non-exhastive diagnostic: add note re. scrutinee type

src/test/ui/pattern/usefulness/refutable-pattern-errors.stderr

@@ -3,6 +3,8 @@ error[E0005]: refutable pattern in function argument: `(_, _)` not covered
    |
 LL | fn func((1, (Some(1), 2..=3)): (isize, (Option<isize>, isize))) { }
    |         ^^^^^^^^^^^^^^^^^^^^^ pattern `(_, _)` not covered
+   |
+   = note: the matched value is of type `(isize, (std::option::Option<isize>, isize))`
 
 error[E0005]: refutable pattern in local binding: `(std::i32::MIN..=0i32, _)` and `(2i32..=std::i32::MAX, _)` not covered
   --> $DIR/refutable-pattern-errors.rs:7:9
@@ -12,6 +14,7 @@ LL |     let (1, (Some(1), 2..=3)) = (1, (None, 2));
    |
    = note: `let` bindings require an "irrefutable pattern", like a `struct` or an `enum` with only one variant
    = note: for more information, visit https://doc.rust-lang.org/book/ch18-02-refutability.html
+   = note: the matched value is of type `(i32, (std::option::Option<i32>, i32))`
 help: you might want to use `if let` to ignore the variant that isn't matched
    |
 LL |     if let (1, (Some(1), 2..=3)) = (1, (None, 2)) { /* */ }