Vendor dependencies for 0.3.0 release

vendor/windows-implement/src/gen.rs

@@ -0,0 +1,600 @@
+//! Generates output for the `implement` proc macro.
+//!
+//! Each function in this module focuses on generating one thing, or one kind of thing.
+//! Each takes `ImplementInputs` as its input.  `gen_all` calls all of the `gen_*` functions
+//! and merges them into the final list of output items.
+//!
+//! We use `parse_quote` so that we can verify that a given function generates a well-formed AST
+//! item, within the narrowest possible scope. This allows us to detect errors more quickly during
+//! development. If the input to `parse_quote` cannot be parsed, then the macro will panic and
+//! the panic will point to the specific `parse_quote` call, rather than the entire output of the
+//! `implement` proc macro being unparsable. This greatly aids in development.
+
+use super::*;
+use quote::{quote, quote_spanned};
+use syn::{parse_quote, parse_quote_spanned};
+
+/// Generates code for the `#[implements]` macro.
+pub(crate) fn gen_all(inputs: &ImplementInputs) -> Vec<syn::Item> {
+    let mut items: Vec<syn::Item> = Vec::with_capacity(64);
+
+    items.push(gen_original_impl(inputs));
+    items.push(gen_impl_struct(inputs));
+    items.push(gen_impl_deref(inputs));
+    items.push(gen_impl_impl(inputs));
+    items.push(gen_iunknown_impl(inputs));
+    items.push(gen_impl_com_object_inner(inputs));
+    items.extend(gen_impl_from(inputs));
+    items.extend(gen_impl_com_object_interfaces(inputs));
+
+    for (i, interface_chain) in inputs.interface_chains.iter().enumerate() {
+        items.push(gen_impl_as_impl(inputs, interface_chain, i));
+    }
+
+    items
+}
+
+/// Generates an `impl` block for the original `Foo` type.
+///
+/// This `impl` block will contain `into_outer` and `into_static` (if applicable).
+fn gen_original_impl(inputs: &ImplementInputs) -> syn::Item {
+    let original_ident = &inputs.original_ident;
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+
+    let mut output: syn::ItemImpl = parse_quote! {
+        impl #generics #original_ident::#generics where #constraints {}
+    };
+
+    output.items.push(gen_into_outer(inputs));
+
+    // Static COM objects have a lot of constraints. They can't be generic (open parameters),
+    // because that would be meaningless (an open generic type cannot have a known representation).
+    //
+    // Right now, we can't generate static COM objects that have base classes because we rely on
+    // boxing and then unboxing during construction of aggregated types.
+    if !inputs.is_generic {
+        output.items.push(gen_into_static(inputs));
+    }
+
+    syn::Item::Impl(output)
+}
+
+/// Generates the structure definition for the `Foo_Impl` type.
+fn gen_impl_struct(inputs: &ImplementInputs) -> syn::Item {
+    let impl_ident = &inputs.impl_ident;
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+    let original_ident = &inputs.original_ident;
+    let vis = &inputs.original_type.vis;
+
+    let mut impl_fields = quote! {
+        identity: &'static ::windows_core::IInspectable_Vtbl,
+    };
+
+    for interface_chain in inputs.interface_chains.iter() {
+        let vtbl_ty = interface_chain.implement.to_vtbl_ident();
+        let chain_field_ident = &interface_chain.field_ident;
+        impl_fields.extend(quote! {
+            #chain_field_ident: &'static #vtbl_ty,
+        });
+    }
+
+    impl_fields.extend(quote! {
+        this: #original_ident::#generics,
+        count: ::windows_core::imp::WeakRefCount,
+    });
+
+    parse_quote! {
+        #[repr(C)]
+        #[allow(non_camel_case_types)]
+        #vis struct #impl_ident #generics where #constraints {
+            #impl_fields
+        }
+    }
+}
+
+/// Generates the implementation of `core::ops::Deref` for the generated `Foo_Impl` type.
+fn gen_impl_deref(inputs: &ImplementInputs) -> syn::Item {
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+    let original_ident = &inputs.original_type.ident;
+    let impl_ident = &inputs.impl_ident;
+
+    parse_quote! {
+        impl #generics ::core::ops::Deref for #impl_ident::#generics where #constraints {
+            type Target = #original_ident::#generics;
+
+            #[inline(always)]
+            fn deref(&self) -> &Self::Target {
+                &self.this
+            }
+        }
+    }
+}
+
+/// Generates an `impl` block for the generated `Foo_Impl` block.
