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Auto merge of #56649 - davidtwco:issue-46589, r=pnkfelix

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MIR borrowck doesn't accept the example of iterating and updating a mutable reference

Fixes #46589.

r? @pnkfelix or @nikomatsakis
This commit is contained in:
bors 2018-12-20 07:22:15 +00:00
commit 817dda7df0
21 changed files with 307 additions and 191 deletions
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37
src/test/ui/nll/issue-46589.rs Normal file
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@ -0,0 +1,37 @@
// 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)]
struct Foo;
impl Foo {
fn get_self(&mut self) -> Option<&mut Self> {
Some(self)
}
fn new_self(&mut self) -> &mut Self {
self
}
fn trigger_bug(&mut self) {
let other = &mut (&mut *self);
*other = match (*other).get_self() {
Some(s) => s,
None => (*other).new_self()
//~^ ERROR cannot borrow `**other` as mutable more than once at a time [E0499]
};
let c = other;
}
}
fn main() {}

15
src/test/ui/nll/issue-46589.stderr Normal file
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@ -0,0 +1,15 @@
error[E0499]: cannot borrow `**other` as mutable more than once at a time
--> $DIR/issue-46589.rs:29:21
|
LL | *other = match (*other).get_self() {
| -------- first mutable borrow occurs here
LL | Some(s) => s,
LL | None => (*other).new_self()
| ^^^^^^^^
| |
| second mutable borrow occurs here
| first borrow later used here
error: aborting due to previous error
For more information about this error, try `rustc --explain E0499`.

2
src/test/ui/nll/loan_ends_mid_block_pair.rs
View file

@ -27,10 +27,8 @@ fn nll_fail() {
//~| ERROR (Mir) [E0506]
data.0 = 'f';
//~^ ERROR (Ast) [E0506]
//~| ERROR (Mir) [E0506]
data.0 = 'g';
//~^ ERROR (Ast) [E0506]
//~| ERROR (Mir) [E0506]
capitalize(c);
}

48
src/test/ui/nll/loan_ends_mid_block_pair.stderr
View file

@ -17,7 +17,7 @@ LL | data.0 = 'f';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
error[E0506]: cannot assign to `data.0` because it is borrowed (Ast)
--> $DIR/loan_ends_mid_block_pair.rs:31:5
--> $DIR/loan_ends_mid_block_pair.rs:30:5
|
LL | let c = &mut data.0;
| ------ borrow of `data.0` occurs here
@ -26,7 +26,7 @@ LL | data.0 = 'g';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
error[E0506]: cannot assign to `data.0` because it is borrowed (Ast)
--> $DIR/loan_ends_mid_block_pair.rs:41:5
--> $DIR/loan_ends_mid_block_pair.rs:39:5
|
LL | let c = &mut data.0;
| ------ borrow of `data.0` occurs here
@ -34,21 +34,21 @@ LL | capitalize(c);
LL | data.0 = 'e';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
error[E0506]: cannot assign to `data.0` because it is borrowed (Ast)
--> $DIR/loan_ends_mid_block_pair.rs:41:5
|
LL | let c = &mut data.0;
| ------ borrow of `data.0` occurs here
...
LL | data.0 = 'f';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
error[E0506]: cannot assign to `data.0` because it is borrowed (Ast)
--> $DIR/loan_ends_mid_block_pair.rs:43:5
|
LL | let c = &mut data.0;
| ------ borrow of `data.0` occurs here
...
LL | data.0 = 'f';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
error[E0506]: cannot assign to `data.0` because it is borrowed (Ast)
--> $DIR/loan_ends_mid_block_pair.rs:45:5
|
LL | let c = &mut data.0;
| ------ borrow of `data.0` occurs here
...
LL | data.0 = 'g';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
@ -64,30 +64,6 @@ LL | data.0 = 'e';
LL | capitalize(c);
| - borrow later used here
error[E0506]: cannot assign to `data.0` because it is borrowed (Mir)
--> $DIR/loan_ends_mid_block_pair.rs:28:5
|
LL | let c = &mut data.0;
| ----------- borrow of `data.0` occurs here
...
LL | data.0 = 'f';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
...
LL | capitalize(c);
| - borrow later used here
error[E0506]: cannot assign to `data.0` because it is borrowed (Mir)
--> $DIR/loan_ends_mid_block_pair.rs:31:5
|
LL | let c = &mut data.0;
| ----------- borrow of `data.0` occurs here
...
LL | data.0 = 'g';
| ^^^^^^^^^^^^ assignment to borrowed `data.0` occurs here
...
LL | capitalize(c);
| - borrow later used here
error: aborting due to 9 previous errors
error: aborting due to 7 previous errors
For more information about this error, try `rustc --explain E0506`.