How to remove the key from the `redBlackTree` with comparator" a <= b "?

[via Digitalmars-d-learn]

On Sunday, 7 June 2015 at 18:50:47 UTC, anonymous wrote:
> Do not use '<=' as a comparison function with RedBlackTree. It 
> doesn't meet the requirements.
>
> Quoting the documentation [1]:
>> Note that less should produce a strict ordering. That is, for 
>> two unequal elements a and b, less(a, b) == !less(b, a). 
>> less(a, a) should always equal false.
>
> This doesn't hold for '<='.

Could we add a static check for this?