StructuralSearchReplace: next steps

[matklad]

#3099 implemented initial version of SSR.

This issue collects things we need to do to make this really production-read

• add docs to https://github.com/rust-analyzer/rust-analyzer/blob/master/docs/user/features.md
• improve matching code to handle trivia
• improve matching code to handle semantically equivalent transformations (for example, the order of the fields)
• add support for matchers other than $expr

@mikhail-m1 any other things I've missed?

[matklad]

The most important feature here is documentation!

[adamrk]

What kinds of things are you thinking about for the second item?

[matklad]

White space differences should not matter for natching

[adamrk]

Made an initial change for the whitespace, but there's two points I'm not certain about:

1. The Rust reference says whitespace is defined by the Unicode property Pattern_White_Space, but the char method is_whitespace uses the Unicode property White_Space instead and they're not exactly the same. I didn't notice any code in rust-analyzer for checking Pattern_White_Space so I assume we don't really care about the difference and it's fine to use is_whitespace?
2. It seems like we might want to completely ignore whitespace in certain situations (e.g. match f(x) with f( x ), but I don't think we can do that in general. The current change only matches various forms of whitespace with each other, but doesn't ignore any whitespace. Any opinions on that?

[adamrk]

Actually I think for my second question it's fine to throw out all whitespace tokens. I can't actually think of any situations where it would be a problem.

[flodiebold]

Note that there's an is_trivia method on SyntaxKind, you don't need to implement this yourself. E.g. some_token.kind().is_trivia().

[matklad]

Yeah, the line that checks for Pattern_White_Space is in the rustc_lexer crate, which we share with the compiler

…

On Sat, 22 Feb 2020 at 23:18, Florian Diebold ***@***.***> wrote: Note that there's an is_trivia method on SyntaxKind, you don't need to implement this yourself. E.g. some_token.kind().is_trivia(). — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#3186>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AANB3M2QY4CRZWSFQLYQ6D3REGQDNANCNFSM4KWONEZA> .

[adamrk]

Cool, thanks.