glib_macros/downgrade_derive/enums.rs
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// Take a look at the license at the top of the repository in the LICENSE file.
use proc_macro::TokenStream;
use quote::{format_ident, quote};
use syn::{Generics, Ident};
use super::fields::{derive_downgrade_fields, DowngradeStructParts};
use crate::utils::crate_ident_new;
/// This function derives a weak type for a given strong enum and
/// implementations of `Downgrade` and `Upgrade` traits.
///
/// # Example
///
/// ```rust,ignore
/// #[derive(glib::Downgrade)]
/// enum Choice {
/// This(X, Y),
/// That { x: X, y: Y },
/// }
/// ```
///
/// Here is what will be derived:
///
/// ```rust,ignore
/// enum ChoiceWeak {
/// This(<X as Downgrade>::Weak, <Y as Downgrade>::Weak),
/// That {
/// x: <X as Downgrade>::Weak,
/// y: <Y as Downgrade>::Weak,
/// },
/// }
///
/// impl glib::clone::Downgrade for Choice {
/// type Weak = ChoiceWeak;
///
/// fn downgrade(&self) -> Self::Weak {
/// match self {
/// Self::This(ref _0, ref _1) => Self::Weak::This(
/// glib::clone::Downgrade::downgrade(_0),
/// glib::clone::Downgrade::downgrade(_1),
/// ),
/// Self::That { ref x, ref y } => Self::Weak::That(
/// glib::clone::Downgrade::downgrade(x),
/// glib::clone::Downgrade::downgrade(y),
/// ),
/// }
/// }
/// }
///
/// impl glib::clone::Upgrade for ChoiceWeak {
/// type Strong = Choice;
///
/// fn upgrade(&self) -> Option<Self::Strong> {
/// Some(match self {
/// Self::This(ref _0, ref _1) => Self::Strong::This(
/// glib::clone::Upgrade::upgrade(_0)?,
/// glib::clone::Upgrade::upgrade(_1)?,
/// ),
/// Self::That { ref x, ref y } => Self::Strong::That(
/// glib::clone::Upgrade::upgrade(x)?,
/// glib::clone::Upgrade::upgrade(y)?,
/// ),
/// })
/// }
/// }
/// ```
pub fn derive_downgrade_for_enum(
ident: Ident,
generics: Generics,
data_enum: syn::DataEnum,
) -> TokenStream {
let glib = crate_ident_new();
let weak_type = format_ident!("{}Weak", ident);
let variants: Vec<(Ident, DowngradeStructParts)> = data_enum
.variants
.into_iter()
.map(|variant| (variant.ident, derive_downgrade_fields(variant.fields)))
.collect();
let weak_variants: Vec<_> = variants
.iter()
.map(|(ident, parts)| {
let weak_fields = &parts.weak_fields;
quote! {
#ident #weak_fields
}
})
.collect();
let downgrade_variants: Vec<_> = variants
.iter()
.map(|(ident, parts)| {
let destruct = &parts.destruct;
let downgrade = &parts.downgrade;
quote! {
Self::#ident #destruct => Self::Weak::#ident #downgrade
}
})
.collect();
let upgrade_variants: Vec<_> = variants
.iter()
.map(|(ident, parts)| {
let destruct = &parts.destruct;
let upgrade = &parts.upgrade;
quote! {
Self::#ident #destruct => Self::Strong::#ident #upgrade
}
})
.collect();
let derived = quote! {
pub enum #weak_type #generics {#(
#weak_variants
),*}
impl #generics #glib::clone::Downgrade for #ident #generics {
type Weak = #weak_type #generics;
fn downgrade(&self) -> Self::Weak {
match self {#(
#downgrade_variants
),*}
}
}
impl #generics #glib::clone::Upgrade for #weak_type #generics {
type Strong = #ident #generics;
fn upgrade(&self) -> ::core::option::Option<Self::Strong> {
::core::option::Option::Some(match self {#(
#upgrade_variants
),*})
}
}
};
derived.into()
}