child-of SASS mixin

child-of-example.sass

// thanks : http://thesassway.com/intermediate/referencing-parent-selectors-using-ampersand#comment-2067904467

@mixin child-of($parent) {
	@at-root {
		#{$parent} %child {
			@content;
		}
	}
	@extend %child;
}

body {
	h3 {
		font-size:18px;
		@include child-of('#parent') {
			font-weight:bold;
		}
	}
}