Function Recursion - Wrong order of Evaluation

[schutta]

I have this model test_recursion.mzn, in which the recursive function get_max is defined.

int: n = 3;
set of int: I = 1..n;
array[I] of int: x = [1, 6, 6]; 
array[I] of int: y = [4, 5, 7]; 

function int: get_max(int: xx, int: yy_max, int: i) = 
    if i > n then
        yy_max
    elseif x[i] = xx then
        let {
            int: new_yy_max = max(yy_max, trace("i = \(i)\n", y[i])),
            int: new_i = i + 1,
        } in get_max(xx, new_yy_max, new_i)
    else
        get_max(xx, yy_max, i + 1)
    endif;

set of int: X = { x[i] | i in I };
array[int] of int: dur = [ get_max(s, 1, 1) | s in X ];

solve satisfy;

Using MiniZinc 2.1.5 with this command mzn2fzn test_recursion.mzn aborts with this message

i = 2
i = 3
i = 4
MiniZinc: result of evaluation is undefined: 
  test_recursion.mzn:24:
    with s = 6
  in call 'get_max'
  test_recursion.mzn:7:
  in if-then-else expression
  test_recursion.mzn:20:
  in call 'get_max'
  test_recursion.mzn:7:
  in if-then-else expression
  test_recursion.mzn:14:
  in let expression
  test_recursion.mzn:18:
  in call 'get_max'
  test_recursion.mzn:7:
  in if-then-else expression
  test_recursion.mzn:14:
  in let expression
  test_recursion.mzn:18:
  in call 'get_max'
  test_recursion.mzn:15:
  in call 'max'
  in call 'trace'
  in array access
  array access out of bounds

It seems so, that the compiler internally computes the new index i and then uses it to access the array y leading to an array access error.

BTW: Tested different versions of MiniZinc with the same result except for MiniZinc 1.6 that aborted with a cycle detection error.