tests/ui/borrowck/two-phase-activation-sharing-interference.rs

   1 // revisions: nll_target
   2
   3 // The following revisions are disabled due to missing support from two-phase beyond autorefs
   4 //[nll_beyond] compile-flags: -Z two-phase-beyond-autoref
   5
   6 // This is an important corner case pointed out by Niko: one is
   7 // allowed to initiate a shared borrow during a reservation, but it
   8 // *must end* before the activation occurs.
   9 //
  10 // FIXME: for clarity, diagnostics for these cases might be better off
  11 // if they specifically said "cannot activate mutable borrow of `x`"
  12 //
  13 // The convention for the listed revisions: "lxl" means lexical
  14 // lifetimes (which can be easier to reason about). "nll" means
  15 // non-lexical lifetimes. "nll_target" means the initial conservative
  16 // two-phase borrows that only applies to autoref-introduced borrows.
  17 // "nll_beyond" means the generalization of two-phase borrows to all
  18 // `&mut`-borrows (doing so makes it easier to write code for specific
  19 // corner cases).
  20
  21 #![allow(dead_code)]
  22
  23 fn read(_: &i32) { }
  24
  25 fn ok() {
  26     let mut x = 3;
  27     let y = &mut x;
  28     { let z = &x; read(z); }
  29     //[nll_target]~^ ERROR cannot borrow `x` as immutable because it is also borrowed as mutable
  30     *y += 1;
  31 }
  32
  33 fn not_ok() {
  34     let mut x = 3;
  35     let y = &mut x;
  36     let z = &x;
  37     //[nll_target]~^ ERROR cannot borrow `x` as immutable because it is also borrowed as mutable
  38     *y += 1;
  39     //[lxl_beyond]~^   ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
  40     //[nll_beyond]~^^  ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
  41     read(z);
  42 }
  43
  44 fn should_be_ok_with_nll() {
  45     let mut x = 3;
  46     let y = &mut x;
  47     let z = &x;
  48     //[nll_target]~^ ERROR cannot borrow `x` as immutable because it is also borrowed as mutable
  49     read(z);
  50     *y += 1;
  51     //[lxl_beyond]~^ ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
  52     // (okay with (generalized) nll today)
  53 }
  54
  55 fn should_also_eventually_be_ok_with_nll() {
  56     let mut x = 3;
  57     let y = &mut x;
  58     let _z = &x;
  59     //[nll_target]~^ ERROR cannot borrow `x` as immutable because it is also borrowed as mutable
  60     *y += 1;
  61     //[lxl_beyond]~^ ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
  62     // (okay with (generalized) nll today)
  63 }
  64
  65 fn main() { }