tests/ui/mir-dataflow/uninits-2.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_maybe_uninit,stop_after_dataflow)]
  11 fn foo(x: &mut S) {
  12     // `x` is initialized here, so maybe-uninit bit is 0.
  13
  14     rustc_peek(&x); //~ ERROR rustc_peek: bit not set
  15
  16     ::std::mem::drop(x);
  17
  18     // `x` definitely uninitialized here, so maybe-uninit bit is 1.
  19     rustc_peek(&x);
  20 }
  21 fn main() {
  22     foo(&mut S(13));
  23     foo(&mut S(13));
  24 }