Math: test that implicit conversion of T to Vector<T> won't compile.

"Won't compile" tests are another awesome feature of C++11.

src/Math/Test/Vector2Test.cpp

@@ -107,6 +107,9 @@ void Vector2Test::constructOneValue() {
     Vector2 a(3.0f); /* Not constexpr under GCC < 4.7 */
     #endif
     CORRADE_COMPARE(a, Vector2(3.0f, 3.0f));
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Float, Vector2>::value));
 }
 
 void Vector2Test::constructConversion() {

src/Math/Test/Vector3Test.cpp

@@ -114,6 +114,9 @@ void Vector3Test::constructOneValue() {
     Vector3 a(-3.0f); /* Not constexpr under GCC < 4.7 */
     #endif
     CORRADE_COMPARE(a, Vector3(-3.0f, -3.0f, -3.0f));
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Float, Vector3>::value));
 }
 
 void Vector3Test::constructParts() {

src/Math/Test/Vector4Test.cpp

@@ -111,6 +111,9 @@ void Vector4Test::constructOneValue() {
     Vector4 a(4.3f); /* Not constexpr under GCC < 4.7 */
     #endif
     CORRADE_COMPARE(a, Vector4(4.3f, 4.3f, 4.3f, 4.3f));
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Float, Vector4>::value));
 }
 
 void Vector4Test::constructParts() {

src/Math/Test/VectorTest.cpp

@@ -165,6 +165,9 @@ void VectorTest::constructOneValue() {
     #endif
 
     CORRADE_COMPARE(a, Vector4(7.25f, 7.25f, 7.25f, 7.25f));
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Float, Vector4>::value));
 }
 
 void VectorTest::constructOneComponent() {