Clean code gen

[kimdv]

This is a PR that grew a bit. If it need to be split, I'll do so!

I think it's easier to review commit by commit.

[kimdv]

Maybe we should create a little tool for rewriting the headers 😎

[ahoppen]

Thanks. Could you extract the commit that removes force try to a separate PR because I’ve got opinions on that one. All the other commits are looking good to me and we can merge them in one PR.

Regarding force try: Instead of throwing, I think we should fatalError as close to the point where the syntax error was introduced as possible instead of throwing an error from the main function because that makes fixing the bugs easier. My vision for this has been that:

1. For each function that throws (i.e. the ones in SyntaxNodeWithBody.swift) we add a variant in CodeGeneration that doesn’t throw but has a label on the PartialSyntaxNodeString parameter that’s named validating or something of the sort. When the original function throws, this function fatalErrors
2. In CodeGeneration we add an initializer init(validating node: Self) to SyntaxProtocol. This initializer fatalErrors whenever node has a syntax error. And we’d use this initializer whenever we are creating a syntax node from string interpolation in CodeGeneration

That way we would restore the behavior prior to #1290 in CodeGeneration because that kind of behavior was actually really nice for code generation IMO.

[kimdv]

@swift-ci please test