enum string[] a = ["a"];

extern(C) void main() {
        int i = 0;
        auto s = a[i];
}
---------------
Error: TypeInfo cannot be used with -betterC

On Tuesday, 14 August 2018 at 13:01:57 UTC, learnfirst1 wrote:
>
> enum string[] a = ["a"];
>
> extern(C) void main() {
>         int i = 0;
>         auto s = a[i];
> }
> ---------------
> Error: TypeInfo cannot be used with -betterC

Yes. https://issues.dlang.org/show_bug.cgi?id=19169

On Tuesday, 14 August 2018 at 13:16:50 UTC, Nicholas Wilson wrote:
> On Tuesday, 14 August 2018 at 13:01:57 UTC, learnfirst1 wrote:
>>
>> enum string[] a = ["a"];
>>
>> extern(C) void main() {
>>         int i = 0;
>>         auto s = a[i];
>> }
>> ---------------
>> Error: TypeInfo cannot be used with -betterC
>
> Yes. https://issues.dlang.org/show_bug.cgi?id=19169

This seems to be because dynamic array literals are allocated by default. So that is possibly not a bug, per se but the error message is definitely not helpful.

On Tuesday, 14 August 2018 at 13:01:57 UTC, learnfirst1 wrote:
>
> enum string[] a = ["a"];
>
> extern(C) void main() {
>         int i = 0;
>         auto s = a[i];
> }
> ---------------
> Error: TypeInfo cannot be used with -betterC

You can use `static immutable` as a workaround for now:

https://run.dlang.io/is/7HEPst

On Tuesday, 14 August 2018 at 13:01:57 UTC, learnfirst1 wrote:
>
> enum string[] a = ["a"];
>
> extern(C) void main() {
>         int i = 0;
>         auto s = a[i];
> }
> ---------------
> Error: TypeInfo cannot be used with -betterC

Workaround: https://run.dlang.io/is/NZykl0

Source: https://p0nce.github.io/d-idioms/

On Tuesday, 14 August 2018 at 16:31:38 UTC, Paul Backus wrote:
> On Tuesday, 14 August 2018 at 13:01:57 UTC, learnfirst1 wrote:
>>
>> enum string[] a = ["a"];
>>
>> extern(C) void main() {
>>         int i = 0;
>>         auto s = a[i];
>> }
>> ---------------
>> Error: TypeInfo cannot be used with -betterC
>
> Workaround: https://run.dlang.io/is/NZykl0
>
> Source: https://p0nce.github.io/d-idioms/

FYI: staticArray will be part of 2.082, it already works with dmd-nightly:

https://run.dlang.io/is/tC7tix

On Tuesday, 14 August 2018 at 17:22:42 UTC, Seb wrote:

> FYI: staticArray will be part of 2.082, it already works with dmd-nightly:

That just seems wrong.  Isn't the fact that `staticArray` is needed a bug in the compiler?  I think the compiler could have lowered to something like that automatically to avoid the library workaround.

Mike

On Tuesday, 14 August 2018 at 17:49:32 UTC, Mike Franklin wrote:
> On Tuesday, 14 August 2018 at 17:22:42 UTC, Seb wrote:
>
>> FYI: staticArray will be part of 2.082, it already works with dmd-nightly:
>
> That just seems wrong.  Isn't the fact that `staticArray` is needed a bug in the compiler?  I think the compiler could have lowered to something like that automatically to avoid the library workaround.
>
> Mike

It's not a bug, it's all about how the type system is set up. The type of an array literal expression like `[1, 2, 3]` is `int[]` (a slice of an array of ints), so no matter if you do:

auto readonly(T)(const(T)[] x) { return x; }

auto             arr1 = [1, 2, 3];
auto             arr2 = [1, 2, 3].readonly;
const            arr3 = [1, 2, 3];
enum             arr4 = [1, 2, 3];
static immutable arr5 = [1, 2, 3];
scope            arr6 = [1, 2, 3];

In all instances the type will be `int[]` modulo type qualifiers.

Static arrays are completely different types, that just happen to accept
assignments from slices. Their two defining properties are:
1. Their length is fixed at compile-time, meaning that you can do:

import std.array, std.meta;
auto x = [1, 2, 3, 4, 5].staticArray;
enum length = x.length;
pragma (msg, length);
alias seq = AliasSeq!(0, 42, length);
static foreach (i; 0 .. length) { }
static foreach (i; seq) { }


2. Where slices are reference types, static arrays are value types which means that each assignment will copy an entire array.

Basically they behave like a `struct { int _arr_0 = 0, _arr_1 = 1, _arr_2 = 2; }`.

https://run.dlang.io/is/iD9ydu

On Wednesday, 15 August 2018 at 08:14:53 UTC, Petar Kirov [ZombineDev] wrote:
>
> https://run.dlang.io/is/iD9ydu

I made a typo in one of the comments. Here's the fixed version:
https://run.dlang.io/is/HRqYcZ

On Wednesday, 15 August 2018 at 08:14:53 UTC, Petar Kirov [ZombineDev] wrote:

> It's not a bug, it's all about how the type system is set up. The type of an array literal expression like `[1, 2, 3]` is `int[]` (a slice of an array of ints), so no matter if you do:
>
> auto readonly(T)(const(T)[] x) { return x; }
>
> auto             arr1 = [1, 2, 3];
> auto             arr2 = [1, 2, 3].readonly;
> const            arr3 = [1, 2, 3];
> enum             arr4 = [1, 2, 3];
> static immutable arr5 = [1, 2, 3];
> scope            arr6 = [1, 2, 3];
>
> In all instances the type will be `int[]` modulo type qualifiers.
>
> Static arrays are completely different types, that just happen to accept
> assignments from slices. Their two defining properties are:
> 1. Their length is fixed at compile-time, meaning that you can do:
>
> import std.array, std.meta;
> auto x = [1, 2, 3, 4, 5].staticArray;
> enum length = x.length;
> pragma (msg, length);
> alias seq = AliasSeq!(0, 42, length);
> static foreach (i; 0 .. length) { }
> static foreach (i; seq) { }
>
>
> 2. Where slices are reference types, static arrays are value types which means that each assignment will copy an entire array.
>
> Basically they behave like a `struct { int _arr_0 = 0, _arr_1 = 1, _arr_2 = 2; }`.
>
> https://run.dlang.io/is/iD9ydu

Thanks for the detailed explanation; it make sense now.

Mike