vendor/windows-implement-0.56.0/src/lib.rs - toolchain/rustc - Git at Google

 /*!
 Learn more about Rust for Windows here: <https://github.com/microsoft/windows-rs>
 */

 use quote::{quote, ToTokens};

 /// Implements one or more COM interfaces.
 ///
 /// # Example
 ///
 /// Here is a [more complete tutorial](https://kennykerr.ca/rust-getting-started/how-to-implement-com-interface.html).
 ///
 /// ```rust,ignore
 /// #[interface("094d70d6-5202-44b8-abb8-43860da5aca2")]
 /// unsafe trait IValue: IUnknown {
 ///     fn GetValue(&self, value: *mut i32) -> HRESULT;
 /// }
 ///
 /// #[implement(IValue)]
 /// struct Value(i32);
 ///
 /// impl IValue_Impl for Value {
 ///     unsafe fn GetValue(&self, value: *mut i32) -> HRESULT {
 ///         *value = self.0;
 ///         HRESULT(0)
 ///     }
 /// }
 ///
 /// fn main() {
 ///     let rust_instance = Value(123);
 ///     let com_object: IValue = rust_instance.into();
 ///     // You can now call interface methods on com_object.
 /// }
 /// ```
 #[proc_macro_attribute]
 pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro::TokenStream) -> proc_macro::TokenStream {
     let attributes = syn::parse_macro_input!(attributes as ImplementAttributes);
     let interfaces_len = proc_macro2::Literal::usize_unsuffixed(attributes.implement.len());

     let identity_type = if let Some(first) = attributes.implement.first() {
         first.to_ident()
     } else {
         quote! { ::windows_core::IInspectable }
     };

     let original_type2 = original_type.clone();
     let original_type2 = syn::parse_macro_input!(original_type2 as syn::ItemStruct);
     let original_ident = original_type2.ident;
     let mut constraints = quote! {};

     if let Some(where_clause) = original_type2.generics.where_clause {
         where_clause.predicates.to_tokens(&mut constraints);
     }

     let generics = if original_type2.generics.lt_token.is_some() {
         let mut params = quote! {};
         original_type2.generics.params.to_tokens(&mut params);
         quote! { <#params> }
     } else {
         quote! { <> }
     };

     let impl_ident = quote::format_ident!("{}_Impl", original_ident);
     let vtbl_idents = attributes.implement.iter().map(|implement| implement.to_vtbl_ident());
     let vtbl_idents2 = vtbl_idents.clone();

     let vtable_news = attributes.implement.iter().enumerate().map(|(enumerate, implement)| {
         let vtbl_ident = implement.to_vtbl_ident();
         let offset = proc_macro2::Literal::isize_unsuffixed(-1 - enumerate as isize);
         quote! { #vtbl_ident::new::<Self, #original_ident::#generics, #offset>() }
     });

     let offset = attributes.implement.iter().enumerate().map(|(offset, _)| proc_macro2::Literal::usize_unsuffixed(offset));

     let queries = attributes.implement.iter().enumerate().map(|(count, implement)| {
         let vtbl_ident = implement.to_vtbl_ident();
         let offset = proc_macro2::Literal::usize_unsuffixed(count);
         quote! {
             else if #vtbl_ident::matches(iid) {
                 &self.vtables.#offset as *const _ as *mut _
             }
         }
     });

     let trust_level = proc_macro2::Literal::usize_unsuffixed(attributes.trust_level);

     let conversions = attributes.implement.iter().enumerate().map(|(enumerate, implement)| {
         let interface_ident = implement.to_ident();
         let offset = proc_macro2::Literal::usize_unsuffixed(enumerate);
         quote! {
             impl #generics ::core::convert::From<#original_ident::#generics> for #interface_ident where #constraints {
                 fn from(this: #original_ident::#generics) -> Self {
                     let this = #impl_ident::#generics::new(this);
                     let mut this = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
                     let vtable_ptr = &this.vtables.#offset;
                     // SAFETY: interfaces are in-memory equivalent to pointers to their vtables.
                     unsafe { ::core::mem::transmute(vtable_ptr) }
                 }
             }
             impl #generics ::windows_core::AsImpl<#original_ident::#generics> for #interface_ident where #constraints {
                 // SAFETY: the offset is guranteed to be in bounds, and the implementation struct
                 // is guaranteed to live at least as long as `self`.
                 unsafe fn as_impl(&self) -> &#original_ident::#generics {
                     let this = ::windows_core::Interface::as_raw(self);
                     // Subtract away the vtable offset plus 1, for the `identity` field, to get
                     // to the impl struct which contains that original implementation type.
                     let this = (this as *mut *mut ::core::ffi::c_void).sub(1 + #offset) as *mut #impl_ident::#generics;
                     &(*this).this
                 }
             }
         }
     });

