Using .into() when type inference is impossible

Question

I\'m hoping to be able to use .into() to convert a value in a context where type inference is impossible. This is typically when I want to convert a temporary v

Answer 1

I don't think there is a better way. Since the type parameter is on the trait, not the method into(), the turbofish operator into::() doesn't work. As you said, you can make it work by using the fully-qualified-syntax:

Into::::into(a)

Note, that Into is reexported in std::prelude, which means that you never have to specify the full path, as the trait is always in scope.

Of course, there is also always the possibility to bind your temporary to a name and use the type annotation of the let-binding:

let tmp: i32 = a.into();

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It might be better in the future, though! There is an Type Ascription for Expressions RFC, which was already accepted and implemented. The feature is still unstable, but if it's implemented you could write something like:

println!("{}", (a.into(): i32));   // still unstable :/