Merge pull request #1571 from dtolnay/pr1233

Touch up PR 1233

Author: dtolnay

tests/cxx_gen.rs

@@ -34,25 +34,26 @@ fn test_impl_annotation() {
 const BRIDGE1: &str = r#"
     #[cxx::bridge]
     mod ffi {
-        unsafe extern "C++" {
+        extern "C++" {
             type CppType;
         }
 
         extern "Rust" {
-            fn rust_method_cpp_context(self: Pin<&mut CppType>);
+            fn rust_method_cpp_receiver(self: Pin<&mut CppType>);
         }
     }
 "#;
 
-// Ensure that implementing a Rust method on a C++ type only causes generation
-// of the implementation.
+// Ensure that implementing a Rust method on an opaque C++ type only causes
+// generation of the member function definition, not a member function
+// declaration in a class definition.
 //
-// The header should be implemented in the C++ class definition and the Rust
-// implementation in the usual way.
+// The member function declaration will come from whichever header provides the
+// C++ class definition.
 //
-// This allows for developers and crates that are generating both C++ and Rust
-// code to have a C++ method implemented in Rust without having to use a
-// free method and passing through the C++ "this" as an argument.
+// This allows for developers and crates that are producing both C++ and Rust
+// code to have a C++ method implemented in Rust without having to use a free
+// function and passing through the C++ "this" as an argument.
 #[test]
 fn test_extern_rust_method_on_c_type() {
     let opt = Opt::default();
@@ -61,17 +62,14 @@ fn test_extern_rust_method_on_c_type() {
     let header = str::from_utf8(&generated.header).unwrap();
     let implementation = str::from_utf8(&generated.implementation).unwrap();
 
-    // To avoid continual breakage we won't test every byte.
-    // Let's look for the major features.
-
-    // Check that the header doesn't have the Rust method
-    assert!(!header.contains("rust_method_cpp_context"));
+    // Check that the header doesn't have the Rust method.
+    assert!(!header.contains("rust_method_cpp_receiver"));
 
-    // Check that there is a cxxbridge to the Rust method
+    // Check that there is a generated C signature bridging to the Rust method.
     assert!(implementation
-        .contains("void cxxbridge1$CppType$rust_method_cpp_context(::CppType &self) noexcept;"));
+        .contains("void cxxbridge1$CppType$rust_method_cpp_receiver(::CppType &self) noexcept;"));
 
-    // Check that there is a implementation on the C++ class calling the Rust method
-    assert!(implementation.contains("void CppType::rust_method_cpp_context() noexcept {"));
-    assert!(implementation.contains("cxxbridge1$CppType$rust_method_cpp_context(*this);"));
+    // Check that there is an implementation on the C++ class calling the Rust method.
+    assert!(implementation.contains("void CppType::rust_method_cpp_receiver() noexcept {"));
+    assert!(implementation.contains("cxxbridge1$CppType$rust_method_cpp_receiver(*this);"));
 }

tests/ffi/lib.rs

@@ -324,7 +324,7 @@ pub mod ffi {
         fn set(self: &mut R, n: usize) -> usize;
         fn r_method_on_shared(self: &Shared) -> String;
         fn r_get_array_sum(self: &Array) -> i32;
-        // Ensure that a Rust method can be implemented on a C++ type
+        // Ensure that a Rust method can be implemented on an opaque C++ type.
         fn r_method_on_c_get_mut(self: Pin<&mut C>) -> &mut usize;
 
         #[cxx_name = "rAliasedFunction"]
@@ -450,7 +450,7 @@ impl ffi::Array {
     }
 }
 
-// A Rust method implemented on the C++ type
+// A Rust method implemented on an opaque C++ type.
 impl ffi::C {
     pub fn r_method_on_c_get_mut(self: core::pin::Pin<&mut Self>) -> &mut usize {
         self.getMut()

tests/ffi/tests.h

@@ -54,8 +54,9 @@ class C {
   rust::String cOverloadedMethod(int32_t x) const;
   rust::String cOverloadedMethod(rust::Str x) const;
   static size_t c_static_method();
-  // Note that the implementation of this method is generated by CXX itself
-  // which is then bridged to a Rust method but with the C++ type as self
+  // Unlike the other contents of this class, the C++ definition of this member
+  // function is generated by CXX and forwards to a Rust method implementation
+  // in an `impl ffi::C` block.
   size_t &r_method_on_c_get_mut() noexcept;
 
 private: