Try passing uncopyable types by value

[bsilver8192]

It results in generated Rust code that doesn't compile. Not sure if
there's an easy fix, or if this would make more sense as copies of these
tests which are skipped. Also not sure if there's an existing bug that
is intended to include this one, or of it should be a new bug.

[adetaylor]

I don't think you're quite right... the test is indeed failing, but the error I'm seeing is presented in the test code itself not in generated code:

error[E0277]: the trait bound `root::A: CopyNew` is not satisfied
 --> /var/folders/9l/cjqbc3ws3bxcjh6h2rykj90800m02d/T/.tmpCftczo/input.rs:1:247
  |
1 | ... . as_mut () . set (42) ; ffi :: take_a (& * stack_obj) ; } # [link (name = "autocxx-demo")] extern { }
  |                              -------------  ^^^^^^^^^^^^^ the trait `CopyNew` is not implemented for `root::A`
  |                              |
  |                              required by a bound introduced by this call
  |
  = note: required because of the requirements on the impl of `ValueParam<root::A>` for `&root::A`
note: required by a bound in `take_a`
 --> /var/folders/9l/cjqbc3ws3bxcjh6h2rykj90800m02d/T/.tmpgPCYdY/autocxx-ffi-default-gen.rs:1:1095
  |
1 | ...; 32] } pub fn take_a (a : impl autocxx :: ValueParam < root :: A >) { let mut a_space = autocxx :: ValueParamHandler :: new (a) ; let...
  |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `take_a`

That's exactly saying "hey, you can't pass this here, because it doesn't have a copy constructor!" which is just the way it's supposed to work. What do you expect to see?

I do want us to be a bit more flexible here in what types of parameters we accept as value params, but I initially went for the conservative option in order to avoid too many merge conflicts with your work in #843. I just raised #873 to note future ambitions here.

[bsilver8192]

You're right, ValueParam isn't implemented for that type, so never mind. Still something that'd be nice to support eventually. Thanks for waiting on #843, thinking about how they'll play together is why I came up with this.