[Wilfred]

tree-sitter has first class support for parsing errors as ERROR nodes in the output tree. I treat these as just another atom in the s-expression.

In practise I haven't noticed any issues yet. I suspect that difftastic doesn't see many syntax errors because users have fixed most of them by the time they run the diff. When you look at diffs of committed code you hopefully have no parse errors at all.

The tree-sitter parsers could still reject valid code I suppose. I worry slightly more about the parsers getting precedence/associativity wrong, but it would be hard to construct an example that produce identical parse trees due to incorrect precedence.