pub fn from_value_opt<T: FromValue>(v: Value) -> Result<T, Value>
Will return Err(v) if could not convert v to T
Prefix searches with a type followed by a colon (e.g.
fn:) to restrict the search to a given type.
Accepted types are: fn, mod,
struct, enum,
trait, typedef (or
tdef).
Search functions by type signature (e.g.
vec -> usize)