     let tokens = quote! {
         #[repr(C)]
         struct #impl_ident #generics where #constraints {
             identity: *const ::windows_core::IInspectable_Vtbl,
             vtables: (#(*const #vtbl_idents,)*),
              this: #original_ident::#generics,
             count: ::windows_core::imp::WeakRefCount,
         }
         impl #generics #impl_ident::#generics where #constraints {
             const VTABLES: (#(#vtbl_idents2,)*) = (#(#vtable_news,)*);
             const IDENTITY: ::windows_core::IInspectable_Vtbl = ::windows_core::IInspectable_Vtbl::new::<Self, #identity_type, 0>();
             fn new(this: #original_ident::#generics) -> Self {
                 Self {
                     identity: &Self::IDENTITY,
                     vtables:(#(&Self::VTABLES.#offset,)*),
                     this,
                     count: ::windows_core::imp::WeakRefCount::new(),
                 }
             }
         }
          impl #generics ::windows_core::IUnknownImpl for #impl_ident::#generics where #constraints {
             type Impl = #original_ident::#generics;
             fn get_impl(&self) -> &Self::Impl {
                 &self.this
             }
             unsafe fn QueryInterface(&self, iid: *const ::windows_core::GUID, interface: *mut *mut ::core::ffi::c_void) -> ::windows_core::HRESULT {
                 if iid.is_null() || interface.is_null() {
                     return ::windows_core::HRESULT(-2147467261); // E_POINTER
                 }

                 let iid = &*iid;

                 *interface = if iid == &<::windows_core::IUnknown as ::windows_core::Interface>::IID
                     || iid == &<::windows_core::IInspectable as ::windows_core::Interface>::IID
                     || iid == &<::windows_core::imp::IAgileObject as ::windows_core::Interface>::IID {
                         &self.identity as *const _ as *mut _
                 } #(#queries)* else {
                     ::core::ptr::null_mut()
                 };

                 if !(*interface).is_null() {
                     self.count.add_ref();
                     return ::windows_core::HRESULT(0);
                 }

                 *interface = self.count.query(iid, &self.identity as *const _ as *mut _);

                 if (*interface).is_null() {
                     ::windows_core::HRESULT(-2147467262) // E_NOINTERFACE
                 } else {
                     ::windows_core::HRESULT(0)
                 }
             }
             fn AddRef(&self) -> u32 {
                 self.count.add_ref()
             }
             unsafe fn Release(&self) -> u32 {
                 let remaining = self.count.release();
                 if remaining == 0 {
                     _ = ::std::boxed::Box::from_raw(self as *const Self as *mut Self);
                 }
                 remaining
             }
             unsafe fn GetTrustLevel(&self, value: *mut i32) -> ::windows_core::HRESULT {
                 if value.is_null() {
                     return ::windows_core::HRESULT(-2147467261); // E_POINTER
                 }
                 *value = #trust_level;
                 ::windows_core::HRESULT(0)
             }
          }
         impl #generics #original_ident::#generics where #constraints {
             /// Try casting as the provided interface
             ///
             /// # Safety
             ///
             /// This function can only be safely called if `self` has been heap allocated and pinned using
             /// the mechanisms provided by `implement` macro.
             unsafe fn cast<I: ::windows_core::Interface>(&self) -> ::windows_core::Result<I> {
                 let boxed = (self as *const _ as *const *mut ::core::ffi::c_void).sub(1 + #interfaces_len) as *mut #impl_ident::#generics;
                 let mut result = ::std::ptr::null_mut();
                 _ = <#impl_ident::#generics as ::windows_core::IUnknownImpl>::QueryInterface(&*boxed, &I::IID, &mut result);
                 ::windows_core::Type::from_abi(result)
             }
         }
         impl #generics ::core::convert::From<#original_ident::#generics> for ::windows_core::IUnknown where #constraints {
             fn from(this: #original_ident::#generics) -> Self {
                 let this = #impl_ident::#generics::new(this);
                 let boxed = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
                 unsafe {
                     ::core::mem::transmute(&boxed.identity)
                 }
             }
         }
         impl #generics ::core::convert::From<#original_ident::#generics> for ::windows_core::IInspectable where #constraints {
             fn from(this: #original_ident::#generics) -> Self {
                 let this = #impl_ident::#generics::new(this);
                 let boxed = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
                 unsafe {
                     ::core::mem::transmute(&boxed.identity)
                 }
             }
         }
         #(#conversions)*
     };

