error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
  --> $DIR/E0512.rs:4:23
   |
LL |     unsafe { takes_u8(::std::mem::transmute(0u16)); }
   |                       ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: source type: `u16` (16 bits)
   = note: target type: `u8` (8 bits)

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0512`.