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use crate::attr::{DataAttr, Field, FieldKind, Fields};
use quote::{quote, quote_spanned};
use syn::{spanned::Spanned, Data, DataEnum, DataStruct};
pub(crate) fn derive_data_impl(
input: syn::DeriveInput,
) -> Result<proc_macro2::TokenStream, syn::Error> {
match &input.data {
Data::Struct(s) => derive_struct(&input, s),
Data::Enum(e) => derive_enum(&input, e),
Data::Union(u) => Err(syn::Error::new(
u.union_token.span(),
"Data implementations cannot be derived from unions",
)),
}
}
fn derive_struct(
input: &syn::DeriveInput,
s: &DataStruct,
) -> Result<proc_macro2::TokenStream, syn::Error> {
let ident = &input.ident;
let impl_generics = generics_bounds(&input.generics);
let (_, ty_generics, where_clause) = &input.generics.split_for_impl();
let fields = Fields::<DataAttr>::parse_ast(&s.fields)?;
let diff = if fields.len() > 0 {
let same_fns = fields
.iter()
.filter(|f| f.attrs != DataAttr::Ignore)
.map(Field::same_fn_path_tokens);
let fields = fields
.iter()
.filter(|f| f.attrs != DataAttr::Ignore)
.map(Field::ident_tokens);
quote!( #( #same_fns(&self.#fields, &other.#fields) )&&* )
} else {
quote!(true)
};
let res = quote! {
impl<#impl_generics> ::druid::Data for #ident #ty_generics #where_clause {
fn same(&self, other: &Self) -> bool {
#diff
}
}
};
Ok(res)
}
fn ident_from_str(s: &str) -> proc_macro2::Ident {
proc_macro2::Ident::new(s, proc_macro2::Span::call_site())
}
fn is_c_style_enum(s: &DataEnum) -> bool {
s.variants.iter().all(|variant| match &variant.fields {
syn::Fields::Named(fs) => fs.named.is_empty(),
syn::Fields::Unnamed(fs) => fs.unnamed.is_empty(),
syn::Fields::Unit => true,
})
}
fn derive_enum(
input: &syn::DeriveInput,
s: &DataEnum,
) -> Result<proc_macro2::TokenStream, syn::Error> {
let ident = &input.ident;
let impl_generics = generics_bounds(&input.generics);
let (_, ty_generics, where_clause) = &input.generics.split_for_impl();
if is_c_style_enum(s) {
let res = quote! {
impl<#impl_generics> ::druid::Data for #ident #ty_generics #where_clause {
fn same(&self, other: &Self) -> bool { self == other }
}
};
return Ok(res);
}
let cases: Vec<proc_macro2::TokenStream> = s
.variants
.iter()
.map(|variant| {
let fields = Fields::<DataAttr>::parse_ast(&variant.fields)?;
let variant = &variant.ident;
let tests: Vec<_> = fields
.iter()
.filter(|f| f.attrs != DataAttr::Ignore)
.map(|field| {
let same_fn = field.same_fn_path_tokens();
let var_left = ident_from_str(&format!("__self_{}", field.ident_string()));
let var_right = ident_from_str(&format!("__other_{}", field.ident_string()));
quote!( #same_fn(#var_left, #var_right) )
})
.collect();
if let FieldKind::Named = fields.kind {
let lefts: Vec<_> = fields
.iter()
.map(|field| {
let ident = field.ident_tokens();
let var = ident_from_str(&format!("__self_{}", field.ident_string()));
quote!( #ident: #var )
})
.collect();
let rights: Vec<_> = fields
.iter()
.map(|field| {
let ident = field.ident_tokens();
let var = ident_from_str(&format!("__other_{}", field.ident_string()));
quote!( #ident: #var )
})
.collect();
Ok(quote! {
(#ident :: #variant { #( #lefts ),* }, #ident :: #variant { #( #rights ),* }) => {
#( #tests )&&*
}
})
} else {
let vars_left: Vec<_> = fields
.iter()
.map(|field| ident_from_str(&format!("__self_{}", field.ident_string())))
.collect();
let vars_right: Vec<_> = fields
.iter()
.map(|field| ident_from_str(&format!("__other_{}", field.ident_string())))
.collect();
if fields.iter().count() > 0 {
Ok(quote! {
( #ident :: #variant( #(#vars_left),* ), #ident :: #variant( #(#vars_right),* )) => {
#( #tests )&&*
}
})
} else {
Ok(quote! {
( #ident :: #variant , #ident :: #variant ) => { true }
})
}
}
})
.collect::<Result<Vec<proc_macro2::TokenStream>, syn::Error>>()?;
let res = quote! {
impl<#impl_generics> ::druid::Data for #ident #ty_generics #where_clause {
fn same(&self, other: &Self) -> bool {
match (self, other) {
#( #cases ),*
_ => false,
}
}
}
};
Ok(res)
}
fn generics_bounds(generics: &syn::Generics) -> proc_macro2::TokenStream {
let res = generics.params.iter().map(|gp| {
use syn::GenericParam::*;
match gp {
Type(ty) => {
let ident = &ty.ident;
let bounds = &ty.bounds;
if bounds.is_empty() {
quote_spanned!(ty.span()=> #ident : ::druid::Data)
} else {
quote_spanned!(ty.span()=> #ident : #bounds + ::druid::Data)
}
}
Lifetime(lf) => quote!(#lf),
Const(cst) => quote!(#cst),
}
});
quote!( #( #res, )* )
}