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    use proc_macro2::TokenStream;
    use quote::format_ident;

    use internals::ast::{Container, Data, Field, Style, Variant};

    // Suppress dead_code warnings that would otherwise appear when using a remote
    // derive. Other than this pretend code, a struct annotated with remote derive
    // never has its fields referenced and an enum annotated with remote derive
    // never has its variants constructed.
    //
    //     warning: field is never used: `i`
    //      --> src/main.rs:4:20
    //       |
    //     4 | struct StructDef { i: i32 }
    //       |                    ^^^^^^
    //
    //     warning: variant is never constructed: `V`
    //      --> src/main.rs:8:16
    //       |
    //     8 | enum EnumDef { V }
    //       |                ^
    //
    pub fn pretend_used(cont: &Container, is_packed: bool) -> TokenStream {
        let pretend_fields = pretend_fields_used(cont, is_packed);
        let pretend_variants = pretend_variants_used(cont);

        quote! {
            #pretend_fields
            #pretend_variants
        }
    }

    // For structs with named fields, expands to:
    //
    //     match None::<&T> {
    //         Some(T { a: __v0, b: __v1 }) => {}
    //         _ => {}
    //     }
    //
    // For packed structs on sufficiently new rustc, expands to:
    //
    //     match None::<&T> {
    //         Some(__v @ T { a: _, b: _ }) => {
    //             let _ = addr_of!(__v.a);
    //             let _ = addr_of!(__v.b);
    //         }
    //         _ => {}
    //     }
    //
    // For packed structs on older rustc, we assume Sized and !Drop, and expand to:
    //
    //     match None::<T> {
    //         Some(T { a: __v0, b: __v1 }) => {}
    //         _ => {}
    //     }
    //
    // For enums, expands to the following but only including struct variants:
    //
    //     match None::<&T> {
    //         Some(T::A { a: __v0 }) => {}
    //         Some(T::B { b: __v0 }) => {}
    //         _ => {}
    //     }
    //
    fn pretend_fields_used(cont: &Container, is_packed: bool) -> TokenStream {
        match &cont.data {
            Data::Enum(variants) => pretend_fields_used_enum(cont, variants),
            Data::Struct(Style::Struct, fields) => {
                if is_packed {
                    pretend_fields_used_struct_packed(cont, fields)
                } else {
                    pretend_fields_used_struct(cont, fields)
                }
            }
            Data::Struct(_, _) => quote!(),
        }
    }

    fn pretend_fields_used_struct(cont: &Container, fields: &[Field]) -> TokenStream {
        let type_ident = &cont.ident;
        let (_, ty_generics, _) = cont.generics.split_for_impl();

        let members = fields.iter().map(|field| &field.member);
        let placeholders = (0usize..).map(|i| format_ident!("__v{}", i));

        quote! {
            match _serde::__private::None::<&#type_ident #ty_generics> {
                _serde::__private::Some(#type_ident { #(#members: #placeholders),* }) => {}
                _ => {}
            }
        }
    }

    fn pretend_fields_used_struct_packed(cont: &Container, fields: &[Field]) -> TokenStream {
        let type_ident = &cont.ident;
        let (_, ty_generics, _) = cont.generics.split_for_impl();

        let members = fields.iter().map(|field| &field.member).collect::<Vec<_>>();

        #[cfg(not(no_ptr_addr_of))]
        {
            quote! {
                match _serde::__private::None::<&#type_ident #ty_generics> {
                    _serde::__private::Some(__v @ #type_ident { #(#members: _),* }) => {
                        #(
                            let _ = _serde::__private::ptr::addr_of!(__v.#members);
                        )*
                    }
                    _ => {}
                }
            }
        }

        #[cfg(no_ptr_addr_of)]
        {
            let placeholders = (0usize..).map(|i| format_ident!("__v{}", i));

            quote! {
                match _serde::__private::None::<#type_ident #ty_generics> {
                    _serde::__private::Some(#type_ident { #(#members: #placeholders),* }) => {}
                    _ => {}
                }
            }
        }
    }

    fn pretend_fields_used_enum(cont: &Container, variants: &[Variant]) -> TokenStream {
        let type_ident = &cont.ident;
        let (_, ty_generics, _) = cont.generics.split_for_impl();

        let patterns = variants
            .iter()
            .filter_map(|variant| match variant.style {
                Style::Struct => {
                    let variant_ident = &variant.ident;
                    let members = variant.fields.iter().map(|field| &field.member);
                    let placeholders = (0usize..).map(|i| format_ident!("__v{}", i));
                    Some(quote!(#type_ident::#variant_ident { #(#members: #placeholders),* }))
                }
                _ => None,
            })
            .collect::<Vec<_>>();

        quote! {
            match _serde::__private::None::<&#type_ident #ty_generics> {
                #(
                    _serde::__private::Some(#patterns) => {}
                )*
                _ => {}
            }
        }
    }

    // Expands to one of these per enum variant:
    //
    //     match None {
    //         Some((__v0, __v1,)) => {
    //             let _ = E::V { a: __v0, b: __v1 };
    //         }
    //         _ => {}
    //     }
    //
    fn pretend_variants_used(cont: &Container) -> TokenStream {
        let variants = match &cont.data {
            Data::Enum(variants) => variants,
            Data::Struct(_, _) => {
                return quote!();
            }
        };

        let type_ident = &cont.ident;
        let (_, ty_generics, _) = cont.generics.split_for_impl();
        let turbofish = ty_generics.as_turbofish();

        let cases = variants.iter().map(|variant| {
            let variant_ident = &variant.ident;
            let placeholders = &(0..variant.fields.len())
                .map(|i| format_ident!("__v{}", i))
                .collect::<Vec<_>>();

            let pat = match variant.style {
                Style::Struct => {
                    let members = variant.fields.iter().map(|field| &field.member);
                    quote!({ #(#members: #placeholders),* })
                }
                Style::Tuple | Style::Newtype => quote!(( #(#placeholders),* )),
                Style::Unit => quote!(),
            };

            quote! {
                match _serde::__private::None {
                    _serde::__private::Some((#(#placeholders,)*)) => {
                        let _ = #type_ident::#variant_ident #turbofish #pat;
                    }
                    _ => {}
                }
            }
        });

        quote!(#(#cases)*)
    }