Math: test that implicit conversion vector <-> complex/quat can't compile.

src/Math/Test/ComplexTest.cpp

@@ -126,6 +126,10 @@ void ComplexTest::constructFromVector() {
 
     constexpr Vector2 b(a);
     CORRADE_COMPARE(b, vec);
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Vector2, Complex>::value));
+    CORRADE_VERIFY(!(std::is_convertible<Complex, Vector2>::value));
 }
 
 void ComplexTest::constructCopy() {

src/Math/Test/DualComplexTest.cpp

@@ -121,6 +121,9 @@ void DualComplexTest::constructDefault() {
 void DualComplexTest::constructFromVector() {
     constexpr DualComplex a(Vector2(1.5f, -3.0f));
     CORRADE_COMPARE(a, DualComplex({1.0f, 0.0f}, {1.5f, -3.0f}));
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Vector2, DualComplex>::value));
 }
 
 void DualComplexTest::constructCopy() {

src/Math/Test/DualQuaternionTest.cpp

@@ -119,6 +119,9 @@ void DualQuaternionTest::constructDefault() {
 void DualQuaternionTest::constructFromVector() {
     constexpr DualQuaternion a(Vector3(1.0f, 2.0f, 3.0f));
     CORRADE_COMPARE(a, DualQuaternion({{0.0f, 0.0f, 0.0f}, 1.0f}, {{1.0f, 2.0f, 3.0f}, 0.0f}));
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Vector3, DualQuaternion>::value));
 }
 
 void DualQuaternionTest::constructCopy() {

src/Math/Test/QuaternionTest.cpp

@@ -128,6 +128,9 @@ void QuaternionTest::constructDefault() {
 void QuaternionTest::constructFromVector() {
     constexpr Quaternion a(Vector3(1.0f, 2.0f, 3.0f));
     CORRADE_COMPARE(a, Quaternion({1.0f, 2.0f, 3.0f}, 0.0f));
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<Vector3, Quaternion>::value));
 }
 
 void QuaternionTest::constructCopy() {