[Issue 525] New: can't use array variable in tuple index

[Don Clugston]

d-bugmail at puremagic.com wrote:
> http://d.puremagic.com/issues/show_bug.cgi?id=525
> 
>            Summary: can't use array variable in tuple index
>            Product: D
>            Version: unspecified
>           Platform: All
>         OS/Version: All
>             Status: NEW
>           Severity: normal
>           Priority: P2
>          Component: DMD
>         AssignedTo: bugzilla at digitalmars.com
>         ReportedBy: lovesyao at hotmail.com
> 
> 
> import std.typetuple;
> const int[] test=[1];
> alias TypeTuple!(ulong,uint,ushort,ubyte) tuple;
> static assert(is(tuple[1]==uint));//ok
> static assert(is(tuple[test[0]]==uint));//failed
> 
> Output:
> tuple_bug.d(5): static assert  (is((ulong, uint, ushort, ubyte)[void[0]] ==
> uint)) is false
> 
> 
This is because there's no constant folding of array indexes and slices.
A simpler example:
---------
const int a[] = [1,2,3];
const int b = a[2];
---------
Error: non-constant expression (a)[2]