1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
|
//@ revisions: nll_target
// The nll_beyond revision is disabled due to missing support from two-phase beyond autorefs
//@ unused-revision-names: nll_beyond
//@[nll_beyond]compile-flags: -Z two-phase-beyond-autoref
//@[nll_beyond]should-fail
// This is a corner case that the current implementation is (probably)
// treating more conservatively than is necessary. But it also does
// not seem like a terribly important use case to cover.
//
// So this test is just making a note of the current behavior, with
// the caveat that in the future, the rules may be loosened, at which
// point this test might be thrown out.
//
// The convention for the listed revisions: "lxl" means lexical
// lifetimes (which can be easier to reason about). "nll" means
// non-lexical lifetimes. "nll_target" means the initial conservative
// two-phase borrows that only applies to autoref-introduced borrows.
// "nll_beyond" means the generalization of two-phase borrows to all
// `&mut`-borrows (doing so makes it easier to write code for specific
// corner cases).
fn main() {
let mut vec = vec![0, 1];
let delay: &mut Vec<_>;
{
let shared = &vec;
// we reserve here, which could (on its own) be compatible
// with the shared borrow. But in the current implementation,
// its an error.
delay = &mut vec;
//[nll_beyond]~^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable
//[nll_target]~^^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable
shared[0];
}
// the &mut-borrow only becomes active way down here.
//
// (At least in theory; part of the reason this test fails is that
// the constructed MIR throws in extra &mut reborrows which
// flummoxes our attempt to delay the activation point here.)
delay.push(2);
}
|