     let mut tokens: proc_macro::TokenStream = tokens.into();
     tokens.extend(core::iter::once(original_type));
     tokens
 }

 #[derive(Default)]
 struct ImplementType {
     type_name: String,
     generics: Vec<ImplementType>,
 }

 impl ImplementType {
     fn to_ident(&self) -> proc_macro2::TokenStream {
         let type_name = syn::parse_str::<proc_macro2::TokenStream>(&self.type_name).expect("Invalid token stream");
         let generics = self.generics.iter().map(|g| g.to_ident());
         quote! { #type_name<#(#generics,)*> }
     }
     fn to_vtbl_ident(&self) -> proc_macro2::TokenStream {
         let ident = self.to_ident();
         quote! {
             <#ident as ::windows_core::Interface>::Vtable
         }
     }
 }

 #[derive(Default)]
 struct ImplementAttributes {
     pub implement: Vec<ImplementType>,
     pub trust_level: usize,
 }

 impl syn::parse::Parse for ImplementAttributes {
     fn parse(cursor: syn::parse::ParseStream<'_>) -> syn::parse::Result<Self> {
         let mut input = Self::default();

         while !cursor.is_empty() {
             input.parse_implement(cursor)?;
         }

         Ok(input)
     }
 }

 impl ImplementAttributes {
     fn parse_implement(&mut self, cursor: syn::parse::ParseStream<'_>) -> syn::parse::Result<()> {
         let tree = cursor.parse::<UseTree2>()?;
         self.walk_implement(&tree, &mut String::new())?;

         if !cursor.is_empty() {
             cursor.parse::<syn::Token![,]>()?;
         }

         Ok(())
     }

     fn walk_implement(&mut self, tree: &UseTree2, namespace: &mut String) -> syn::parse::Result<()> {
         match tree {
             UseTree2::Path(input) => {
                 if !namespace.is_empty() {
                     namespace.push_str("::");
                 }

                 namespace.push_str(&input.ident.to_string());
                 self.walk_implement(&input.tree, namespace)?;
             }
             UseTree2::Name(_) => {
                 self.implement.push(tree.to_element_type(namespace)?);
             }
             UseTree2::Group(input) => {
                 for tree in &input.items {
                     self.walk_implement(tree, namespace)?;
                 }
             }
             UseTree2::TrustLevel(input) => self.trust_level = *input,
         }

         Ok(())
     }
 }

 enum UseTree2 {
     Path(UsePath2),
     Name(UseName2),
     Group(UseGroup2),
     TrustLevel(usize),
 }

 impl UseTree2 {
     fn to_element_type(&self, namespace: &mut String) -> syn::parse::Result<ImplementType> {
         match self {
             UseTree2::Path(input) => {
                 if !namespace.is_empty() {
                     namespace.push_str("::");
                 }

                 namespace.push_str(&input.ident.to_string());
                 input.tree.to_element_type(namespace)
             }
             UseTree2::Name(input) => {
                 let mut type_name = input.ident.to_string();

                 if !namespace.is_empty() {
                     type_name = format!("{namespace}::{type_name}");
                 }

                 let mut generics = vec![];

                 for g in &input.generics {
                     generics.push(g.to_element_type(&mut String::new())?);
                 }

