global g: int;

@pure
fun f_pure(): builder {
    var b: builder = beginCell();
    g = g + 1;
    return b;
}

fun main(): int {
    g = 0;
    f_pure();
    return g;
}

/**
@compilation_should_fail
@stderr
"""
an impure operation in a pure function
g = g + 1;
"""
*/