// This assumes the packed and non-packed structs are different sizes. // the error points to the start of the file, not the line with the // transmute // error-pattern: cannot transmute between types of different sizes, or dependently-sized types use std::mem; #[repr(packed)] struct Foo<T,S> { bar: T, baz: S } struct Oof<T, S> { rab: T, zab: S } fn main() { let foo = Foo { bar: [1u8, 2, 3, 4, 5], baz: 10i32 }; unsafe { let oof: Oof<[u8; 5], i32> = mem::transmute(foo); println!("{:?} {:?}", &oof.rab[..], oof.zab); } }