Missing line information for calls to diverging functions

Under some circumstances, rustc emits debug information with missing line numbers for calls to diverging functions.

fn main() {
    if True == False {
        // unreachable
        diverge();
    }

    diverge();
}

#[derive(PartialEq)]
pub enum MyBool {
    True,
    False,
}

use MyBool::*;

fn diverge() -> ! {
    panic!();
}

Compiling with rustc main.rs -g --emit=llvm-ir -Clto and then inspecting the debug info for main in the .ll file, the line information is 0:

call void @_ZN4main7diverge17h595c254fa559ce50E(), !dbg !3943
!3943 = !DILocation(line: 0, scope: !3942)

If the unreachable call is removed, the line info matches the source file as expected:

!4340 = !DILocation(line: 16, column: 4, scope: !4338)

I get the same behavior with the latest stable

rustc 1.33.0 (2aa4c46cf 2019-02-28)
binary: rustc
commit-hash: 2aa4c46cfdd726e97360c2734835aa3515e8c858
commit-date: 2019-02-28
host: x86_64-unknown-linux-gnu
release: 1.33.0
LLVM version: 8.0

and with the latest nightly

rustc 1.35.0-nightly (237bf3244 2019-03-28)
binary: rustc
commit-hash: 237bf3244fffef501cf37d4bda00e1fce3fcfb46
commit-date: 2019-03-28
host: x86_64-unknown-linux-gnu
release: 1.35.0-nightly
LLVM version: 8.0

cc @japaric

[nagisa]

Off top of my head the probable reason is that the line info is gathered from the "return slot" which would, obviously, be absent for diverging calls.

[jrmuizel]

I filed an llvm bug about this: https://bugs.llvm.org/show_bug.cgi?id=42878

[wesleywiser]

Visited during wg-debugging triage. This appears to be fixed and so this just needs a regression test: https://rust.godbolt.org/z/E5hKx1f5P

[Enselic]

#144034 adds a test (and gives more info on when this was fixed)

@rustbot claim