internal compiler error: unprintable span

[rillian]

Trying to access a struct member from a macro inside a parameterized closure, I get:

src/lib.rs:407:26: 266:22 error: attempted access of field `trace` on type `&mut C`, but no field with that name was found
(internal compiler error: unprintable span)
src/lib.rs:407:21: 407:95 note: in this expansion of log! (defined in src/lib.rs)

The code may well be wrong, but I thought the internal compiler error was worth reporting.

[rillian]

Code showing the issue is available at https://notabug.org/rillian/mp4parse-rust/src/issue-31011

I see this with both 1.5 stable and 17 nightly.

cc @gankro

[rillian]

Here's a simpler example: https://play.rust-lang.org/?gist=fd7e6bbc22a85d299bdd

[rillian]

And an even simpler one: https://play.rust-lang.org/?gist=8d172764fd95ff346bed

[rillian]

The ICE does not occur without the macro. This prints the compile error cleanly: https://play.rust-lang.org/?gist=7459e2ba9918ba9e56c1

[wesleywiser]

It seems that this happens when the span the compiler wants to print out starts in one location and ends in another (for example, starts in a macro expansion but ends in the actual program input). See these related issues #29084, #28308, #25385, #28288.