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| -rw-r--r-- | src/doc/book/lifetimes.md | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/src/doc/book/lifetimes.md b/src/doc/book/lifetimes.md index f7d9c94bc45..e865609f217 100644 --- a/src/doc/book/lifetimes.md +++ b/src/doc/book/lifetimes.md @@ -56,8 +56,12 @@ To fix this, we have to make sure that step four never happens after step three. The ownership system in Rust does this through a concept called lifetimes, which describe the scope that a reference is valid for. -When we have a function that takes an argument by reference, we can be -implicit or explicit about the lifetime of the reference: +**Note** It's important to understand that lifetime annotations are +_descriptive_, not _prescriptive_. This means that how long a reference is valid +is determined by the code, not by the annotations. The annotations, however, +give information about lifetimes to the compiler that uses them to check the +validity of references. The compiler can do so without annotations in simple +cases, but needs the programmers support in complex scenarios. ```rust // implicit |