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enums.rs
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enums.rs
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use proc_macro2::TokenStream;
use quote::{format_ident, quote, ToTokens};
use syn::{Field, Fields, FieldsNamed, FieldsUnnamed, ItemEnum, Result, Variant};
use crate::utils::collect_cfg;
use super::Context;
pub(super) fn parse(cx: &mut Context, mut item: ItemEnum) -> Result<TokenStream> {
if item.variants.is_empty() {
return Err(syn::Error::new(
item.brace_token.span,
"#[pin_project] attribute may not be used on enums without variants",
));
}
let has_field = item.variants.iter().try_fold(false, |has_field, v| {
if let Some((_, e)) = &v.discriminant {
Err(error!(e, "#[pin_project] attribute may not be used on enums with discriminants"))
} else if let Fields::Unit = v.fields {
Ok(has_field)
} else {
Ok(true)
}
})?;
if !has_field {
return Err(error!(
item.variants,
"#[pin_project] attribute may not be used on enums that have no field"
));
}
let (proj_variants, proj_arms) = variants(cx, &mut item)?;
let proj_ident = &cx.proj_ident;
let proj_generics = cx.proj_generics();
let where_clause = item.generics.split_for_impl().2;
let mut proj_items = quote! {
#[allow(clippy::mut_mut)] // This lint warns `&mut &mut <ty>`.
#[allow(dead_code)] // This lint warns unused fields/variants.
enum #proj_ident #proj_generics #where_clause { #(#proj_variants,)* }
};
let project_body = quote! {
match self.as_mut().get_unchecked_mut() {
#(#proj_arms,)*
}
};
let project_into_body = quote! {
match self.get_unchecked_mut() {
#(#proj_arms,)*
}
};
proj_items.extend(cx.make_proj_impl(&project_body, &project_into_body));
let mut item = item.into_token_stream();
item.extend(proj_items);
Ok(item)
}
fn variants(cx: &mut Context, item: &mut ItemEnum) -> Result<(Vec<TokenStream>, Vec<TokenStream>)> {
let mut proj_variants = Vec::with_capacity(item.variants.len());
let mut proj_arms = Vec::with_capacity(item.variants.len());
for Variant { attrs, fields, ident, .. } in &mut item.variants {
let (proj_pat, proj_body, proj_fields) = match fields {
Fields::Unnamed(fields) => unnamed(cx, fields)?,
Fields::Named(fields) => named(cx, fields)?,
Fields::Unit => (TokenStream::new(), TokenStream::new(), TokenStream::new()),
};
let cfg = collect_cfg(attrs);
let Context { orig_ident, proj_ident, .. } = &cx;
proj_variants.push(quote! {
#(#cfg)* #ident #proj_fields
});
proj_arms.push(quote! {
#(#cfg)* #orig_ident::#ident #proj_pat => {
#proj_ident::#ident #proj_body
}
});
}
Ok((proj_variants, proj_arms))
}
fn named(
cx: &mut Context,
FieldsNamed { named: fields, .. }: &mut FieldsNamed,
) -> Result<(TokenStream, TokenStream, TokenStream)> {
let mut proj_pat = Vec::with_capacity(fields.len());
let mut proj_body = Vec::with_capacity(fields.len());
let mut proj_fields = Vec::with_capacity(fields.len());
for Field { attrs, ident, ty, .. } in fields {
let cfg = collect_cfg(attrs);
if cx.find_pin_attr(attrs)? {
let lifetime = &cx.lifetime;
proj_fields.push(quote! {
#(#cfg)* #ident: ::core::pin::Pin<&#lifetime mut #ty>
});
proj_body.push(quote! {
#(#cfg)* #ident: ::core::pin::Pin::new_unchecked(#ident)
});
} else {
let lifetime = &cx.lifetime;
proj_fields.push(quote! {
#(#cfg)* #ident: &#lifetime mut #ty
});
proj_body.push(quote! {
#(#cfg)* #ident: #ident
});
}
proj_pat.push(quote! {
#(#cfg)* #ident
});
}
let proj_pat = quote!({ #(#proj_pat),* });
let proj_body = quote!({ #(#proj_body),* });
let proj_fields = quote!({ #(#proj_fields),* });
Ok((proj_pat, proj_body, proj_fields))
}
fn unnamed(
cx: &mut Context,
FieldsUnnamed { unnamed: fields, .. }: &mut FieldsUnnamed,
) -> Result<(TokenStream, TokenStream, TokenStream)> {
let mut proj_pat = Vec::with_capacity(fields.len());
let mut proj_body = Vec::with_capacity(fields.len());
let mut proj_fields = Vec::with_capacity(fields.len());
for (i, Field { attrs, ty, .. }) in fields.iter_mut().enumerate() {
let id = format_ident!("_x{}", i);
let cfg = collect_cfg(attrs);
if !cfg.is_empty() {
return Err(error!(
cfg.first(),
"`cfg` attributes on the field of tuple variants are not supported"
));
}
if cx.find_pin_attr(attrs)? {
let lifetime = &cx.lifetime;
proj_fields.push(quote! {
::core::pin::Pin<&#lifetime mut #ty>
});
proj_body.push(quote! {
::core::pin::Pin::new_unchecked(#id)
});
} else {
let lifetime = &cx.lifetime;
proj_fields.push(quote! {
&#lifetime mut #ty
});
proj_body.push(quote! {
#id
});
}
proj_pat.push(quote! {
#id
});
}
let proj_pat = quote!((#(#proj_pat),*));
let proj_body = quote!((#(#proj_body),*));
let proj_fields = quote!((#(#proj_fields),*));
Ok((proj_pat, proj_body, proj_fields))
}