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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 http://mozilla.org/MPL/2.0/. */
use quote;
use syn;
use synstructure;
pub fn derive(input: syn::DeriveInput) -> quote::Tokens {
let name = &input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let mut where_clause = where_clause.clone();
for param in &input.generics.ty_params {
where_clause.predicates.push(where_predicate(syn::Ty::Path(None, param.ident.clone().into()), None));
}
let computed_value_type = syn::Path::from(syn::PathSegment {
ident: name.clone(),
parameters: syn::PathParameters::AngleBracketed(syn::AngleBracketedParameterData {
lifetimes: input.generics.lifetimes.iter().map(|l| {
l.lifetime.clone()
}).collect(),
types: input.generics.ty_params.iter().map(|ty| {
syn::Ty::Path(
Some(syn::QSelf {
ty: Box::new(syn::Ty::Path(None, ty.ident.clone().into())),
position: 3,
}),
syn::Path {
global: true,
segments: vec![
"values".into(),
"computed".into(),
"ToComputedValue".into(),
"ComputedValue".into(),
],
},
)
}).collect(),
.. Default::default()
}),
});
let to_body = match_body(&input, |field| {
quote!(::values::computed::ToComputedValue::to_computed_value(#field, context))
});
let from_body = match_body(&input, |field| {
quote!(::values::computed::ToComputedValue::from_computed_value(#field))
});
quote! {
impl #impl_generics ::values::computed::ToComputedValue for #name #ty_generics #where_clause {
type ComputedValue = #computed_value_type;
#[allow(unused_variables)]
#[inline]
fn to_computed_value(&self, context: &::values::computed::Context) -> Self::ComputedValue {
match *self {
#to_body
}
}
#[inline]
fn from_computed_value(computed: &Self::ComputedValue) -> Self {
match *computed {
#from_body
}
}
}
}
}
fn match_body<F>(input: &syn::DeriveInput, f: F) -> quote::Tokens
where F: Fn(&synstructure::BindingInfo) -> quote::Tokens,
{
let by_ref = synstructure::BindStyle::Ref.into();
let by_value = synstructure::BindStyle::Move.into();
synstructure::each_variant(&input, &by_ref, |fields, variant| {
let name = if let syn::Body::Enum(_) = input.body {
format!("{}::{}", input.ident, variant.ident).into()
} else {
variant.ident.clone()
};
let (computed_value, computed_fields) = synstructure::match_pattern(&name, &variant.data, &by_value);
let fields_pairs = fields.iter().zip(computed_fields.iter());
let mut computations = quote!();
computations.append_all(fields_pairs.map(|(field, computed_field)| {
let expr = f(field);
quote!(let #computed_field = #expr;)
}));
Some(quote!(
#computations
#computed_value
))
})
}
/// `#ty: ::values::computed::ToComputedValue<ComputedValue = #computed_value,>`
fn where_predicate(ty: syn::Ty, computed_value: Option<syn::Ty>) -> syn::WherePredicate {
syn::WherePredicate::BoundPredicate(syn::WhereBoundPredicate {
bound_lifetimes: vec![],
bounded_ty: ty,
bounds: vec![syn::TyParamBound::Trait(
syn::PolyTraitRef {
bound_lifetimes: vec![],
trait_ref: trait_ref(computed_value),
},
syn::TraitBoundModifier::None
)],
})
}
/// `::values::computed::ToComputedValue<ComputedValue = #computed_value,>`
fn trait_ref(computed_value: Option<syn::Ty>) -> syn::Path {
syn::Path {
global: true,
segments: vec![
"values".into(),
"computed".into(),
syn::PathSegment {
ident: "ToComputedValue".into(),
parameters: syn::PathParameters::AngleBracketed(
syn::AngleBracketedParameterData {
bindings: trait_bindings(computed_value),
.. Default::default()
}
),
}
],
}
}
/// `ComputedValue = #computed_value,`
fn trait_bindings(computed_value: Option<syn::Ty>) -> Vec<syn::TypeBinding> {
computed_value.into_iter().map(|ty| {
syn::TypeBinding {
ident: "ComputedValue".into(),
ty: ty,
}
}).collect()
}
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