//@ aux-build:two_macros.rs macro_rules! define_vec { () => { extern crate std as Vec; } } define_vec!(); mod m { fn check() { Vec::panic!(); //~ ERROR `Vec` is ambiguous } } macro_rules! define_other_core { () => { extern crate std as core; //~^ ERROR macro-expanded `extern crate` items cannot shadow names passed with `--extern` } } define_other_core!(); fn main() {}