rust: module inspection prototype

[axic]

No description provided.

[axic]

So I think these are the options for having inspection on the module (which is still available through an instance):
a) either we have this owned flag here and disallow instantiation of a non-owned module
b) introduce a ModuleInspection or some other abstraction which has it, and that can be obtained as module.inspect() or instance.inspect() (this can be seen in one of the earlier commits)

[chfast]

This look ok, although fragile. And I'd rather name the flag instantiated so it is clear it can be instantiated once.

Can't Rust magic memory annotations handle this?

[axic]

Can't Rust magic memory annotations handle this?

One workaround, where I maintain an "instance of module" in the instance and return the reference on it. Since instantiate() requires to own the input, a reference can't be passed so it will not compile.

i.e.

struct Instance {
  instance: NonNull<sys::FizzyInstance>,
  module: Module,
}

impl Instance {
    pub fn get_module(&self) -> &Module {
       &self.module
    }
}

// Then this will be a compilation error: instance.get_module().instantiate() 

Added nastyness is that in instantiate() need to drop module from being managed (i.e. core::mem::forget(instance.module)), otherwise we end up with the same problem.

[gumb0]

Not necessary to save module in Instance, you can call fizzy_get_instance_module

[axic]

The downside of the ModuleInspection option is that need to assign its lifetime bound to the underlying Module/Instance.

[axic]

Not necessary to save module in Instance, you can call fizzy_get_instance_module

That is what is being done in this PR. For that one needs to extend the Module as in this PR.

An alternative approach is to save the module in the instance and return it as a reference.

[gumb0]

I imagined I guess some combination of your approaches: don't change Module, but have Instance::get_module(&self) -> Module that will call fizzy_get_instance_module, wrap in Module and call core::mem::forget before returning it.

[codecov]

Codecov Report

Merging #728 (4f6b02e) into master (3581284) will decrease coverage by 0.09%.
The diff coverage is 79.24%.

@@            Coverage Diff             @@
##           master     #728      +/-   ##
==========================================
- Coverage   99.27%   99.18%   -0.10%     
==========================================
  Files          88       88              
  Lines       13296    13332      +36     
==========================================
+ Hits        13200    13223      +23     
- Misses         96      109      +13     

Flag	Coverage Δ
rust	97.26% <79.24%> (-1.22%)	⬇️
spectests	89.92% <ø> (ø)
unittests	99.22% <ø> (ø)
unittests-32	99.32% <ø> (ø)

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Impacted Files	Coverage Δ
bindings/rust/src/lib.rs	97.53% <79.24%> (-1.24%)	⬇️