Perhaps I simply don't see the ambiguity after having used Scss, Less and the like for a long time, but isn't the simple `&` by far the best option here? The other two are absurdly verbose without offering any real benefit.
The simple '&' requires infinite lookahead to parse.
Afaict the lookahead problem refers not to the proposals, but to a syntax without these extra markers altogether. Which is why all the proposals have some markers.
So what? That's a complete non-problem.
no it doesn't, the simple no-prefix solution requires infinite lookahead