let fields = if let syn::Data::Struct(ref struc) = input.data {

&struc.fields

} else {

bail_span!(

input,

"#[pystruct_sequence] can only be on a struct declaration"

)

};

let field_names: Vec<_> = match fields {

syn::Fields::Named(fields) => fields

.named

.iter()

.map(|field| field.ident.as_ref().unwrap())

.collect(),

_ => bail_span!(

input,

"#[pystruct_sequence] can only be on a struct with named fields"

),

};

Ok(field_names)

let field_names = field_names(&input)?;

let ty = &input.ident;

let ret = quote! {

impl ::rustpython_vm::types::PyStructSequence for #ty {

const FIELD_NAMES: &'static [&'static str] = &[#(stringify!(#field_names)),*];

fn into_tuple(self, vm: &::rustpython_vm::VirtualMachine) -> ::rustpython_vm::builtins::PyTuple {

let items = vec![#(::rustpython_vm::convert::ToPyObject::to_pyobject(

self.#field_names,

vm,

)),*];

::rustpython_vm::builtins::PyTuple::new_unchecked(items.into_boxed_slice())

}

}

impl ::rustpython_vm::convert::ToPyObject for #ty {

fn to_pyobject(self, vm: &::rustpython_vm::VirtualMachine) -> ::rustpython_vm::PyObjectRef {

::rustpython_vm::types::PyStructSequence::into_struct_sequence(self, vm).into()

}

}

};

Ok(ret)

let field_names = field_names(&input)?;

let ty = &input.ident;

let ret = quote! {

impl ::rustpython_vm::TryFromObject for #ty {

fn try_from_object(vm: &::rustpython_vm::VirtualMachine, seq: ::rustpython_vm::PyObjectRef) -> ::rustpython_vm::PyResult<Self> {

const LEN: usize = #ty::FIELD_NAMES.len();

let seq = Self::try_elements_from::<LEN>(seq, vm)?;

// TODO: this is possible to be written without iterator

let mut iter = seq.into_iter();

Ok(Self {#(

#field_names: iter.next().unwrap().clone().try_into_value(vm)?

),*})

}

}

};

Ok(ret)