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C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.P-mediumMedium priorityMedium priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.regression-from-stable-to-stablePerformance or correctness regression from one stable version to another.Performance or correctness regression from one stable version to another.
Description
The compile time for the following code has increased significantly since the last stable:
extern crate futures;
use futures::{future, IntoFuture, Future};
fn main() {
let t: std::result::Result<(), ()> = Ok(());
let f = t
.into_future()
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()))
.and_then(|_| future::ok(()));
f.wait();
}
Ignoring the fact that the translation
phase takes forever (tracked in #38528), the borrow checking
phase now takes orders of magnitude longer than on the last stable:
$ cargo +stable rustc -- -Z time-passes | grep "borrow checking"
time: 0.000; rss: 88MB borrow checking $ cargo +nightly rustc -- -Z time-passes | grep "borrow checking"
time: 1.173; rss: 101MB borrow checking
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C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.P-mediumMedium priorityMedium priorityT-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.regression-from-stable-to-stablePerformance or correctness regression from one stable version to another.Performance or correctness regression from one stable version to another.