A lifetime was declared more than once in the same scope.
Erroneous code example:
fn foo<'a, 'b, 'a>(x: &'a str, y: &'b str, z: &'a str) { // error! }
Two lifetimes cannot have the same name. To fix this example, change the second 'a
lifetime into something else ('c
for example):
fn foo<'a, 'b, 'c>(x: &'a str, y: &'b str, z: &'c str) { // ok! }