Adding an argument to a function is a really compelling case for syntactic diffs.
Line numbers remain super tricky: mapping overlapping positions spanning multiple lines back to lines isn't quite right yet.
miniblog.
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TIL rustc has a style guide for suggestions! https://rustc-dev-guide.rust-lang.org/diagnostics.html#suggestion-style-guide
They recommend avoiding 'did you mean' or 'the following' in favour of direct suggestions and highlighted positions.
Lessons learned from writing a linter/static analysis tool for shell scripts: https://www.vidarholen.net/contents/blog/?p=859
(Preserve positions, use error codes and document them, and there's a tradeoff between beginner mistakes and advanced mistakes!)
How has V8 reduced memory without hurting runtime performance? Lazily building function feedback data, GCing little used bytecodes, and even avoiding generating source positions!