error[E0369]: cannot multiply `&T` by `&T`
  --> $DIR/issue-35668.rs:2:23
   |
LL |     a.iter().map(|a| a*a)
   |                      -^- &T
   |                      |
   |                      &T
   |
help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
   |
LL | fn func<'a, T>(a: &'a [T]) -> impl Iterator<Item=&'a T> where &T: Mul<&T> {
   |                                                         +++++++++++++++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0369`.