error[E0615]: attempted to take value of method `unwrap` on type `Option<{integer}>`
  --> $DIR/issue-88803-call-expr-method.rs:7:12
   |
LL |         (a.unwrap)()
   |            ^^^^^^ method, not a field
   |
help: remove wrapping parentheses to call the method
   |
LL -         (a.unwrap)()
LL +         a.unwrap()
   |

error: aborting due to previous error

For more information about this error, try `rustc --explain E0615`.