                 Ok(ImplementType { type_name, generics })
             }
             UseTree2::Group(input) => Err(syn::parse::Error::new(input.brace_token.span.join(), "Syntax not supported")),
             _ => unimplemented!(),
         }
     }
 }

 struct UsePath2 {
     pub ident: syn::Ident,
     pub tree: Box<UseTree2>,
 }

 struct UseName2 {
     pub ident: syn::Ident,
     pub generics: Vec<UseTree2>,
 }

 struct UseGroup2 {
     pub brace_token: syn::token::Brace,
     pub items: syn::punctuated::Punctuated<UseTree2, syn::Token![,]>,
 }

 impl syn::parse::Parse for UseTree2 {
     fn parse(input: syn::parse::ParseStream<'_>) -> syn::parse::Result<UseTree2> {
         let lookahead = input.lookahead1();
         if lookahead.peek(syn::Ident) {
             use syn::ext::IdentExt;
             let ident = input.call(syn::Ident::parse_any)?;
             if input.peek(syn::Token![::]) {
                 input.parse::<syn::Token![::]>()?;
                 Ok(UseTree2::Path(UsePath2 { ident, tree: Box::new(input.parse()?) }))
             } else if input.peek(syn::Token![=]) {
                 if ident != "TrustLevel" {
                     return Err(syn::parse::Error::new(ident.span(), "Unrecognized key-value pair"));
                 }
                 input.parse::<syn::Token![=]>()?;
                 let span = input.span();
                 let value = input.call(syn::Ident::parse_any)?;
                 match value.to_string().as_str() {
                     "Partial" => Ok(UseTree2::TrustLevel(1)),
                     "Full" => Ok(UseTree2::TrustLevel(2)),
                     _ => Err(syn::parse::Error::new(span, "`TrustLevel` must be `Partial` or `Full`")),
                 }
             } else {
                 let generics = if input.peek(syn::Token![<]) {
                     input.parse::<syn::Token![<]>()?;
                     let mut generics = Vec::new();
                     loop {
                         generics.push(input.parse::<UseTree2>()?);

                         if input.parse::<syn::Token![,]>().is_err() {
                             break;
                         }
                     }
                     input.parse::<syn::Token![>]>()?;
                     generics
                 } else {
                     Vec::new()
                 };

                 Ok(UseTree2::Name(UseName2 { ident, generics }))
             }
         } else if lookahead.peek(syn::token::Brace) {
             let content;
             let brace_token = syn::braced!(content in input);
             let items = content.parse_terminated(UseTree2::parse, syn::Token![,])?;

             Ok(UseTree2::Group(UseGroup2 { brace_token, items }))
         } else {
             Err(lookahead.error())
         }
     }
 }
	/*!
	Learn more about Rust for Windows here: <https://github.com/microsoft/windows-rs>
	*/

	use quote::{quote, ToTokens};

	/// Implements one or more COM interfaces.
	///
	/// # Example
	///
	/// Here is a [more complete tutorial](https://kennykerr.ca/rust-getting-started/how-to-implement-com-interface.html).
	///
	/// ```rust,ignore
	/// #[interface("094d70d6-5202-44b8-abb8-43860da5aca2")]
	/// unsafe trait IValue: IUnknown {
	/// fn GetValue(&self, value: *mut i32) -> HRESULT;
	/// }
	///
	/// #[implement(IValue)]
	/// struct Value(i32);
	///
	/// impl IValue_Impl for Value {
	/// unsafe fn GetValue(&self, value: *mut i32) -> HRESULT {
	/// *value = self.0;
	/// HRESULT(0)
	/// }
	/// }
	///
	/// fn main() {
	/// let rust_instance = Value(123);
	/// let com_object: IValue = rust_instance.into();
	/// // You can now call interface methods on com_object.
	/// }
	/// ```
	#[proc_macro_attribute]
	pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro::TokenStream) -> proc_macro::TokenStream {
	let attributes = syn::parse_macro_input!(attributes as ImplementAttributes);
	let interfaces_len = proc_macro2::Literal::usize_unsuffixed(attributes.implement.len());

	let identity_type = if let Some(first) = attributes.implement.first() {
	first.to_ident()
	} else {
	quote! { ::windows_core::IInspectable }
	};

	let original_type2 = original_type.clone();
	let original_type2 = syn::parse_macro_input!(original_type2 as syn::ItemStruct);
	let original_ident = original_type2.ident;
	let mut constraints = quote! {};

	if let Some(where_clause) = original_type2.generics.where_clause {
	where_clause.predicates.to_tokens(&mut constraints);
	}

