https://issues.dlang.org/show_bug.cgi?id=17036
[email protected] changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |[email protected] --- Comment #1 from [email protected] --- --- struct S0 { void x[1]; } pragma(msg, S0.init); --- As you can see this outputs `S0([cast(ubyte)0u]`, let's assume that the compiler is right and try using that value as initializer --- auto x = S0([cast(ubyte)0u]; // and I thought you couldn't cast a ubyte into a void --- gives a fairly explicative error, which is what one would rightfully expect --- cannot implicitly convert expression ([cast(ubyte)0u]) of type ubyte[] to void[1] --- on the other hand using the `.init` directly works perfectly..isn't that weird ? --- auto x = S0.init; // works --- Let's take a step back, where's the initializer coming from? Here it is [1], you sneaky bastard! So what happens here is that a zero-initialized TypeSArray is created with a void[1] type bolted on, the trick falls short when the struct initializer (the aforementioned `S0([cast(ubyte)0u]` that now has a S0(void[1]) type) is run trough dtemplate `matchArg` and trough the CTFE engine where nothing is done beside losing our bolted-on type. What happens next is where the error originates, the new initializer gets trough the semantic phase --- ArrayLiteralExp::semantic('[cast(ubyte)0u]') --- if you're familiar with the inner workings I'll also add that `type` is null right now and the deduced type is `ubyte[]` which is the technically right answer but the wrong one in this context. ugh. Here's where the shit hits the fan --- ArrayLiteralExp::implicitConvTo(this=[cast(ubyte)0u], type=ubyte[], t=void[1]) TypeDArray::implicitConvTo(to = void[1]) this = ubyte[] --- What to do? One could try not to lose the hacked-up type of the array, relax the rules for casts to `void[N]`, emit a `void` initializer instead of a zeroing the array (which is what one would expect since void has no default initializer), hope for the best, use another lang^Hthat's it! [1] https://github.com/dlang/dmd/blob/master/src/mtype.d#L5040 --
