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|
use crate::utils::{
add_extra_type_param_bound_op_output, named_to_vec, unnamed_to_vec,
};
use proc_macro2::{Span, TokenStream};
use quote::{quote, ToTokens};
use std::iter;
use syn::{Data, DataEnum, DeriveInput, Field, Fields, Ident, Index};
pub fn expand(input: &DeriveInput, trait_name: &str) -> TokenStream {
let trait_ident = Ident::new(trait_name, Span::call_site());
let method_name = trait_name.to_lowercase();
let method_ident = &Ident::new(&method_name, Span::call_site());
let input_type = &input.ident;
let generics = add_extra_type_param_bound_op_output(&input.generics, &trait_ident);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let (output_type, block) = match input.data {
Data::Struct(ref data_struct) => match data_struct.fields {
Fields::Unnamed(ref fields) => (
quote!(#input_type#ty_generics),
tuple_content(input_type, &unnamed_to_vec(fields), method_ident),
),
Fields::Named(ref fields) => (
quote!(#input_type#ty_generics),
struct_content(input_type, &named_to_vec(fields), method_ident),
),
_ => panic!("Unit structs cannot use derive({})", trait_name),
},
Data::Enum(ref data_enum) => {
enum_output_type_and_content(input, data_enum, method_ident)
}
_ => panic!("Only structs and enums can use derive({})", trait_name),
};
quote!(
impl#impl_generics ::core::ops::#trait_ident for #input_type#ty_generics #where_clause {
type Output = #output_type;
#[inline]
fn #method_ident(self) -> #output_type {
#block
}
}
)
}
fn tuple_content<T: ToTokens>(
input_type: &T,
fields: &[&Field],
method_ident: &Ident,
) -> TokenStream {
let mut exprs = vec![];
for i in 0..fields.len() {
let i = Index::from(i);
// generates `self.0.add()`
let expr = quote!(self.#i.#method_ident());
exprs.push(expr);
}
quote!(#input_type(#(#exprs),*))
}
fn struct_content(
input_type: &Ident,
fields: &[&Field],
method_ident: &Ident,
) -> TokenStream {
let mut exprs = vec![];
for field in fields {
// It's safe to unwrap because struct fields always have an identifier
let field_id = field.ident.as_ref();
// generates `x: self.x.not()`
let expr = quote!(#field_id: self.#field_id.#method_ident());
exprs.push(expr)
}
quote!(#input_type{#(#exprs),*})
}
fn enum_output_type_and_content(
input: &DeriveInput,
data_enum: &DataEnum,
method_ident: &Ident,
) -> (TokenStream, TokenStream) {
let input_type = &input.ident;
let (_, ty_generics, _) = input.generics.split_for_impl();
let mut matches = vec![];
let mut method_iter = iter::repeat(method_ident);
// If the enum contains unit types that means it can error.
let has_unit_type = data_enum.variants.iter().any(|v| v.fields == Fields::Unit);
for variant in &data_enum.variants {
let subtype = &variant.ident;
let subtype = quote!(#input_type::#subtype);
match variant.fields {
Fields::Unnamed(ref fields) => {
// The patern that is outputted should look like this:
// (Subtype(vars)) => Ok(TypePath(exprs))
let size = unnamed_to_vec(fields).len();
let vars: &Vec<_> = &(0..size)
.map(|i| Ident::new(&format!("__{}", i), Span::call_site()))
.collect();
let method_iter = method_iter.by_ref();
let mut body = quote!(#subtype(#(#vars.#method_iter()),*));
if has_unit_type {
body = quote!(::core::result::Result::Ok(#body))
}
let matcher = quote! {
#subtype(#(#vars),*) => {
#body
}
};
matches.push(matcher);
}
Fields::Named(ref fields) => {
// The patern that is outputted should look like this:
// (Subtype{a: __l_a, ...} => {
// Ok(Subtype{a: __l_a.neg(__r_a), ...})
// }
let field_vec = named_to_vec(fields);
let size = field_vec.len();
let field_names: &Vec<_> = &field_vec
.iter()
.map(|f| f.ident.as_ref().unwrap())
.collect();
let vars: &Vec<_> = &(0..size)
.map(|i| Ident::new(&format!("__{}", i), Span::call_site()))
.collect();
let method_iter = method_iter.by_ref();
let mut body =
quote!(#subtype{#(#field_names: #vars.#method_iter()),*});
if has_unit_type {
body = quote!(::core::result::Result::Ok(#body))
}
let matcher = quote! {
#subtype{#(#field_names: #vars),*} => {
#body
}
};
matches.push(matcher);
}
Fields::Unit => {
let message = format!("Cannot {}() unit variants", method_ident);
matches.push(quote!(#subtype => ::core::result::Result::Err(#message)));
}
}
}
let body = quote!(
match self {
#(#matches),*
}
);
let output_type = if has_unit_type {
quote!(::core::result::Result<#input_type#ty_generics, &'static str>)
} else {
quote!(#input_type#ty_generics)
};
(output_type, body)
}
|
