error[E0308]: mismatched types
  --> $DIR/closure-no-fn-1.rs:6:29
   |
LL |     let foo: fn(u8) -> u8 = |v: u8| { a += v; a };
   |              ------------   ^^^^^^^^^^^^^^^^^^^^^ expected fn pointer, found closure
   |              |
   |              expected due to this
   |
   = note: expected fn pointer `fn(u8) -> u8`
                 found closure `{closure@$DIR/closure-no-fn-1.rs:6:29: 6:36}`
note: closures can only be coerced to `fn` types if they do not capture any variables
  --> $DIR/closure-no-fn-1.rs:6:39
   |
LL |     let foo: fn(u8) -> u8 = |v: u8| { a += v; a };
   |                                       ^ `a` captured here

error: aborting due to 1 previous error

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