+///
+/// This generates:
+///
+/// ```rust,ignore
+/// const VTABLE_IDENTITY = IInspectable_Vtbl = ...;
+/// const VTABLE_INTERFACE1_IFOO: IFoo_Vtbl = ...;
+/// const VTABLE_INTERFACE2_IBAR: IBar_Vtbl = ...;
+/// ```
+///
+/// These constants are used when constructing vtables. The benefit of using constants instead
+/// of directly generating these expressions is that it allows us to overcome limitations in
+/// using generics in constant contexts. Right now, Rust has a lot of limitations around using
+/// constants in constant contexts. Fortunately, associated constants (constants defined within
+/// `impl` blocks) work in stable Rust, even for generic types.
+fn gen_impl_impl(inputs: &ImplementInputs) -> syn::Item {
+    let impl_ident = &inputs.impl_ident;
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+
+    let mut output: syn::ItemImpl = parse_quote! {
+        impl #generics #impl_ident::#generics where #constraints {}
+    };
+
+    // This is here so that IInspectable::GetRuntimeClassName can work properly.
+    // For a test case for this, see crates/tests/misc/component_client.
+    let identity_type = if let Some(first) = inputs.interface_chains.first() {
+        first.implement.to_ident()
+    } else {
+        quote! { ::windows_core::IInspectable }
+    };
+
+    output.items.push(parse_quote! {
+        const VTABLE_IDENTITY: ::windows_core::IInspectable_Vtbl =
+            ::windows_core::IInspectable_Vtbl::new::<
+                #impl_ident::#generics,
+                #identity_type,
+                0,
+            >();
+    });
+
+    for (interface_index, interface_chain) in inputs.interface_chains.iter().enumerate() {
+        let vtbl_ty = interface_chain.implement.to_vtbl_ident();
+        let vtable_const_ident = &interface_chain.vtable_const_ident;
+
+        let chain_offset_in_pointers: isize = -1 - interface_index as isize;
+        output.items.push(parse_quote! {
+            const #vtable_const_ident: #vtbl_ty = #vtbl_ty::new::<
+                #impl_ident::#generics,
+                #chain_offset_in_pointers,
+            >();
+        });
+    }
+
+    syn::Item::Impl(output)
+}
+
+/// Generates the `IUnknownImpl` implementation for the `Foo_Impl` type.
+fn gen_iunknown_impl(inputs: &ImplementInputs) -> syn::Item {
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+    let impl_ident = &inputs.impl_ident;
+    let original_ident = &inputs.original_type.ident;
+
+    let trust_level = proc_macro2::Literal::usize_unsuffixed(inputs.trust_level);
+
+    let mut output: syn::ItemImpl = parse_quote! {
+        impl #generics ::windows_core::IUnknownImpl for #impl_ident::#generics where #constraints {
+            type Impl = #original_ident::#generics;
+
+            #[inline(always)]
+            fn get_impl(&self) -> &Self::Impl {
+                &self.this
+            }
+
+            #[inline(always)]
+            fn get_impl_mut(&mut self) -> &mut Self::Impl {
+                &mut self.this
+            }
+
+            #[inline(always)]
+            fn into_inner(self) -> Self::Impl {
+                self.this
+            }
+
+            #[inline(always)]
+            fn AddRef(&self) -> u32 {
+                self.count.add_ref()
+            }
+
+            #[inline(always)]
+            unsafe fn Release(self_: *mut Self) -> u32 {
+                let remaining = (*self_).count.release();
+                if remaining == 0 {
+                    _ = ::windows_core::imp::Box::from_raw(self_);
+                }
+                remaining
+            }
+
+            #[inline(always)]
+            fn is_reference_count_one(&self) -> bool {
+                self.count.is_one()
+            }
+
+            unsafe fn GetTrustLevel(&self, value: *mut i32) -> ::windows_core::HRESULT {
+                if value.is_null() {
+                    return ::windows_core::imp::E_POINTER;
+                }
+                *value = #trust_level;
+                ::windows_core::HRESULT(0)
+            }
+
+            fn to_object(&self) -> ::windows_core::ComObject<Self::Impl> {
+                self.count.add_ref();
+                unsafe {
+                    ::windows_core::ComObject::from_raw(
+                        ::core::ptr::NonNull::new_unchecked(self as *const Self as *mut Self)
+                    )
+                }
+            }
+        }
+    };
+
+    let query_interface_fn = gen_query_interface(inputs);
+    output.items.push(syn::ImplItem::Fn(query_interface_fn));
+
+    syn::Item::Impl(output)
+}
+
+/// Generates the implementation of `ComObjectInner`.
