src/test/ui/consts/promote-not.rs

   1 // ignore-tidy-linelength
   2 // Test various things that we do not want to promote.
   3 #![allow(unconditional_panic, const_err)]
   4 #![feature(const_fn_union)]
   5
   6 use std::cell::Cell;
   7
   8 // We do not promote mutable references.
   9 static mut TEST1: Option<&mut [i32]> = Some(&mut [1, 2, 3]); //~ ERROR temporary value dropped while borrowed
  10
  11 static mut TEST2: &'static mut [i32] = {
  12     let x = &mut [1,2,3]; //~ ERROR temporary value dropped while borrowed
  13     x
  14 };
  15
  16 // We do not promote fn calls in `fn`, including `const fn`.
  17 pub const fn promote_cal(b: bool) -> i32 {
  18     const fn foo() { [()][42] }
  19
  20     if b {
  21         let _x: &'static () = &foo(); //~ ERROR temporary value dropped while borrowed
  22     }
  23     13
  24 }
  25
  26 // We do not promote union field accesses in `fn.
  27 union U { x: i32, y: i32 }
  28 pub const fn promote_union() {
  29     let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
  30 }
  31
  32 // We do not promote union field accesses in `const`, either.
  33 const TEST_UNION: () = {
  34     let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
  35 };
  36
  37 // In a `const`, we do not promote things with interior mutability. Not even if we "project it away".
  38 const TEST_INTERIOR_MUT: () = {
  39     // The "0." case is already ruled out by not permitting any interior mutability in `const`.
  40     let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
  41 };
  42
  43 fn main() {
  44     // We must not promote things with interior mutability. Not even if we "project it away".
  45     let _val: &'static _ = &(Cell::new(1), 2).0; //~ ERROR temporary value dropped while borrowed
  46     let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
  47
  48     // No promotion of fallible operations.
  49     let _val: &'static _ = &(1/0); //~ ERROR temporary value dropped while borrowed
  50     let _val: &'static _ = &(1/(1-1)); //~ ERROR temporary value dropped while borrowed
  51     let _val: &'static _ = &(1%0); //~ ERROR temporary value dropped while borrowed
  52     let _val: &'static _ = &(1%(1-1)); //~ ERROR temporary value dropped while borrowed
  53     let _val: &'static _ = &([1,2,3][4]+1); //~ ERROR temporary value dropped while borrowed
  54 }