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Re:Rust web framework, Iron by steveklabnik on Sunday August 16, 2015 @06:58PM (#10070588)
They could do something like

    let _ = something_returning_result()
But without the let, there's a warning. And culturally speaking, let _ is discouraged for this reason. If I want to ignore an error condition, I unwrap() instead, so at least my dumb decision will blow up in my face later instead of faint silently.
Re:Rust web framework, Iron by Manishearth on Sunday August 16, 2015 @08:18PM (#10070803)
I think they were talking about the compiler-enforced exhaustive match, not must_use.

The fact that you must acknowledge the existence of the error value before accessing the meaty success value (either with a match, an unwrap, or a try) is a great feature in Rust.

must_use forcing you to handle errors for things you don't need the meaty success value of is just icing on the cake.