error[E0283]: type annotations needed --> $DIR/issue-16966.rs:2:12 | LL | panic!(std::default::Default::default()); | -------^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^- | | | | | cannot infer type | required by a bound introduced by this call | = note: cannot satisfy `_: Any` note: required by a bound in `begin_panic` --> $SRC_DIR/std/src/panicking.rs:LL:COL error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0283`.