Changelog for the `singletons-base` project =========================================== 3.2 [2023.03.12] ---------------- * Require building with GHC 9.6. * The kinds of the promoted `Error` and `ErrorWithoutStackTrace` functions have been monomorphized to `Symbol`. A previous release generalized the kinds of these arguments to allow passing arguments besides `Symbol`s, but this change introduces ambiguity in derived code when `OverloadedString`s is enabled. See [#89](https://github.com/goldfirere/singletons/issues/89) for the full story. If you were relying on the previous, kind-polymorphic behavior of `Error`, you can instead use the new `Data.Singletons.Base.PolyError` module that provides `PolyError`, a version of `Error` with a kind-polymorphic argument. * `Data.Ord.Singletons` and `Data.Singletons.Base.TH` no longer define a `thenCmp :: Ordering -> Ordering -> Ordering` function, as this is not something that has ever existed in `base`. The existence of a `thenCmp` function was solely motivated by the code generated by derived `Ord` instances, but `singletons-base` now uses `(<>) @Ordering` instead. * `GHC.TypeLits.Singletons` now re-exports the `SChar`, `SNat`, and `SSymbol` singleton types offered by `GHC.TypeLits` in `base-4.18.0.0` rather than defining its own versions. The versions of `SChar`, `SNat`, and `SSymbol` offered by `GHC.TypeLits` are nearly identical, minus some minor cosmetic changes (e.g., `GHC.TypeLits` defines pattern synonyms for `SNat` _et a._ instead of data constructors). * `GHC.TypeLits.Singletons` now re-exports the `SSymbol` pattern synonym from `GHC.TypeLits`. `GHC.TypeLits.Singletons` also continues to export `SSym` for backwards compatibility. * `Prelude.Singletons` now re-exports `LiftA2` and `sLiftA2`, mirroring the fact that `Prelude` now re-exports `liftA2` in `base-4.18.0.0`. * Provide `TestEquality` and `TestCoercion` instances for `SNat, `SSymbol`, and `SChar`. 3.1.1 [2022.08.23] ------------------ * Require building with GHC 9.4. 3.1 [2021.10.30] ---------------- * Require building with GHC 9.2. * `singletons-base` now supports type-level `Char`s, a feature added in GHC 9.2. In particular: * Promoting and singling character literal expressions (e.g., `f = 'a'`) is now supported. Promoting (but not singling) character patterns (e.g., `g 'a' = ()`) is also supported. * `GHC.TypeLits.Singletons` now offers singled versions of the `ConsSymbol`, `UnconsSymbol`, `CharToNat`, and `NatToChar` type families that were introduced to `GHC.TypeLits` in GHC 9.2. * `Text.Show.Singletons` now makes use of type-level `Char`s, a feature added in GHC 9.2. As a result, there is no longer any need for the `SChar` type synonym, so it has been removed. * The `PShow` and `SShow` instances for `Symbol` now display escape characters properly rather than returning the input `Symbol` unchanged. * In GHC 9.2, `Nat` is now a synonym for `Natural`. As a result, the bogus `Num`, `Eq`, `Ord`, `Enum`, and `Show` instances for `Nat` in `GHC.TypeLits.Singletons` have been removed, as they have replaced by the corresponding instances for `Natural`. * Add `Data.Functor.{Compose,Product,Sum}.Singletons`. * The types of various entities in `Data.Functor.Const.Singletons` and `Data.Proxy.Singletons` have been tweaked slightly such that their specificities match their term-level counterparts: ```diff -SConst :: forall {k} {a} {b :: k} (x :: a). Sing x -> Sing ('Const @a @b x) +SConst :: forall {k} a (b :: k) (x :: a). Sing x -> Sing ('Const @a @b x) -type ConstSym0 :: forall k a (b :: k). a ~> Const a b +type ConstSym0 :: forall {k} a (b :: k). a ~> Const a b -type ConstSym1 :: forall k a (b :: k). a -> Const a b +type ConstSym1 :: forall {k} a (b :: k). a -> Const a b -type ProxySym0 :: forall k (t :: k). Proxy t +type ProxySym0 :: forall {k} (t :: k). Proxy t ``` * Define instances of `SingI1` and `SingI2` when possible. 3.0 [2021.03.12] ---------------- * The `singletons` library has been split into three libraries: * The new `singletons` library is now a minimal library that only provides `Data.Singletons`, `Data.Singletons.Decide`, `Data.Singletons.Sigma`, and `Data.Singletons.ShowSing` (if compiled with GHC 8.6 or later). `singletons` now supports building GHCs back to GHC 8.0, as well as GHCJS. * The `singletons-th` library defines Template Haskell functionality for promoting and singling term-level definitions, but but nothing else. This library continues to require the latest stable release of GHC. * The `singletons-base` library defines promoted and singled versions of definitions from the `base` library, including the `Prelude`. This library continues to require the latest stable release of GHC. Consult the changelogs for `singletons` and `singletons-th` for changes specific to those libraries. For more information on this split, see the [relevant GitHub discussion](https://github.com/goldfirere/singletons/issues/420). * Require building with GHC 9.0. * The modules in `singletons-base` have been renamed to better reflect the modules from `base` from