#![feature(trace_macros)] fn main() { trace_macros!(); //~ ERROR trace_macros! accepts only `true` or `false` trace_macros!(1); //~ ERROR trace_macros! accepts only `true` or `false` trace_macros!(ident); //~ ERROR trace_macros! accepts only `true` or `false` trace_macros!(for); //~ ERROR trace_macros! accepts only `true` or `false` trace_macros!(true,); //~ ERROR trace_macros! accepts only `true` or `false` trace_macros!(false 1); //~ ERROR trace_macros! accepts only `true` or `false` // should be fine: macro_rules! expando { ($x: ident) => { trace_macros!($x) } } expando!(true); }