Array index not detected as integer

[Henning Kiel]

The following model does not flatten:

model demo
  Real x[8] = {1, 2, 3, 4, 5, 6, 7, 8};
  Real y;
algorithm
  y := 0;
  for j in 1:3 loop
    y := y + x[j * (j + 1) / 2];
  end for;
end demo;

[demo.mo:7:5-7:32:writable] Error: Subscript j * (j + 1) / 2 of type Real is not a subtype of Integer, Boolean or enumeration.
[demo.mo:7:5-7:32:writable] Error: Variable x[j * (j + 1) / 2] not found in scope demo.$for loop scope$.
Error: Error occurred while flattening model demo