http://d.puremagic.com/issues/show_bug.cgi?id=4274

           Summary: Better array of inner structs error message
           Product: D
           Version: future
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: diagnostic
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2010-06-04 18:20:50 PDT ---
This wrong D2 program:

void main() {
    struct Foo {
        void bar() {}
    }
    auto foos = new Foo[1]; // line 5
}


At compile time dmd v2.046 prints:
temp.d(5): Error: cannot have array of inner structs Foo

But for D newbies coming from C or C++ can find that error message cryptic. Using a static struct solves this problem. So a possible error message can be:

temp.d(5): Error: cannot have array of inner structs Foo, you can use a 'static
struct' instead.

This improved error message is not perfect, but it seems better.

(I don't understand why D error messages don't have the ending full stop.)

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nfxjfg@gmail.com changed:

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


--- Comment #1 from nfxjfg@gmail.com 2010-06-05 04:33:03 PDT ---
I don't understand why arrays of inner structs shouldn't be possible.
Is this just another seemingly random restriction with no real foundation of
the dmd compiler?

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--- Comment #2 from bearophile_hugs@eml.cc 2010-06-05 04:50:08 PDT ---
Structs defined inside functions keep a hidden pointer field to the function they are into. If you return the array of nonstatic structs, the scope stops existing and this pointer points to garbage. To avoid this you need 'struct closures', but I prefer to avoid them.

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--- Comment #3 from nfxjfg@gmail.com 2010-06-05 05:04:20 PDT ---
So what? You _can_ have an array of closures.
Why not an array of nested structs?
The compiler should obviously allocate all variables referenced by the struct
on the heap, just like it is done with closures.
Otherwise, it's an half-implemented garbage feature that should be removed
before it causes any more harm.

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--- Comment #4 from nfxjfg@gmail.com 2010-06-05 05:10:24 PDT ---
I just tested it, and it seems for nested structs, the compiler correctly allocates upvalues on the heap. The error message you're receiving doesn't make any sense. At least the reason for it must different.

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nfxjfg@gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|enhancement                 |normal


--- Comment #5 from nfxjfg@gmail.com 2010-06-08 04:28:26 PDT ---
Turning this into a "real" bug; maybe I'm wrong though.

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yebblies <yebblies@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |yebblies@gmail.com
           Platform|x86                         |All
         Resolution|                            |FIXED
         OS/Version|Windows                     |All


--- Comment #6 from yebblies <yebblies@gmail.com> 2011-07-01 21:52:59 EST ---
Arrays of nested structs are now allowed (dmd 1.068 & dmd 2.053)

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