macro_rules! leak { ($ty:ty, $ident:ident) => { ... }; }
Wrap <$ty as ToOwned>::Owned in a type $ident and implement From and test_fuzz::Into for $ident so that convert = "&$ty, $ident" can be used.
<$ty as ToOwned>::Owned
$ident
From
test_fuzz::Into
convert = "&$ty, $ident"