typeable Range

Ppr Range

data Lit Source

Constructors

CharL Char

StringL String

IntegerL Integer

Used for overloaded and non-overloaded literals. We don't have a good way to represent non-overloaded literals at the moment. Maybe that doesn't matter?

A primitive C-style string, type Addr#

Instances

Eq Lit

Data Lit

Show Lit

Typeable Lit

data Pat Source

Pattern in Haskell given in {}

Constructors

LitP Lit

{ 5 or c }

VarP Name

{ x }

TupP [Pat]

{ (p1,p2) }

UnboxedTupP [Pat]

{ () }

ConP Name [Pat]

data T1 = C1 t1 t2; {C1 p1 p1} = e

InfixP Pat Name Pat

foo ({x :+ y}) = e

UInfixP Pat Name Pat

foo ({x :+ y}) = e

See Note [Unresolved infix] at Language.Haskell.TH.Syntax

ParensP Pat

{(p)}

See Note [Unresolved infix] at Language.Haskell.TH.Syntax

TildeP Pat

{ ~p }

BangP Pat

{ !p }

AsP Name Pat

{ x @ p }

WildP

{ _ }

RecP Name [FieldPat]

f (Pt { pointx = x }) = g x

ListP [Pat]

{ [1,2,3] }

SigP Pat Type

{ p :: t }

ViewP Exp Pat

{ e -> p }

Instances

Eq Pat

Data Pat

Show Pat

Typeable Pat

Ppr Pat

type FieldExp = (Name, Exp)Source

type FieldPat = (Name, Pat)Source

data Strict Source

Constructors

IsStrict

NotStrict

Unpacked

Instances

Eq Strict

Data Strict

Show Strict

Typeable Strict

data Foreign Source

Constructors

ImportF Callconv Safety String Name Type

ExportF Callconv String Name Type

Instances

Eq Foreign

Data Foreign

Show Foreign

Typeable Foreign

Ppr Foreign

data Callconv Source

Constructors

CCall

StdCall

Instances

Eq Callconv

Data Callconv

Show Callconv

Typeable Callconv

data Safety Source

Constructors

Unsafe

Safe

Interruptible

Instances

Eq Safety

Data Safety

Show Safety

Typeable Safety

data Pragma Source

Constructors

InlineP Name InlineSpec

SpecialiseP Name Type (Maybe InlineSpec)

Instances

Eq Pragma

Data Pragma

Show Pragma

Typeable Pragma

Ppr Pragma

data InlineSpec Source

Constructors

InlineSpec Bool Bool (Maybe (Bool, Int))

Instances

type StrictType = (Strict, Type)Source

type VarStrictType = (Name, Strict, Type)Source

data FunDep Source

Constructors

FunDep [Name] [Name]

Instances

Eq FunDep

Data FunDep

Show FunDep

Typeable FunDep

Ppr FunDep

data FamFlavour Source

Constructors

TypeFam

DataFam

Instances

data Info Source

Obtained from reify in the Q Monad.

Constructors

ClassI Dec [InstanceDec]

A class is reified to its declaration and a list of its instances

ClassOpI Name Type Name Fixity

TyConI Dec

FamilyI Dec [InstanceDec]

PrimTyConI Name Int Bool

DataConI Name Type Name Fixity

VarI Name Type (Maybe Dec) Fixity

TyVarI Name Type

Instances

Data Info

Show Info

Typeable Info

Ppr Info

data Loc Source

Constructors

Loc

Fields

loc_filename :: String
loc_package :: String
loc_module :: String
loc_start :: CharPos
loc_end :: CharPos

type CharPos = (Int, Int)Source

data Fixity Source

Constructors

Fixity Int FixityDirection

Instances

Eq Fixity

Data Fixity

Show Fixity

Typeable Fixity

data FixityDirection Source

Constructors

InfixL

InfixR

InfixN

Instances

Eq FixityDirection

Data FixityDirection

Show FixityDirection

Typeable FixityDirection

defaultFixity :: Fixity Source

maxPrecedence :: Int Source

Internal functions

returnQ :: a -> Q aSource

bindQ :: Q a -> (a -> Q b) -> Q bSource

sequenceQ :: [Q a] -> Q [a]Source

data NameFlavour Source

Constructors

NameS

An unqualified name; dynamically bound

NameQ ModName

A qualified name; dynamically bound

NameU Int#

A unique local name

NameL Int#

Local name bound outside of the TH AST

NameG NameSpace PkgName ModName

Global name bound outside of the TH AST: An original name (occurrences only, not binders) Need the namespace too to be sure which thing we are naming

Instances

Eq NameFlavour

Data NameFlavour

Although the NameFlavour type is abstract, the Data instance is not. The reason for this is that currently we use Data to serialize values in annotations, and in order for that to work for Template Haskell names introduced via the 'x syntax we need gunfold on NameFlavour to work. Bleh!

The long term solution to this is to use the binary package for annotation serialization and then remove this instance. However, to do _that_ we need to wait on binary to become stable, since boot libraries cannot be upgraded seperately from GHC itself.

This instance cannot be derived automatically due to bug #2701

Ord NameFlavour

Typeable NameFlavour

data NameSpace Source

Constructors

VarName

Variables

DataName

Data constructors

TcClsName

Type constructors and classes; Haskell has them in the same name space for now.

Instances