LLVM assertion when implementing methods that take self by-value on numeric types

[bstrie]

This:

fn main() {
    10u.to_vec();
}

trait ToVec {
    fn to_vec(self);
}

impl ToVec for uint {
    fn to_vec(self){}
}

causes this:

rustc: /media/linhaus/rust/src/llvm/lib/VMCore/Instructions.cpp:2383: static llvm::CastInst* llvm::CastInst::CreatePointerCast(llvm::Value*, llvm::Type*, const llvm::Twine&, llvm::Instruction*): Assertion `S->getType()->isPointerTy() && "Invalid cast"' failed.
Aborted

Changing self to &self makes it work, so it has to do with passing self by-value.

[jdm]

Duplicate of #5321.