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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
* file, You can obtain one at https://mozilla.org/MPL/2.0/. */
use derive_common::cg;
use proc_macro2::TokenStream;
use syn::{DeriveInput, Ident, Path};
use synstructure::{BindStyle, BindingInfo};
pub fn derive_to_value(
mut input: DeriveInput,
trait_path: Path,
output_type_name: Ident,
bind_style: BindStyle,
// Returns whether to apply the field bound for a given item.
mut binding_attrs: impl FnMut(&BindingInfo) -> ToValueAttrs,
// Returns a token stream of the form: trait_path::from_foo(#binding)
mut call_from: impl FnMut(&BindingInfo) -> TokenStream,
mut call_to: impl FnMut(&BindingInfo) -> TokenStream,
// Returns a tokenstream of the form:
// fn from_function_syntax(foobar) -> Baz {
// #first_arg
// }
//
// fn to_function_syntax(foobar) -> Baz {
// #second_arg
// }
mut trait_impl: impl FnMut(TokenStream, TokenStream) -> TokenStream,
) -> TokenStream {
let name = &input.ident;
let mut where_clause = input.generics.where_clause.take();
cg::propagate_clauses_to_output_type(
&mut where_clause,
&input.generics,
&trait_path,
&output_type_name,
);
let moves = match bind_style {
BindStyle::Move | BindStyle::MoveMut => true,
BindStyle::Ref | BindStyle::RefMut => false,
};
let params = input.generics.type_params().collect::<Vec<_>>();
for param in ¶ms {
cg::add_predicate(&mut where_clause, parse_quote!(#param: #trait_path));
}
let computed_value_type = cg::fmap_trait_output(&input, &trait_path, &output_type_name);
let mut add_field_bound = |binding: &BindingInfo| {
let ty = &binding.ast().ty;
let output_type = cg::map_type_params(
ty,
¶ms,
&computed_value_type,
&mut |ident| parse_quote!(<#ident as #trait_path>::#output_type_name),
);
cg::add_predicate(
&mut where_clause,
parse_quote!(
#ty: #trait_path<#output_type_name = #output_type>
),
);
};
let (to_body, from_body) = if params.is_empty() {
let mut s = synstructure::Structure::new(&input);
s.variants_mut().iter_mut().for_each(|v| {
v.bind_with(|_| bind_style);
});
for variant in s.variants() {
for binding in variant.bindings() {
let attrs = binding_attrs(&binding);
assert!(
!attrs.field_bound,
"It is default on a non-generic implementation",
);
if !attrs.no_field_bound {
// Add field bounds to all bindings except the manually
// excluded. This ensures the correctness of the clone() /
// move based implementation.
add_field_bound(binding);
}
}
}
let to_body = if moves {
quote! { self }
} else {
quote! { std::clone::Clone::clone(self) }
};
let from_body = if moves {
quote! { from }
} else {
quote! { std::clone::Clone::clone(from) }
};
(to_body, from_body)
} else {
let to_body = cg::fmap_match(&input, bind_style, |binding| {
let attrs = binding_attrs(&binding);
assert!(
!attrs.no_field_bound,
"It doesn't make sense on a generic implementation"
);
if attrs.field_bound {
add_field_bound(&binding);
}
call_to(&binding)
});
let from_body = cg::fmap_match(&input, bind_style, |binding| call_from(&binding));
let self_ = if moves {
quote! { self }
} else {
quote! { *self }
};
let from_ = if moves {
quote! { from }
} else {
quote! { *from }
};
let to_body = quote! {
match #self_ {
#to_body
}
};
let from_body = quote! {
match #from_ {
#from_body
}
};
(to_body, from_body)
};
input.generics.where_clause = where_clause;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let impl_ = trait_impl(from_body, to_body);
quote! {
impl #impl_generics #trait_path for #name #ty_generics #where_clause {
type #output_type_name = #computed_value_type;
#impl_
}
}
}
pub fn derive(input: DeriveInput) -> TokenStream {
let trait_impl = |from_body, to_body| {
quote! {
#[inline]
fn from_computed_value(from: &Self::ComputedValue) -> Self {
#from_body
}
#[allow(unused_variables)]
#[inline]
fn to_computed_value(&self, context: &crate::values::computed::Context) -> Self::ComputedValue {
#to_body
}
}
};
derive_to_value(
input,
parse_quote!(crate::values::computed::ToComputedValue),
parse_quote!(ComputedValue),
BindStyle::Ref,
|binding| {
let attrs = cg::parse_field_attrs::<ComputedValueAttrs>(&binding.ast());
ToValueAttrs {
field_bound: attrs.field_bound,
no_field_bound: attrs.no_field_bound,
}
},
|binding| quote!(crate::values::computed::ToComputedValue::from_computed_value(#binding)),
|binding| quote!(crate::values::computed::ToComputedValue::to_computed_value(#binding, context)),
trait_impl,
)
}
#[derive(Default)]
pub struct ToValueAttrs {
pub field_bound: bool,
pub no_field_bound: bool,
}
#[derive(Default, FromField)]
#[darling(attributes(compute), default)]
struct ComputedValueAttrs {
field_bound: bool,
no_field_bound: bool,
}
|
