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| -rw-r--r-- | src/doc/trpl/ownership.md | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/src/doc/trpl/ownership.md b/src/doc/trpl/ownership.md index b851f19d22d..f4b5495ba63 100644 --- a/src/doc/trpl/ownership.md +++ b/src/doc/trpl/ownership.md @@ -472,10 +472,15 @@ thread-safe counterpart of `Rc<T>`. ## Lifetime Elision -Earlier, we mentioned *lifetime elision*, a feature of Rust which allows you to -not write lifetime annotations in certain circumstances. All references have a -lifetime, and so if you elide a lifetime (like `&T` instead of `&'a T`), Rust -will do three things to determine what those lifetimes should be. +Rust supports powerful local type inference in function bodies, but it’s +forbidden in item signatures to allow reasoning about the types just based in +the item signature alone. However, for ergonomic reasons a very restricted +secondary inference algorithm called “lifetime elision” applies in function +signatures. It infers only based on the signature components themselves and not +based on the body of the function, only infers lifetime paramters, and does +this with only three easily memorizable and unambiguous rules. This makes +lifetime elision a shorthand for writing an item signature, while not hiding +away the actual types involved as full local inference would if applied to it. When talking about lifetime elision, we use the term *input lifetime* and *output lifetime*. An *input lifetime* is a lifetime associated with a parameter |