http://d.puremagic.com/issues/show_bug.cgi?id=10753

           Summary: std.array.array of a range of structs with immutable
                    fields too
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2013-08-03 07:02:11 PDT ---
import std.algorithm: map;
import std.array: array;
struct Foo {
    immutable dchar d;
}
struct Bar {
    immutable int x;
}
void main() {
    "12".map!Foo.array;
    [1, 2].map!Bar.array;
}



DMD 2.064alpha gives:

...\dmd2\src\phobos\std\array.d(2309): Error: cannot modify struct delegate
Foo[]()

{

return (cast(Foo*)(*this._data).arr)[len..len + 1u];

}

()[0u] Foo with immutable members
...\dmd2\src\phobos\std\array.d(69): Error: template instance
std.array.Appender!(Foo[]).Appender.put!(Foo) error instantiating
temp.d(10):        instantiated from here: array!(MapResult!(Foo, string))
temp.d(10): Error: template instance std.array.array!(MapResult!(Foo, string))
error instantiating
...\dmd2\src\phobos\std\array.d(58): Error: cannot modify struct result[i] Bar
with immutable members
temp.d(11): Error: template instance std.array.array!(MapResult!(Bar, int[]))
error instantiating

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monarchdodra@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |monarchdodra@gmail.com


--- Comment #1 from monarchdodra@gmail.com 2013-08-05 03:06:51 PDT ---
(In reply to comment #0)
> import std.algorithm: map;
> import std.array: array;
> struct Foo {
>     immutable dchar d;
> }
> struct Bar {
>     immutable int x;
> }
> void main() {
>     "12".map!Foo.array;
>     [1, 2].map!Bar.array;
> }
> 
> 
> 
> DMD 2.064alpha gives:
> 
> ...\dmd2\src\phobos\std\array.d(2309): Error: cannot modify struct delegate
> Foo[]()
> 
> {
> 
> return (cast(Foo*)(*this._data).arr)[len..len + 1u];
> 
> }
> 
> ()[0u] Foo with immutable members
> ...\dmd2\src\phobos\std\array.d(69): Error: template instance
> std.array.Appender!(Foo[]).Appender.put!(Foo) error instantiating
> temp.d(10):        instantiated from here: array!(MapResult!(Foo, string))
> temp.d(10): Error: template instance std.array.array!(MapResult!(Foo, string))
> error instantiating
> ...\dmd2\src\phobos\std\array.d(58): Error: cannot modify struct result[i] Bar
> with immutable members
> temp.d(11): Error: template instance std.array.array!(MapResult!(Bar, int[]))
> error instantiating

This is an interesting scenario, as it reveals bugs in several steps of the "tool chain". In regards to "Bar", the first bug is in "std.array.array", and will soon be fixed. Unfortunately, it will pass through std.conv.emplace, which is not fixed, so it will stop working there.

I have an open pull for fixing said conv, but I'm unsure it handles this scenario (I'm pretty confident it actually *doesn't*). I'll double check, but I don't think I'll make any changes to it to support this scenario, I'd rather make slow but confirmed steps to improving emplace.

Still, this is an interesting bug. I'll check back to it often.

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monarchdodra@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE


--- Comment #2 from monarchdodra@gmail.com 2013-08-28 02:17:47 PDT ---
*** This issue has been marked as a duplicate of issue 9528 ***

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