Function vectorcall_type

crates/vm/src/builtins/type.rs:2687–2713

Vectorcall for PyType (PEP 590). Fast path: type(x) returns x.__class__ without constructing FuncArgs. # Implementation note: `slots.vectorcall` dual use CPython has three distinct fields on PyTypeObject: - `tp_vectorcall`: constructor fast path (e.g. `list_vectorcall`) - `tp_vectorcall_offset`: per-instance vectorcall for callables (e.g. functions) - `tp_call`: standard call slot RustPython co

(
    zelf_obj: &PyObject,
    args: Vec<PyObjectRef>,
    nargs: usize,
    kwnames: Option<&[PyObjectRef]>,
    vm: &VirtualMachine,
)

/// If more such types arise, consider splitting into a dedicated
/// `constructor_vectorcall` slot.
fn vectorcall_type(
    zelf_obj: &PyObject,
    args: Vec<PyObjectRef>,
    nargs: usize,
    kwnames: Option<&[PyObjectRef]>,
    vm: &VirtualMachine,
) -> PyResult {
    let zelf: &Py<PyType> = zelf_obj.downcast_ref().unwrap();

    // type(x) fast path: single positional arg, no kwargs
    if zelf.is(vm.ctx.types.type_type) {
        let no_kwargs = kwnames.is_none_or(|kw| kw.is_empty());
        if nargs == 1 && no_kwargs {
            return Ok(args[0].obj_type());
        }
    } else if zelf.slots.call.load().is_none() && zelf.slots.new.load().is_some() {
        // Per-type constructor vectorcall for non-callable types (dict, list, int, etc.)
        // Also guard on slots.new to avoid dispatching for DISALLOW_INSTANTIATION types.
        if let Some(type_vc) = zelf.slots.vectorcall.load() {
            return type_vc(zelf_obj, args, nargs, kwnames, vm);
        }
    }

    // Fallback: construct FuncArgs and use standard call
    let func_args = FuncArgs::from_vectorcall_owned(args, nargs, kwnames);
    PyType::call(zelf, func_args, vm)
}

pub(crate) fn init(ctx: &'static Context) {
    PyType::extend_class(ctx, ctx.types.type_type);