+fn gen_impl_com_object_inner(inputs: &ImplementInputs) -> syn::Item {
+    let original_ident = &inputs.original_type.ident;
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+    let impl_ident = &inputs.impl_ident;
+
+    parse_quote! {
+        impl #generics ::windows_core::ComObjectInner for #original_ident::#generics where #constraints {
+            type Outer = #impl_ident::#generics;
+
+            // IMPORTANT! This function handles assembling the "boxed" type of a COM object.
+            // It immediately moves the box into a heap allocation (box) and returns only a ComObject
+            // reference that points to it. We intentionally _do not_ expose any owned instances of
+            // Foo_Impl to safe Rust code, because doing so would allow unsound behavior in safe Rust
+            // code, due to the adjustments of the reference count that Foo_Impl permits.
+            //
+            // This is why this function returns ComObject<Self> instead of returning #impl_ident.
+
+            fn into_object(self) -> ::windows_core::ComObject<Self> {
+                let boxed = ::windows_core::imp::Box::<#impl_ident::#generics>::new(self.into_outer());
+                unsafe {
+                    let ptr = ::windows_core::imp::Box::into_raw(boxed);
+                    ::windows_core::ComObject::from_raw(
+                        ::core::ptr::NonNull::new_unchecked(ptr)
+                    )
+                }
+            }
+        }
+    }
+}
+
+/// Generates the `query_interface` method.
+fn gen_query_interface(inputs: &ImplementInputs) -> syn::ImplItemFn {
+    let queries = inputs.interface_chains.iter().map(|interface_chain| {
+        let chain_ty = interface_chain.implement.to_vtbl_ident();
+        let chain_field = &interface_chain.field_ident;
+        quote_spanned! {
+            interface_chain.implement.span =>
+            if #chain_ty::matches(&iid) {
+                break 'found &self.#chain_field as *const _ as *const ::core::ffi::c_void;
+            }
+        }
+    });
+
+    // Dynamic casting requires that the object not contain non-static lifetimes.
+    let enable_dyn_casting = inputs.original_type.generics.lifetimes().count() == 0;
+    let dynamic_cast_query = if enable_dyn_casting {
+        quote! {
+            if iid == ::windows_core::DYNAMIC_CAST_IID {
+                // DYNAMIC_CAST_IID is special. We _do not_ increase the reference count for this pseudo-interface.
+                // Also, instead of returning an interface pointer, we simply write the `&dyn Any` directly to the
+                // 'interface' pointer. Since the size of `&dyn Any` is 2 pointers, not one, the caller must be
+                // prepared for this. This is not a normal QueryInterface call.
+                //
+                // See the `Interface::cast_to_any` method, which is the only caller that should use DYNAMIC_CAST_ID.
+                (interface as *mut *const dyn core::any::Any).write(self as &dyn ::core::any::Any as *const dyn ::core::any::Any);
+                return ::windows_core::HRESULT(0);
+            }
+        }
+    } else {
+        quote!()
+    };
+
+    let identity_query = if inputs.agile {
+        quote! {
+            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 {
+                break 'found &self.identity as *const _ as *const ::core::ffi::c_void;
+            }
+        }
+    } else {
+        quote! {
+            if iid == <::windows_core::IUnknown as ::windows_core::Interface>::IID
+            || iid == <::windows_core::IInspectable as ::windows_core::Interface>::IID {
+                break 'found &self.identity as *const _ as *const ::core::ffi::c_void;
+            }
+        }
+    };
+
+    let marshal_query = if inputs.agile {
+        quote! {
+            #[cfg(windows)]
+            if iid == <::windows_core::imp::IMarshal as ::windows_core::Interface>::IID {
+                return ::windows_core::imp::marshaler(self.to_interface(), interface);
+            }
+        }
+    } else {
+        quote! {}
+    };
+
+    let tear_off_query = quote! {
+        let tear_off_ptr = self.count.query(&iid, &self.identity as *const _ as *mut _);
+        if !tear_off_ptr.is_null() {
+            *interface = tear_off_ptr;
+            return ::windows_core::HRESULT(0);
+        }
+    };
+
+    parse_quote! {
+        unsafe fn QueryInterface(
+            &self,
+            iid: *const ::windows_core::GUID,
+            interface: *mut *mut ::core::ffi::c_void,
+        ) -> ::windows_core::HRESULT {
+            unsafe {
+                if iid.is_null() || interface.is_null() {
+                    return ::windows_core::imp::E_POINTER;
+                }
+
+                let iid = *iid;
+
+                let interface_ptr: *const ::core::ffi::c_void = 'found: {
+                    #identity_query
+                    #(#queries)*
+                    #marshal_query
+                    #dynamic_cast_query
+                    #tear_off_query
+
+                    *interface = ::core::ptr::null_mut();
+                    return ::windows_core::imp::E_NOINTERFACE;
+                };
+
+                debug_assert!(!interface_ptr.is_null());
+                *interface = interface_ptr as *mut ::core::ffi::c_void;
+                self.count.add_ref();
+                return ::windows_core::HRESULT(0);
+            }
+        }
+    }
+}
+
+/// Generates the `T::into_outer` function. This function is part of how we construct a
+/// `ComObject<T>` from a `T`.
