Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Choose predicates without inference variables over those with them #55453

Merged
merged 1 commit into from
Nov 7, 2018
Merged

Choose predicates without inference variables over those with them #55453

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
42 changes: 33 additions & 9 deletions src/librustc/traits/auto_trait.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -447,27 +447,51 @@ impl<'a, 'tcx> AutoTraitFinder<'a, 'tcx> {
ty::RegionKind::ReLateBound(_, _),
) => {}

(ty::RegionKind::ReLateBound(_, _), _) => {
(ty::RegionKind::ReLateBound(_, _), _) |
(_, ty::RegionKind::ReVar(_)) => {
// One of these is true:
// The new predicate has a HRTB in a spot where the old
// predicate does not (if they both had a HRTB, the previous
// match arm would have executed).
// match arm would have executed). A HRBT is a 'stricter'
// bound than anything else, so we want to keep the newer
// predicate (with the HRBT) in place of the old predicate.
//
// The means we want to remove the older predicate from
// user_computed_preds, since having both it and the new
// OR
//
// The old predicate has a region variable where the new
// predicate has some other kind of region. An region
// variable isn't something we can actually display to a user,
// so we choose ther new predicate (which doesn't have a region
// varaible).
//
// In both cases, we want to remove the old predicate,
// from user_computed_preds, and replace it with the new
// one. Having both the old and the new
// predicate in a ParamEnv would confuse SelectionContext
//
// We're currently in the predicate passed to 'retain',
// so we return 'false' to remove the old predicate from
// user_computed_preds
return false;
}
(_, ty::RegionKind::ReLateBound(_, _)) => {
// This is the opposite situation as the previous arm - the
// old predicate has a HRTB lifetime in a place where the
// new predicate does not. We want to leave the old
(_, ty::RegionKind::ReLateBound(_, _)) |
(ty::RegionKind::ReVar(_), _) => {
// This is the opposite situation as the previous arm.
// One of these is true:
//
// The old predicate has a HRTB lifetime in a place where the
// new predicate does not.
//
// OR
//
// The new predicate has a region variable where the old
// predicate has some other type of region.
//
// We want to leave the old
// predicate in user_computed_preds, and skip adding
// new_pred to user_computed_params.
should_add_new = false
}
},
_ => {}
}
}
Expand Down
40 changes: 40 additions & 0 deletions src/test/rustdoc/issue-54705.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.


pub trait ScopeHandle<'scope> {}



// @has issue_54705/struct.ScopeFutureContents.html
// @has - '//*[@id="synthetic-implementations-list"]/*[@class="impl"]//*/code' "impl<'scope, S> \
// Send for ScopeFutureContents<'scope, S> where S: Sync"
//
// @has - '//*[@id="synthetic-implementations-list"]/*[@class="impl"]//*/code' "impl<'scope, S> \
// Sync for ScopeFutureContents<'scope, S> where S: Sync"
pub struct ScopeFutureContents<'scope, S>
where S: ScopeHandle<'scope>,
{
dummy: &'scope S,
this: Box<ScopeFuture<'scope, S>>,
}

struct ScopeFuture<'scope, S>
where S: ScopeHandle<'scope>,
{
contents: ScopeFutureContents<'scope, S>,
}

unsafe impl<'scope, S> Send for ScopeFuture<'scope, S>
where S: ScopeHandle<'scope>,
{}
unsafe impl<'scope, S> Sync for ScopeFuture<'scope, S>
where S: ScopeHandle<'scope>,
{}