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Auto merge of #54802 - davidtwco:issue-53040, r=pnkfelix

Browse source 
[nll] better error message when returning refs to upvars

Fixes #53040.

r? @nikomatsakis
This commit is contained in:
bors 2018-10-10 14:51:01 +00:00
commit e1041c6cd1
12 changed files with 214 additions and 68 deletions
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14
src/test/ui/borrowck/borrowck-describe-lvalue.ast.nll.stderr
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@ -20,24 +20,22 @@ LL | //[mir]~^ ERROR cannot borrow `x` as mutable more than o
LL | *y = 1;
| ------ first borrow later used here
error: unsatisfied lifetime constraints
error: captured variable cannot escape `FnMut` closure body
--> $DIR/borrowck-describe-lvalue.rs:305:16
|
LL | || {
| --
| ||
| |return type of closure is [closure@$DIR/borrowck-describe-lvalue.rs:305:16: 311:18 x:&'2 mut i32]
| lifetime `'1` represents this closure's body
LL | / || { //[mir]~ ERROR unsatisfied lifetime constraints
| - inferred to be a `FnMut` closure
LL | / || { //[mir]~ ERROR captured variable cannot escape `FnMut` closure body
LL | | let y = &mut x;
LL | | &mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time
LL | | //[mir]~^ ERROR cannot borrow `x` as mutable more than once at a time
LL | | *y = 1;
LL | | drop(y);
LL | | }
| |_________________^ returning this value requires that `'1` must outlive `'2`
| |_________________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body
|
= note: closure implements `FnMut`, so references to captured variables can't escape the closure
= note: `FnMut` closures only have access to their captured variables while they are executing...
= note: ...therefore, they cannot allow references to captured variables to escape
error[E0503]: cannot use `f.x` because it was mutably borrowed
--> $DIR/borrowck-describe-lvalue.rs:53:9

14
src/test/ui/borrowck/borrowck-describe-lvalue.mir.stderr
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@ -20,24 +20,22 @@ LL | //[mir]~^ ERROR cannot borrow `x` as mutable more than o
LL | *y = 1;
| ------ first borrow later used here
error: unsatisfied lifetime constraints
error: captured variable cannot escape `FnMut` closure body
--> $DIR/borrowck-describe-lvalue.rs:305:16
|
LL | || {
| --
| ||
| |return type of closure is [closure@$DIR/borrowck-describe-lvalue.rs:305:16: 311:18 x:&'2 mut i32]
| lifetime `'1` represents this closure's body
LL | / || { //[mir]~ ERROR unsatisfied lifetime constraints
| - inferred to be a `FnMut` closure
LL | / || { //[mir]~ ERROR captured variable cannot escape `FnMut` closure body
LL | | let y = &mut x;
LL | | &mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time
LL | | //[mir]~^ ERROR cannot borrow `x` as mutable more than once at a time
LL | | *y = 1;
LL | | drop(y);
LL | | }
| |_________________^ returning this value requires that `'1` must outlive `'2`
| |_________________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body
|
= note: closure implements `FnMut`, so references to captured variables can't escape the closure
= note: `FnMut` closures only have access to their captured variables while they are executing...
= note: ...therefore, they cannot allow references to captured variables to escape
error[E0503]: cannot use `f.x` because it was mutably borrowed
--> $DIR/borrowck-describe-lvalue.rs:53:9

2
src/test/ui/borrowck/borrowck-describe-lvalue.rs
View file

@ -302,7 +302,7 @@ fn main() {
// FIXME(#49824) -- the free region error below should probably not be there
let mut x = 0;
|| {
|| { //[mir]~ ERROR unsatisfied lifetime constraints
|| { //[mir]~ ERROR captured variable cannot escape `FnMut` closure body
let y = &mut x;
&mut x; //[ast]~ ERROR cannot borrow `**x` as mutable more than once at a time
//[mir]~^ ERROR cannot borrow `x` as mutable more than once at a time

