//-
// Copyright 2017, 2018 The proptest developers
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
//! Provides higher order `Arbitrary` traits.
//! This is mainly for use by `proptest_derive`.
//!
//! ## Stability note
//!
//! This trait is mainly defined for `proptest_derive` to simplify the
//! mechanics of deriving recursive types. If you have custom containers
//! and want to support recursive for those, it is a good idea to implement
//! this trait.
//!
//! There are clearer and terser ways that work better with
//! inference such as using `proptest::collection::vec(..)`
//! to achieve the same result.
//!
//! For these reasons, the traits here are deliberately
//! not exported in a convenient way.
use crate::std_facade::fmt;
use crate::strategy::{BoxedStrategy, Strategy};
/// `ArbitraryF1` lets you lift a [`Strategy`] to unary
/// type constructors such as `Box`, `Vec`, and `Option`.
///
/// The trait corresponds to
/// [Haskell QuickCheck's `Arbitrary1` type class][HaskellQC].
///
/// [HaskellQC]:
/// https://hackage.haskell.org/package/QuickCheck-2.10.1/docs/Test-QuickCheck-Arbitrary.html#t:Arbitrary1
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
pub trait ArbitraryF1<A: fmt::Debug>: fmt::Debug + Sized {
//==========================================================================
// Implementation note #1
//==========================================================================
// It might be better to do this with generic associated types by
// having an associated type:
//
// `type Strategy<A>: Strategy<Value = Self>;`
//
// But with this setup we will likely loose the ability to add bounds
// such as `Hash + Eq` on `A` which is needed for `HashSet`. We might
// be able to regain this ability with a ConstraintKinds feature.
//
// This alternate formulation will likely work better with type inference.
//
//==========================================================================
// Implementation note #2
//==========================================================================
//
// Until `-> impl Trait` has been stabilized, `BoxedStrategy` must be
// used. This incurs an unfortunate performance penalty - but since
// we are dealing with testing, it is better to provide slowed down and
// somewhat less general functionality than no functionality at all.
// Implementations should just use `.boxed()` in the end.
//==========================================================================
/// The type of parameters that [`lift1_with`] accepts for
/// configuration of the lifted and generated [`Strategy`]. Parameters
/// must implement [`Default`].
///
/// [`lift1_with`]:
/// trait.ArbitraryF1.html#tymethod.lift1_with
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
/// [`Default`]:
/// https://doc.rust-lang.org/nightly/std/default/trait.Default.html
type Parameters: Default;
/// Lifts a given [`Strategy`] to a new [`Strategy`] for the (presumably)
/// bigger type. This is useful for lifting a `Strategy` for `SomeType`
/// to a container such as `Vec<SomeType>`.
///
/// Calling this for the type `X` is the equivalent of using
/// [`X::lift1_with(base, Default::default())`].
///
/// This method is defined in the trait for optimization for the
/// default if you want to do that. It is a logic error to not
/// preserve the semantics when overriding.
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
///
/// [`X::lift1_with(base, Default::default())`]:
/// trait.ArbitraryF1.html#tymethod.lift1_with
fn lift1<AS>(base: AS) -> BoxedStrategy<Self>
where
AS: Strategy<Value = A> + 'static,
{
Self::lift1_with(base, Self::Parameters::default())
}
/// Lifts a given [`Strategy`] to a new [`Strategy`] for the (presumably)
/// bigger type. This is useful for lifting a `Strategy` for `SomeType`
/// to a container such as `Vec` of `SomeType`. The composite strategy is
/// passed the arguments given in `args`.
///
/// If you wish to use the [`default()`] arguments,
/// use [`lift1`] instead.
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
///
/// [`lift1`]: trait.ArbitraryF1.html#method.lift1
///
/// [`default()`]:
/// https://doc.rust-lang.org/nightly/std/default/trait.Default.html
fn lift1_with<AS>(base: AS, args: Self::Parameters) -> BoxedStrategy<Self>
where
AS: Strategy<Value = A> + 'static;
}
/// `ArbitraryF2` lets you lift [`Strategy`] to binary
/// type constructors such as `Result`, `HashMap`.
