* {@code Map<T, Something>} to {@code Map<String, Something>} etc. Similarly, {@code formal} and
   * {@code actual} can be {@code Map<K, V>} and {@code Map<String, Integer>} respectively, or they
   * can be {@code E[]} and {@code String[]} respectively, or even any arbitrary combination
   * thereof.
   *
   * @param formal The type whose type variables or itself is mapped to other type(s). It's almost

   * {@code Map<T, Something>} to {@code Map<String, Something>} etc. Similarly, {@code formal} and
   * {@code actual} can be {@code Map<K, V>} and {@code Map<String, Integer>} respectively, or they
   * can be {@code E[]} and {@code String[]} respectively, or even any arbitrary combination
   * thereof.
   *
   * @param formal The type whose type variables or itself is mapped to other type(s). It's almost

   * fine for the synthetic TypeVariable to be unequal to any native TypeVariable anyway.
   */
  @SuppressWarnings("UnusedTypeParameter") // It's used reflectively.
  static final class NativeTypeVariableEquals<X> {
    static final boolean NATIVE_TYPE_VARIABLE_ONLY =
        !NativeTypeVariableEquals.class.getTypeParameters()[0].equals(

   * fine for the synthetic TypeVariable to be unequal to any native TypeVariable anyway.
   */
  @SuppressWarnings("UnusedTypeParameter") // It's used reflectively.
  static final class NativeTypeVariableEquals<X> {
    static final boolean NATIVE_TYPE_VARIABLE_ONLY =
        !NativeTypeVariableEquals.class.getTypeParameters()[0].equals(