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//! Thread-safe cloneable wrappers over closures that carry `Send + Sync` bounds.
//!
//! ### Examples
//!
//! ```
//! use {
//! fp_library::{
//! brands::*,
//! functions::*,
//! },
//! std::thread,
//! };
//!
//! let f = send_lift_fn_new::<ArcFnBrand, _, _>(|x: i32| x * 2);
//!
//! // Can be sent to another thread
//! let handle = thread::spawn(move || {
//! assert_eq!(f(5), 10);
//! });
//! handle.join().unwrap();
//! ```
#[fp_macros::document_module]
mod inner {
use {
crate::dispatch::{
ClosureMode,
Ref,
Val,
},
fp_macros::*,
std::ops::Deref,
};
/// Abstraction for thread-safe cloneable wrappers over closures.
///
/// This trait mirrors [`CloneFn`] with additional `Send + Sync` bounds on the
/// wrapped closure and the wrapper itself. It is a separate, independent trait
/// (not a supertrait of `CloneFn`) because its [`Of`](Self::Of) associated type
/// derefs to `dyn Fn + Send + Sync`, which is a different unsized type than the
/// `dyn Fn` target used by `CloneFn::Of`. Types like
/// [`FnBrand<P>`](crate::brands::FnBrand) implement both traits when the
/// pointer `P` supports it ([`ArcFnBrand`][crate::brands::ArcFnBrand]
/// implements both; [`RcFnBrand`][crate::brands::RcFnBrand] implements only
/// `CloneFn`).
///
/// The `Mode` parameter selects whether the wrapped closure takes its input
/// by value (`Val`, the default) or by reference (`Ref`).
///
/// The lifetime `'a` ensures the function doesn't outlive referenced data,
/// while generic types `A` and `B` represent the input and output types, respectively.
///
/// By explicitly requiring that both type parameters outlive the application lifetime `'a`,
/// we provide the compiler with the necessary guarantees to handle trait objects
/// (like `dyn Fn`) commonly used in thread-safe function wrappers. This resolves potential
/// E0310 errors where the compiler cannot otherwise prove that captured variables in
/// closures satisfy the required lifetime bounds.
#[document_type_parameters(
"Selects whether the wrapped closure takes its input by value (`Val`) or by reference (`Ref`). Defaults to `Val`."
)]
pub trait SendCloneFn<Mode: ClosureMode = Val> {
/// The type of the thread-safe cloneable function wrapper.
///
/// This associated type represents the concrete type of the wrapper (e.g., `Arc<dyn Fn(A) -> B + Send + Sync>`)
/// that implements `Clone`, `Send`, `Sync` and dereferences to the underlying closure.
type Of<'a, A: 'a, B: 'a>: 'a
+ Clone
+ Send
+ Sync
+ Deref<Target = Mode::SendTarget<'a, A, B>>;
}
/// A trait for constructing thread-safe cloneable function wrappers from closures.
///
/// Separated from [`SendCloneFn`] because the `new` method's parameter type
/// depends on the closure mode (`Fn(A) -> B + Send + Sync` for `Val`), and a single
/// trait method cannot have a mode-dependent signature.
pub trait SendLiftFn: SendCloneFn<Val> {
/// Creates a new thread-safe cloneable function wrapper.
///
/// This method wraps a closure into a thread-safe cloneable function wrapper.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The input type of the function.",
"The output type of the function."
)]
///
#[document_parameters("The closure to wrap. Must be `Send + Sync`.")]
#[document_returns("The wrapped thread-safe cloneable function.")]
#[document_examples]
///
/// ```
/// use {
/// fp_library::{
/// brands::*,
/// functions::*,
/// },
/// std::thread,
/// };
///
/// let f = send_lift_fn_new::<ArcFnBrand, _, _>(|x: i32| x * 2);
///
/// // Can be sent to another thread
/// let handle = thread::spawn(move || {
/// assert_eq!(f(5), 10);
/// });
/// handle.join().unwrap();
/// ```
fn new<'a, A: 'a, B: 'a>(
f: impl 'a + Fn(A) -> B + Send + Sync
) -> <Self as SendCloneFn>::Of<'a, A, B>;
}
/// Creates a new thread-safe cloneable function wrapper.
///
/// Free function version that dispatches to [the type class' associated function][`SendLiftFn::new`].
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The brand of the thread-safe cloneable function wrapper.",
"The input type of the function.",
"The output type of the function."
)]
///
#[document_parameters("The closure to wrap. Must be `Send + Sync`.")]
#[document_returns("The wrapped thread-safe cloneable function.")]
#[document_examples]
///
/// ```
/// use {
/// fp_library::{
/// brands::*,
/// functions::*,
/// },
/// std::thread,
/// };
///
/// let f = send_lift_fn_new::<ArcFnBrand, _, _>(|x: i32| x * 2);
///
/// // Can be sent to another thread
/// let handle = thread::spawn(move || {
/// assert_eq!(f(5), 10);
/// });
/// handle.join().unwrap();
/// ```
pub fn new<'a, Brand, A, B>(
f: impl 'a + Fn(A) -> B + Send + Sync
) -> <Brand as SendCloneFn>::Of<'a, A, B>
where
Brand: SendLiftFn, {
<Brand as SendLiftFn>::new(f)
}
/// A trait for constructing thread-safe Ref-mode cloneable function wrappers.
///
/// This mirrors [`SendLiftFn`] but for by-reference closures (`Fn(&A) -> B + Send + Sync`).
pub trait SendRefLiftFn: SendCloneFn<Ref> {
/// Creates a new thread-safe cloneable by-reference function wrapper.
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The input type (the closure receives `&A`).",
"The output type of the function."
)]
///
#[document_parameters("The by-reference closure to wrap. Must be `Send + Sync`.")]
#[document_returns("The wrapped thread-safe cloneable by-reference function.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let f = send_ref_lift_fn_new::<ArcFnBrand, _, _>(|x: &i32| *x * 2);
/// assert_eq!(f(&5), 10);
/// ```
fn ref_new<'a, A: 'a, B: 'a>(
f: impl 'a + Fn(&A) -> B + Send + Sync
) -> <Self as SendCloneFn<Ref>>::Of<'a, A, B>;
}
/// Creates a new thread-safe cloneable by-reference function wrapper.
///
/// Free function version that dispatches to [`SendRefLiftFn::ref_new`].
#[document_signature]
///
#[document_type_parameters(
"The lifetime of the function and its captured data.",
"The brand of the thread-safe cloneable function wrapper.",
"The input type (the closure receives `&A`).",
"The output type of the function."
)]
///
#[document_parameters("The by-reference closure to wrap. Must be `Send + Sync`.")]
#[document_returns("The wrapped thread-safe cloneable by-reference function.")]
#[document_examples]
///
/// ```
/// use fp_library::{
/// brands::*,
/// functions::*,
/// };
///
/// let f = send_ref_lift_fn_new::<ArcFnBrand, _, _>(|x: &i32| *x * 2);
/// assert_eq!(f(&5), 10);
/// ```
pub fn ref_new<'a, Brand, A, B>(
f: impl 'a + Fn(&A) -> B + Send + Sync
) -> <Brand as SendCloneFn<Ref>>::Of<'a, A, B>
where
Brand: SendRefLiftFn, {
<Brand as SendRefLiftFn>::ref_new(f)
}
}
pub use inner::*;