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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
use darling::{FromDeriveInput, FromField};
use proc_macro2::{Span, TokenStream};
use quote::{quote, TokenStreamExt};
use syn::{self, parse_quote, DeriveInput, Field, Ident, WherePredicate};
use synstructure::{self, BindStyle, BindingInfo, VariantInfo};
pub(crate) fn parse_input_attrs<A>(input: &DeriveInput) -> A
where
A: FromDeriveInput,
{
match A::from_derive_input(input) {
Ok(attrs) => attrs,
Err(e) => panic!("failed to parse input attributes: {}", e),
}
}
pub(crate) fn parse_field_attrs<A>(field: &Field) -> A
where
A: FromField,
{
match A::from_field(field) {
Ok(attrs) => attrs,
Err(e) => panic!("failed to parse field attributes: {}", e),
}
}
pub(crate) fn add_predicate(where_clause: &mut Option<syn::WhereClause>, pred: WherePredicate) {
where_clause
.get_or_insert(parse_quote!(where))
.predicates
.push(pred);
}
pub(crate) fn fmap2_match<F, G>(
input: &DeriveInput,
bind_style: BindStyle,
mut f: F,
mut g: G,
) -> TokenStream
where
F: FnMut(&BindingInfo) -> TokenStream,
G: FnMut(&BindingInfo) -> Option<TokenStream>,
{
let mut s = synstructure::Structure::new(input);
s.variants_mut().iter_mut().for_each(|v| {
v.bind_with(|_| bind_style);
});
s.each_variant(|variant| {
let (mapped, mapped_fields) = value(variant, "mapped");
let fields_pairs = variant.bindings().iter().zip(mapped_fields.iter());
let mut computations = quote!();
computations.append_all(fields_pairs.map(|(field, mapped_field)| {
let expr = f(field);
quote! { let #mapped_field = #expr; }
}));
computations.append_all(
mapped_fields
.iter()
.map(|mapped_field| match g(mapped_field) {
Some(expr) => quote! { let #mapped_field = #expr; },
None => quote!(),
}),
);
computations.append_all(mapped);
Some(computations)
})
}
fn value<'a>(variant: &'a VariantInfo, prefix: &str) -> (TokenStream, Vec<BindingInfo<'a>>) {
let mut v = variant.clone();
v.bindings_mut().iter_mut().for_each(|b| {
b.binding = Ident::new(&format!("{}_{}", b.binding, prefix), Span::call_site())
});
v.bind_with(|_| BindStyle::Move);
(v.pat(), v.bindings().to_vec())
}