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|
use proc_macro2::Ident;
use quote::quote;
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;
use syn::spanned::Spanned;
use syn::{
Attribute, Generics, ImplItem, Pat, PatIdent, Path, Signature, Token, TraitItem,
TraitItemConst, TraitItemFn, TraitItemMacro, TraitItemType, Type, Visibility, WhereClause,
braced, parse_macro_input,
};
pub(crate) fn extension(
attr: proc_macro::TokenStream,
input: proc_macro::TokenStream,
) -> proc_macro::TokenStream {
let ExtensionAttr { vis, trait_ } = parse_macro_input!(attr as ExtensionAttr);
let Impl { attrs, generics, self_ty, items, wc } = parse_macro_input!(input as Impl);
let headers: Vec<_> = items
.iter()
.map(|item| match item {
ImplItem::Fn(f) => TraitItem::Fn(TraitItemFn {
attrs: scrub_attrs(&f.attrs),
sig: scrub_header(f.sig.clone()),
default: None,
semi_token: Some(Token)),
}),
ImplItem::Const(ct) => TraitItem::Const(TraitItemConst {
attrs: scrub_attrs(&ct.attrs),
const_token: ct.const_token,
ident: ct.ident.clone(),
generics: ct.generics.clone(),
colon_token: ct.colon_token,
ty: ct.ty.clone(),
default: None,
semi_token: ct.semi_token,
}),
ImplItem::Type(ty) => TraitItem::Type(TraitItemType {
attrs: scrub_attrs(&ty.attrs),
type_token: ty.type_token,
ident: ty.ident.clone(),
generics: ty.generics.clone(),
colon_token: None,
bounds: Punctuated::new(),
default: None,
semi_token: ty.semi_token,
}),
ImplItem::Macro(mac) => TraitItem::Macro(TraitItemMacro {
attrs: scrub_attrs(&mac.attrs),
mac: mac.mac.clone(),
semi_token: mac.semi_token,
}),
ImplItem::Verbatim(stream) => TraitItem::Verbatim(stream.clone()),
_ => unimplemented!(),
})
.collect();
quote! {
#(#attrs)*
#vis trait #trait_ {
#(#headers)*
}
impl #generics #trait_ for #self_ty #wc {
#(#items)*
}
}
.into()
}
/// Only keep `#[doc]` attrs.
fn scrub_attrs(attrs: &[Attribute]) -> Vec<Attribute> {
attrs
.into_iter()
.cloned()
.filter(|attr| {
let ident = &attr.path().segments[0].ident;
ident == "doc" || ident == "must_use"
})
.collect()
}
/// Scrub arguments so that they're valid for trait signatures.
fn scrub_header(mut sig: Signature) -> Signature {
for (idx, input) in sig.inputs.iter_mut().enumerate() {
match input {
syn::FnArg::Receiver(rcvr) => {
// `mut self` -> `self`
if rcvr.reference.is_none() {
rcvr.mutability.take();
}
}
syn::FnArg::Typed(arg) => match &mut *arg.pat {
Pat::Ident(arg) => {
// `ref mut ident @ pat` -> `ident`
arg.by_ref.take();
arg.mutability.take();
arg.subpat.take();
}
_ => {
// `pat` -> `__arg0`
arg.pat = Box::new(
PatIdent {
attrs: vec![],
by_ref: None,
mutability: None,
ident: Ident::new(&format!("__arg{idx}"), arg.pat.span()),
subpat: None,
}
.into(),
)
}
},
}
}
sig
}
struct ExtensionAttr {
vis: Visibility,
trait_: Path,
}
impl Parse for ExtensionAttr {
fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
let vis = input.parse()?;
let _: Token![trait] = input.parse()?;
let trait_ = input.parse()?;
Ok(ExtensionAttr { vis, trait_ })
}
}
struct Impl {
attrs: Vec<Attribute>,
generics: Generics,
self_ty: Type,
items: Vec<ImplItem>,
wc: Option<WhereClause>,
}
impl Parse for Impl {
fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
let attrs = input.call(Attribute::parse_outer)?;
let _: Token![impl] = input.parse()?;
let generics = input.parse()?;
let self_ty = input.parse()?;
let wc = input.parse()?;
let content;
let _brace_token = braced!(content in input);
let mut items = Vec::new();
while !content.is_empty() {
items.push(content.parse()?);
}
Ok(Impl { attrs, generics, self_ty, items, wc })
}
}
|
