Inappropriate generated type for function-returning-function

Input C/C++ Header

void (*(*xDlSym)(const char *))(void);

Bindgen Invocation

$ bindgen input.h

Actual Results

/* automatically generated by rust-bindgen 0.69.1 */

extern "C" {
    pub static mut xDlSym: ::std::option::Option<
        unsafe extern "C" fn(
            arg3: *const ::std::os::raw::c_char,
        ) -> ::std::option::Option<
            unsafe extern "C" fn(
                arg3: *const ::std::os::raw::c_char,
            ),
        >,
    >;
}

Expected Results

extern "C" {
    pub static mut xDlSym: ::std::option::Option<
        unsafe extern "C" fn(
            arg3: *const ::std::os::raw::c_char,
        ) -> ::std::option::Option<
            unsafe extern "C" fn(
-               arg3: *const ::std::os::raw::c_char,
            ),
        >,
    >;
}

The original C signature is hard to read: it describes a function pointer xDlSym that takes a single const char * argument and returns another function pointer of type void (*)(void). But in the bindgen-generated output, the returned function pointer has the inappropriate type void (*)(const char *) instead.

This affects the public API of libsqlite3-sys here; the reproducer is minimized from that situation.

Start with the minimal input.h declaration and run the bindgen invocation shown in the issue to reproduce the generated Rust type. Compare the returned function pointer's parameter list with the expected output and add coverage for this function-returning-function case; done when the generated binding matches the expected signature.