More helpful error messages

[aaronjanse]

It would be great if rnix-parser has errors more descriptive than "unexpected X," perhaps prompting the user how to fix the code if we can guess what's missing (e.g. a semicolon for the last value in an attr set)?

Existing error messages at the time of writing:

rnix-parser/src/parser.rs

Lines 22 to 37 in fa6ddde

	#[derive(Clone, Debug, PartialEq)]
	#[non_exhaustive]
	pub enum ParseError {
	/// Unexpected is used when the cause cannot be specified further
	Unexpected(TextRange),
	/// UnexpectedExtra is used when there are additional tokens to the root in the tree
	UnexpectedExtra(TextRange),
	/// UnexpectedWanted is used when specific tokens are expected, but different one is found
	UnexpectedWanted(SyntaxKind, TextRange, Box<[SyntaxKind]>),
	/// UnexpectedDoubleBind is used when a pattern is bound twice
	UnexpectedDoubleBind(TextRange),
	/// UnexpectedEOF is used when the end of file is reached, while tokens are still expected
	UnexpectedEOF,
	/// UnexpectedEOFWanted is used when specific tokens are expected, but the end of file is reached
	UnexpectedEOFWanted(Box<[SyntaxKind]>),
	}

[Ma27]

Seems reasonable. Will be out of scope for 0.10. though, hope that's OK :)

[Ma27]

In case someone wants to take over, feel free.... Otherwise I'll look into it as soon as we're working on 1.0.

[elikoga]

Just to be clear, this is about improving the Display impl for ParseError? As in expanding on the strings

See

rnix-parser/src/parser.rs

Lines 43 to 79 in 01e6582

	"error node at {}..{}",
	usize::from(range.start()),
	usize::from(range.end())
	)
	}
	ParseError::UnexpectedExtra(range) => {
	write!(
	f,
	"unexpected token at {}..{}",
	usize::from(range.start()),
	usize::from(range.end())
	)
	}
	ParseError::UnexpectedWanted(got, range, kinds) => write!(
	f,
	"unexpected {:?} at {}..{}, wanted any of {:?}",
	got,
	usize::from(range.start()),
	usize::from(range.end()),
	kinds
	),
	ParseError::UnexpectedDoubleBind(range) => {
	write!(
	f,
	"unexpected double bind at {}..{}",
	usize::from(range.start()),
	usize::from(range.end())
	)
	}
	ParseError::UnexpectedEOF => write!(f, "unexpected end of file"),
	ParseError::UnexpectedEOFWanted(kinds) => {
	write!(f, "unexpected end of file, wanted any of {:?}", kinds)
	}
	ParseError::DuplicatedArgs(range, ident) => {
	write!(
	f,
	"argument `{}` is duplicated in {}..{}",