Error code E0803

A trait implementation returns a reference without an explicit lifetime linking it to self. It commonly arises in generic trait implementations requiring explicit lifetime bounds.

Erroneous code example:

#![allow(unused)] fn main() { trait DataAccess<T> { fn get_ref(&self) -> T; } struct Container<'a> { value: &'a f64, } // Attempting to implement reference return impl<'a> DataAccess<&f64> for Container<'a> { fn get_ref(&self) -> &f64 { // Error: Lifetime mismatch self.value } } }

The trait method returns &f64 requiring an independent lifetime The struct Container<'a> carries lifetime parameter 'a The compiler cannot verify if the returned reference satisfies 'a constraints Solution Explicitly bind lifetimes to clarify constraints:

#![allow(unused)] fn main() { // Modified trait with explicit lifetime binding trait DataAccess<'a, T> { fn get_ref(&'a self) -> T; } struct Container<'a> { value: &'a f64, } // Correct implementation (bound lifetimes) impl<'a> DataAccess<'a, &'a f64> for Container<'a> { fn get_ref(&'a self) -> &'a f64 { self.value } } }