Auto merge of #16378 - roife:fix/issue-15470, r=Veykril

fix: better handling of SelfParam in assist 'inline_call'

fix #15470.

The current `inline_call` directly translates `&self` into `let ref this = ...;` and `&mut self` into `let ref mut this = ...;`. However, it does not handle some complex scenarios.

This PR addresses the following transformations (assuming the receiving object is `obj`):

- `self`: `let this = obj`
- `mut self`: `let mut this = obj`
- `&self`: `let this = &obj`
- `&mut self`
  + If `obj` is `let mut obj = ...`, use a mutable reference: `let this = &mut obj`
  + If `obj` is `let obj = &mut ...;`, perform a reborrow: `let this = &mut *obj`

crates/syntax/src/ast/make.rs

@@ -595,6 +595,9 @@ pub fn expr_macro_call(f: ast::Expr, arg_list: ast::ArgList) -> ast::Expr {
 pub fn expr_ref(expr: ast::Expr, exclusive: bool) -> ast::Expr {
     expr_from_text(&if exclusive { format!("&mut {expr}") } else { format!("&{expr}") })
 }
+pub fn expr_reborrow(expr: ast::Expr) -> ast::Expr {
+    expr_from_text(&format!("&mut *{expr}"))
+}
 pub fn expr_closure(pats: impl IntoIterator<Item = ast::Param>, expr: ast::Expr) -> ast::Expr {
     let params = pats.into_iter().join(", ");
     expr_from_text(&format!("|{params}| {expr}"))