test.rs

extern crate libc;

#[repr(C)]
struct ApiFromC {
	some_data: *mut libc::c_void,
	some_function: extern fn(data: *mut libc::c_void),
	// ...
}

struct RustAPI {
	api_from_c: *mut ApiFromC,
}

impl RustAPI {
	fn call_c_api(&self) {
		unsafe {
			(*self.api_from_c).some_function((*self.api_from_c).some_data)
		}
	}
}

#[no_mangle]
pub extern fn call_from_c(api: *mut ApiFromC) {
	let test = RustAPI { api_from_c : api };
	test.call_c_api();
}

// error

   Compiling api_test v0.1.0 (file:///C:/Users/dcollin/Documents/api_test)
src\lib.rs:17:23: 17:66 error: no method named `some_function` found for type `ApiFromC` in the current scope
src\lib.rs:17                   (*self.api_from_c).some_function((*self.api_from_c).some_data)
                                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src\lib.rs:17:23: 17:66 note: did you mean to write `(*self.api_from_c).some_function`?
src\lib.rs:17                   (*self.api_from_c).some_function((*self.api_from_c).some_data)
                                                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
error: aborting due to previous error
Could not compile `api_test`.