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Remove pin_project! function-like macro and add #[pinned_drop] attribute
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,185 @@ | ||
| use proc_macro2::{Ident, Span, TokenStream}; | ||
| use quote::{quote, quote_spanned}; | ||
| use syn::{ | ||
| parse::{Parse, ParseStream}, | ||
| Attribute, Generics, Item, Meta, NestedMeta, Result, Type, | ||
| }; | ||
|
|
||
| use crate::utils::{crate_path, Nothing}; | ||
|
|
||
| mod enums; | ||
| mod structs; | ||
|
|
||
| /// The annotation for pinned type. | ||
| const PIN: &str = "pin"; | ||
|
|
||
| pub(super) fn attribute(args: TokenStream, input: TokenStream) -> TokenStream { | ||
| parse(args, input).unwrap_or_else(|e| e.to_compile_error()) | ||
| } | ||
|
|
||
| #[derive(Clone, Copy)] | ||
| struct Args { | ||
| pinned_drop: Option<Span>, | ||
| unsafe_unpin: Option<Span>, | ||
| } | ||
|
|
||
| impl Args { | ||
| fn impl_drop(self, generics: &Generics) -> ImplDrop<'_> { | ||
| ImplDrop::new(generics, self.pinned_drop) | ||
| } | ||
|
|
||
| fn impl_unpin(self, generics: &Generics) -> ImplUnpin { | ||
| ImplUnpin::new(generics, self.unsafe_unpin) | ||
| } | ||
| } | ||
|
|
||
| impl Parse for Args { | ||
| fn parse(input: ParseStream<'_>) -> Result<Self> { | ||
| let mut pinned_drop = None; | ||
| let mut unsafe_unpin = None; | ||
| while !input.is_empty() { | ||
| let i = input.parse::<Ident>()?; | ||
| match &*i.to_string() { | ||
| "PinnedDrop" => pinned_drop = Some(i.span()), | ||
| "unsafe_Unpin" => unsafe_unpin = Some(i.span()), | ||
| _ => return Err(error!(i, "an invalid argument was passed")), | ||
| } | ||
| } | ||
| Ok(Self { pinned_drop, unsafe_unpin }) | ||
| } | ||
| } | ||
|
|
||
| fn parse(args: TokenStream, input: TokenStream) -> Result<TokenStream> { | ||
| let args = syn::parse2(args)?; | ||
| match syn::parse2(input)? { | ||
| Item::Struct(item) => { | ||
| ensure_not_packed(&item.attrs)?; | ||
| structs::parse(args, item) | ||
| } | ||
| Item::Enum(item) => { | ||
| ensure_not_packed(&item.attrs)?; | ||
| enums::parse(args, item) | ||
| } | ||
| item => Err(error!(item, "may only be used on structs or enums")), | ||
| } | ||
| } | ||
|
|
||
| fn ensure_not_packed(attrs: &[Attribute]) -> Result<()> { | ||
| for meta in attrs.iter().filter_map(|attr| attr.parse_meta().ok()) { | ||
| if let Meta::List(l) = meta { | ||
| if l.ident == "repr" { | ||
| for repr in l.nested.iter() { | ||
| if let NestedMeta::Meta(Meta::Word(w)) = repr { | ||
| if w == "packed" { | ||
| return Err(error!( | ||
| w, | ||
| "pin_project may not be used on #[repr(packed)] types" | ||
| )); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| Ok(()) | ||
| } | ||
|
|
||
| /// Makes the generics of projected type from the reference of the original generics. | ||
| fn proj_generics(generics: &Generics) -> Generics { | ||
| let mut generics = generics.clone(); | ||
| generics.params.insert(0, syn::parse_quote!('__a)); | ||
| generics | ||
| } | ||
|
|
||
| // ================================================================================================= | ||
| // Drop implementation | ||
|
|
||
| struct ImplDrop<'a> { | ||
| generics: &'a Generics, | ||
| pinned_drop: Option<Span>, | ||
| } | ||
|
|
||
| impl<'a> ImplDrop<'a> { | ||
| fn new(generics: &'a Generics, pinned_drop: Option<Span>) -> Self { | ||
| Self { generics, pinned_drop } | ||
| } | ||
|
|
||
| fn build(self, ident: &Ident) -> TokenStream { | ||
| let (impl_generics, ty_generics, where_clause) = self.generics.split_for_impl(); | ||
|
|
||
| if let Some(pinned_drop) = self.pinned_drop { | ||
| let crate_path = crate_path(); | ||
| let call = quote_spanned! { pinned_drop => | ||
| ::#crate_path::__private::UnsafePinnedDrop::pinned_drop(pinned_self) | ||
| }; | ||
|
|
||
| quote! { | ||
| impl #impl_generics ::core::ops::Drop for #ident #ty_generics #where_clause { | ||
| fn drop(&mut self) { | ||
| // Safety - we're in 'drop', so we know that 'self' will | ||
| // never move again | ||
| let pinned_self = unsafe { ::core::pin::Pin::new_unchecked(self) }; | ||
| // We call `pinned_drop` only once. Since `UnsafePinnedDrop::pinned_drop` | ||
| // is an unsafe function and a private API, it is never called again in safe | ||
| // code *unless the user uses a maliciously crafted macro*. | ||
| unsafe { | ||
| #call; | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } else { | ||
| quote! { | ||
| impl #impl_generics ::core::ops::Drop for #ident #ty_generics #where_clause { | ||
| fn drop(&mut self) { | ||
| // Do nothing. The precense of this Drop | ||
| // impl ensures that the user can't provide one of their own | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
|
||
| // ================================================================================================= | ||
| // conditional Unpin implementation | ||
|
|
||
| struct ImplUnpin { | ||
| generics: Generics, | ||
| unsafe_unpin: bool, | ||
| } | ||
|
|
||
| impl ImplUnpin { | ||
| fn new(generics: &Generics, unsafe_unpin: Option<Span>) -> Self { | ||
| let mut generics = generics.clone(); | ||
| if let Some(unsafe_unpin) = unsafe_unpin { | ||
| let crate_path = crate_path(); | ||
| generics.make_where_clause().predicates.push( | ||
| syn::parse2(quote_spanned! { unsafe_unpin => | ||
| ::#crate_path::__private::Wrapper<Self>: ::#crate_path::__private::UnsafeUnpin | ||
| }) | ||
| .unwrap(), | ||
| ); | ||
| } | ||
|
|
||
| Self { generics, unsafe_unpin: unsafe_unpin.is_some() } | ||
| } | ||
|
|
||
| fn push(&mut self, ty: &Type) { | ||
| // We only add bounds for automatically generated impls | ||
| if !self.unsafe_unpin { | ||
| self.generics | ||
| .make_where_clause() | ||
| .predicates | ||
| .push(syn::parse_quote!(#ty: ::core::marker::Unpin)); | ||
| } | ||
| } | ||
|
|
||
| /// Creates `Unpin` implementation. | ||
| fn build(self, ident: &Ident) -> TokenStream { | ||
| let (impl_generics, ty_generics, where_clause) = self.generics.split_for_impl(); | ||
| quote! { | ||
| impl #impl_generics ::core::marker::Unpin for #ident #ty_generics #where_clause {} | ||
| } | ||
| } | ||
| } |
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