| //@ 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); |
| } |
