pub static EXPLICIT_OUTLIVES_REQUIREMENTS: &'static Lint
Expand description
The explicit_outlives_requirements
lint detects unnecessary
lifetime bounds that can be inferred.
Example
#![deny(explicit_outlives_requirements)]
#![deny(warnings)]
struct SharedRef<'a, T>
where
T: 'a,
{
data: &'a T,
}
{{produces}}
Explanation
If a struct
contains a reference, such as &'a T
, the compiler
requires that T
outlives the lifetime 'a
. This historically
required writing an explicit lifetime bound to indicate this
requirement. However, this can be overly explicit, causing clutter and
unnecessary complexity. The language was changed to automatically
infer the bound if it is not specified. Specifically, if the struct
contains a reference, directly or indirectly, to T
with lifetime
'x
, then it will infer that T: 'x
is a requirement.
This lint is “allow” by default because it can be noisy for existing code that already had these requirements. This is a stylistic choice, as it is still valid to explicitly state the bound. It also has some false positives that can cause confusion.
See RFC 2093 for more details.