We might also consider letting the language semantics invade the editor. Hazel integrates its parser into the text editor, so rather than getting a red squiggly when you break a rule you're just unable to break the rules. It represents code you haven't yet written as a "typed hole" so instead of

    1 +

The + would cause the following to appear

    1 + <int>

where <int> is the typed hole, reminding you to put an expression there which is an integer. It's perhaps a smaller leap than using shapes and space, but it's one I'd like to feel out a bit sometime.