Suggest if let on let refutable binding

src/test/ui/error-codes/E0005.stderr

@@ -3,6 +3,13 @@ error[E0005]: refutable pattern in local binding: `None` not covered
    |
 LL |     let Some(y) = x;
    |         ^^^^^^^ pattern `None` not covered
+   |
+   = 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
+help: you might want to use `if let` to ignore the variant that isn't matched
+   |
+LL |     if let Some(y) = x { /* */ }
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error