[Issue 11929] Disallow `ref` in front tuple expansion in foreach over range

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=11929



--- Comment #4 from Denis Shelomovskij <verylonglogin.reg at gmail.com> 2014-01-16 11:57:32 MSK ---
(In reply to comment #3)
> (In reply to comment #2)
> >
> > Ranges of tuples generally contains generated somehow based on source ranges
> > tuples (e.g. `zip` and `group`) so access to tuple elements by `ref` is a
> > nonsense. As D type system doesn't provide head const I see no way to mark
> > tuple elements non-`ref`able so I suggest to disallow such access in general as
> > I'm not aware of cases where such functionality is needed. And even if there
> > are such cases IHO its support doesn't worth potential confusion.
> 
> I still don't understand the scope of proposed limitation. Foreach over ranges
> or foreach in general?

Neither. For tuple expansion in `foreach` over range only as written in
description.

> By the way, what you are asking can be reformulated as:
> 
> void foo(ref int i) { i = 0; }
> 
> void main()
> {
>    int i = 1;
>    i.foo(); //oops, i = 0, let's ban ref attribute in function parameters
> }
> 
> Why one should put 'ref' (supposedly unconsciously?) and then complain about
> it?

Your example is about a requirement to explicitly specify `ref` in function
call expression like in C#, it's another already discussed issue. Function
calls has nothing to do with this bug report.

In this issue it's proposed to disable `ref` in front tuple expansion case
because in general created tuple is a temporary.

Also I noted the issue exists in `foreach` over ranges in general, not just in
tuple expansion case so I filed Issue 11934 for range problem and Issue 11935
that is a better solution for the problem described in this one.

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