Function try_gen_trivial_is_bit_valid 

pub(crate) fn try_gen_trivial_is_bit_valid(
    ast: &DeriveInput,
    top_level: Trait,
    zerocopy_crate: &Path,
) -> Option<TokenStream>

Attempts to generate a TryFromBytes::is_bit_valid instance that unconditionally returns true.

This is possible when the top_level trait is FromBytes and there are no generic type parameters. In this case, we know that compilation will succeed only if the type is unconditionally FromBytes. Type parameters are not supported because a type with type parameters could be TryFromBytes but not FromBytes depending on its type parameters, and so deriving a trivial is_bit_valid would be either unsound or, assuming we add a defensive Self: FromBytes bound (as we currently do), overly restrictive. Consider, for example, that Foo<bool> ought to be TryFromBytes but not FromBytes in this example:

#[derive(FromBytes)]
#[repr(transparent)]
struct Foo<T>(T);

This should be used where possible. Using this impl is faster to codegen, faster to compile, and is friendlier on the optimizer.