Add test with opaque C++ type containing lifetime

Author: dtolnay

tests/ffi/lib.rs

@@ -209,6 +209,15 @@ pub mod ffi {
         type Job = crate::module::ffi::Job;
     }
 
+    unsafe extern "C++" {
+        type Borrow<'a>;
+
+        fn c_return_borrow<'a>(s: &'a CxxString) -> UniquePtr<Borrow<'a>>;
+
+        #[rust_name = "c_return_borrow_elided"]
+        fn c_return_borrow(s: &CxxString) -> UniquePtr<Borrow>;
+    }
+
     #[repr(u32)]
     #[derive(Hash)]
     enum COwnedEnum {

tests/ffi/tests.cc

@@ -207,6 +207,12 @@ ::A::B::ABEnum c_return_nested_ns_enum(uint16_t n) {
   }
 }
 
+Borrow::Borrow(const std::string &s) : s(s) {}
+
+std::unique_ptr<Borrow> c_return_borrow(const std::string &s) {
+  return std::unique_ptr<Borrow>(new Borrow(s));
+}
+
 void c_take_primitive(size_t n) {
   if (n == 2020) {
     cxx_test_suite_set_correct();

tests/ffi/tests.h

@@ -77,6 +77,11 @@ enum COwnedEnum {
   CVAL2,
 };
 
+struct Borrow {
+  Borrow(const std::string &s);
+  const std::string &s;
+};
+
 size_t c_return_primitive();
 Shared c_return_shared();
 ::A::AShared c_return_ns_shared();
@@ -110,6 +115,7 @@ size_t c_return_sum(size_t n1, size_t n2);
 Enum c_return_enum(uint16_t n);
 ::A::AEnum c_return_ns_enum(uint16_t n);
 ::A::B::ABEnum c_return_nested_ns_enum(uint16_t n);
+std::unique_ptr<Borrow> c_return_borrow(const std::string &s);
 
 void c_take_primitive(size_t n);
 void c_take_shared(Shared shared);