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librustc: Make sure lifetimes in for loop heads outlive the for loop

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itself.

This breaks code like:

    for &x in my_vector.iter() {
        my_vector[2] = "wibble";
        ...
    }

Change this code to not invalidate iterators. For example:

    for i in range(0, my_vector.len()) {
        my_vector[2] = "wibble";
        ...
    }

The `for-loop-does-not-borrow-iterators` test for #8372 was incorrect
and has been removed.

Closes #16820.

[breaking-change]
This commit is contained in:
Patrick Walton 2014-09-08 09:50:18 -07:00
parent d8a26184dc
commit 3ca53d3a10
3 changed files with 23 additions and 30 deletions
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4
src/librustc/middle/typeck/check/regionck.rs
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@ -769,6 +769,10 @@ fn visit_expr(rcx: &mut Rcx, expr: &ast::Expr) {
}
rcx.visit_expr(&**head, ());
type_of_node_must_outlive(rcx,
infer::AddrOf(expr.span),
head.id,
ty::ReScope(expr.id));
let repeating_scope = rcx.set_repeating_scope(body.id);
rcx.visit_block(&**body, ());

19
src/test/compile-fail/borrowck-for-loop-head-linkage.rs Normal file
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@ -0,0 +1,19 @@
// Copyright 2014 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.
fn main() {
let mut vector = vec![1u, 2];
for &x in vector.iter() {
let cap = vector.capacity();
vector.grow(cap, &0u); //~ ERROR cannot borrow
*vector.get_mut(1u) = 5u; //~ ERROR cannot borrow
}
}

30
src/test/run-pass/for-loop-does-not-borrow-iterators.rs
View File

@ -1,30 +0,0 @@
// Copyright 2014 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.
// The `for` loop use to keep a mutable borrow when executing its body,
// making it impossible to re-use the iterator as follows.
// https://github.com/rust-lang/rust/issues/8372
//
// This was fixed in https://github.com/rust-lang/rust/pull/15809
pub fn main() {
let mut for_loop_values = Vec::new();
let mut explicit_next_call_values = Vec::new();
let mut iter = range(1i, 10);
for i in iter {
for_loop_values.push(i);
explicit_next_call_values.push(iter.next());
}
assert_eq!(for_loop_values, vec![1, 3, 5, 7, 9]);
assert_eq!(explicit_next_call_values, vec![Some(2), Some(4), Some(6), Some(8), None]);
}