	let generics = if original_type2.generics.lt_token.is_some() {
	let mut params = quote! {};
	original_type2.generics.params.to_tokens(&mut params);
	quote! { <#params> }
	} else {
	quote! { <> }
	};

	let impl_ident = quote::format_ident!("{}_Impl", original_ident);
	let vtbl_idents = attributes.implement.iter().map(\|implement\| implement.to_vtbl_ident());
	let vtbl_idents2 = vtbl_idents.clone();

	let vtable_news = attributes.implement.iter().enumerate().map(\|(enumerate, implement)\| {
	let vtbl_ident = implement.to_vtbl_ident();
	let offset = proc_macro2::Literal::isize_unsuffixed(-1 - enumerate as isize);
	quote! { #vtbl_ident::new::<Self, #original_ident::#generics, #offset>() }
	});

	let offset = attributes.implement.iter().enumerate().map(\|(offset, _)\| proc_macro2::Literal::usize_unsuffixed(offset));

	let queries = attributes.implement.iter().enumerate().map(\|(count, implement)\| {
	let vtbl_ident = implement.to_vtbl_ident();
	let offset = proc_macro2::Literal::usize_unsuffixed(count);
	quote! {
	else if #vtbl_ident::matches(iid) {
	&self.vtables.#offset as const _ as mut _
	}
	}
	});

	let trust_level = proc_macro2::Literal::usize_unsuffixed(attributes.trust_level);

	let conversions = attributes.implement.iter().enumerate().map(\|(enumerate, implement)\| {
	let interface_ident = implement.to_ident();
	let offset = proc_macro2::Literal::usize_unsuffixed(enumerate);
	quote! {
	impl #generics ::core::convert::From<#original_ident::#generics> for #interface_ident where #constraints {
	fn from(this: #original_ident::#generics) -> Self {
	let this = #impl_ident::#generics::new(this);
	let mut this = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
	let vtable_ptr = &this.vtables.#offset;
	// SAFETY: interfaces are in-memory equivalent to pointers to their vtables.
	unsafe { ::core::mem::transmute(vtable_ptr) }
	}
	}
	impl #generics ::windows_core::AsImpl<#original_ident::#generics> for #interface_ident where #constraints {
	// SAFETY: the offset is guranteed to be in bounds, and the implementation struct
	// is guaranteed to live at least as long as `self`.
	unsafe fn as_impl(&self) -> &#original_ident::#generics {
	let this = ::windows_core::Interface::as_raw(self);
	// Subtract away the vtable offset plus 1, for the `identity` field, to get
	// to the impl struct which contains that original implementation type.
	let this = (this as mut mut ::core::ffi::c_void).sub(1 + #offset) as *mut #impl_ident::#generics;
	&(*this).this
	}
	}
	}
	});

	let tokens = quote! {
	#[repr(C)]
	struct #impl_ident #generics where #constraints {
	identity: *const ::windows_core::IInspectable_Vtbl,
	vtables: (#(const #vtbl_idents,)),
	this: #original_ident::#generics,
	count: ::windows_core::imp::WeakRefCount,
	}
	impl #generics #impl_ident::#generics where #constraints {
	const VTABLES: (#(#vtbl_idents2,)) = (#(#vtable_news,));
	const IDENTITY: ::windows_core::IInspectable_Vtbl = ::windows_core::IInspectable_Vtbl::new::<Self, #identity_type, 0>();
	fn new(this: #original_ident::#generics) -> Self {
	Self {
	identity: &Self::IDENTITY,
	vtables:(#(&Self::VTABLES.#offset,)*),
	this,
	count: ::windows_core::imp::WeakRefCount::new(),
	}
	}
	}
	impl #generics ::windows_core::IUnknownImpl for #impl_ident::#generics where #constraints {
	type Impl = #original_ident::#generics;
	fn get_impl(&self) -> &Self::Impl {
	&self.this
	}
	unsafe fn QueryInterface(&self, iid: const ::windows_core::GUID, interface: mut *mut ::core::ffi::c_void) -> ::windows_core::HRESULT {
	if iid.is_null() \|\| interface.is_null() {
	return ::windows_core::HRESULT(-2147467261); // E_POINTER
	}

	let iid = &*iid;

