ICE regression: "missing expansion backtrace"

[est31]

The following code ICE's on nightly and beta, but does not ICE on stable:

include!(line!());

For an example that doesn't give an immediate compile error (but later on bc it can't find the file):

include!(concat!("help-files/", file!()));

The ICE looks like:

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

thread 'rustc' panicked at 'missing expansion backtrace', /checkout/src/libcore/option.rs:794

[est31]

Last working nightly: rustc 1.17.0-nightly (e1cec5d4b 2017-03-29)
First broken nightly: rustc 1.18.0-nightly (5c94997b6 2017-03-30)
list of commits in between.

[est31]

cc @jseyfried

[Mark-Simulacrum]

fe15119 is the commit which broke this, PR #40597.

[nikomatsakis]

triage: P-high

Assigning to @jseyfried, hopefully they have some time to investigate!

[jseyfried]

This is closely related to #40649; fixed in #42006.