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Change #[pinned_drop] to trait implementation
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,69 +1,160 @@ | ||
| use proc_macro2::TokenStream; | ||
| use quote::quote; | ||
| use syn::{ | ||
| FnArg, GenericArgument, ItemFn, PatType, PathArguments, Result, ReturnType, Type, TypePath, | ||
| TypeReference, TypeTuple, | ||
| }; | ||
| use quote::{quote, quote_spanned, ToTokens}; | ||
| use syn::{parse::Nothing, spanned::Spanned, *}; | ||
|
|
||
| use crate::utils::crate_path; | ||
|
|
||
| pub(crate) fn attribute(input: &ItemFn) -> TokenStream { | ||
| parse(input).unwrap_or_else(|e| e.to_compile_error()) | ||
| pub(crate) fn attribute(mut input: ItemImpl) -> TokenStream { | ||
| if let Err(e) = parse(&mut input) { | ||
| let crate_path = crate_path(); | ||
| let self_ty = &input.self_ty; | ||
| let (impl_generics, _, where_clause) = input.generics.split_for_impl(); | ||
|
|
||
| let mut tokens = e.to_compile_error(); | ||
| // Generate a dummy `UnsafePinnedDrop` implementation. | ||
| // In many cases, `#[pinned_drop] impl` is declared after `#[pin_project]`. | ||
| // Therefore, if `pinned_drop` compile fails, you will also get an error | ||
| // about `UnsafePinnedDrop` not being implemented. | ||
| // This can be prevented to some extent by generating a dummy | ||
| // `UnsafePinnedDrop` implementation. | ||
| // We already know that we will get a compile error, so this won't | ||
| // accidentally compile successfully. | ||
| tokens.extend(quote! { | ||
| unsafe impl #impl_generics ::#crate_path::__private::UnsafePinnedDrop | ||
| for #self_ty #where_clause | ||
| { | ||
| unsafe fn drop(self: ::core::pin::Pin<&mut Self>) {} | ||
| } | ||
| }); | ||
| tokens | ||
| } else { | ||
| input.into_token_stream() | ||
| } | ||
| } | ||
|
|
||
| fn parse_arg(arg: &FnArg) -> Result<&Type> { | ||
| if let FnArg::Typed(PatType { ty, .. }) = arg { | ||
| if let Type::Path(TypePath { qself: None, path }) = &**ty { | ||
| let ty = &path.segments[path.segments.len() - 1]; | ||
| fn parse_method(method: &ImplItemMethod) -> Result<()> { | ||
| fn get_ty_path(ty: &Type) -> Option<&Path> { | ||
| if let Type::Path(TypePath { qself: None, path }) = ty { Some(path) } else { None } | ||
| } | ||
|
|
||
| const INVALID_ARGUMENT: &str = "method `drop` must take an argument `self: Pin<&mut Self>`"; | ||
|
|
||
| if method.sig.ident != "drop" { | ||
| return Err(error!( | ||
| method.sig.ident, | ||
| "method `{}` is not a member of trait `PinnedDrop", method.sig.ident, | ||
| )); | ||
| } | ||
|
|
||
| if let ReturnType::Type(_, ty) = &method.sig.output { | ||
| match &**ty { | ||
| Type::Tuple(TypeTuple { elems, .. }) if elems.is_empty() => {} | ||
| _ => return Err(error!(ty, "method `drop` must return the unit type")), | ||
| } | ||
| } | ||
|
|
||
| if method.sig.inputs.len() != 1 { | ||
| if method.sig.inputs.is_empty() { | ||
| return Err(syn::Error::new(method.sig.paren_token.span, INVALID_ARGUMENT)); | ||
| } else { | ||
| return Err(error!(&method.sig.inputs, INVALID_ARGUMENT)); | ||
| } | ||
| } | ||
|
|
||
| if let FnArg::Typed(PatType { pat, ty, .. }) = &method.sig.inputs[0] { | ||
| // !by_ref (mutability) ident !subpat: path | ||
| if let (Pat::Ident(PatIdent { by_ref: None, ident, subpat: None, .. }), Some(path)) = | ||
| (&**pat, get_ty_path(ty)) | ||
| { | ||
| let ty = &path.segments.last().unwrap(); | ||
| if let PathArguments::AngleBracketed(args) = &ty.arguments { | ||
| if args.args.len() == 1 && ty.ident == "Pin" { | ||
| // (mut) self: (path::)Pin<args> | ||
| if ident == "self" && args.args.len() == 1 && ty.ident == "Pin" { | ||
| // &mut <elem> | ||
| if let GenericArgument::Type(Type::Reference(TypeReference { | ||
