# Changelog for [`template-haskell` package](http://hackage.haskell.org/package/template-haskell)

## 2.21.0.0

  * Record fields now belong to separate `NameSpace`s, keyed by the parent of
    the record field. This is the name of the first constructor of the parent type,
    even if this constructor does not have the field in question.  

    This change enables TemplateHaskell support for `DuplicateRecordFields`.

## 2.20.0.0

  * The `Ppr.pprInfixT` function has gained a `Precedence` argument. 
  * The values of named precedence levels like `Ppr.appPrec` have changed.

  * Add `TypeDataD` constructor to the `Dec` type for `type data`
    declarations (GHC proposal #106).
  * Add `instance Lift (Fixed a)`

## 2.19.0.0

  * Add `DefaultD` constructor to support Haskell `default` declarations.

  * Add support for Overloaded Record Dot.
    Introduces `getFieldE :: Quote m => m Exp -> String -> m Exp` and
    `projectionE :: Quote m => [String] -> m Exp`.
  * Add `instance Lift ByteArray`.

  * Add `PromotedInfixT` and `PromotedUInfixT`, which are analogs to `InfixT`
    and `UInfixT` that ensure that if a dynamically bound name (i.e. a name
    with `NameFlavour` `NameS` or `NameQ`; the flavours produced by `mkName`)
    is used as operator, it will be bound to a promoted data constructor rather
    than a type constructor, if both are in scope.

  * Add a `vendor-filepath` Cabal flag to the `template-haskell` package. If
    this flag is set then `template-haskell` will not depend on the `filepath`
    package and will instead use  some modules from `filepath` that have been
    copied into the  `template-haskell` source tree.

## 2.18.0.0
  * The types of `ConP` and `conP` have been changed to allow for an additional list
    of type applications preceding the argument patterns.

  * Add support for the `Char` kind (#11342): we extend the `TyLit` data type with
    the constructor `CharTyLit` that reflects type-level characters.

  * Add `putDoc` and `getDoc` which allow Haddock documentation to be attached
    to module headers, declarations, function arguments and instances, as well
    as queried. These are quite low level operations, so for convenience there
    are several combinators that can be used with `Dec`s directly, including
    `withDecDoc`/`withDecsDoc` as well as `_doc` counterparts to many of the
    `Dec` helper functions.

  * Add `newDeclarationGroup` to document the effect of visibility while
    reifying types and instances.

## 2.17.0.0
  * Typed Quotations now return a value of type `Code m a` (GHC Proposal #195).
    The main motiviation is to make writing instances easier and make it easier to
    store `Code` values in type-indexed maps.

  * Implement Overloaded Quotations (GHC Proposal #246). This patch modifies a
    few fundamental things in the API. All the library combinators are generalised
    to be in terms of a new minimal class `Quote`. The types of `lift`, `liftTyped`,
    and `liftData` are modified to return `m Exp` rather than `Q Exp`. Instances
    written in terms of `Q` are now disallowed. The types of `unsafeTExpCoerce`
    and `unTypeQ` are also generalised in terms of `Quote` rather than specific
    to `Q`.

  * Implement Explicit specificity in type variable binders (GHC Proposal #99).
    In `Language.Haskell.TH.Syntax`, `TyVarBndr` is now annotated with a `flag`,
    denoting the additional argument to its constructors `PlainTV` and `KindedTV`.
    `flag` is either the `Specificity` of the type variable (`SpecifiedSpec` or
    `InferredSpec`) or `()`.

  * Fix Eq/Ord instances for `Bytes`: we were comparing pointers while we should
    compare the actual bytes (#16457).

  * Fix Show instance for `Bytes`: we were showing the pointer value while we
    want to show the contents (#16457).

  * Add `Semigroup` and `Monoid` instances for `Q` (#18123).

  * Add `MonadFix` instance for `Q` (#12073).

  * Add support for QualifiedDo. The data constructors `DoE` and `MDoE` got a new
    `Maybe ModName` argument to describe the qualifier of do blocks.

  * The argument to `TExpQ` can now be levity polymorphic.

## 2.16.0.0 *Jan 2020*

  * Bundled with GHC 8.10.1

  * Add support for tuple sections. (#15843) The type signatures of `TupE` and
    `UnboxedTupE` have changed from `[Exp] -> Exp` to `[Maybe Exp] -> Exp`.
    The type signatures of `tupE` and `unboxedTupE` remain the same for
    backwards compatibility.

