Single-argument panic!() with a non-static item gives confusing error message

[shepmaster]

fn main() {
    let a = vec![1];
    let b = &a[0];

    panic!(b);
}

Generates the error:

err.rs:3:14: 3:15 error: `a` does not live long enough
err.rs:3     let b = &a[0];
                      ^
note: reference must be valid for the static lifetime...
err.rs:2:20: 6:2 note: ...but borrowed value is only valid for the block suffix following statement 0 at 2:19

This is quite confusing. The problem really is that we are trying to pass something to panic! / rt::begin_unwind that isn't static, but the error message doesn't implicate panic! at all.

Meta

rustc 1.0.0-dev (c6ca2205e 2015-03-19) (built 2015-03-19)
binary: rustc
commit-hash: c6ca2205eae522387237057812b7901a2c5d3906
commit-date: 2015-03-19
build-date: 2015-03-19
host: x86_64-apple-darwin
release: 1.0.0-dev

Originally from Stack Overflow

[steveklabnik]

Triage: no change.

[estebank]

Triage: no change (including under nll).

[estebank]

Current output:

error[E0597]: `a` does not live long enough
 --> src/main.rs:3:14
  |
3 |     let b = &a[0];
  |              ^ borrowed value does not live long enough
4 | 
5 |     panic!(b);
  |     ---------- argument requires that `a` is borrowed for `'static`
6 | }
  | - `a` dropped here while still borrowed
  |
  = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)