+fn gen_into_outer(inputs: &ImplementInputs) -> syn::ImplItem {
+    let generics = &inputs.generics;
+    let impl_ident = &inputs.impl_ident;
+
+    let mut initializers = quote! {
+        identity: &#impl_ident::#generics::VTABLE_IDENTITY,
+    };
+
+    for interface_chain in inputs.interface_chains.iter() {
+        let vtbl_field_ident = &interface_chain.field_ident;
+        let vtable_const_ident = &interface_chain.vtable_const_ident;
+
+        initializers.extend(quote_spanned! {
+            interface_chain.implement.span =>
+            #vtbl_field_ident: &#impl_ident::#generics::#vtable_const_ident,
+        });
+    }
+
+    // If the type is generic then into_outer() cannot be a const fn.
+    let maybe_const = if inputs.is_generic {
+        quote!()
+    } else {
+        quote!(const)
+    };
+
+    parse_quote! {
+        // This constructs an "outer" object. This should only be used by the implementation
+        // of the outer object, never by application code.
+        //
+        // The callers of this function (`into_static` and `into_object`) are both responsible
+        // for maintaining one of our invariants: Application code never has an owned instance
+        // of the outer (implementation) type. into_static() maintains this invariant by
+        // returning a wrapped StaticComObject value, which owns its contents but never gives
+        // application code a way to mutably access its contents. This prevents the refcount
+        // shearing problem.
+        //
+        // TODO: Make it impossible for app code to call this function, by placing it in a
+        // module and marking this as private to the module.
+        #[inline(always)]
+        #maybe_const fn into_outer(self) -> #impl_ident::#generics {
+            #impl_ident::#generics {
+                #initializers
+                count: ::windows_core::imp::WeakRefCount::new(),
+                this: self,
+            }
+        }
+    }
+}
+
+/// Generates the `T::into_static` function. This function is part of how we construct a
+/// `StaticComObject<T>` from a `T`.
+fn gen_into_static(inputs: &ImplementInputs) -> syn::ImplItem {
+    assert!(!inputs.is_generic);
+    parse_quote! {
+        /// This converts a partially-constructed COM object (in the sense that it contains
+        /// application state but does not yet have vtable and reference count constructed)
+        /// into a `StaticComObject`. This allows the COM object to be stored in static
+        /// (global) variables.
+        pub const fn into_static(self) -> ::windows_core::StaticComObject<Self> {
+            ::windows_core::StaticComObject::from_outer(self.into_outer())
+        }
+    }
+}
+
+/// Generates `From`-based conversions.
+///
+/// These conversions convert from the user's type `T` to `ComObject<T>` or to an interface
+/// implemented by `T`. These conversions are shorthand for calling `ComObject::new(value)`.
+///
+/// We can only generate conversions from `T` to the roots of each interface chain. We can't
+/// generate `From` conversions from `T` to an interface that is inherited by an interface chain,
+/// because this proc macro does not have access to any information about the inheritance chain
+/// of interfaces that are referenced.
+///
+/// For example:
+///
+/// ```rust,ignore
+/// #[implement(IFoo3)]
+/// struct MyType;
+/// ```
+///
+/// If `IFoo3` inherits from `IFoo2`, then this code will _not_ generate a conversion for `IFoo2`.
+/// However, user code can still do this:
+///
+/// ```rust,ignore
+/// let ifoo2 = IFoo3::from(MyType).into();
+/// ```
+///
+/// This works because the `IFoo3` type has an `Into` impl for `IFoo2`.
