TypeVariable<?> variable = new TypeParameter<T>() {}.typeVariable;
    TypeVariable<?> expected =
        TypeParameterTest.class.getDeclaredMethod("testCaptureTypeParameter")
            .getTypeParameters()[0];
    assertEquals(expected, variable);
  }

  public void testConcreteTypeRejected() {
    assertThrows(IllegalArgumentException.class, () -> new TypeParameter<String>() {});
  }

    final TypeSignature typeSignature;

    MethodSignature(Method method) {
      name = method.getName();
      parameterTypes = asList(method.getParameterTypes());
      typeSignature = new TypeSignature(method.getTypeParameters());
    }

    @Override
    public boolean equals(@Nullable Object obj) {
      if (obj instanceof MethodSignature) {
        MethodSignature other = (MethodSignature) obj;

    final TypeSignature typeSignature;

    MethodSignature(Method method) {
      name = method.getName();
      parameterTypes = asList(method.getParameterTypes());
      typeSignature = new TypeSignature(method.getTypeParameters());
    }

    @Override
    public boolean equals(@Nullable Object obj) {
      if (obj instanceof MethodSignature) {
        MethodSignature other = (MethodSignature) obj;