//ww:run-exit 70
// Migrated from 775_io_vtable_run row reader_set_happy.
package main;
import io;
fn myread(s: io.stream, buf: []u8) (size | io.eof | io.error) = {
    return 7: size;
};
export fn main() i32 = {
    let vt: io.vtable;
    vt.reader = (&myread): *io.reader;
    let v: io.stream = &vt;
    let buf: [4]u8;
    let bs: []u8 = buf[0:4];
    let r = io.read(v, bs);
    if (r is size) {
        let n = r as size;
        if (n == 7: size) { return 70; };
        return 71;
    };
    return 99;
};