This works:
void main() {
    int[string][] a1 = [["cc":0]];
}

This doesn't work:
void main() {
    int[string][] a2 = [["cc":0], ["DD":10]];
}

Gives:
test.d(3): Error: Integer constant expression expected instead of "cc"
test.d(3): Error: Integer constant expression expected instead of "cc"
Error: incompatible types for (([0]) ? (["DD":10])): 'int[1u]' and 'int[string]'
test.d(3): Error: cannot implicitly convert expression ([(__error),(__error)]) of type int[2u] to int[string][]
Error: cannot cast int to int[string]
Error: cannot cast int to int[string]