Allow for non-HRESULT return types in COM (#1595)

Author: rylev

crates/libs/interface/src/lib.rs

@@ -111,8 +111,9 @@ impl Interface {
                         quote! { #pat }
                     })
                     .collect::<Vec<_>>();
+                let ret = &m.ret;
                 quote! {
-                    #vis unsafe fn #name(&self, #(#args),*) -> ::windows::core::HRESULT {
+                    #vis unsafe fn #name(&self, #(#args),*) #ret {
                         (::windows::core::Interface::vtable(self).#name)(::core::mem::transmute_copy(self), #(#params),*)
                     }
                 }
@@ -135,9 +136,10 @@ impl Interface {
                 let name = &m.name;
                 let docs = &m.docs;
                 let args = m.gen_args();
+                let ret = &m.ret;
                 quote! {
                     #(#docs)*
-                    unsafe fn #name(&self, #(#args),*) -> ::windows::core::HRESULT;
+                    unsafe fn #name(&self, #(#args),*) #ret;
                 }
             })
             .collect::<Vec<_>>();
@@ -181,8 +183,9 @@ impl Interface {
                         quote! { #pat }
                     })
                     .collect::<Vec<_>>();
+                let ret = &m.ret;
                 quote! {
-                    unsafe extern "system" fn #name<Identity: ::windows::core::IUnknownImpl, Impl: #trait_name, const OFFSET: isize>(this: *mut ::core::ffi::c_void, #(#args),*) -> ::windows::core::HRESULT {
+                    unsafe extern "system" fn #name<Identity: ::windows::core::IUnknownImpl, Impl: #trait_name, const OFFSET: isize>(this: *mut ::core::ffi::c_void, #(#args),*) #ret {
                         let this = (this as *mut ::windows::core::RawPtr).offset(OFFSET) as *mut Identity;
                         let this = (*this).get_impl() as *mut Impl;
                         (*this).#name(#(#params),*).into()

crates/tests/nightly_interface/tests/com.rs

@@ -8,10 +8,10 @@ pub unsafe trait ICustomUri: IUnknown {
     unsafe fn GetPropertyBSTR(&self, property: Uri_PROPERTY, value: *mut BSTR, flags: u32) -> HRESULT;
     unsafe fn GetPropertyLength(&self) -> HRESULT;
     unsafe fn GetPropertyDWORD(&self, property: Uri_PROPERTY, value: *mut u32, flags: u32) -> HRESULT;
-    unsafe fn HasProperty(&self) -> HRESULT;
+    unsafe fn HasProperty(&self); // Note: this definition is missing its return value
     unsafe fn GetAbsoluteUri(&self) -> HRESULT;
     unsafe fn GetAuthority(&self) -> HRESULT;
-    unsafe fn GetDisplayUri(&self) -> HRESULT;
+    unsafe fn GetDisplayUri(&self) -> i32;
     unsafe fn GetDomain(&self, value: *mut BSTR) -> HRESULT;
     // etc
 }
@@ -35,7 +35,7 @@ impl ICustomUri_Impl for CustomUri {
         *value = 123;
         S_OK
     }
-    unsafe fn HasProperty(&self) -> HRESULT {
+    unsafe fn HasProperty(&self) {
         todo!()
     }
     unsafe fn GetAbsoluteUri(&self) -> HRESULT {
@@ -44,7 +44,7 @@ impl ICustomUri_Impl for CustomUri {
     unsafe fn GetAuthority(&self) -> HRESULT {
         todo!()
     }
-    unsafe fn GetDisplayUri(&self) -> HRESULT {
+    unsafe fn GetDisplayUri(&self) -> i32 {
         todo!()
     }
     unsafe fn GetDomain(&self, value: *mut BSTR) -> HRESULT {