src/test/ui/union/union-unsafe.rs

   1 // revisions: mir thir
   2 // [thir]compile-flags: -Z thir-unsafeck
   3
   4 #![feature(untagged_unions)]
   5 use std::mem::ManuallyDrop;
   6 use std::cell::RefCell;
   7
   8 union U1 {
   9     a: u8
  10 }
  11
  12 union U2 {
  13     a: ManuallyDrop<String>
  14 }
  15
  16 union U3<T> {
  17     a: ManuallyDrop<T>
  18 }
  19
  20 union U4<T: Copy> {
  21     a: T
  22 }
  23
  24 union URef {
  25     p: &'static mut i32,
  26 }
  27
  28 union URefCell { // field that does not drop but is not `Copy`, either
  29     a: (RefCell<i32>, i32),
  30 }
  31
  32 fn deref_union_field(mut u: URef) {
  33     // Not an assignment but an access to the union field!
  34     *(u.p) = 13; //~ ERROR access to union field is unsafe
  35 }
  36
  37 fn assign_noncopy_union_field(mut u: URefCell) {
  38     // FIXME(thir-unsafeck)
  39     u.a = (RefCell::new(0), 1); //~ ERROR assignment to union field that might need dropping
  40     u.a.0 = RefCell::new(0); //~ ERROR assignment to union field that might need dropping
  41     u.a.1 = 1; // OK
  42 }
  43
  44 fn generic_noncopy<T: Default>() {
  45     let mut u3 = U3 { a: ManuallyDrop::new(T::default()) };
  46     u3.a = ManuallyDrop::new(T::default()); // OK (assignment does not drop)
  47     *u3.a = T::default(); //~ ERROR access to union field is unsafe
  48 }
  49
  50 fn generic_copy<T: Copy + Default>() {
  51     let mut u3 = U3 { a: ManuallyDrop::new(T::default()) };
  52     u3.a = ManuallyDrop::new(T::default()); // OK
  53     *u3.a = T::default(); //~ ERROR access to union field is unsafe
  54
  55     let mut u4 = U4 { a: T::default() };
  56     u4.a = T::default(); // OK
  57 }
  58
  59 fn main() {
  60     let mut u1 = U1 { a: 10 }; // OK
  61     let a = u1.a; //~ ERROR access to union field is unsafe
  62     u1.a = 11; // OK
  63
  64     let U1 { a } = u1; //~ ERROR access to union field is unsafe
  65     if let U1 { a: 12 } = u1 {} //~ ERROR access to union field is unsafe
  66     // let U1 { .. } = u1; // OK
  67
  68     let mut u2 = U2 { a: ManuallyDrop::new(String::from("old")) }; // OK
  69     u2.a = ManuallyDrop::new(String::from("new")); // OK (assignment does not drop)
  70     *u2.a = String::from("new"); //~ ERROR access to union field is unsafe
  71
  72     let mut u3 = U3 { a: ManuallyDrop::new(0) }; // OK
  73     u3.a = ManuallyDrop::new(1); // OK
  74     *u3.a = 1; //~ ERROR access to union field is unsafe
  75
  76     let mut u3 = U3 { a: ManuallyDrop::new(String::from("old")) }; // OK
  77     u3.a = ManuallyDrop::new(String::from("new")); // OK (assignment does not drop)
  78     *u3.a = String::from("new"); //~ ERROR access to union field is unsafe
  79 }