error: cannot find a built-in macro with name `unknown` --> $DIR/unknown-builtin.rs:6:1 | LL | macro_rules! unknown { () => () } | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error[E0773]: attempted to define built-in macro more than once --> $SRC_DIR/core/src/macros/mod.rs:LL:COL | note: previously defined here --> $DIR/unknown-builtin.rs:9:1 | LL | macro_rules! line { () => () } | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0773`.