Allow implicit matcher construction from nullptr. This allows "nullptr" to be used as a valid matcher for smart pointer types.

PiperOrigin-RevId: 861759501
Change-Id: I09ff55cd532014015725ec61356f480760819b29

googlemock/test/gmock-matchers-comparisons_test.cc

@@ -798,6 +798,7 @@ TEST(ExpectThat, TakesLiterals) {
   EXPECT_THAT(1, 1);
   EXPECT_THAT(1.0, 1.0);
   EXPECT_THAT(std::string(), "");
+  EXPECT_THAT(std::shared_ptr<int>(), nullptr);
 }
 
 TEST(ExpectThat, TakesFunctions) {
@@ -1126,6 +1127,16 @@ TEST(IsNullTest, CanDescribeSelf) {
   EXPECT_EQ("isn't NULL", DescribeNegation(m));
 }
 
+struct SmartPtrHelper {
+  MOCK_METHOD(void, Call, (std::shared_ptr<int>));
+};
+
+TEST(IsNullTest, WorksWithSmartPtr) {
+  SmartPtrHelper helper;
+  EXPECT_CALL(helper, Call(nullptr));
+  helper.Call(nullptr);
+}
+
 // Tests that NotNull() matches any non-NULL pointer of any type.
 TEST(NotNullTest, MatchesNonNullPointer) {
   Matcher<int*> m1 = NotNull();