how.rs/src/explain.rs

103 lines
2.6 KiB
Rust

use std::panic::Location;
use std::sync::Arc;
use crate::{How, IntoContext, Context, Detail};
#[cfg(feature = "backtrace")]
use crate::context::Backtrace;
pub trait Explain {
type Output;
#[track_caller]
#[must_use]
fn context(self, context: impl IntoContext) -> Self::Output;
}
impl Explain for How {
type Output = Self;
#[track_caller]
#[inline]
fn context(mut self, context: impl IntoContext) -> Self {
let mut context = context.into_context();
context.extra.reserve(if cfg!(feature = "backtrace") {
2
} else {
1
});
context.extra.push(Detail::Location(*Location::caller()));
#[cfg(feature = "backtrace")]
context.extra.push({
use std::backtrace::BacktraceStatus::*;
let bt = std::backtrace::Backtrace::capture();
let bt = match bt.status() {
Disabled => Backtrace::Disabled,
Unsupported => Backtrace::Unsupported,
status => Backtrace::Other(status, bt.to_string()),
};
Detail::Backtrace(bt)
});
self.push_context(context);
self
}
}
impl<T, E> Explain for Result<T, E>
where
E: std::error::Error + 'static,
{
type Output = Result<T, How>;
#[inline(always)]
#[track_caller]
fn context(self, context: impl IntoContext) -> Self::Output {
#[cold]
#[track_caller]
fn into_and_context<E, C>(e: E, c: C) -> How
where
E: std::error::Error + 'static,
C: IntoContext,
{
match typeid_cast::cast(e) {
Ok(e) => e,
// TODO: specialize on Send + Sync at runtime or compile time (possibly via
// specialization)
//Err(e) => How::new(Context(ContextInner::Elem(Detail::Error(Arc::new(e))))),
Err(e) => How::new(e.to_string()),
}
.context(c)
}
match self {
Ok(t) => Ok(t),
Err(e) => Err(into_and_context(e, context)),
}
}
}
impl<E> Explain for Arc<E>
where
E: std::error::Error + Send + Sync + 'static,
{
type Output = How;
#[track_caller]
fn context(self, context: impl IntoContext) -> Self::Output {
How::new(Context::new(Detail::Error(self)))
.context(context)
}
}
impl<T> Explain for Option<T> {
type Output = Result<T, How>;
#[inline(always)]
#[track_caller]
fn context(self, context: impl IntoContext) -> Self::Output {
match self {
Some(t) => Ok(t),
None => Err(How::new(context)),
}
}
}