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Better generic support in implement #2986

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Better generic support in implement #2986

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59 changes: 24 additions & 35 deletions crates/libs/implement/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@
Learn more about Rust for Windows here: <https://github.com/microsoft/windows-rs>
*/

use quote::{quote, ToTokens};
use quote::quote;

/// Implements one or more COM interfaces.
///
Expand Down Expand Up @@ -46,19 +46,8 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:
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_generics, type_generics, where_clause) = original_type2.generics.split_for_impl();

let impl_ident = quote::format_ident!("{}_Impl", original_ident);
let vtbl_idents = attributes.implement.iter().map(|implement| implement.to_vtbl_ident());
Expand All @@ -67,7 +56,7 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:
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>() }
quote! { #vtbl_ident::new::<Self, #original_ident::#type_generics, #offset>() }
});

let offset = attributes.implement.iter().enumerate().map(|(offset, _)| proc_macro2::Literal::usize_unsuffixed(offset));
Expand All @@ -88,23 +77,23 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:
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);
impl #impl_generics ::core::convert::From<#original_ident::#type_generics> for #interface_ident #where_clause {
fn from(this: #original_ident::#type_generics) -> Self {
let this = #impl_ident::#type_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 {
impl #impl_generics ::windows_core::AsImpl<#original_ident::#type_generics> for #interface_ident #where_clause {
// 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 {
unsafe fn as_impl(&self) -> &#original_ident::#type_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;
let this = (this as *mut *mut ::core::ffi::c_void).sub(1 + #offset) as *mut #impl_ident::#type_generics;
&(*this).this
}
}
Expand All @@ -113,16 +102,16 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:

let tokens = quote! {
#[repr(C)]
struct #impl_ident #generics where #constraints {
struct #impl_ident #impl_generics #where_clause {
identity: *const ::windows_core::IInspectable_Vtbl,
vtables: (#(*const #vtbl_idents,)*),
this: #original_ident::#generics,
this: #original_ident::#type_generics,
count: ::windows_core::imp::WeakRefCount,
}
impl #generics #impl_ident::#generics where #constraints {
impl #impl_generics #impl_ident::#type_generics #where_clause {
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 {
fn new(this: #original_ident::#type_generics) -> Self {
Self {
identity: &Self::IDENTITY,
vtables:(#(&Self::VTABLES.#offset,)*),
Expand All @@ -131,8 +120,8 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:
}
}
}
impl #generics ::windows_core::IUnknownImpl for #impl_ident::#generics where #constraints {
type Impl = #original_ident::#generics;
impl #impl_generics ::windows_core::IUnknownImpl for #impl_ident::#type_generics #where_clause {
type Impl = #original_ident::#type_generics;
fn get_impl(&self) -> &Self::Impl {
&self.this
}
Expand Down Expand Up @@ -182,32 +171,32 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:
::windows_core::HRESULT(0)
}
}
impl #generics #original_ident::#generics where #constraints {
impl #impl_generics #original_ident::#type_generics #where_clause {
/// 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 boxed = (self as *const _ as *const *mut ::core::ffi::c_void).sub(1 + #interfaces_len) as *mut #impl_ident::#type_generics;
let mut result = ::std::ptr::null_mut();
_ = <#impl_ident::#generics as ::windows_core::IUnknownImpl>::QueryInterface(&*boxed, &I::IID, &mut result);
_ = <#impl_ident::#type_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);
impl #impl_generics ::core::convert::From<#original_ident::#type_generics> for ::windows_core::IUnknown #where_clause {
fn from(this: #original_ident::#type_generics) -> Self {
let this = #impl_ident::#type_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);
impl #impl_generics ::core::convert::From<#original_ident::#type_generics> for ::windows_core::IInspectable #where_clause {
fn from(this: #original_ident::#type_generics) -> Self {
let this = #impl_ident::#type_generics::new(this);
let boxed = ::core::mem::ManuallyDrop::new(::std::boxed::Box::new(this));
unsafe {
::core::mem::transmute(&boxed.identity)
Expand Down
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