More mutability

test.rs

struct S<'l>
{
	data: &'l [u8]
}

struct MS<'l>
{
	data: &'l mut [u8]
}

trait Mut
{
	fn set(&mut self, idx: uint, val: u8);
}

trait Common
{
	fn get<'l>(&'l self) -> &'l [u8];
	
	fn len(&self) -> uint
	{
		self.get().len()
	}
}

impl<'l> Mut for MS<'l>
{
	fn set(&mut self, idx: uint, val: u8)
	{
		self.data[idx] = val;
	}
}

impl<'l> Common for MS<'l>
{
	fn get<'m>(&'m self) -> &'m [u8]
	{
		self.data.as_slice()
	}
}

impl<'l> Common for S<'l>
{
	fn get<'m>(&'m self) -> &'m [u8]
	{
		self.data
	}
}

fn main()
{
	let mut ms = MS{ data: &mut [0u8] };
	let s = S{ data: &[0u8] };
	ms.set(0, 5);
	ms.set(0, 5);
	s.len();
	ms.len();
}