which they take inspiration. In particular, the following module renamings have been applied: * `Data.Singletons.CustomStar` -> `Data.Singletons.Base.CustomStar` * `Data.Singletons.Prelude` -> `Prelude.Singletons` * `Data.Singletons.Prelude.Applicative` -> `Control.Applicative.Singletons` * `Data.Singletons.Prelude.Bool` -> `Data.Bool.Singletons` * `Data.Singletons.Prelude.Const` -> `Data.Functor.Const.Singletons` * `Data.Singletons.Prelude.Either` -> `Data.Either.Singletons` * `Data.Singletons.Prelude.Enum` -> `Data.Singletons.Base.Enum` * `Data.Singletons.Prelude.Eq` -> `Data.Eq.Singletons` * `Data.Singletons.Prelude.Foldable` -> `Data.Foldable.Singletons` * `Data.Singletons.Prelude.Function` -> `Data.Function.Singletons` * `Data.Singletons.Prelude.Functor` -> `Data.Functor.Const.Singletons` * `Data.Singletons.Prelude.Identity` -> `Data.Functor.Identity.Singletons` * `Data.Singletons.Prelude.IsString` -> `Data.String.Singletons` * `Data.Singletons.Prelude.Ord` -> `Data.Ord.Singletons` * `Data.Singletons.Prelude.List` -> `Data.List.Singletons` * `Data.Singletons.Prelude.List.NonEmpty` -> `Data.List.NonEmpty.Singletons` * `Data.Singletons.Prelude.Maybe` -> `Data.Maybe.Singletons` * `Data.Singletons.Prelude.Monad` -> `Control.Monad.Singletons` * `Data.Singletons.Prelude.Monad.Fail` -> `Control.Monad.Fail.Singletons` * `Data.Singletons.Prelude.Monad.Zip` -> `Control.Monad.Zip.Singletons` * `Data.Singletons.Prelude.Monoid` -> `Data.Monoid.Singletons` * `Data.Singletons.Prelude.Proxy` -> `Data.Proxy.Singletons` * `Data.Singletons.Prelude.Semigroup` -> `Data.Semigroup.Singletons` * `Data.Singletons.Prelude.Show` -> `Data.Show.Singletons` * `Data.Singletons.Prelude.Traversable` -> `Data.Traversable.Singletons` * `Data.Singletons.Prelude.Tuple` -> `Data.Tuple.Singletons` * `Data.Singletons.Prelude.Void` -> `Data.Void.Singletons` * `Data.Singletons.TH` -> `Data.Singletons.Base.TH` * `Data.Singletons.TypeError` -> `Data.Singletons.Base.TypeError` * `Data.Singletons.TypeLits` -> `GHC.TypeLits.Singletons` * `Data.Singletons.TypeRepTYPE` -> `Data.Singletons.Base.TypeRepTYPE` Note that modules that do not correspond to any particular module in `base` now have the prefix `Data.Singletons.Base.*`. This includes `Data.Singletons.Base.Enum`, a special module that exists to provide a home for the `Succ` and `Pred` promoted type families that is separate from `Prelude.Singletons` (which exports everything from `PEnum` _except_ `Succ` and `Pred`). This is done in an effort to make importing `Prelude.Singletons` less likely to induce name clashes with code that works over unary natural numbers, which often use the names "`Succ`" and "`Pred`". * An effort has been made to make the API of `Prelude.Singletons` more closely mirror that of the `Prelude` in `base`. As a result, `Prelude.Singletons` now exports some different functions than it used to. In particular, it now exports the following: * `Until`/`sUntil`/`UntilSym{N}` * `type (++@#@$$$)` * `type (.@#@$$$$)` * `FlipSym3` * `type (!!)`/`(%!!)`/`type (!!@#@{$})` * `Length`/`sLength`/`LengthSym{N}` * `DropWhile`/`sDropWhile` * `LookupSym{N}` * `Unzip3Sym{N}` `Prelude.Singletons` also used to export some things that were _not_ exported by the `Prelude`. Accordingly, these exports have been removed from `Prelude.Singletons`. They are: * `(^)`/`(%^)`/`type (^@#@{$})`. Although the `Prelude` does define a function named `(^)`, it is more general than the one defined in `singletons-base`, which only works on `Nat`s. Import `GHC.TypeLits.Singletons` if you wish to use the `Nat`-specific versions. * `DefaultEq`, which has no counterpart in the `Prelude`. Import `Data.Eq.Singletons` if you wish to use this. * `bool_`, which has no counterpart in the `Prelude`. Import `Data.Bool.Singletons` if you wish to use this. * Two previously public-facing modules—`Data.Singletons.Prelude.Base` and `Data.Singletons.Prelude.Num`—have been turned into internal modules. The contents of these modules are re-exported from `Prelude.Singletons`, so that can be used instead. * Due to the `singletons` package split, the `Eq`, `Ord`, etc. instances for `SomeSing` are no longer provided in the `Data.Singletons` module in the `singletons` library. Instead, they are now provided in a new `Data.Singletons.Base.SomeSing` module, which defines `Eq`, `Ord`, etc. instances for `SomeSing` as orphans. * The `PEq` class no longer uses `DefaultEq` as its default implementation for `(==)`. `DefaultEq`, despite its name, is actually not a suitable implementation for `(==)` for a good majority of singleton types (see the discussion in [this GitHub issue](https://github.com/goldfirere/singletons/issues/457) for more information). `(==)`'s default is now defined in terms of `(/=)`, just like its term-level counterpart in the `Eq` class. * Since `base-4.15.0.0` now deprecates `Data.Singletons.Option` (in anticipation of its removal in a future version of `base`), this library no longer offers a singleton type for `Option`. Accordingly, the `option_` function has also been removed.