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

   1 // General test of maybe_inits 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_maybe_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, so we get an error report here.
  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
  30     // `z` may be initialized here.
  31     rustc_peek(&z);
  32
  33     // `y` is definitely uninitialized here.
  34     rustc_peek(&y);  //~ ERROR rustc_peek: bit not set
  35
  36     // `x` is still (definitely) initialized (replace above is a reborrow).
  37     rustc_peek(&x);
  38
  39     ::std::mem::drop(x);
  40
  41     // `x` is *definitely* uninitialized here
  42     rustc_peek(&x); //~ ERROR rustc_peek: bit not set
  43
  44     // `ret` is now definitely initialized (via `if` above).
  45     rustc_peek(&ret);
  46
  47     ret
  48 }
  49
  50 fn main() {
  51     foo(true, &mut S(13), S(14), S(15));
  52     foo(false, &mut S(13), S(14), S(15));
  53 }