warning: non-local `macro_rules!` definition, `#[macro_export]` macro should be written at top level module
  --> $DIR/non_local_defs.rs:9:1
   |
LL | macro_rules! a_macro { () => {} }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: remove the `#[macro_export]` or make this doc-test a standalone test with its own `fn main() { ... }`
   = note: a `macro_rules!` definition is non-local if it is nested inside an item and has a `#[macro_export]` attribute
   = note: `#[warn(non_local_definitions)]` on by default

warning: 1 warning emitted