+fn gen_impl_from(inputs: &ImplementInputs) -> Vec<syn::Item> {
+    let mut items = Vec::new();
+
+    let original_ident = &inputs.original_type.ident;
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+
+    items.push(parse_quote! {
+        impl #generics ::core::convert::From<#original_ident::#generics> for ::windows_core::IUnknown where #constraints {
+            #[inline(always)]
+            fn from(this: #original_ident::#generics) -> Self {
+                let com_object = ::windows_core::ComObject::new(this);
+                com_object.into_interface()
+            }
+        }
+    });
+
+    items.push(parse_quote! {
+        impl #generics ::core::convert::From<#original_ident::#generics> for ::windows_core::IInspectable where #constraints {
+            #[inline(always)]
+            fn from(this: #original_ident::#generics) -> Self {
+                let com_object = ::windows_core::ComObject::new(this);
+                com_object.into_interface()
+            }
+        }
+    });
+
+    for interface_chain in inputs.interface_chains.iter() {
+        let interface_ident = interface_chain.implement.to_ident();
+
+        items.push(parse_quote_spanned! {
+            interface_chain.implement.span =>
+            impl #generics ::core::convert::From<#original_ident::#generics> for #interface_ident where #constraints {
+                #[inline(always)]
+                fn from(this: #original_ident::#generics) -> Self {
+                    let com_object = ::windows_core::ComObject::new(this);
+                    com_object.into_interface()
+                }
+            }
+        });
+    }
+
+    items
+}
+
+/// Generates the `ComObjectInterface` implementation for each interface chain.
+///
+/// Each of these `impl` blocks says "this COM object implements this COM interface".
+/// It allows the `ComObject` type to do conversions from the `ComObject` to `IFoo` instances,
+/// _without_ doing a `QueryInterface` call.
+fn gen_impl_com_object_interfaces(inputs: &ImplementInputs) -> Vec<syn::Item> {
+    let mut items = Vec::new();
+
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+    let impl_ident = &inputs.impl_ident;
+
+    items.push(parse_quote! {
+        impl #generics ::windows_core::ComObjectInterface<::windows_core::IUnknown> for #impl_ident::#generics where #constraints {
+            #[inline(always)]
+            fn as_interface_ref(&self) -> ::windows_core::InterfaceRef<'_, ::windows_core::IUnknown> {
+                unsafe {
+                    let interface_ptr = &self.identity;
+                    ::core::mem::transmute(interface_ptr)
+                }
+            }
+        }
+    });
+
+    items.push(parse_quote! {
+        impl #generics ::windows_core::ComObjectInterface<::windows_core::IInspectable> for #impl_ident::#generics where #constraints {
+            #[inline(always)]
+            fn as_interface_ref(&self) -> ::windows_core::InterfaceRef<'_, ::windows_core::IInspectable> {
+                unsafe {
+                    let interface_ptr = &self.identity;
+                    ::core::mem::transmute(interface_ptr)
+                }
+            }
+        }
+    });
+
+    for interface_chain in inputs.interface_chains.iter() {
+        let chain_field = &interface_chain.field_ident;
+        let interface_ident = interface_chain.implement.to_ident();
+
+        items.push(parse_quote_spanned! {
+            interface_chain.implement.span =>
+            #[allow(clippy::needless_lifetimes)]
+            impl #generics ::windows_core::ComObjectInterface<#interface_ident> for #impl_ident::#generics where #constraints {
+                #[inline(always)]
+                fn as_interface_ref(&self) -> ::windows_core::InterfaceRef<'_, #interface_ident> {
+                    unsafe {
+                        ::core::mem::transmute(&self.#chain_field)
+                    }
+                }
+            }
+        });
+    }
+
+    items
+}
+
+/// Generates the implementation of the `AsImpl` trait for a given interface chain.
+fn gen_impl_as_impl(
+    inputs: &ImplementInputs,
+    interface_chain: &InterfaceChain,
+    interface_chain_index: usize,
+) -> syn::Item {
+    let generics = &inputs.generics;
+    let constraints = &inputs.constraints;
+    let interface_ident = interface_chain.implement.to_ident();
+    let original_ident = &inputs.original_type.ident;
+    let impl_ident = &inputs.impl_ident;
+
+    parse_quote_spanned! {
+        interface_chain.implement.span =>
+        impl #generics ::windows_core::AsImpl<#original_ident::#generics> for #interface_ident where #constraints {
+            // SAFETY: the offset is guaranteed to be in bounds, and the implementation struct
+            // is guaranteed to live at least as long as `self`.
