glib_macros/downgrade_derive/fields.rs
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// Take a look at the license at the top of the repository in the LICENSE file.
use proc_macro2::TokenStream;
use quote::{format_ident, quote};
use syn::{Fields, FieldsNamed, FieldsUnnamed, Ident, Type};
use crate::utils::crate_ident_new;
/// Parts needed to derive Downgrade and Upgrade implementation.
pub struct DowngradeStructParts {
/// Inner part of weak type declaration
pub weak_fields: TokenStream,
/// Term needed to finish declaration. It is usually blank but is `;` for tuple structs.
pub end_of_struct: TokenStream,
/// Destructuring pattern
pub destruct: TokenStream,
/// Downgrade code
pub downgrade: TokenStream,
/// Upgrade code
pub upgrade: TokenStream,
}
/// This function generates parts needed to derive Downgrade and Upgrade
/// implementations.
///
/// # Example
///
/// Let's assume following types are declared.
///
/// ```rust,ignore
/// struct Unnamed(X, Y);
///
/// struct Named {
/// x: X,
/// y: Y,
/// }
///
/// enum Choice {
/// This(X, Y),
/// That { x: X, y: Y },
/// }
/// ```
///
/// ## weak_fields
///
/// For the struct `Unnamed` and for a enum's variant `Choice::This`
/// it will be `(<X as Downgrade>::Weak, <Y as Downgrade>::Weak)`.
/// For the struct `Named` and for a enum's variant `Choice::That`
/// it will be `{ x: <X as Downgrade>::Weak, y: <Y as Downgrade>::Weak, }`.
///
/// ## end_of_struct
///
/// It is a semicolon (`;`) for an `Unnamed` and is blank for the rest.
///
/// ## destruct
///
/// For the struct `Unnamed` and for a enum's variant `Choice::This`
/// it will be `(ref _0, ref _1)`.
/// For the struct `Named` and for a enum's variant `Choice::That`
/// it will be `{ ref x, ref y }`.
/// So it can be used as a destructuring pattern for values of both types,
/// strong and weak.
///
/// ```rust,ignore
/// let Unnamed (ref _0, ref _1) = <expression>;
/// let Named { ref x, ref y } = <expression>;
///
/// match <expression> {
/// Choice::This (ref _0, ref _1) => ... ,
/// Choice::That { ref x, ref y } => ... ,
/// }
/// ```
///
/// # downgrade
///
/// ```rust,ignore
/// (
/// glib::clone::Downgrade::downgrade(_0),
/// glib::clone::Downgrade::downgrade(_1),
/// )
///
/// {
/// x: glib::clone::Downgrade::downgrade(x),
/// y: glib::clone::Downgrade::downgrade(y),
/// }
/// ```
///
/// # upgrade
///
/// ```rust,ignore
/// (
/// glib::clone::Upgrade::upgrade(_0)?,
/// glib::clone::Upgrade::upgrade(_1)?,
/// )
///
/// {
/// x: glib::clone::Upgrade::upgrade(x)?,
/// y: glib::clone::Upgrade::upgrade(y)?,
/// }
/// ```
pub fn derive_downgrade_fields(fields: syn::Fields) -> DowngradeStructParts {
let glib = crate_ident_new();
match fields {
Fields::Unnamed(FieldsUnnamed { unnamed, .. }) => {
let fields: Vec<Type> = unnamed
.into_pairs()
.map(|pair| pair.into_value())
.map(|field| field.ty)
.collect();
let weak_fields: Vec<_> = fields
.iter()
.map(|ty| {
quote! {
<#ty as #glib::clone::Downgrade>::Weak
}
})
.collect();
let field_ident: Vec<Ident> =
(0..fields.len()).map(|i| format_ident!("_{}", i)).collect();
DowngradeStructParts {
weak_fields: quote! {
(#(
#weak_fields
),*)
},
end_of_struct: quote!(;),
destruct: quote! {
(#(
ref #field_ident
),*)
},
downgrade: quote! {
(#(
#glib::clone::Downgrade::downgrade(#field_ident)
),*)
},
upgrade: quote! {
(#(
#glib::clone::Upgrade::upgrade(#field_ident)?
),*)
},
}
}
Fields::Named(FieldsNamed { named, .. }) => {
let fields: Vec<(Ident, Type)> = named
.into_pairs()
.map(|pair| pair.into_value())
.map(|field| (field.ident.expect("Field ident is specified"), field.ty))
.collect();
let weak_fields: Vec<_> = fields
.iter()
.map(|(ident, ty)| {
quote! {
#ident: <#ty as #glib::clone::Downgrade>::Weak
}
})
.collect();
let field_ident: Vec<_> = fields.iter().map(|(ident, _ty)| ident).collect();
DowngradeStructParts {
weak_fields: quote! {
{#(
#weak_fields
),*}
},
end_of_struct: quote!(),
destruct: quote! {
{#(
ref #field_ident
),*}
},
downgrade: quote! {
{#(
#field_ident: #glib::clone::Downgrade::downgrade(#field_ident)
),*}
},
upgrade: quote! {
{#(
#field_ident: #glib::clone::Upgrade::upgrade(#field_ident)?
),*}
},
}
}
Fields::Unit => DowngradeStructParts {
weak_fields: quote! {},
end_of_struct: quote! { ; },
destruct: quote! {},
downgrade: quote! {},
upgrade: quote! {},
},
}
}