On Wednesday, 5 February 2020 at 01:06:46 UTC, rous wrote:
This is an example program that illustrates the issue:import std.variant: Algebraic, This; import std.stdio: writeln; alias Foo = Algebraic!(This[], int); void main() { Foo x = 5; Foo y = 10; Foo z = [x,y]; pragma(msg, typeof(x)); pragma(msg, typeof(y)); pragma(msg, typeof(z)); pragma(msg, typeof(z[0])); }At compile time, it prints VariantN!(16LU, This[], int) three times and then VariantN!32LU.
The problem is that you are indexing directly into the Algebraic, using VariantN.opIndex [1], which returns a generic, non-Algebraic Variant. Instead, you should use visit [2] or tryVisit [3] to access the array contained inside the Algebraic, and index into that.
For example: auto w = z.tryVisit!((Foo[] arr) => arr[0]); static assert(is(typeof(w) == Foo)); [1] https://dlang.org/phobos/std_variant.html#.VariantN.opIndex [2] https://dlang.org/phobos/std_variant.html#.visit [3] https://dlang.org/phobos/std_variant.html#.tryVisit
