[Issue 10753] std.array.array of a range of structs with immutable fields too

[d-bugmail at puremagic.com]

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


monarchdodra at gmail.com changed:

           What    |Removed                     |Added
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                 CC|                            |monarchdodra at gmail.com


--- Comment #1 from monarchdodra at 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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