temporary value dropped while borrowed

Code

I tried this code:

pub const fn concat(_x: &[u8], _y: &[u8]) -> [u8; 1024] {
    [0u8; 1024]
}

const _: &[u8] = &concat(
    if b"".len() > 0 {
        &concat(b"", b"")
    } else {
        b""
    },
    b""
);

I expected to see this happen: compiles

Instead, this happened: fails to compile with the following error:

error[E0716]: temporary value dropped while borrowed
 --> <source>:7:10
  |
5 | const _: &[u8] = &concat(
  |                   ------ borrow later used by call
6 |     if b"".len() > 0 {
7 |         &concat(b"", b"")
  |          ^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
8 |     } else {
  |     - temporary value is freed at the end of this statement
  |
  = note: consider using a `let` binding to create a longer lived value

Version it worked on

It most recently worked on: 1.78.0

Version with regression

rustc --version --verbose:

rustc 1.79.0 (129f3b996 2024-06-10)

@rustbot modify labels: +regression-from-stable-to-stable -regression-untriaged

Start by reproducing the provided const-evaluation example with rustc 1.79.0, then compare its behavior with 1.78.0 using the same snippet. Done means identifying the regression and restoring the expected successful compilation, with coverage for this case where appropriate.