Allow traits to be implemented for almost all types

[cburgdorf]

What was wrong?

Currently traits can only be implemented for structs. The reason for that is that prior to monomorphization we do not know the Location of a type generic type (e.g. T) and for that reason hard coded it to Location::Memory which would exclude primitive types such as u8.

How was it fixed?

I made attempts to get rid of Location in the analyzer entirely but I kept failing. Then I realized that we actually don't yet allow to assign generic arguments anyway. Since the location is only relevant for when variables are assigned we could have used Location::Value and it would have worked exactly the same, it's superfluous information for now.
Hence, I thought we could introduce a Location::Unresolved for now and in return lift the restriction to allow traits to be implemented for all base types, arrays and tuples.

In addition this fixes two ICEs related to calling to_mem() or clone() on a generic type.

E.g.

trait Double {
  fn double(self) -> u256;
}

impl Double for u8 {
  fn double(self) -> u256 {
    return u256(self + self)
  }
}

impl Double for u16 {
  fn double(self) -> u256 {
    return u256(self + self)
  }
}

impl Double for (u256, u256) {
  fn double(self) -> u256 {
    return u256(self.item0 + self.item0 + self.item1 + self.item1)
  }
}

struct Runner {
  pub fn run<T: Double>(self, _ val: T) -> u256 {
    return val.double()
  }
}


contract Example {
  pub fn generic_compute(self) {
    let runner: Runner = Runner();
    assert runner.run(u8(1)) == 2
    assert runner.run(u16(1000)) == 2000
    assert runner.run((1, 1)) == 4
  }
}

[sbillig]

👍 😎 👍