Enforce indents/continuations must follow a line break

[zaneduffield]

Currently, it's possible get FormattingData into a semi-invalid state pretty easily.

pasfmt/core/src/lang.rs

Lines 373 to 379 in bd8e1e8

	pub struct FormattingData {
	ignored: bool,
	pub newlines_before: usize,
	pub indentations_before: usize,
	pub continuations_before: usize,
	pub spaces_before: usize,
	}

You can set indentations_before to a non-zero value despite newlines_before being zero.
There's no good reason to want indentations before a token without any line breaks preceding them. It's not even useful for alignment, because you would want to use spaces for that.
The same is true of continuations.

It should be possible to leverage the type system to enforce that every indentation or continuation is preceded by a line break. In particular the NonZero* types in std::num would be useful.