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
   5 use std::cell::Cell;
   6
   7 // We do not promote mutable references.
   8 static mut TEST1: Option<&mut [i32]> = Some(&mut [1, 2, 3]); //~ ERROR temporary value dropped while borrowed
   9
  10 static mut TEST2: &'static mut [i32] = {
  11     let x = &mut [1,2,3]; //~ ERROR temporary value dropped while borrowed
  12     x
  13 };
  14
  15 // We do not promote fn calls in `fn`, including `const fn`.
  16 pub const fn promote_cal(b: bool) -> i32 {
  17     const fn foo() { [()][42] }
  18
  19     if b {
  20         let _x: &'static () = &foo(); //~ ERROR temporary value dropped while borrowed
  21     }
  22     13
  23 }
  24
  25 // We do not promote union field accesses in `fn.
  26 union U { x: i32, y: i32 }
  27 pub const fn promote_union() {
  28     let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
  29 }
  30
  31 // We do not promote union field accesses in `const`, either.
  32 const TEST_UNION: () = {
  33     let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
  34 };
  35
  36 // In a `const`, we do not promote things with interior mutability. Not even if we "project it away".
  37 const TEST_INTERIOR_MUT: () = {
  38     // The "0." case is already ruled out by not permitting any interior mutability in `const`.
  39     let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
  40 };
  41
  42 const TEST_DROP: String = String::new();
  43
  44 fn main() {
  45     // We must not promote things with interior mutability. Not even if we "project it away".
  46     let _val: &'static _ = &(Cell::new(1), 2).0; //~ ERROR temporary value dropped while borrowed
  47     let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
  48
  49     // No promotion of fallible operations.
  50     let _val: &'static _ = &(1/0); //~ ERROR temporary value dropped while borrowed
  51     let _val: &'static _ = &(1/(1-1)); //~ ERROR temporary value dropped while borrowed
  52     let _val: &'static _ = &(1%0); //~ ERROR temporary value dropped while borrowed
  53     let _val: &'static _ = &(1%(1-1)); //~ ERROR temporary value dropped while borrowed
  54     let _val: &'static _ = &([1,2,3][4]+1); //~ ERROR temporary value dropped while borrowed
  55
  56     // No promotion of temporaries that need to be dropped.
  57     let _val: &'static _ = &TEST_DROP;
  58     //~^ ERROR temporary value dropped while borrowed
  59     let _val: &'static _ = &&TEST_DROP;
  60     //~^ ERROR temporary value dropped while borrowed
  61     //~| ERROR temporary value dropped while borrowed
  62     let _val: &'static _ = &(&TEST_DROP,);
  63     //~^ ERROR temporary value dropped while borrowed
  64     //~| ERROR temporary value dropped while borrowed
  65     let _val: &'static _ = &[&TEST_DROP; 1];
  66     //~^ ERROR temporary value dropped while borrowed
  67     //~| ERROR temporary value dropped while borrowed
  68 }