Bug 4274 – Better array of inner structs error message

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.)

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?

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.

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.

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.

Turning this into a "real" bug; maybe I'm wrong though.

Arrays of nested structs are now allowed (dmd 1.068 & dmd 2.053)

Commit pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/b754fbe2883bd182e7a2e6e23e7cbad97bedcd64 Update container.d BUG4274 already squashed.