error[E0308]: mismatched types
  --> $DIR/hrtb-exists-forall-fn.rs:17:34
   |
LL |     let _: for<'b> fn(&'b u32) = foo();
   |            -------------------   ^^^^^ one type is more general than the other
   |            |
   |            expected due to this
   |
   = note: expected fn pointer `for<'b> fn(&'b _)`
              found fn pointer `fn(&_)`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.