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Remove redundant Backtrace provide_ref from ContextError #281

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Merged
merged 2 commits into from
Oct 21, 2022
Merged

Remove redundant Backtrace provide_ref from ContextError #281

merged 2 commits into from
Oct 21, 2022

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dtolnay
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@dtolnay dtolnay commented Oct 20, 2022

Back when this line was added in 46d3d2c, it was necessary in order for the following program to successfully obtain the requested backtrace:

#![feature(error_generic_member_access)]

use anyhow::anyhow;
use std::backtrace::Backtrace;

fn main() {
    let error = anyhow!("...").context("...");
    (&*error).request_ref::<Backtrace>().unwrap();
}

However #268 made it redundant, as now self.error.provide(demand) has become a call to:

anyhow/src/error.rs

Lines 534 to 536 in cccc785

fn provide<'a>(&'a self, demand: &mut Demand<'a>) {
unsafe { ErrorImpl::provide(self.inner.by_ref(), demand) }
}

which calls:

anyhow/src/error.rs

Lines 911 to 916 in cccc785

unsafe fn provide<'a>(this: Ref<'a, Self>, demand: &mut Demand<'a>) {
if let Some(backtrace) = &this.deref().backtrace {
demand.provide_ref(backtrace);
}
Self::error(this).provide(demand);
}

@dtolnay dtolnay merged commit 6874b52 into master Oct 21, 2022
@dtolnay dtolnay deleted the redundantprovide branch October 21, 2022 00:02
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@dtolnay