+            #[inline(always)]
+            unsafe fn as_impl_ptr(&self) -> ::core::ptr::NonNull<#original_ident::#generics> {
+                unsafe {
+                    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 + #interface_chain_index) as *mut #impl_ident::#generics;
+                    ::core::ptr::NonNull::new_unchecked(::core::ptr::addr_of!((*this).this) as *const #original_ident::#generics as *mut #original_ident::#generics)
+                }
+            }
+        }
+    }
+}

vendor/windows-implement/src/lib.rs

@@ -0,0 +1,406 @@
+//! Implement COM interfaces for Rust types.
+//!
+//! Take a look at [macro@implement] for an example.
+//!
+//! Learn more about Rust for Windows here: <https://github.com/microsoft/windows-rs>
+
+use quote::{quote, ToTokens};
+
+mod r#gen;
+use r#gen::gen_all;
+
+#[cfg(test)]
+mod tests;
+
+/// Implements one or more COM interfaces.
+///
+/// # Example
+/// ```rust,no_run
+/// use windows_core::*;
+///
+/// #[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_Impl {
+///     unsafe fn GetValue(&self, value: *mut i32) -> HRESULT {
+///         *value = self.0;
+///         HRESULT(0)
+///     }
+/// }
+///
+/// let object: IValue = Value(123).into();
+/// // Call interface methods...
+/// ```
+#[proc_macro_attribute]
+pub fn implement(
+    attributes: proc_macro::TokenStream,
+    type_tokens: proc_macro::TokenStream,
+) -> proc_macro::TokenStream {
+    implement_core(attributes.into(), type_tokens.into()).into()
+}
+
+fn implement_core(
+    attributes: proc_macro2::TokenStream,
+    item_tokens: proc_macro2::TokenStream,
+) -> proc_macro2::TokenStream {
+    let attributes = syn::parse2::<ImplementAttributes>(attributes).unwrap();
+    let original_type = syn::parse2::<syn::ItemStruct>(item_tokens).unwrap();
+
+    // Do a little thinking and assemble ImplementInputs.  We pass ImplementInputs to
+    // all of our gen_* function.
+    let inputs = ImplementInputs {
+        original_ident: original_type.ident.clone(),
+        interface_chains: convert_implements_to_interface_chains(attributes.implement),
+        trust_level: attributes.trust_level,
+        agile: attributes.agile,
+        impl_ident: quote::format_ident!("{}_Impl", &original_type.ident),
+        constraints: {
+            if let Some(where_clause) = &original_type.generics.where_clause {
+                where_clause.predicates.to_token_stream()
+            } else {
+                quote!()
+            }
+        },
+        generics: if !original_type.generics.params.is_empty() {
+            let mut params = quote! {};
+            original_type.generics.params.to_tokens(&mut params);
+            quote! { <#params> }
+        } else {
+            quote! { <> }
+        },
+        is_generic: !original_type.generics.params.is_empty(),
+        original_type,
+    };
+
+    let items = gen_all(&inputs);
+    let mut tokens = inputs.original_type.into_token_stream();
+    for item in items {
+        tokens.extend(item.into_token_stream());
+    }
+
+    tokens
+}
+
+/// This provides the inputs to the `gen_*` functions, which generate the proc macro output.
+struct ImplementInputs {
+    /// The user's type that was marked with `#[implement]`.
+    original_type: syn::ItemStruct,
+
+    /// The identifier for the user's original type definition.
+    original_ident: syn::Ident,
+
+    /// The list of interface chains that this type implements.
+    interface_chains: Vec<InterfaceChain>,
+
+    /// The "trust level", which is returned by `IInspectable::GetTrustLevel`.
+    trust_level: usize,
+
+    /// Determines whether `IAgileObject` and `IMarshal` are implemented automatically.
+    agile: bool,
+
+    /// The identifier of the `Foo_Impl` type.
+    impl_ident: syn::Ident,
+
+    /// The list of constraints needed for this `Foo_Impl` type.
+    constraints: proc_macro2::TokenStream,
+
+    /// The list of generic parameters for this `Foo_Impl` type, including `<` and `>`.
+    /// If there are no generics, this contains `<>`.
+    generics: proc_macro2::TokenStream,
+
+    /// True if the user type has any generic parameters.
+    is_generic: bool,
+}
+
+/// Describes one COM interface chain.
+struct InterfaceChain {
+    /// The name of the field for the vtable chain, e.g. `interface4_ifoo`.
