Errors caused by macros aren't always reported

[jdm]

This source file

fn main() {
#warn("%?", str::connect(["a", "b"] + [], "::"));
}

causes the following very inscrutable failure:

godot:src jdm$ RUST_LOG=rustc=0,::rt::backtrace rust/build/x86_64-apple-darwin/stage2/bin/rustc -g rust_dbg2.rs 
rust: upcall fail 'option none', ../src/rustc/rustc.rc:1
error: internal compiler error unexpected failure
note: The compiler hit an unexpected failure path. This is a bug. Try running with RUST_LOG=rustc=0,::rt::backtrace to get further details and report the results to github.com/mozilla/rust/issues
rust: upcall fail 'explicit failure', ../src/rustc/driver/rustc.rs:180
rust: domain main @0x103032200 root task failed

[jdm]

Never mind, this has to do with building with -g. I'll figure out precisely what's up.