[LANG-1749] Add stricter type checks for parameterized types in method

src/main/java/org/apache/commons/lang3/reflect/TypeUtils.java

@@ -1080,6 +1080,17 @@ private static boolean isAssignable(final Type type, final ParameterizedType toP
         }
         // get the target type's type arguments including owner type arguments
         final Map<TypeVariable<?>, Type> toTypeVarAssigns = getTypeArguments(toParameterizedType, toClass, typeVarAssigns);
+        // Class<T> is not assignable to Class<S> if T is not S (even if T extends S)
+        if (toClass.equals(Class.class)) {
+            final TypeVariable<?>[] typeParams = toClass.getTypeParameters();
+            if (typeParams.length > 0) {
+                final Type toTypeArg = unrollVariableAssignments(typeParams[0], toTypeVarAssigns);
+                final Type fromTypeArg = unrollVariableAssignments(typeParams[0], fromTypeVarAssigns);
+                if (toTypeArg != null && (fromTypeArg == null || !toTypeArg.equals(fromTypeArg))) {
+                    return false;
+                }
+            }
+        }
         // now to check each type argument
         for (final TypeVariable<?> var : toTypeVarAssigns.keySet()) {
             final Type toTypeArg = unrollVariableAssignments(var, toTypeVarAssigns);

src/test/java/org/apache/commons/lang3/reflect/TypeUtilsTest.java

@@ -773,6 +773,33 @@ void testIsAssignableGenericArrayTypeToWildcardType() {
                 () -> String.format("TypeUtils.isAssignable(%s, %s)", testType, paramType));
     }
 
+    @Test
+    void testIsAssignable_ClassWithParameterizedType() {
+        final ParameterizedType topre1 = TypeUtils.parameterize(TestIF.class, TypeUtils.wildcardType().build());
+        final Type to1 = TypeUtils.parameterize(Class.class, TypeUtils.wildcardType().withUpperBounds(topre1).build());
+        final Type from1 = TypeUtils.parameterize(Class.class, TestIF.class);
+        assertFalse(TypeUtils.isAssignable(from1, to1), "Class<TestIF> should not be assignable to Class<? extends TestIF<?>>");
+
+        final ParameterizedType topre2 = TypeUtils.parameterize(TestIF.class, TypeUtils.wildcardType().build());
+        final Type to2 = TypeUtils.parameterize(Class.class, TypeUtils.wildcardType().withUpperBounds(topre2).build());
+        final Type from2 = TypeUtils.parameterize(Class.class, TestImpl.class);
+        assertFalse(TypeUtils.isAssignable(from2, to2), "Class<TestImpl> should not be assignable to Class<? extends TestIF<?>>");
+
+        final ParameterizedType topre3 = TypeUtils.parameterize(TestIF.class, Number.class);
+        final Type to3 = TypeUtils.parameterize(Class.class, TypeUtils.wildcardType().withUpperBounds(topre3).build());
+        final Type from3 = TypeUtils.parameterize(Class.class, TestImpl2.class);
+        assertFalse(TypeUtils.isAssignable(from3, to3), "Class<TestImpl2> should not be assignable to Class<? extends TestIF<Number>>");
+    }
+
+    private interface TestIF<T> {
+    }
+
+    private static class TestImpl<T> implements TestIF<T> {
+    }
+
+    private static class TestImpl2<R> implements TestIF<Number> {
+    }
+
     @Test
     void testIsAssignableGenericClassHierarchy() throws NoSuchFieldException {
         /*