error[E0282]: type annotations needed --> $DIR/issue-24013.rs:5:13 | LL | unsafe {swap::<&mut _>(transmute(&a), transmute(&b))}; | ^^^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `swap` | help: consider specifying the generic argument | LL | unsafe {swap::<&mut _>(transmute(&a), transmute(&b))}; | ~~~~~~~~~~ error: aborting due to previous error For more information about this error, try `rustc --explain E0282`.