[Issue 1983] Delegates violate const

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=1983

--- Comment #30 from timon.gehr at gmx.ch ---
(In reply to Bolpat from comment #28)
> However, I make myself aware that this is an implementation detail and in principle, other implementations are possible where the context pointer is not actually part of the delegate object but externalized to a global associative array.

Sorry, but this falls flat on its face because a `pure` function cannot access
a mutable global associative array. The context pointer is indeed part of the
delegate.

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