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Auto merge of #53212 - sunjay:nll-raw-cast, r=nikomatsakis
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NLL - Prevent where clauses from extending the lifetime of bindings

Fixes #53123

r? @nikomatsakis
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bors committed Aug 15, 2018
2 parents afd0a2f + 6447651 commit 81cfaad
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Showing 2 changed files with 49 additions and 1 deletion.
15 changes: 14 additions & 1 deletion src/librustc/traits/select.rs
Original file line number Diff line number Diff line change
Expand Up @@ -226,6 +226,7 @@ pub struct SelectionCache<'tcx> {
/// parameter environment.
#[derive(PartialEq,Eq,Debug,Clone)]
enum SelectionCandidate<'tcx> {
/// If has_nested is false, there are no *further* obligations
BuiltinCandidate { has_nested: bool },
ParamCandidate(ty::PolyTraitRef<'tcx>),
ImplCandidate(DefId),
Expand Down Expand Up @@ -2039,12 +2040,20 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
}

match other.candidate {
// Prefer BuiltinCandidate { has_nested: false } to anything else.
// This is a fix for #53123 and prevents winnowing from accidentally extending the
// lifetime of a variable.
BuiltinCandidate { has_nested: false } => true,
ParamCandidate(ref cand) => match victim.candidate {
AutoImplCandidate(..) => {
bug!(
"default implementations shouldn't be recorded \
when there are other valid candidates");
}
// Prefer BuiltinCandidate { has_nested: false } to anything else.
// This is a fix for #53123 and prevents winnowing from accidentally extending the
// lifetime of a variable.
BuiltinCandidate { has_nested: false } => false,
ImplCandidate(..) |
ClosureCandidate |
GeneratorCandidate |
Expand Down Expand Up @@ -2072,6 +2081,10 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
"default implementations shouldn't be recorded \
when there are other valid candidates");
}
// Prefer BuiltinCandidate { has_nested: false } to anything else.
// This is a fix for #53123 and prevents winnowing from accidentally extending the
// lifetime of a variable.
BuiltinCandidate { has_nested: false } => false,
ImplCandidate(..) |
ClosureCandidate |
GeneratorCandidate |
Expand Down Expand Up @@ -2115,7 +2128,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
FnPointerCandidate |
BuiltinObjectCandidate |
BuiltinUnsizeCandidate |
BuiltinCandidate { .. } => {
BuiltinCandidate { has_nested: true } => {
match victim.candidate {
ParamCandidate(ref cand) => {
// Prefer these to a global where-clause bound
Expand Down
35 changes: 35 additions & 0 deletions src/test/run-pass/nll/issue-53123-raw-pointer-cast.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
// Copyright 2016 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.

#![feature(nll)]
#![allow(unused_variables)]

pub trait TryTransform {
fn try_transform<F>(self, f: F)
where
Self: Sized,
F: FnOnce(Self);
}

impl<'a, T> TryTransform for &'a mut T {
fn try_transform<F>(self, f: F)
where
// The bug was that `Self: Sized` caused the lifetime of `this` to "extend" for all
// of 'a instead of only lasting as long as the binding is used (for just that line).
Self: Sized,
F: FnOnce(Self),
{
let this: *mut T = self as *mut T;
f(self);
}
}

fn main() {
}

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