Adds ability to override GetTrustLevel return value

crates/libs/core/src/inspectable.rs

@@ -17,6 +17,15 @@ impl IInspectable {
             Ok(std::mem::transmute(abi))
         }
     }
+
+    /// Gets the trust level of the current object.
+    pub fn GetTrustLevel(&self) -> Result<i32> {
+        unsafe {
+            let mut value = 0;
+            (self.vtable().GetTrustLevel)(std::mem::transmute_copy(self), &mut value).ok()?;
+            Ok(value)
+        }
+    }
 }
 
 #[doc(hidden)]
@@ -60,14 +69,16 @@ impl IInspectable_Vtbl {
             *value = std::mem::transmute(h);
             HRESULT(0)
         }
-        unsafe extern "system" fn GetTrustLevel(_: *mut std::ffi::c_void, value: *mut i32) -> HRESULT {
-            // Note: even if we end up implementing this in future, it still doesn't need a this pointer
-            // since the data to be returned is type- not instance-specific so can be shared for all
-            // interfaces.
-            *value = 0;
-            HRESULT(0)
+        unsafe extern "system" fn GetTrustLevel<T: IUnknownImpl, const OFFSET: isize>(this: *mut std::ffi::c_void, value: *mut i32) -> HRESULT {
+            let this = (this as *mut *mut std::ffi::c_void).offset(OFFSET) as *mut T;
+            (*this).GetTrustLevel(value)
+        }
+        Self {
+            base: IUnknown_Vtbl::new::<Identity, OFFSET>(),
+            GetIids,
+            GetRuntimeClassName: GetRuntimeClassName::<Name>,
+            GetTrustLevel: GetTrustLevel::<Identity, OFFSET>,
         }
-        Self { base: IUnknown_Vtbl::new::<Identity, OFFSET>(), GetIids, GetRuntimeClassName: GetRuntimeClassName::<Name>, GetTrustLevel }
     }
 }
 

crates/libs/core/src/unknown.rs

@@ -72,15 +72,20 @@ pub trait IUnknownImpl {
     /// This function is safe to call as long as the interface pointer is non-null and valid for writes
     /// of an interface pointer.
     unsafe fn QueryInterface(&self, iid: *const GUID, interface: *mut *mut std::ffi::c_void) -> HRESULT;
+
     /// Increments the reference count of the interface
     fn AddRef(&self) -> u32;
+
     /// Decrements the reference count causing the interface's memory to be freed when the count is 0
     ///
     /// # Safety
     ///
     /// This function should only be called when the interfacer pointer is no longer used as calling `Release`
     /// on a non-aliased interface pointer and then using that interface pointer may result in use after free.
     unsafe fn Release(&self) -> u32;
+
+    /// Gets the trust level of the current object.
+    unsafe fn GetTrustLevel(&self, value: *mut i32) -> HRESULT;
 }
 
 #[cfg(feature = "implement")]

crates/libs/implement/src/lib.rs

@@ -74,6 +74,8 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:
         }
     });
 
+    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);
@@ -162,6 +164,13 @@ pub fn implement(attributes: proc_macro::TokenStream, original_type: proc_macro:
                 }
                 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
@@ -225,6 +234,7 @@ impl ImplementType {
 #[derive(Default)]
 struct ImplementAttributes {
     pub implement: Vec<ImplementType>,
+    pub trust_level: usize,
 }
 
 impl syn::parse::Parse for ImplementAttributes {
@@ -269,6 +279,7 @@ impl ImplementAttributes {
                     self.walk_implement(tree, namespace)?;
                 }
             }
+            UseTree2::TrustLevel(input) => self.trust_level = *input,
         }
 
         Ok(())
@@ -279,6 +290,7 @@ enum UseTree2 {
     Path(UsePath2),
     Name(UseName2),
     Group(UseGroup2),
+    TrustLevel(usize),
 }
 
 impl UseTree2 {
@@ -308,6 +320,7 @@ impl UseTree2 {
                 Ok(ImplementType { type_name, generics })
             }
             UseTree2::Group(input) => Err(syn::parse::Error::new(input.brace_token.span.join(), "Syntax not supported")),
+            _ => unimplemented!(),
         }
     }
 }
@@ -336,6 +349,18 @@ impl syn::parse::Parse for UseTree2 {
             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![<]>()?;

crates/tests/implement/tests/trust_level.rs

@@ -0,0 +1,54 @@
+#![allow(non_snake_case)]
+
+use windows::core::*;
+use windows::Foundation::*;
+
+#[implement(IStringable)]
+struct BaseTrust;
+
+impl IStringable_Impl for BaseTrust {
+    fn ToString(&self) -> Result<HSTRING> {
+        Ok("BaseTrust".into())
+    }
+}
+
+#[implement(IClosable, TrustLevel = Partial, IStringable)]
+struct PartialTrust;
+
+impl IStringable_Impl for PartialTrust {
+    fn ToString(&self) -> Result<HSTRING> {
+        Ok("PartialTrust".into())
+    }
+}
+
+impl IClosable_Impl for PartialTrust {
+    fn Close(&self) -> Result<()> {
+        Ok(())
+    }
+}
+
+#[implement(IStringable, TrustLevel = Full)]
+struct FullTrust;
+
+impl IStringable_Impl for FullTrust {
+    fn ToString(&self) -> Result<HSTRING> {
+        Ok("FullTrust".into())
+    }
+}
+
+#[test]
+fn test() -> Result<()> {
+    let base: IStringable = BaseTrust.into();
+    assert_eq!(base.ToString()?, "BaseTrust");
+    assert_eq!(base.cast::<IInspectable>()?.GetTrustLevel()?, 0);
+
+    let partial: IStringable = PartialTrust.into();
+    assert_eq!(partial.ToString()?, "PartialTrust");
+    assert_eq!(partial.cast::<IInspectable>()?.GetTrustLevel()?, 1);
+
+    let full: IStringable = FullTrust.into();
+    assert_eq!(full.ToString()?, "FullTrust");
+    assert_eq!(full.cast::<IInspectable>()?.GetTrustLevel()?, 2);
+
+    Ok(())
+}