why won't byPair work with a const AA?

[H. S. Teoh via Digitalmars-d-learn]

On Tue, Aug 01, 2017 at 10:04:18AM -0400, Steven Schveighoffer via Digitalmars-d-learn wrote:
> On 7/30/17 12:19 AM, Matthew Gamble wrote:
[...]
> > import std.array;
> > import std.algorithm;
> > 
> > class A
> > {
> >      this() { aa = ["a":1, "b" : 2, "c" : 3]; }
> >      auto pairs() @property const { return
> > aa.byPair.array.sort().release; }
> > private:
> >      int[string] aa;
> > }
> > 
> > If I remove const from the pairs function it compiles fine. I'm just
> > not sure this is a behavior I want. Any help/recommendation would be
> > appreciated.
> 
> byPair must store a pointer to the data in the AA. If you mark the AA
> const, then it must store a const pointer to AA data.
[...]

Actually, there's nothing about the implementation of both byKeyValue
(the underlying implementation in druntime) and byPair in std.array that
would preclude them from being used with const AA's.  The only flaw is
that the declaration of byPair doesn't match const AA's:

	https://issues.dlang.org/show_bug.cgi?id=17711

Here's the fix:

	https://github.com/dlang/phobos/pull/5668


T

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