.foo
    text-align: center

    .bar
        color: red

- becomes -

.foo {
    text-align: center;
}

    .foo .bar {
        color: red;
    }

--------------------------------

.foo
    text-align: center

    &.bar
        color: red

- becomes -

.foo {
    text-align: center;
}

    .foo.bar {
        color: red;
    }