12
src/test/ui/issues/issue-40510-1.nll.stderr
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@ -1,15 +1,13 @@
error: unsatisfied lifetime constraints
error: captured variable cannot escape `FnMut` closure body
--> $DIR/issue-40510-1.rs:18:9
|
LL | || {
| --
| ||
| |return type of closure is &'2 mut std::boxed::Box<()>
| lifetime `'1` represents this closure's body
| - inferred to be a `FnMut` closure
LL | &mut x
| ^^^^^^ returning this value requires that `'1` must outlive `'2`
| ^^^^^^ returns a reference to a captured variable which escapes the closure body
|
= note: closure implements `FnMut`, so references to captured variables can't escape the closure
= note: `FnMut` closures only have access to their captured variables while they are executing...
= note: ...therefore, they cannot allow references to captured variables to escape
error: aborting due to previous error

12
src/test/ui/issues/issue-40510-3.nll.stderr
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@ -1,17 +1,15 @@
error: unsatisfied lifetime constraints
error: captured variable cannot escape `FnMut` closure body
--> $DIR/issue-40510-3.rs:18:9
|
LL | || {
| --
| ||
| |return type of closure is [closure@$DIR/issue-40510-3.rs:18:9: 20:10 x:&'2 mut std::vec::Vec<()>]
| lifetime `'1` represents this closure's body
| - inferred to be a `FnMut` closure
LL | / || {
LL | | x.push(())
LL | | }
| |_________^ returning this value requires that `'1` must outlive `'2`
| |_________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body
|
= note: closure implements `FnMut`, so references to captured variables can't escape the closure
= note: `FnMut` closures only have access to their captured variables while they are executing...
= note: ...therefore, they cannot allow references to captured variables to escape
error: aborting due to previous error

12
src/test/ui/issues/issue-49824.nll.stderr
View file

@ -1,17 +1,15 @@
error: unsatisfied lifetime constraints
error: captured variable cannot escape `FnMut` closure body
--> $DIR/issue-49824.rs:22:9
|
LL | || {
| --
| ||
| |return type of closure is [closure@$DIR/issue-49824.rs:22:9: 24:10 x:&'2 mut i32]
| lifetime `'1` represents this closure's body
| - inferred to be a `FnMut` closure
LL | / || {
LL | | let _y = &mut x;
LL | | }
| |_________^ returning this value requires that `'1` must outlive `'2`
| |_________^ returns a closure that contains a reference to a captured variable, which then escapes the closure body
|
= note: closure implements `FnMut`, so references to captured variables can't escape the closure
= note: `FnMut` closures only have access to their captured variables while they are executing...
= note: ...therefore, they cannot allow references to captured variables to escape
error: aborting due to previous error

16
src/test/ui/nll/issue-53040.rs Normal file
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@ -0,0 +1,16 @@
// Copyright 2017 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)]
fn main() {
let mut v: Vec<()> = Vec::new();
|| &mut v;
}

13
src/test/ui/nll/issue-53040.stderr Normal file
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@ -0,0 +1,13 @@
error: captured variable cannot escape `FnMut` closure body
--> $DIR/issue-53040.rs:15:8
|
LL | || &mut v;
| - ^^^^^^ returns a reference to a captured variable which escapes the closure body
| |
| inferred to be a `FnMut` closure
|
= note: `FnMut` closures only have access to their captured variables while they are executing...
= note: ...therefore, they cannot allow references to captured variables to escape
error: aborting due to previous error

12
src/test/ui/regions/regions-return-ref-to-upvar-issue-17403.nll.stderr
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@ -1,13 +1,13 @@
error: unsatisfied lifetime constraints
error: captured variable cannot escape `FnMut` closure body
--> $DIR/regions-return-ref-to-upvar-issue-17403.rs:17:24
|
LL | let mut f = || &mut x; //~ ERROR cannot infer
| -- ^^^^^^ returning this value requires that `'1` must outlive `'2`
| ||
| |return type of closure is &'2 mut i32
| lifetime `'1` represents this closure's body
| - ^^^^^^ returns a reference to a captured variable which escapes the closure body
| |
| inferred to be a `FnMut` closure
|
= note: closure implements `FnMut`, so references to captured variables can't escape the closure
= note: `FnMut` closures only have access to their captured variables while they are executing...
= note: ...therefore, they cannot allow references to captured variables to escape
error: aborting due to previous error