@supports ( --x : y , z ) { a { color: red; } }
@supports ( --x : ) { a { color: red; } }
@supports (--x: ) { a { color: red; } }
@supports ( --x y , z ) { a { color: red; } }
@supports ( --x ) { a { color: red; } }
@supports ( ) { a { color: red; } }
@supports ( . --x : y , z ) { a { color: red; } }