	*interface = if iid == &<::windows_core::IUnknown as ::windows_core::Interface>::IID
	\|\| iid == &<::windows_core::IInspectable as ::windows_core::Interface>::IID
	\|\| iid == &<::windows_core::imp::IAgileObject as ::windows_core::Interface>::IID {
	&self.identity as const _ as mut _
	} #(#queries)* else {
	::core::ptr::null_mut()
	};

	if !(*interface).is_null() {
	self.count.add_ref();
	return ::windows_core::HRESULT(0);
	}

	interface = self.count.query(iid, &self.identity as const _ as *mut _);

	if (*interface).is_null() {
	::windows_core::HRESULT(-2147467262) // E_NOINTERFACE
	} else {
	::windows_core::HRESULT(0)
	}
	}
	fn AddRef(&self) -> u32 {
	self.count.add_ref()
	}
	unsafe fn Release(&self) -> u32 {
	let remaining = self.count.release();
	if remaining == 0 {
	_ = ::std::boxed::Box::from_raw(self as const Self as mut Self);
	}
	remaining
	}
	unsafe fn GetTrustLevel(&self, value: *mut i32) -> ::windows_core::HRESULT {
	if value.is_null() {
	return ::windows_core::HRESULT(-2147467261); // E_POINTER
	}
	*value = #trust_level;
	::windows_core::HRESULT(0)
	}
	}
	impl #generics #original_ident::#generics where #constraints {
	/// Try casting as the provided interface
	///
	/// # Safety
	///
	/// This function can only be safely called if `self` has been heap allocated and pinned using
	/// the mechanisms provided by `implement` macro.
	unsafe fn cast<I: ::windows_core::Interface>(&self) -> ::windows_core::Result<I> {
	let boxed = (self as const _ as const mut ::core::ffi::c_void).sub(1 + #interfaces_len) as mut #impl_ident::#generics;
	let mut result = ::std::ptr::null_mut();
	_ = <#impl_ident::#generics as ::windows_core::IUnknownImpl>::QueryInterface(&*boxed, &I::IID, &mut result);
	::windows_core::Type::from_abi(result)
	}
	}
	impl #generics ::core::convert::From<#original_ident::#generics> for ::windows_core::IUnknown where #constraints {
	fn from(this: #original_ident::#generics) -> Self {
	let this = #impl_ident::#generics::new(this);
	let boxed = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
	unsafe {
	::core::mem::transmute(&boxed.identity)
	}
	}
	}
	impl #generics ::core::convert::From<#original_ident::#generics> for ::windows_core::IInspectable where #constraints {
	fn from(this: #original_ident::#generics) -> Self {
	let this = #impl_ident::#generics::new(this);
	let boxed = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
	unsafe {
	::core::mem::transmute(&boxed.identity)
	}
	}
	}
	#(#conversions)*
	};

	let mut tokens: proc_macro::TokenStream = tokens.into();
	tokens.extend(core::iter::once(original_type));
	tokens
	}

	#[derive(Default)]
	struct ImplementType {
	type_name: String,
	generics: Vec<ImplementType>,
	}

	impl ImplementType {
	fn to_ident(&self) -> proc_macro2::TokenStream {
	let type_name = syn::parse_str::<proc_macro2::TokenStream>(&self.type_name).expect("Invalid token stream");
	let generics = self.generics.iter().map(\|g\| g.to_ident());
	quote! { #type_name<#(#generics,)*> }
	}
	fn to_vtbl_ident(&self) -> proc_macro2::TokenStream {
	let ident = self.to_ident();
	quote! {
	<#ident as ::windows_core::Interface>::Vtable
	}
	}
	}

	#[derive(Default)]
	struct ImplementAttributes {
	pub implement: Vec<ImplementType>,
	pub trust_level: usize,
	}

	impl syn::parse::Parse for ImplementAttributes {
	fn parse(cursor: syn::parse::ParseStream<'_>) -> syn::parse::Result<Self> {
	let mut input = Self::default();

	while !cursor.is_empty() {
	input.parse_implement(cursor)?;
	}

	Ok(input)
	}
	}

	impl ImplementAttributes {
	fn parse_implement(&mut self, cursor: syn::parse::ParseStream<'_>) -> syn::parse::Result<()> {
	let tree = cursor.parse::<UseTree2>()?;
	self.walk_implement(&tree, &mut String::new())?;

