“Truly Hygienic” Let Statements in Rust (sabrinajewson.org)

submitted 5 days ago by hallettj@leminal.space to c/rust@programming.dev

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A short post on how variable names can leak out of macros if there is a name collision with a constant. I thought this was a delightful read!

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[-] livingcoder@programming.dev 7 points 5 days ago

This was a great post, but is the last state of the macro actually bad for performance in any way? I get that it's ugly (and we should only choose to make code less readable like this when there's actually an issue) but is it worse for runtime performance?

[-] arendjr@programming.dev 1 points 4 days ago

Runtime performance is entirely unaffected by the use of macros. It can have a negative impact on compile-time performance though, if you overdo it.

[-] livingcoder@programming.dev 2 points 4 days ago

I understand that the macro only affects compile time but I'm talking about the extra function that's included in the resulting source code when the macro is expanded during compile. Based on other feedback, it looks like the unused function is optimized away.