+    field_ident: syn::Ident,
+
+    /// The name of the associated constant item for the vtable chain's initializer,
+    /// e.g. `INTERFACE4_IFOO_VTABLE`.
+    vtable_const_ident: syn::Ident,
+
+    implement: ImplementType,
+}
+
+struct ImplementType {
+    type_name: String,
+    generics: Vec<ImplementType>,
+
+    /// The best span for diagnostics.
+    span: proc_macro2::Span,
+}
+
+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,
+    pub agile: bool,
+}
+
+impl syn::parse::Parse for ImplementAttributes {
+    fn parse(cursor: syn::parse::ParseStream) -> syn::parse::Result<Self> {
+        let mut input = Self {
+            agile: true,
+            ..Default::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,
+            UseTree2::Agile(agile) => self.agile = *agile,
+        }
+
+        Ok(())
+    }
+}
+
+enum UseTree2 {
+    Path(UsePath2),
+    Name(UseName2),
+    Group(UseGroup2),
+    TrustLevel(usize),
+    Agile(bool),
+}
+
+impl UseTree2 {
+    fn to_element_type(&self, namespace: &mut String) -> syn::parse::Result<ImplementType> {
+        match self {
+            Self::Path(input) => {
+                if !namespace.is_empty() {
+                    namespace.push_str("::");
+                }
+
+                namespace.push_str(&input.ident.to_string());
+                input.tree.to_element_type(namespace)
+            }
+            Self::Name(input) => {
+                let mut type_name = input.ident.to_string();
+                let span = input.ident.span();
+
+                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,
+                    span,
+                })
+            }
+            Self::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<Self> {
+        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(Self::Path(UsePath2 {
+                    ident,
+                    tree: Box::new(input.parse()?),
+                }))
+            } else if input.peek(syn::Token![=]) {
+                if ident == "TrustLevel" {
+                    input.parse::<syn::Token![=]>()?;
+                    let span = input.span();
+                    let value = input.call(syn::Ident::parse_any)?;
+                    match value.to_string().as_str() {
+                        "Partial" => Ok(Self::TrustLevel(1)),
+                        "Full" => Ok(Self::TrustLevel(2)),
+                        _ => Err(syn::parse::Error::new(
+                            span,
+                            "`TrustLevel` must be `Partial` or `Full`",
+                        )),
+                    }
+                } else if ident == "Agile" {
+                    input.parse::<syn::Token![=]>()?;
+                    let span = input.span();
+                    let value = input.call(syn::Ident::parse_any)?;
+                    match value.to_string().as_str() {
+                        "true" => Ok(Self::Agile(true)),
+                        "false" => Ok(Self::Agile(false)),
+                        _ => Err(syn::parse::Error::new(
+                            span,
+                            "`Agile` must be `true` or `false`",
+                        )),
+                    }
+                } else {
+                    Err(syn::parse::Error::new(
+                        ident.span(),
+                        "Unrecognized key-value pair",
+                    ))
+                }
+            } else {
+                let generics = if input.peek(syn::Token![<]) {
+                    input.parse::<syn::Token![<]>()?;
+                    let mut generics = Vec::new();
+                    loop {
+                        generics.push(input.parse::<Self>()?);
+
+                        if input.parse::<syn::Token![,]>().is_err() {
+                            break;
+                        }
+                    }
+                    input.parse::<syn::Token![>]>()?;
+                    generics
+                } else {
+                    Vec::new()
+                };
+
+                Ok(Self::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(Self::parse, syn::Token![,])?;
+
+            Ok(Self::Group(UseGroup2 { brace_token, items }))
+        } else {
+            Err(lookahead.error())
+        }
+    }
+}
+
+fn convert_implements_to_interface_chains(implements: Vec<ImplementType>) -> Vec<InterfaceChain> {
+    let mut chains = Vec::with_capacity(implements.len());
+
+    for (i, implement) in implements.into_iter().enumerate() {
+        // Create an identifier for this interface chain.
+        // We only use this for naming fields; it is never visible to the developer.
+        // This helps with debugging.
+        //
+        // We use i + 1 so that it matches the numbering of our interface offsets. Interface 0
+        // is the "identity" interface.
