thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: SourceNotAvailable

[dwrensha]

I'm seeing an internal compiler error on the following input (found by fuzz-rustc):

fn a() -> i32 {3}

pub fn main() {
    assert_eq!(a, 0);
}

$ rustc main.rs
thread 'rustc' panicked at 'called `Result::unwrap()` on an `Err` value: SourceNotAvailable { filename: Real("/rustc/76b11980ad416c3ad6143504c2277757ecacf9b5/src/libcore/macros/mod.rs") }', src/librustc_typeck/check/op.rs:524:41
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

error: internal compiler error: unexpected panic

note: the compiler unexpectedly panicked. this is a bug.

note: we would appreciate a bug report: https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#bug-reports

note: rustc 1.44.0-nightly (76b11980a 2020-04-01) running on x86_64-unknown-linux-gnu

[dwrensha]

Report from cargo-bisect-rustc:

searched nightlies: from nightly-2020-03-09 to nightly-2020-04-02
regressed nightly: nightly-2020-03-11
searched commits: from 3dbade6 to 1581278
regressed commit: 1581278

[Centril]

Fixed by #70725.