# Error code E0310

A parameter type is missing a lifetime constraint or has a lifetime that does not live long enough.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    // This won't compile because T is not constrained to the static lifetime
    // the reference needs
    struct Foo<T> {
        foo: &'static T
    }
    }

Type parameters in type definitions have lifetimes associated with them that represent how long the data stored within them is guaranteed to live. This lifetime must be as long as the data needs to be alive, and missing the constraint that denotes this will cause this error.

This will compile, because it has the constraint on the type parameter:

    #![allow(unused)]
    fn main() {
    struct Foo<T: 'static> {
        foo: &'static T
    }
    }