Poor error while expanding macro_rules with bad match

[ScatteredRay]

With this block of code:

macro_rules! object {
  ($foo:ident) => (
    match $bar {
    }
  )
}

object!(baz)

I get the error

rust: task failed at 'No entry found for key: &{repr: 41}', /Users/indy/dev/guava/dep/rust-0.6/src/libcore/hashmap.rs:521
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug
note: try running with RUST_LOG=rustc=1,::rt::backtrace to get further details and report the results to github.com/mozilla/rust/issues
rust: task failed at 'explicit failure', /Users/indy/dev/guava/dep/rust-0.6/src/librustc/rustc.rc:357
rust: domain main @0x7fbe4100c210 root task failed`

This error should be improved.

[Aatch]

This has been fixed, now produces: unknown macro variable 'bar'