| mutability: Some(_), | ||
| elem, | ||
| .. | ||
| })) = &args.args[0] | ||
| { | ||
| return Ok(&**elem); | ||
| if get_ty_path(elem).map_or(false, |path| path.is_ident("Self")) { | ||
| if method.sig.unsafety.is_some() { | ||
| return Err(error!( | ||
| method.sig.unsafety, | ||
| "implementing the method `drop` is not unsafe" | ||
| )); | ||
| } | ||
| return Ok(()); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| Err(error!(arg, "#[pinned_drop] function must take a argument `Pin<&mut Type>`")) | ||
| Err(error!(method.sig.inputs[0], INVALID_ARGUMENT)) | ||
| } | ||
|
|
||
| fn parse(item: &ItemFn) -> Result<TokenStream> { | ||
| if let ReturnType::Type(_, ty) = &item.sig.output { | ||
| match &**ty { | ||
| Type::Tuple(TypeTuple { elems, .. }) if elems.is_empty() => {} | ||
| _ => return Err(error!(ty, "#[pinned_drop] function must return the unit type")), | ||
| fn parse(item: &mut ItemImpl) -> Result<()> { | ||
| if let Some((_, path, _)) = &mut item.trait_ { | ||
| if path.is_ident("PinnedDrop") { | ||
| let crate_path = crate_path(); | ||
|
|
||
| *path = syn::parse2(quote_spanned! { path.span() => | ||
| ::#crate_path::__private::UnsafePinnedDrop | ||
| }) | ||
| .unwrap(); | ||
| } else { | ||
| return Err(error!( | ||
| path, | ||
| "#[pinned_drop] may only be used on implementation for the `PinnedDrop` trait" | ||
| )); | ||
| } | ||
| } | ||
| if item.sig.inputs.len() != 1 { | ||
| } else { | ||
| return Err(error!( | ||
| item.sig.inputs, | ||
| "#[pinned_drop] function must take exactly one argument" | ||
| item.self_ty, | ||
| "#[pinned_drop] may only be used on implementation for the `PinnedDrop` trait" | ||
| )); | ||
| } | ||
|
|
||
| let crate_path = crate_path(); | ||
| let type_ = parse_arg(&item.sig.inputs[0])?; | ||
| let fn_name = &item.sig.ident; | ||
| let (impl_generics, _, where_clause) = item.sig.generics.split_for_impl(); | ||
|
|
||
| Ok(quote! { | ||
| unsafe impl #impl_generics ::#crate_path::__private::UnsafePinnedDrop for #type_ #where_clause { | ||
| unsafe fn pinned_drop(self: ::core::pin::Pin<&mut Self>) { | ||
| // Declare the #[pinned_drop] function *inside* our pinned_drop function | ||
| // This guarantees that it's impossible for any other user code | ||
| // to call it. | ||
| #item | ||
| // #[pinned_drop] function is a free function - if it were part of a trait impl, | ||
| // it would be possible for user code to call it by directly invoking the trait. | ||
| #fn_name(self) | ||
| if item.unsafety.is_some() { | ||
| return Err(error!(item.unsafety, "implementing the trait `PinnedDrop` is not unsafe")); | ||
| } | ||
| item.unsafety = Some(token::Unsafe::default()); | ||
|
|
||
| if item.items.is_empty() { | ||
| return Err(error!(item, "not all trait items implemented, missing: `drop`")); | ||
| } else { | ||
| for (i, item) in item.items.iter().enumerate() { | ||
| match item { | ||
| ImplItem::Const(item) => { | ||
| return Err(error!( | ||
| item, | ||
| "const `{}` is not a member of trait `PinnedDrop`", item.ident | ||
| )); | ||
| } | ||
| ImplItem::Type(item) => { | ||
| return Err(error!( | ||
| item, | ||
| "type `{}` is not a member of trait `PinnedDrop`", item.ident | ||
| )); | ||
| } | ||
| ImplItem::Method(method) => { | ||
| parse_method(method)?; | ||
| if i != 0 { | ||
| return Err(error!(method, "duplicate definitions with name `drop`")); | ||
| } | ||
| } | ||
| _ => { | ||
| let _: Nothing = syn::parse2(item.to_token_stream())?; | ||
| } | ||
| } | ||
| } | ||
| }) | ||
| } | ||
|
|
||
| if let ImplItem::Method(method) = &mut item.items[0] { | ||
| method.sig.unsafety = Some(token::Unsafe::default()); | ||
| } | ||
|
|
||
| Ok(()) | ||
| } |
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