Attributes generated by a macro argument provided by another macro crashes the compiler

[pietroalbini]

I was working on a macro in a project of mine, and while I was experimenting the compiler started crashing. I managed to reduce the problem to this minimal example:

macro_rules! foo {
    ($name:ident, $doc:expr) => {
        // It doesn't matter which attribute is used
        // For example the bug exists also with the serde attribute
        #[doc = $doc]
        static $name: &'static str = "foo";
    };
}

macro_rules! bar {
    () => { "bar" }
}

foo!(BAZ, bar!());

fn main() {
    assert_eq!(BAZ, "bar");
}

When I try to compile this, I get this output:

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

note: rustc 1.20.0 (f3d6973f4 2017-08-27) running on x86_64-unknown-linux-gnu

note: run with `RUST_BACKTRACE=1` for a backtrace

thread 'rustc' panicked at 'no entry found for key', /checkout/src/libcore/option.rs:819:4
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
stack backtrace:
   0: std::sys::imp::backtrace::tracing::imp::unwind_backtrace
             at /checkout/src/libstd/sys/unix/backtrace/tracing/gcc_s.rs:49
   1: std::sys_common::backtrace::_print
             at /checkout/src/libstd/sys_common/backtrace.rs:71
   2: std::panicking::default_hook::{{closure}}
             at /checkout/src/libstd/sys_common/backtrace.rs:60
             at /checkout/src/libstd/panicking.rs:380
   3: std::panicking::default_hook
             at /checkout/src/libstd/panicking.rs:390
   4: std::panicking::rust_panic_with_hook
             at /checkout/src/libstd/panicking.rs:611
   5: std::panicking::begin_panic_new
             at /checkout/src/libstd/panicking.rs:553
   6: std::panicking::begin_panic_fmt
             at /checkout/src/libstd/panicking.rs:521
   7: rust_begin_unwind
             at /checkout/src/libstd/panicking.rs:497
   8: core::panicking::panic_fmt
             at /checkout/src/libcore/panicking.rs:92
   9: core::option::expect_failed
             at /checkout/src/libcore/option.rs:819
  10: rustc_resolve::macros::<impl rustc_resolve::Resolver<'a>>::resolve_macro_to_def
  11: rustc_resolve::macros::<impl syntax::ext::base::Resolver for rustc_resolve::Resolver<'a>>::resolve_invoc
  12: syntax::ext::expand::MacroExpander::expand
  13: syntax::ext::expand::MacroExpander::expand_crate
  14: rustc_driver::driver::phase_2_configure_and_expand::{{closure}}
  15: rustc_driver::driver::phase_2_configure_and_expand
  16: rustc_driver::driver::compile_input
  17: rustc_driver::run_compiler

Note: I'm using rust 1.20 on this machine, but I tested the example on the playground and it crashes even on the latest stable.

If I change the macro invocation to foo!(BAZ, "bar"); it compiles successfully, and it fails with every other macro I passes as argument.

[sinkuu]

This have been fixed in nightly (#44851).