Suggest unwrapping when private method name is available in inner type

[estebank]

Given

fn main() {
    let maybe_vec = Some(vec![1,2,3]);
    assert_eq!(maybe_vec.len(), 3);
}

suggest unwraping maybe_vec to call .len() on the Vec<_>.

error[E0624]: method `len` is private
  --> $DIR/enum-method-probe.rs:61:9
   |
LL |     res.len();
   |         ^^^ private method
  --> $SRC_DIR/core/src/option.rs:LL:COL
   |
   = note: private method defined here
   |
note: the method `len` exists on the type `Vec<{integer}>`
  --> $SRC_DIR/alloc/src/vec/mod.rs:LL:COL
help: consider using `Option::expect` to unwrap the `Vec<{integer}>` value, panicking if the value is an `Option::None`
   |
LL |     res.expect("REASON").len();
   |        +++++++++++++++++

When a method isn't available, we emit E0599, but when it is private we emit E0624. We now just invoke the same suggestion logic from the later that we already did in the former.

Fix #143795.

[rustbot]

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[lcnr]

@bors r+ rollup

[bors]

📌 Commit 78fc7c3 has been approved by lcnr

It is now in the queue for this repository.