Possible to declare functions that will warn on unused results in Rust? [duplicate]

Question

Does Rust have a way to declare a function, where not using its result will warn - for any types?

Something like GCC's __attribute__((warn_unused_result));?

Answer 1

As of 1.27, #[must_use] works for functions too.

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It appears that the #[must_use] attribute is only applicable to structs, enums and unions (union is not available in stable Rust yet, though): source. I think this means you can't override it for a function.

Answer 2

Yes, if you don't mind wrapping said types.

The #[must_use] attribute, as answered by @ljedrz, only applies to types. However, in Rust, creating new types is painless and has not impact on performance. Therefore, just wrap your type in a MustUse<T> type, and have your function resolve this.

struct MustUse<T>(T);