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|
use proc_macro2::{Span, TokenStream};
use syn::Ident;
use internals::ast::{Container, Data, Field, Style};
// 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) -> TokenStream {
let pretend_fields = pretend_fields_used(cont);
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: ref __v0, b: ref __v1 }) => {}
// _ => {}
// }
//
// For enums, expands to the following but only including struct variants:
//
// match None::<T> {
// Some(T::A { a: ref __v0 }) => {}
// Some(T::B { b: ref __v0 }) => {}
// _ => {}
// }
//
// The `ref` is important in case the user has written a Drop impl on their
// type. Rust does not allow destructuring a struct or enum that has a Drop
// impl.
fn pretend_fields_used(cont: &Container) -> TokenStream {
let type_ident = &cont.ident;
let (_, ty_generics, _) = cont.generics.split_for_impl();
let patterns = match &cont.data {
Data::Enum(variants) => variants
.iter()
.filter_map(|variant| match variant.style {
Style::Struct => {
let variant_ident = &variant.ident;
let pat = struct_pattern(&variant.fields);
Some(quote!(#type_ident::#variant_ident #pat))
}
_ => None,
})
.collect::<Vec<_>>(),
Data::Struct(Style::Struct, fields) => {
let pat = struct_pattern(fields);
vec![quote!(#type_ident #pat)]
}
Data::Struct(_, _) => {
return quote!();
}
};
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| Ident::new(&format!("__v{}", i), Span::call_site()))
.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)*)
}
fn struct_pattern(fields: &[Field]) -> TokenStream {
let members = fields.iter().map(|field| &field.member);
let placeholders =
(0..fields.len()).map(|i| Ident::new(&format!("__v{}", i), Span::call_site()));
quote!({ #(#members: ref #placeholders),* })
}
|
