blocks in blocks need to have a semicolon

[CohenArthur]

The following code fails with a parsing error on the 5th line, while it should be valid

if true {
    mut b = 1;
    if true {
        b = 0;
    }

    b
} else {
    15
}

Adding a semicolon at the end of the inner if fixes the parsing but isn't really what we want:

if true {
    mut b = 1;
    if true {
        b = 0;
    };

    b
} else {
    15
}