[Issue 5749] argument evaluation order of chained function from right

[d-bugmail at puremagic.com]

https://d.puremagic.com/issues/show_bug.cgi?id=5749


Kenji Hara <k.hara.pg at gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code
           Severity|enhancement                 |major


--- Comment #8 from Kenji Hara <k.hara.pg at gmail.com> 2013-11-25 18:28:48 PST ---
(In reply to comment #7)
> This patch seems important.

The root issue is very similar to bug 8396. When method call is used, the side
effect of callable entity (evaluation of 'this' object + getting member
function pointer) is not ordered before the arguments evaluation.

I think this is not intended behavior. For example, this code evaluates
function arguments left-to-right.

extern (C) int printf(const char*, ...);
void main()
{
    void delegate(int) foo(int i)
    {
        printf("i: %d\n", i);
        return (a){ foo(a); };
    }
    auto getFunc() { return &foo; }

    int i;
    getFunc()(++i)(++i);
    // getFunc() is evaluated before the first ++i expression,
    // and getFunc()(++i) is evaluated before the second ++i expression.
}

Because l-to-r evaluation is enforced by the glue-layer code
https://github.com/D-Programming-Language/dmd/blob/7360ae8611add4dc0a89cd870a6ac6490fb2a19b/src/e2ir.c#L3706

The code was introduce by the commit:
https://github.com/D-Programming-Language/dmd/commit/80e2319878bee3bb139a20c0bc1b85b1ec04b892

If you comment out the part, above example code will be broken.

Therefore, I'll change this issue to 'wrong-code' bug.

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