Comment by icebraining

How I think it should be: the IDE would actually do the syntax checking and reference resolving work, so any program you have written is in fact pre-validated.

But IDEs already do that. An example I'm familiar with is Java on Eclipse - it validates the code as you're writing it and marking compilation errors. Your others example have been done as well.

You're right that you need an AST to do the properly, but when there's a cheap and reliable way to convert a blob of text to an AST - parsing - the distinction is somewhat irrelevant.