tests/ui/mir-dataflow/def-inits-1.rs

   1 // General test of maybe_uninits state computed by MIR dataflow.
   2
   3 #![feature(core_intrinsics, rustc_attrs)]
   4
   5 use std::intrinsics::rustc_peek;
   6 use std::mem::{drop, replace};
   7
   8 struct S(i32);
   9
  10 #[rustc_mir(rustc_peek_definite_init,stop_after_dataflow)]
  11 fn foo(test: bool, x: &mut S, y: S, mut z: S) -> S {
  12     let ret;
  13     // `ret` starts off uninitialized
  14     rustc_peek(&ret);  //~ ERROR rustc_peek: bit not set
  15
  16     // All function formal parameters start off initialized.
  17
  18     rustc_peek(&x);
  19     rustc_peek(&y);
  20     rustc_peek(&z);
  21
  22     ret = if test {
  23         ::std::mem::replace(x, y)
  24     } else {
  25         z = y;
  26         z
  27     };
  28
  29     // `z` may be uninitialized here.
  30     rustc_peek(&z); //~ ERROR rustc_peek: bit not set
  31
  32     // `y` is definitely uninitialized here.
  33     rustc_peek(&y); //~ ERROR rustc_peek: bit not set
  34
  35     // `x` is still (definitely) initialized (replace above is a reborrow).
  36     rustc_peek(&x);
  37
  38     ::std::mem::drop(x);
  39
  40     // `x` is *definitely* uninitialized here
  41     rustc_peek(&x); //~ ERROR rustc_peek: bit not set
  42
  43     // `ret` is now definitely initialized (via `if` above).
  44     rustc_peek(&ret);
  45
  46     ret
  47 }
  48 fn main() {
  49     foo(true, &mut S(13), S(14), S(15));
  50     foo(false, &mut S(13), S(14), S(15));
  51 }