Missing selector such as ‘.identifier’ or ‘[0]’.

mengikuti modul maps menit ke 7
void main(){
//jika kita sudah mengetahui kunci dan juga isi
var weekDays = {
‘Day1’ = ‘Mon’;
‘Day2’ = ‘Tue’;
‘Day3’ = ‘Wed’;
‘Day4’ = ‘Thu’
};

print(weekDays[‘Day2’]);
}

namun muncul pesan error diline 4 (‘Day1’ = ‘Mon’) : Missing selector such as ‘.identifier’ or ‘[0]’ dan Expected to find ‘}’.
dan dibaris print muncul pesan error : The operator ‘[]’ isn’t defined for the type ‘Set<String>’.

salahnya dimana y?
terima kasih