Expand Magnum tag tests with what Corrade tags have also tested.

src/Magnum/Test/TagsTest.cpp

@@ -34,10 +34,12 @@ struct TagsTest: TestSuite::Tester {
     explicit TagsTest();
 
     void noDefaultConstructor();
+    void inlineDefinition();
 };
 
 TagsTest::TagsTest() {
-    addTests({&TagsTest::noDefaultConstructor});
+    addTests({&TagsTest::noDefaultConstructor,
+              &TagsTest::inlineDefinition});
 }
 
 void TagsTest::noDefaultConstructor() {
@@ -45,6 +47,11 @@ void TagsTest::noDefaultConstructor() {
     CORRADE_VERIFY(!std::is_default_constructible<NoCreateT>::value);
 }
 
+void TagsTest::inlineDefinition() {
+    CORRADE_VERIFY((std::is_same<decltype(NoInit), const NoInitT>::value));
+    CORRADE_VERIFY((std::is_same<decltype(NoCreate), const NoCreateT>::value));
+}
+
 }}}
 
 CORRADE_TEST_MAIN(Magnum::Test::TagsTest)