mutable keyword

[Johan Engelen via Digitalmars-d-learn]

On Thursday, 19 May 2016 at 23:21:14 UTC, Jonathan M Davis wrote:
>
> No. D's const and immutable provide no backdoors. Rather, they 
> provide strong guarantees. So, if a variable is const, then it 
> cannot be mutated (even internally) except via a mutable 
> reference to the same data.

The "even internally" is incorrect, and I think needs fixing: 
currently you can synchronize on an immutable/const object, but 
the synchronize implementation will write to __monitor inside the 
object (the field after vptr) and gone is the guarantee. This 
means that you cannot put immutable objects in readonly data, for 
example. We had to make TypeInfo objects mutable in LDC exactly 
because of optimization errors due to this const guarantee 
breakage.
I still have to write up a detailed bug report about it...

- Johan