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|
use crate::internals::ast::{Container, Data, Field, Style, Variant};
use proc_macro2::TokenStream;
use quote::{format_ident, quote};
// 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<_>>();
quote! {
match _serde::__private::None::<&#type_ident #ty_generics> {
_serde::__private::Some(__v @ #type_ident { #(#members: _),* }) => {
#(
let _ = _serde::__private::ptr::addr_of!(__v.#members);
)*
}
_ => {}
}
}
}
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)*)
}
|
