feat: handle self-param outside of methods when renaming

crates/ide/src/rename.rs

@@ -421,7 +421,8 @@ fn text_edit_from_self_param(self_param: &ast::SelfParam, new_name: &str) -> Opt
         None
     }
 
-    let impl_def = self_param.syntax().ancestors().find_map(ast::Impl::cast)?;
+    match self_param.syntax().ancestors().find_map(ast::Impl::cast) {
+        Some(impl_def) => {
             let type_name = target_type_name(&impl_def)?;
 
             let mut replacement_text = String::from(new_name);
@@ -435,6 +436,14 @@ fn text_edit_from_self_param(self_param: &ast::SelfParam, new_name: &str) -> Opt
 
             Some(TextEdit::replace(self_param.syntax().text_range(), replacement_text))
         }
+        None => {
+            cov_mark::hit!(rename_self_outside_of_methods);
+            let mut replacement_text = String::from(new_name);
+            replacement_text.push_str(": _");
+            Some(TextEdit::replace(self_param.syntax().text_range(), replacement_text))
+        }
+    }
+}
 
 #[cfg(test)]
 mod tests {
@@ -1977,6 +1986,26 @@ impl Foo {
         );
     }
 
+    #[test]
+    fn test_self_outside_of_methods() {
+        cov_mark::check!(rename_self_outside_of_methods);
+        check(
+            "foo",
+            r#"
+fn f($0self) -> i32 {
+    use self as _;
+    self.i
+}
+"#,
+            r#"
+fn f(foo: _) -> i32 {
+    use self as _;
+    foo.i
+}
+"#,
+        );
+    }
+
     #[test]
     fn test_self_in_path_to_parameter() {
         check(