Function call with multiple, same arguments should be rejected

[phorward]

The behavior of specifying the same named argument multiple times is invalid.

Tokay 0.6.4
>>> add : @a, b { a + b }
>>> add(2,3)
5
>>> add(a=2, a=3)
Line 1, column 1: add() expected argument 'b'
>>> add(a=2, a=3, b=3)
5

in short

add : @a, b { a + b }
add(2,3)  # 5
add(a=2, a=3)  # ERR:Line 1, column 1: add() expected argument 'b'
add(a=2, a=3, b=3)  # 5