src/test/compile-fail/borrowck/borrowck-union-borrow.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // ignore-tidy-linelength
  12
  13 #![feature(untagged_unions)]
  14
  15 #[derive(Clone, Copy)]
  16 union U {
  17     a: u8,
  18     b: u64,
  19 }
  20
  21 fn main() {
  22     unsafe {
  23         let mut u = U { b: 0 };
  24         // Imm borrow, same field
  25         {
  26             let ra = &u.a;
  27             let ra2 = &u.a; // OK
  28         }
  29         {
  30             let ra = &u.a;
  31             let a = u.a; // OK
  32         }
  33         {
  34             let ra = &u.a;
  35             let rma = &mut u.a; //~ ERROR cannot borrow `u.a` as mutable because it is also borrowed as immutable
  36         }
  37         {
  38             let ra = &u.a;
  39             u.a = 1; //~ ERROR cannot assign to `u.a` because it is borrowed
  40         }
  41         // Imm borrow, other field
  42         {
  43             let ra = &u.a;
  44             let rb = &u.b; // OK
  45         }
  46         {
  47             let ra = &u.a;
  48             let b = u.b; // OK
  49         }
  50         {
  51             let ra = &u.a;
  52             let rmb = &mut u.b; //~ ERROR cannot borrow `u` (via `u.b`) as mutable because `u` is also borrowed as immutable (via `u.a`)
  53         }
  54         {
  55             let ra = &u.a;
  56             u.b = 1; //~ ERROR cannot assign to `u.b` because it is borrowed
  57         }
  58         // Mut borrow, same field
  59         {
  60             let rma = &mut u.a;
  61             let ra = &u.a; //~ ERROR cannot borrow `u.a` as immutable because it is also borrowed as mutable
  62         }
  63         {
  64             let ra = &mut u.a;
  65             let a = u.a; //~ ERROR cannot use `u.a` because it was mutably borrowed
  66         }
  67         {
  68             let rma = &mut u.a;
  69             let rma2 = &mut u.a; //~ ERROR cannot borrow `u.a` as mutable more than once at a time
  70         }
  71         {
  72             let rma = &mut u.a;
  73             u.a = 1; //~ ERROR cannot assign to `u.a` because it is borrowed
  74         }
  75         // Mut borrow, other field
  76         {
  77             let rma = &mut u.a;
  78             let rb = &u.b; //~ ERROR cannot borrow `u` (via `u.b`) as immutable because `u` is also borrowed as mutable (via `u.a`)
  79         }
  80         {
  81             let ra = &mut u.a;
  82             let b = u.b; //~ ERROR cannot use `u.b` because it was mutably borrowed
  83         }
  84         {
  85             let rma = &mut u.a;
  86             let rmb2 = &mut u.b; //~ ERROR cannot borrow `u` (via `u.b`) as mutable more than once at a time
  87         }
  88         {
  89             let rma = &mut u.a;
  90             u.b = 1; //~ ERROR cannot assign to `u.b` because it is borrowed
  91         }
  92     }
  93 }