+
+        let mut ident_string = format!("interface{}", i + 1);
+
+        let suffix = get_interface_ident_suffix(&implement.type_name);
+        if !suffix.is_empty() {
+            ident_string.push('_');
+            ident_string.push_str(&suffix);
+        }
+        let field_ident = syn::Ident::new(&ident_string, implement.span);
+
+        let mut vtable_const_string = ident_string.clone();
+        vtable_const_string.make_ascii_uppercase();
+        vtable_const_string.insert_str(0, "VTABLE_");
+        let vtable_const_ident = syn::Ident::new(&vtable_const_string, implement.span);
+
+        chains.push(InterfaceChain {
+            implement,
+            field_ident,
+            vtable_const_ident,
+        });
+    }
+
+    chains
+}
+
+fn get_interface_ident_suffix(type_name: &str) -> String {
+    let mut suffix = String::new();
+    for c in type_name.chars() {
+        let c = c.to_ascii_lowercase();
+
+        if suffix.len() >= 20 {
+            break;
+        }
+
+        if c.is_ascii_alphanumeric() {
+            suffix.push(c);
+        }
+    }
+
+    suffix
+}

vendor/windows-implement/src/tests.rs

@@ -0,0 +1,135 @@
+//! These tests are just a way to quickly run the `#[implement]` macro and see its output.
+//! They don't check the output in any way.
+//!
+//! This exists because of some difficulties of running `cargo expand` against the `#[implement]`
+//! macro. It's also just really convenient. You can see the output by using `--nocapture` and
+//! you'll probably want to restrict the output to a single thread:
+//!
+//! ```text
+//! cargo test -p windows-implement --lib -- --nocapture --test-threads=1
+//! ```
+
+use std::io::{Read, Write};
+use std::process::{Command, Stdio};
+
+use proc_macro2::TokenStream;
+use quote::quote;
+
+fn implement(attributes: TokenStream, item_tokens: TokenStream) -> String {
+    let out_tokens = crate::implement_core(attributes, item_tokens);
+    let tokens_string = out_tokens.to_string();
+
+    let out_string = rustfmt(&tokens_string);
+    println!("// output of #[implement] :");
+    println!();
+    println!("{}", out_string);
+    out_string
+}
+
+fn rustfmt(input: &str) -> String {
+    let mut rustfmt = Command::new("rustfmt");
+
+    rustfmt.stdin(Stdio::piped());
+    rustfmt.stdout(Stdio::piped());
+    rustfmt.stderr(Stdio::inherit());
+
+    let mut child = match rustfmt.spawn() {
+        Ok(c) => c,
+        Err(e) => {
+            eprintln!("failed to spawn rustfmt: {e:?}");
+            return input.to_string();
+        }
+    };
+
+    let mut stdout = child.stdout.take().unwrap();
+
+    // spawn thread to read stdout
+    let stdout_thread = std::thread::spawn(move || {
+        let mut buf = String::new();
+        stdout.read_to_string(&mut buf).unwrap();
+        buf
+    });
+
+    // write unformatted into stdin
+    let mut stdin = child.stdin.take().unwrap();
+    stdin.write_all(input.as_bytes()).unwrap();
+    drop(stdin);
+
+    let stdout_string: String = stdout_thread.join().unwrap();
+
+    let exit = child.wait().unwrap();
+    if !exit.success() {
+        eprintln!("rustfmt terminated with failure status code");
+        return input.to_string();
+    }
+
+    stdout_string
+}
+
+#[test]
+fn simple_type() {
+    implement(
+        quote!(IFoo),
+        quote! {
+            struct Foo {
+                x: u32,
+            }
+        },
+    );
+}
+
+#[test]
+fn zero_sized_type() {
+    implement(
+        quote!(IFoo),
+        quote! {
+            struct Foo;
+        },
+    );
+}
+
+#[test]
+fn no_interfaces() {
+    implement(
+        quote!(),
+        quote! {
+            struct Foo {}
+        },
+    );
+}
+
+#[test]
+fn generic_no_lifetime() {
+    implement(
+        quote!(IAsyncOperationWithProgress<T, P>, IAsyncInfo),
+        quote! {
+            struct OperationWithProgress<T, P>(SyncState<IAsyncOperationWithProgress<T, P>>)
+            where
+                T: RuntimeType + 'static,
+                P: RuntimeType + 'static;
+
+        },
+    );
+}
+
+#[test]
+fn generic_with_lifetime() {
+    implement(
+        quote!(),
+        quote! {
+            pub struct Foo<'a> {
+                pub x: &'a [u8],
+            }
+        },
+    );
+}
+
+#[test]
+fn tuple_type() {
+    implement(
+        quote!(IFoo),
+        quote! {
+            struct Foo(pub i32);
+        },
+    );
+}