error[E0201]: duplicate definitions with name `bar`: --> $DIR/issue-8153.rs:11:5 | LL | fn bar(&self) -> isize; | ----------------------- item in trait ... LL | fn bar(&self) -> isize {1} | -------------------------- previous definition here LL | fn bar(&self) -> isize {2} | ^^^^^^^^^^^^^^^^^^^^^^^^^^ duplicate definition error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0201`.