  * Introduce a `liftTyped` method to the `Lift` class and set the default
    implementations of `lift` in terms of `liftTyped`.

  * Add a `ForallVisT` constructor to `Type` to represent visible, dependent
    quantification.

  * Introduce support for `Bytes` literals (raw bytes embedded into the output
    binary)

  * Make the `Lift` typeclass levity-polymorphic and add instances for unboxed
    tuples, unboxed sums, `Int#`, `Word#`, `Addr#`, `Float#`, and `Double#`.

  * Introduce `reifyType` to reify the type or kind of a thing referenced by
    `Name`.

## 2.15.0.0 *May 2019*

  * Bundled with GHC 8.8.1

  * In `Language.Haskell.TH.Syntax`, `DataInstD`, `NewTypeInstD`, `TySynEqn`,
    and `RuleP` now all have a `Maybe [TyVarBndr]` argument, which contains a
    list of quantified type variables if an explicit `forall` is present, and
    `Nothing` otherwise. `DataInstD`, `NewTypeInstD`, `TySynEqn` also now use
    a single `Type` argument to represent the left-hand-side to avoid
    malformed type family equations and allow visible kind application.

    Correspondingly, in `Language.Haskell.TH.Lib.Internal`, `pragRuleD`,
    `dataInstD`, `newtypeInstD`, and `tySynEqn` now all have a
    `Maybe [TyVarBndrQ]` argument. Non-API-breaking versions of these
    functions can be found in `Language.Haskell.TH.Lib`. The type signature
    of `tySynEqn` has also changed from `[TypeQ] -> TypeQ -> TySynEqnQ` to
    `(Maybe [TyVarBndrQ]) -> TypeQ -> TypeQ -> TySynEqnQ`, for the same reason
    as in `Language.Haskell.TH.Syntax` above. Consequently, `tySynInstD` also
    changes from `Name -> TySynEqnQ -> DecQ` to `TySynEqnQ -> DecQ`.

  * Add `Lift` instances for `NonEmpty` and `Void`

  * `addForeignFilePath` now support assembler sources (#16180).

## 2.14.0.0 *September 2018*

  * Bundled with GHC 8.6.1

  * Introduce an `addForeignFilePath` function, as well as a corresponding
    `qAddForeignFile` class method to `Quasi`. Unlike `addForeignFile`, which
    takes the contents of the file as an argument, `addForeignFilePath` takes
    as an argument a path pointing to a foreign file. A new `addForeignSource`
    function has also been added which takes a file's contents as an argument.

    The old `addForeignFile` function is now deprecated in favor of
    `addForeignSource`, and the `qAddForeignFile` method of `Quasi` has been
    removed entirely.

  * Introduce an `addTempFile` function, as well as a corresponding
    `qAddTempFile` method to `Quasi`, which requests a temporary file of
    a given suffix.

  * Add a `ViaStrategy` constructor to `DerivStrategy`.

  * Add support for `-XImplicitParams` via `ImplicitParamT`,
    `ImplicitParamVarE`, and `ImplicitParamBindD`.

  * Add support for `-XRecursiveDo` via `MDoE` and `RecS`.

## 2.13.0.0 *March 2018*

  * Bundled with GHC 8.4.1

  * `Language.Haskell.TH.FamFlavour`, which was deprecated in 2.11,
    has been removed.

  * Add support for overloaded labels. Introduces `labelE :: String -> ExpQ`.

  * Add `KindQ`, `TyVarBndrQ`, and `FamilyResultSigQ` aliases to
    `Language.Haskell.TH.Lib`.

  * Add `Language.Haskell.TH.Lib.Internal` module, which exposes some
    additional functionality that is used internally in GHC's integration
    with Template Haskell. This is not a part of the public API, and as
    such, there are no API guarantees for this module from version to version.

