Is this a violation of const?

[Salih Dincer]

On Saturday, 30 July 2022 at 10:02:50 UTC, Timon Gehr wrote:
> 
> It's a `const` hole, plain and simple.

This code, which consists of 26 lines, does not compile in DMD 
2.087.  I am getting this error:

> constHole.d(15): Error: mutable method `source.Updater.opCall` 
> is not callable using a `const` object
constHole.d(15):        Consider adding `const` or `inout` to 
source.Updater.opCall
constHole.d(21): Error: function `source.Updater.opCall(string 
s)` is not callable using argument types `(string*)`
constHole.d(21):        cannot pass argument `&s.s` of type 
`string*` to parameter `string s`

SDB at 79