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NLL migration in the 2018 edition needs two-phase borrows too! #52975

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14 changes: 11 additions & 3 deletions src/librustc/ty/context.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1395,10 +1395,18 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
}

/// If true, we should enable two-phase borrows checks. This is
/// done with either `-Ztwo-phase-borrows` or with
/// `#![feature(nll)]`.
/// done with either: `-Ztwo-phase-borrows`, `#![feature(nll)]`,
/// or by opting into an edition after 2015.
pub fn two_phase_borrows(self) -> bool {
self.features().nll || self.sess.opts.debugging_opts.two_phase_borrows
if self.features().nll || self.sess.opts.debugging_opts.two_phase_borrows {
return true;
}

match self.sess.edition() {
Edition::Edition2015 => false,
Edition::Edition2018 => true,
_ => true,
}
}

/// What mode(s) of borrowck should we run? AST? MIR? both?
Expand Down
Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
// 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.

// This is a regression test for #52967, where we discovered that in
// the initial deployment of NLL for the 2018 edition, I forgot to
// turn on two-phase-borrows in addition to `-Z borrowck=migrate`.

// revisions: ast zflags edition
//[zflags]compile-flags: -Z borrowck=migrate -Z two-phase-borrows
//[edition]compile-flags: --edition 2018

// run-pass

fn the_bug() {
let mut stuff = ("left", "right");
match stuff {
(ref mut left, _) if *left == "left" => { *left = "new left"; }
_ => {}
}
assert_eq!(stuff, ("new left", "right"));
}

fn main() {
the_bug();
}