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
|
//@ revisions: nll_target
// The following revisions are disabled due to missing support for two_phase_beyond_autoref
//@ unused-revision-names: nll_beyond
//@[nll_beyond] compile-flags: -Z two_phase_beyond_autoref
// This is the second counter-example from Niko's blog post
// smallcultfollowing.com/babysteps/blog/2017/03/01/nested-method-calls-via-two-phase-borrowing/
//
// It is "artificial". It is meant to illustrate directly that we
// should allow an aliasing access during reservation, but *not* while
// the mutable borrow is active.
//
// 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() {
/*0*/ let mut i = 0;
/*1*/ let p = &mut i; // (reservation of `i` starts here)
/*2*/ let j = i; // OK: `i` is only reserved here
//[nll_target]~^ ERROR cannot use `i` because it was mutably borrowed [E0503]
/*3*/ *p += 1; // (mutable borrow of `i` starts here, since `p` is used)
/*4*/ let k = i; //[nll_beyond]~ ERROR cannot use `i` because it was mutably borrowed [E0503]
//[nll_target]~^ ERROR cannot use `i` because it was mutably borrowed [E0503]
/*5*/ *p += 1;
let _ = (j, k, p);
}
|
