122 lines
3.2 KiB
Rust
122 lines
3.2 KiB
Rust
// Tagged dispatch mechanism for resolving the behavior of `anyhow!($expr)`.
|
|
//
|
|
// When anyhow! is given a single expr argument to turn into anyhow::Error, we
|
|
// want the resulting Error to pick up the input's implementation of source()
|
|
// and backtrace() if it has a std::error::Error impl, otherwise require nothing
|
|
// more than Display and Debug.
|
|
//
|
|
// Expressed in terms of specialization, we want something like:
|
|
//
|
|
// trait AnyhowNew {
|
|
// fn new(self) -> Error;
|
|
// }
|
|
//
|
|
// impl<T> AnyhowNew for T
|
|
// where
|
|
// T: Display + Debug + Send + Sync + 'static,
|
|
// {
|
|
// default fn new(self) -> Error {
|
|
// /* no std error impl */
|
|
// }
|
|
// }
|
|
//
|
|
// impl<T> AnyhowNew for T
|
|
// where
|
|
// T: std::error::Error + Send + Sync + 'static,
|
|
// {
|
|
// fn new(self) -> Error {
|
|
// /* use std error's source() and backtrace() */
|
|
// }
|
|
// }
|
|
//
|
|
// Since specialization is not stable yet, instead we rely on autoref behavior
|
|
// of method resolution to perform tagged dispatch. Here we have two traits
|
|
// AdhocKind and TraitKind that both have an anyhow_kind() method. AdhocKind is
|
|
// implemented whether or not the caller's type has a std error impl, while
|
|
// TraitKind is implemented only when a std error impl does exist. The ambiguity
|
|
// is resolved by AdhocKind requiring an extra autoref so that it has lower
|
|
// precedence.
|
|
//
|
|
// The anyhow! macro will set up the call in this form:
|
|
//
|
|
// #[allow(unused_imports)]
|
|
// use $crate::__private::{AdhocKind, TraitKind};
|
|
// let error = $msg;
|
|
// (&error).anyhow_kind().new(error)
|
|
|
|
use crate::Error;
|
|
use core::fmt::{Debug, Display};
|
|
|
|
#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
|
|
use crate::StdError;
|
|
#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
|
|
use alloc::boxed::Box;
|
|
|
|
pub struct Adhoc;
|
|
|
|
#[doc(hidden)]
|
|
pub trait AdhocKind: Sized {
|
|
#[inline]
|
|
fn anyhow_kind(&self) -> Adhoc {
|
|
Adhoc
|
|
}
|
|
}
|
|
|
|
impl<T> AdhocKind for &T where T: ?Sized + Display + Debug + Send + Sync + 'static {}
|
|
|
|
impl Adhoc {
|
|
#[cold]
|
|
pub fn new<M>(self, message: M) -> Error
|
|
where
|
|
M: Display + Debug + Send + Sync + 'static,
|
|
{
|
|
Error::construct_from_adhoc(message, backtrace!())
|
|
}
|
|
}
|
|
|
|
pub struct Trait;
|
|
|
|
#[doc(hidden)]
|
|
pub trait TraitKind: Sized {
|
|
#[inline]
|
|
fn anyhow_kind(&self) -> Trait {
|
|
Trait
|
|
}
|
|
}
|
|
|
|
impl<E> TraitKind for E where E: Into<Error> {}
|
|
|
|
impl Trait {
|
|
#[cold]
|
|
pub fn new<E>(self, error: E) -> Error
|
|
where
|
|
E: Into<Error>,
|
|
{
|
|
error.into()
|
|
}
|
|
}
|
|
|
|
#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
|
|
pub struct Boxed;
|
|
|
|
#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
|
|
#[doc(hidden)]
|
|
pub trait BoxedKind: Sized {
|
|
#[inline]
|
|
fn anyhow_kind(&self) -> Boxed {
|
|
Boxed
|
|
}
|
|
}
|
|
|
|
#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
|
|
impl BoxedKind for Box<dyn StdError + Send + Sync> {}
|
|
|
|
#[cfg(any(feature = "std", not(anyhow_no_core_error)))]
|
|
impl Boxed {
|
|
#[cold]
|
|
pub fn new(self, error: Box<dyn StdError + Send + Sync>) -> Error {
|
|
let backtrace = backtrace_if_absent!(&*error);
|
|
Error::construct_from_boxed(error, backtrace)
|
|
}
|
|
}
|