///
/// The trait corresponds to
/// [Haskell QuickCheck's `Arbitrary2` type class][HaskellQC].
///
/// [HaskellQC]:
/// https://hackage.haskell.org/package/QuickCheck-2.10.1/docs/Test-QuickCheck-Arbitrary.html#t:Arbitrary2
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
pub trait ArbitraryF2<A: fmt::Debug, B: fmt::Debug>:
fmt::Debug + Sized
{
/// The type of parameters that [`lift2_with`] accepts for
/// configuration of the lifted and generated [`Strategy`]. Parameters
/// must implement [`Default`].
///
/// [`lift2_with`]: trait.ArbitraryF2.html#tymethod.lift2_with
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
///
/// [`Default`]:
/// https://doc.rust-lang.org/nightly/std/default/trait.Default.html
type Parameters: Default;
/// Lifts two given strategies to a new [`Strategy`] for the (presumably)
/// bigger type. This is useful for lifting a `Strategy` for `Type1`
/// and one for `Type2` to a container such as `HashMap<Type1, Type2>`.
///
/// Calling this for the type `X` is the equivalent of using
/// [`X::lift2_with(base, Default::default())`].
///
/// This method is defined in the trait for optimization for the
/// default if you want to do that. It is a logic error to not
/// preserve the semantics when overriding.
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
///
/// [`X::lift2_with(base, Default::default())`]:
/// trait.Arbitrary.html#tymethod.lift2_with
fn lift2<AS, BS>(fst: AS, snd: BS) -> BoxedStrategy<Self>
where
AS: Strategy<Value = A> + 'static,
BS: Strategy<Value = B> + 'static,
{
Self::lift2_with(fst, snd, Self::Parameters::default())
}
/// Lifts two given strategies to a new [`Strategy`] for the (presumably)
/// bigger type. This is useful for lifting a `Strategy` for `Type1`
/// and one for `Type2` to a container such as `HashMap<Type1, Type2>`.
/// The composite strategy is passed the arguments given in `args`.
///
/// If you wish to use the [`default()`] arguments,
/// use [`lift2`] instead.
///
/// [`Strategy`]: ../proptest/strategy/trait.Strategy.html
///
/// [`lift2`]: trait.ArbitraryF2.html#method.lift2
///
/// [`default()`]:
/// https://doc.rust-lang.org/nightly/std/default/trait.Default.html
fn lift2_with<AS, BS>(
fst: AS,
snd: BS,
args: Self::Parameters,
) -> BoxedStrategy<Self>
where
AS: Strategy<Value = A> + 'static,
BS: Strategy<Value = B> + 'static;
}
macro_rules! lift1 {
([$($bounds : tt)*] $typ: ty, $params: ty;
$base: ident, $args: ident => $logic: expr) => {
impl<A: ::core::fmt::Debug + $($bounds)*>
$crate::arbitrary::functor::ArbitraryF1<A>
for $typ {
type Parameters = $params;
fn lift1_with<S>($base: S, $args: Self::Parameters)
-> $crate::strategy::BoxedStrategy<Self>
where
S: $crate::strategy::Strategy<Value = A> + 'static
{
$crate::strategy::Strategy::boxed($logic)
}
}
};
([$($bounds : tt)*] $typ: ty; $base: ident => $logic: expr) => {
lift1!([$($bounds)*] $typ, (); $base, _args => $logic);
};
([$($bounds : tt)*] $typ: ty; $mapper: expr) => {
lift1!(['static + $($bounds)*] $typ; base =>
$crate::strategy::Strategy::prop_map(base, $mapper));
};
([$($bounds : tt)*] $typ: ty) => {
lift1!(['static + $($bounds)*] $typ; base =>
$crate::strategy::Strategy::prop_map_into(base));
};
}