https://d.puremagic.com/issues/show_bug.cgi?id=12420

           Summary: [AA] Can't set associative array with array as key
                    value using key type
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: regression
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: verylonglogin.reg@gmail.com


--- Comment #0 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2014-03-20 14:02:44 MSK ---
This code should compile:
---
void main()
{
    int[char[]] aa;
    aa[new char[1]] = 5; // line 4
}
---
main.d(4): Error: associative arrays can only be assigned values with immutable
keys, not char[]
---

Also the error message is wrong. The compiler expects an array of not-mutable
elements (yes, `cast(const)` will work). This incorrect compiler hack [1] was
introduced trying to fix Issue 2954 (see Comment 8 of that issue). I propose to
remove the hack.

And yes, it's a regression from 2010. )


[1] http://www.dsource.org/projects/dmd/changeset/749

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--- Comment #1 from Kenji Hara <k.hara.pg@gmail.com> 2014-03-29 20:21:09 PDT ---
(In reply to comment #0)
> This code should compile:
> ---
> void main()
> {
>     int[char[]] aa;
>     aa[new char[1]] = 5; // line 4
> }
> ---
> main.d(4): Error: associative arrays can only be assigned values with immutable
> keys, not char[]
> ---

I agree with the conclusion, the reason in my thought is:

`new char[1]` makes unique data and have no foreign reference, so it can be implicitly convertible to immutable(char[]). Therefore directly using it in the index part of the AA element setting will be allowed.

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #2 from Kenji Hara <k.hara.pg@gmail.com> 2014-03-29 20:51:15 PDT ---
https://github.com/D-Programming-Language/dmd/pull/3408

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--- Comment #3 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2014-03-30 12:27:43 MSK ---
(In reply to comment #1)
> I agree with the conclusion, the reason in my thought is:
> 
> `new char[1]` makes unique data and have no foreign reference, so it can be implicitly convertible to immutable(char[]). Therefore directly using it in the index part of the AA element setting will be allowed.

Looks like you misunderstood me. The word `immutable` shouldn't be here, it's just an incorrect error message. Currently we have no rules disallowing non-`immutable` associative array keys. I filed Issue 12491 for this.

This issue will be auto-fixed if Issue 2954 will be fixed by applying a correct check to ensure key expression can be implicitly converted to AA key type in case of setting AA value.

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