shape_collide and body_collide_shape from IPhysicsServer2DExtension gives compilation error

[Ughuuu]

The following 2 functions:

#[godot_api]
impl IPhysicsServer2DExtension for RapierPhysicsServer2D {
...
    unsafe fn shape_collide(&mut self, shape_A: Rid, xform_A: Transform2D, motion_A: Vector2, shape_B: Rid, xform_B: Transform2D, motion_B: Vector2, results: * mut c_void, result_max: i32, result_count: * mut i32,) -> bool {
        false
    }

    unsafe fn body_collide_shape(&mut self, body: Rid, body_shape: i32, shape: Rid, shape_xform: Transform2D, motion: Vector2, results: * mut c_void, result_max: i32, result_count: * mut i32,) -> bool {
    }
...
}

When implemented to a IPhysicsServer2DExtension gives the following error:

17 | #[godot_api]
   | ^^^^^^^^^^^^ the trait `ToGodot` is not implemented for `*mut i32`, which is required by `(bool, godot::prelude::Rid, godot::prelude::Transform2D, godot::prelude::Vector2, godot::prelude::Rid, godot::prelude::Transform2D, godot::prelude::Vector2, *mut c_void, i32, *mut i32): PtrcallSignatureTuple`
   |
   = help: the trait `ToGodot` is implemented for `i32`
   = note: required for `(bool, Rid, Transform2D, Vector2, Rid, Transform2D, Vector2, *mut c_void, i32, *mut i32)` to implement `PtrcallSignatureTuple`

[lilizoey]

This happens because we only implement ToGodot/FromGodot for native class pointers, but not primitive pointers even if they show up in parameters of functions. as a simple fix we could just manually implement this, but a more proper long term fix would be to have the codegen find all used pointer types and automatically implement the traits for them.

[lilizoey]

from what i can tell, these are the pointers used which i think dont have the trait impls:

*mut *const u8
*mut i32
*mut f64
*mut u8

[Bromeon]

This happens because we only implement ToGodot/FromGodot for native class pointers, but not primitive pointers even if they show up in parameters of functions. as a simple fix we could just manually implement this, but a more proper long term fix would be to have the codegen find all used pointer types and automatically implement the traits for them.

Here's a ripgrep command to find pointers in the API spec, here's for version 4.4:

rg '"type": ".+\*"' extension_api.json -N | sort | uniq

yields:

        "type": "AudioFrame*"
        "type": "CaretInfo*"
"type": "const Glyph*"
        "type": "const uint8_t **"
        "type": "const uint8_t*"
        "type": "const void*"
        "type": "float*"
        "type": "int32_t*"
        "type": "PhysicsServer2DExtensionMotionResult*"
        "type": "PhysicsServer2DExtensionRayResult*"
        "type": "PhysicsServer2DExtensionShapeRestInfo*"
        "type": "PhysicsServer2DExtensionShapeResult*"
        "type": "PhysicsServer3DExtensionMotionResult*"
        "type": "PhysicsServer3DExtensionRayResult*"
        "type": "PhysicsServer3DExtensionShapeRestInfo*"
        "type": "PhysicsServer3DExtensionShapeResult*"
        "type": "ScriptLanguageExtensionProfilingInfo*"
        "type": "uint8_t*"
        "type": "void*"
"type": "void*"

I checked that FromGodot is implemented for the above. It's also implemented for PhysicsServer3DExtensionMotionCollision, even though that is never used as a pointer parameter, but rather a field of another native struct.

---

It seems like the manual approach has worked well enough for a year, and this changes rarely enough that it's probably not worth automating. Especially since there's quite a bit of overlap between native structs and other pointer parameters, which may complicate an implementation slightly.

I'd suggest:

• we keep adding these impls manually.
• when new APIs pop up, it's a good reminder to check if we can create safe versions of them, see #1130.
• closing this issue, as the original bug reported has been solved.