	if !cursor.is_empty() {
	cursor.parse::<syn::Token![,]>()?;
	}

	Ok(())
	}

	fn walk_implement(&mut self, tree: &UseTree2, namespace: &mut String) -> syn::parse::Result<()> {
	match tree {
	UseTree2::Path(input) => {
	if !namespace.is_empty() {
	namespace.push_str("::");
	}

	namespace.push_str(&input.ident.to_string());
	self.walk_implement(&input.tree, namespace)?;
	}
	UseTree2::Name(_) => {
	self.implement.push(tree.to_element_type(namespace)?);
	}
	UseTree2::Group(input) => {
	for tree in &input.items {
	self.walk_implement(tree, namespace)?;
	}
	}
	UseTree2::TrustLevel(input) => self.trust_level = *input,
	}

	Ok(())
	}
	}

	enum UseTree2 {
	Path(UsePath2),
	Name(UseName2),
	Group(UseGroup2),
	TrustLevel(usize),
	}

	impl UseTree2 {
	fn to_element_type(&self, namespace: &mut String) -> syn::parse::Result<ImplementType> {
	match self {
	UseTree2::Path(input) => {
	if !namespace.is_empty() {
	namespace.push_str("::");
	}

	namespace.push_str(&input.ident.to_string());
	input.tree.to_element_type(namespace)
	}
	UseTree2::Name(input) => {
	let mut type_name = input.ident.to_string();

	if !namespace.is_empty() {
	type_name = format!("{namespace}::{type_name}");
	}

	let mut generics = vec![];

	for g in &input.generics {
	generics.push(g.to_element_type(&mut String::new())?);
	}

	Ok(ImplementType { type_name, generics })
	}
	UseTree2::Group(input) => Err(syn::parse::Error::new(input.brace_token.span.join(), "Syntax not supported")),
	_ => unimplemented!(),
	}
	}
	}

	struct UsePath2 {
	pub ident: syn::Ident,
	pub tree: Box<UseTree2>,
	}

	struct UseName2 {
	pub ident: syn::Ident,
	pub generics: Vec<UseTree2>,
	}

	struct UseGroup2 {
	pub brace_token: syn::token::Brace,
	pub items: syn::punctuated::Punctuated<UseTree2, syn::Token![,]>,
	}

	impl syn::parse::Parse for UseTree2 {
	fn parse(input: syn::parse::ParseStream<'_>) -> syn::parse::Result<UseTree2> {
	let lookahead = input.lookahead1();
	if lookahead.peek(syn::Ident) {
	use syn::ext::IdentExt;
	let ident = input.call(syn::Ident::parse_any)?;
	if input.peek(syn::Token![::]) {
	input.parse::<syn::Token![::]>()?;
	Ok(UseTree2::Path(UsePath2 { ident, tree: Box::new(input.parse()?) }))
	} else if input.peek(syn::Token![=]) {
	if ident != "TrustLevel" {
	return Err(syn::parse::Error::new(ident.span(), "Unrecognized key-value pair"));
	}
	input.parse::<syn::Token![=]>()?;
	let span = input.span();
	let value = input.call(syn::Ident::parse_any)?;
	match value.to_string().as_str() {
	"Partial" => Ok(UseTree2::TrustLevel(1)),
	"Full" => Ok(UseTree2::TrustLevel(2)),
	_ => Err(syn::parse::Error::new(span, "`TrustLevel` must be `Partial` or `Full`")),
	}
	} else {
	let generics = if input.peek(syn::Token![<]) {
	input.parse::<syn::Token![<]>()?;
	let mut generics = Vec::new();
	loop {
	generics.push(input.parse::<UseTree2>()?);

	if input.parse::<syn::Token![,]>().is_err() {
	break;
	}
	}
	input.parse::<syn::Token![>]>()?;
	generics
	} else {
	Vec::new()
	};

	Ok(UseTree2::Name(UseName2 { ident, generics }))
	}
	} else if lookahead.peek(syn::token::Brace) {
	let content;
	let brace_token = syn::braced!(content in input);
	let items = content.parse_terminated(UseTree2::parse, syn::Token![,])?;

	Ok(UseTree2::Group(UseGroup2 { brace_token, items }))
	} else {
	Err(lookahead.error())
	}
	}
	}