rust/tests/ui/consts/promote-not.rs

// ignore-tidy-linelength
// Test various things that we do not want to promote.
#![allow(unconditional_panic)]

use std::cell::Cell;

// We do not promote mutable references.
static mut TEST1: Option<&mut [i32]> = Some(&mut [1, 2, 3]); //~ ERROR temporary value dropped while borrowed

static mut TEST2: &'static mut [i32] = {
    let x = &mut [1,2,3]; //~ ERROR temporary value dropped while borrowed
    x
};

// We do not promote fn calls in `fn`, including `const fn`.
pub const fn promote_cal(b: bool) -> i32 {
    const fn foo() { [()][42] }

    if b {
        let _x: &'static () = &foo(); //~ ERROR temporary value dropped while borrowed
    }
    13
}

// We do not promote union field accesses in `fn.
union U { x: i32, y: i32 }
pub const fn promote_union() {
    let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
}

// We do not promote union field accesses in `const`, either.
const TEST_UNION: () = {
    let _x: &'static i32 = &unsafe { U { x: 0 }.x }; //~ ERROR temporary value dropped while borrowed
};

// In a `const`, we do not promote things with interior mutability. Not even if we "project it away".
const TEST_INTERIOR_MUT: () = {
    // The "0." case is already ruled out by not permitting any interior mutability in `const`.
    let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
};

const TEST_DROP: String = String::new();

fn main() {
    // We must not promote things with interior mutability. Not even if we "project it away".
    let _val: &'static _ = &(Cell::new(1), 2).0; //~ ERROR temporary value dropped while borrowed
    let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed

    // No promotion of fallible operations.
    let _val: &'static _ = &(1/0); //~ ERROR temporary value dropped while borrowed
    let _val: &'static _ = &(1/(1-1)); //~ ERROR temporary value dropped while borrowed
    let _val: &'static _ = &(1%0); //~ ERROR temporary value dropped while borrowed
    let _val: &'static _ = &(1%(1-1)); //~ ERROR temporary value dropped while borrowed
    let _val: &'static _ = &([1,2,3][4]+1); //~ ERROR temporary value dropped while borrowed

    // No promotion of temporaries that need to be dropped.
    let _val: &'static _ = &TEST_DROP;
    //~^ ERROR temporary value dropped while borrowed
    let _val: &'static _ = &&TEST_DROP;
    //~^ ERROR temporary value dropped while borrowed
    //~| ERROR temporary value dropped while borrowed
    let _val: &'static _ = &(&TEST_DROP,);
    //~^ ERROR temporary value dropped while borrowed
    //~| ERROR temporary value dropped while borrowed
    let _val: &'static _ = &[&TEST_DROP; 1];
    //~^ ERROR temporary value dropped while borrowed
    //~| ERROR temporary value dropped while borrowed
}