  * `MonadIO` is now a superclass of `Quasi`, `qRunIO` has a default
    implementation `qRunIO = liftIO`

  * Add `MonadIO Q` instance

## 2.12.0.0 *July 2017*

  * Bundled with GHC 8.2.1

  * Add support for pattern synonyms. This introduces one new constructor to
    `Info` (`PatSynI`), two new constructors to `Dec` (`PatSynD` and
    `PatSynSigD`), and two new data types (`PatSynDir` and `PatSynArgs`),
    among other changes. (#8761)

  * Add support for unboxed sums. (#12478)

  * Add support for visible type applications. (#12530)

  * Add support for attaching deriving strategies to `deriving` statements
    (#10598)

  * Add support for `COMPLETE` pragmas. (#13098)

  * `unboxedTupleTypeName` and `unboxedTupleDataName` now work for unboxed
    0-tuples and 1-tuples (#12977)

  * `Language.Haskell.TH` now reexports all of `Language.Haskell.TH.Lib`.
    (#12992). This causes `Language.Haskell.TH` to export more types and
    functions that it did before:
    - `TExp`, `BangQ`, and `FieldExpQ`
    - `unboxedTupP`, `unboxedTupE` and `unboundVarE`
    - `infixLD`, `infixRD`, and `infixND`
    - `unboxedTupleT` and `wildCardT`
    - `plainTV` and `kindedTV`
    - `interruptible` and `funDep`
    - `valueAnnotation`, `typeAnnotation`, and `moduleAnnotation`

  * Add support for overloaded labels.

## 2.11.0.0  *May 2016*

  * Bundled with GHC 8.0.1

  * The compiler can now resolve infix operator fixities in types on its own.
    The `UInfixT` constructor of `Type` is analoguous to `UInfixE` for expressions
    and can contain a tree of infix type applications which will be reassociated
    according to the fixities of the operators. The `ParensT` constructor can be
    used to explicitly group expressions.

  * Add `namePackage` and `nameSpace`

  * Make `dataToQa` and `dataToExpQ` able to handle `Data` instances whose
    `toConstr` implementation relies on a function instead of a data
    constructor (#10796)

  * Add `Show` instances for `NameFlavour` and `NameSpace`

  * Remove `FamilyD` and `FamFlavour`.  Add `DataFamilyD` and `OpenTypeFamilyD`
    as the representation of data families and open type families
    respectively. (#6018)

  * Add `TypeFamilyHead` for common elements of `OpenTypeFamilyD` and
    `ClosedTypeFamilyD` (#10902)

  * The `Strict` datatype was split among different datatypes: three for
    writing the strictness information of data constructors' fields as denoted
    in Haskell source code (`SourceUnpackedness` and `SourceStrictness`, as
    well as `Bang`), and one for strictness information after a constructor is
    compiled (`DecidedStrictness`). `Strict`, `StrictType` and `VarStrictType`
    have been deprecated in favor of `Bang`, `BangType` and `VarBangType`.
    (#10697)

  * Add `reifyConStrictness` to query a data constructor's `DecidedStrictness`
    values for its fields (#10697)

  * The `ClassOpI`, `DataConI`, and `VarI` constructors no longer have a
    `Fixity` field. Instead, all `Fixity` information for a given `Name` is
    now determined through the `reifyFixity` function, which returns `Just` the
    fixity if there is an explicit fixity declaration for that `Name`, and
    `Nothing` otherwise (#10704 and #11345)

  * Add `MonadFail Q` instance for GHC 8.0 and later (#11661)

  * Add support for OVERLAP(S/PED/PING) pragmas on instances


## 2.10.0.0  *Mar 2015*

  * Bundled with GHC 7.10.1
  * Remove build-dependency on `containers` package
  * Make `Pred` a type synonym of `Type`, and deprecate `classP`/`equalP` (#7021)
  * Add support for `LINE` pragma via `prageLineD` and `LineP`
  * Replace `Int#` with `!Int` in `NameFlavour` constructors
  * Derive `Generic` for TH types (#9527)
  * Add `standaloneDerivD` (#8100)
  * Add support for generic default signatures via `defaultSigD` (#9064)
  * Add `Lift` instances for `()` and `Rational`
  * Derive new `Show` and `Data` instances for `Loc`
  * Derive `Eq` instances for `Loc`, `Info`, and `ModuleInfo`
  * Make calling conventions available in template haskell consistent
    with those from GHC (#9703)
  * Add support for `-XStaticValues` via `staticE`
  * Add `Ord` instances to TH types
  * Merge some instances from `th-orphans` (`Ppr` instances for `Lit`
    and `Loc` as well as `Lift` instances for numeric types
  * Put parens around `(ty :: kind)` when pretty-printing TH syntax