Improving an error message: "cannot bind by-move into a pattern guard"

[steveklabnik]

Issue by catamorphism
Saturday Jan 26, 2013 at 20:41 GMT

For earlier discussion, see rust-lang/rust#4649

This issue was labelled with: A-diagnostics, A-windows, B-RFC, I-papercut in the Rust repository

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Based on an IRC conversation just now, I can think of two ways to improve this error message:

1. Because pattern guards use the "if" keyword, someone may have written one by accident. Then, if they see this error message, they're going to ask "what's a pattern guard"? The error could explain this (it's a little hard to figure out right now since the entire pattern gets underlined, not the guard).
2. Probably more importantly, the error should suggest what to do to fix it.

The error in question is in rustc::middle::check_match.

[Centril]

Closing in favor of rust-lang/rust#45600.