--unpretty everybody_loops is not compatible with const fn.

[kennytm]

Test case:

#![feature(const_fn)]
const fn foo() -> u32 {
    1
}
fn main() {
    foo();
}

everybody_loops (#19964) will generate this, as expected:

$ rustc -Z unstable-options --unpretty everybody_loops 1.rs
#![feature(const_fn)]
const fn foo() -> u32 { loop  { } }
fn main() { loop  { } }

However, loop is not supported in const fn, so this will produce E0019

$ rustc -Z unstable-options --unpretty everybody_loops 1.rs | rustc -
error[E0019]: constant function contains unimplemented expression type
 --> <anon>:3:25
  |
3 | const fn foo() -> u32 { loop  { } }
  |                         ^^^^^^^^^

error: aborting due to previous error

[jyn514]

Now that const_if_match and const_loop have been stabilized, this no longer gives an error (currently only on nightly, but will hit stable in a few months). So I think this can be closed.

[jryans]

@rustbot label A-pretty

[jyn514]

This works on latest nightly:

$ rustc -Z unpretty=everybody_loops const.rs | rustc - -A warnings
$

[camelid]

However, note that everybody_loops currently does not replace const fn bodies:

input code

const fn foo() -> u32 {
    1
}
fn main() {
    foo();
}

everybody_loops

#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use ::std::prelude::v1::*;
#[macro_use]
extern crate std;
const fn foo() -> u32 { 1 }
fn main() { loop  { } }