1 files changed, 126 insertions, 0 deletions
diff --git a/build/clang-plugin/tests/TestTemporaryLifetimeBound.cpp b/build/clang-plugin/tests/TestTemporaryLifetimeBound.cpp
new file mode 100644
index 0000000000..0c51182cab
--- /dev/null
+++ b/build/clang-plugin/tests/TestTemporaryLifetimeBound.cpp
@@ -0,0 +1,126 @@
+#define MOZ_LIFETIME_BOUND __attribute__((annotate("moz_lifetime_bound")))
+
+struct Foo {};
+
+struct Bar {
+  MOZ_LIFETIME_BOUND const Foo &AsFoo() const; // expected-note {{member function declared here}} expected-note {{member function declared here}} expected-note {{member function declared here}} expected-note {{member function declared here}} expected-note {{member function declared here}}
+  MOZ_LIFETIME_BOUND operator const Foo &() const; // expected-note {{member function declared here}} expected-note {{member function declared here}} expected-note {{member function declared here}} expected-note {{member function declared here}} expected-note {{member function declared here}} expected-note {{member function declared here}}
+};
+
+Bar MakeBar() { return Bar(); }
+
+Bar testReturnsInstance_Constructed() { return Bar(); }
+
+const Foo &testReturnsReference_Static() {
+  static constexpr auto bar = Bar{};
+  return bar;
+}
+
+/* TODO This is bad as well... but not related to a temporary.
+const Foo& testReturnsReference_Local() {
+  constexpr auto bar = Bar{};
+  return bar;
+}
+*/
+
+const Foo &testReturnsReferenceToTemporaryViaLifetimeBound_Constructed() {
+  return Bar(); // expected-error {{cannot return result of lifetime-bound function 'operator const Foo &' on temporary of type 'Bar'}}
+}
+
+const Foo &testReturnsReferenceToTemporaryViaLifetimeBound2_Constructed() {
+  return static_cast<const Foo &>(Bar()); // expected-error {{cannot return result of lifetime-bound function 'operator const Foo &' on temporary of type 'Bar'}}
+}
+
+const Foo &testReturnsReferenceToTemporaryViaLifetimeBound3_Constructed() {
+  return Bar().AsFoo(); // expected-error {{cannot return result of lifetime-bound function 'AsFoo' on temporary of type 'Bar'}}
+}
+
+const Foo &
+testReturnsReferenceToTemporaryViaLifetimeBound4_Constructed(bool aCond) {
+  static constexpr Foo foo;
+  return aCond ? foo : Bar().AsFoo(); // expected-error {{cannot return result of lifetime-bound function 'AsFoo' on temporary of type 'Bar'}}
+}
+
+Foo testReturnsValueViaLifetimeBoundFunction_Constructed() { return Bar(); }
+
+Foo testReturnsValueViaLifetimeBoundFunction2_Constructed() {
+  return static_cast<const Foo &>(Bar());
+}
+
+Foo testReturnsValueViaLifetimeBoundFunction3_Constructed() {
+  return Bar().AsFoo();
+}
+
+Bar testReturnInstance_Returned() { return MakeBar(); }
+
+const Foo &testReturnsReferenceToTemporaryViaLifetimeBound_Returned() {
+  return MakeBar(); // expected-error {{cannot return result of lifetime-bound function 'operator const Foo &' on temporary of type 'Bar'}}
+}
+
+const Foo &testReturnsReferenceToTemporaryViaLifetimeBound2_Returned() {
+  return static_cast<const Foo &>(MakeBar()); // expected-error {{cannot return result of lifetime-bound function 'operator const Foo &' on temporary of type 'Bar'}}
+}
+
+const Foo &testReturnsReferenceToTemporaryViaLifetimeBound3_Returned() {
+  return MakeBar().AsFoo(); // expected-error {{cannot return result of lifetime-bound function 'AsFoo' on temporary of type 'Bar'}}
+}
+
+Foo testReturnsValueViaLifetimeBoundFunction_Returned() { return MakeBar(); }
+
+Foo testReturnsValueViaLifetimeBoundFunction2_Returned() {
+  return static_cast<const Foo &>(MakeBar());
+}
+
+Foo testReturnsValueViaLifetimeBoundFunction3_Returned() {
+  return MakeBar().AsFoo();
+}
+
+void testNoLifetimeExtension() {
+  const Foo &foo = Bar(); // expected-error {{cannot bind result of lifetime-bound function 'operator const Foo &' on temporary of type 'Bar' to reference, does not extend lifetime}}
+}
+
+void testNoLifetimeExtension2() {
+  const auto &foo = static_cast<const Foo &>(MakeBar()); // expected-error {{cannot bind result of lifetime-bound function 'operator const Foo &' on temporary of type 'Bar' to reference, does not extend lifetime}}
+}
+
+void testNoLifetimeExtension3() {
+  const Foo &foo = Bar().AsFoo(); // expected-error {{cannot bind result of lifetime-bound function 'AsFoo' on temporary of type 'Bar' to reference, does not extend lifetime}}
+}
+
+void testNoLifetimeExtension4(bool arg) {
+  const Foo foo;
+  const Foo &fooRef = arg ? foo : Bar().AsFoo(); // expected-error {{cannot bind result of lifetime-bound function 'AsFoo' on temporary of type 'Bar' to reference, does not extend lifetime}}
+}
+
+// While this looks similar to testNoLifetimeExtension4, this is actually fine,
+// as the coerced type of the conditional operator is `Foo` here rather than
+// `const Foo&`, and thus an implicit copy of `Bar().AsFoo()` is created, whose
+// lifetime is actually extended.
+void testLifetimeExtension(bool arg) {
+  const Foo &foo = arg ? Foo() : Bar().AsFoo();
+}
+
+void testConvertToValue() { const Foo foo = Bar(); }
+
+Foo testReturnConvertToValue() {
+  return static_cast<Foo>(Bar());
+}
+
+void FooFunc(const Foo &aFoo);
+
+// We want to allow binding to parameters of the target reference type though.
+// This is the very reason the annotation is required, and the function cannot
+// be restricted to lvalues. Lifetime is not an issue here, as the temporary's
+// lifetime is until the end of the full expression anyway.
+
+void testBindToParameter() {
+  FooFunc(Bar());
+  FooFunc(static_cast<const Foo &>(Bar()));
+  FooFunc(Bar().AsFoo());
+  FooFunc(MakeBar());
+}
+
+// This should be OK, because the return value isn't necessarily coming from the
+// argument (and it should be OK for any type).
+const Foo &RandomFunctionCall(const Foo &aFoo);
+const Foo &testReturnFunctionCall() { return RandomFunctionCall(Bar()); }