Rollup merge of #44124 - gaurikholkar:return_self, r=arielb1

adding E0623 for return types - both parameters are anonymous

This is a fix for #44018
```
error[E0621]: explicit lifetime required in the type of `self`
  --> $DIR/ex3-both-anon-regions-return-type-is-anon.rs:17:5
   |
16 |   fn foo<'a>(&self, x: &i32) -> &i32 {
   |                        ----     ----
   |                        |
   |                        this parameter and the return type are
                            declared with different lifetimes...
17 |     x
   |     ^ ...but data from `x` is returned here

error: aborting due to previous error
```
It also works for the below case where we have self as anonymous

```
error[E0623]: lifetime mismatch
  --> src/test/ui/lifetime-errors/ex3-both-anon-regions-self-is-anon.rs:17:19
   |
16 |     fn foo<'a>(&self, x: &Foo) -> &Foo {
   |                          ----     ----
   |                          |
   |                          this parameter and the return type are
                            declared with different lifetimes...
17 |         if true { x } else { self }
   |                   ^ ...but data from `x` is returned here

error: aborting due to previous error
```
r? @nikomatsakis

Currently, I have enabled E0621 where return type and self are anonymous, hence WIP.

0 files changed, 0 insertions, 0 deletions