fix: refactor introduce_named_generic assist

Signed-off-by: Tarek <tareknaser360@gmail.com>

Author: tareknaser

crates/ide-assists/src/handlers/introduce_named_generic.rs

@@ -1,9 +1,6 @@
 use ide_db::syntax_helpers::suggest_name;
 use itertools::Itertools;
-use syntax::{
-    ast::{self, syntax_factory::SyntaxFactory, AstNode, HasGenericParams, HasName},
-    SyntaxElement,
-};
+use syntax::ast::{self, syntax_factory::SyntaxFactory, AstNode, HasGenericParams, HasName};
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
 
@@ -25,20 +22,14 @@ pub(crate) fn introduce_named_generic(acc: &mut Assists, ctx: &AssistContext<'_>
 
     let type_bound_list = impl_trait_type.type_bound_list()?;
 
-    // FIXME: Is this node appropriate to use for SyntaxEditor in this case?
-    let parent_node = match ctx.covering_element() {
-        SyntaxElement::Node(n) => n,
-        SyntaxElement::Token(t) => t.parent()?,
-    };
     let make = SyntaxFactory::new();
-
     let target = fn_.syntax().text_range();
     acc.add(
         AssistId("introduce_named_generic", AssistKind::RefactorRewrite),
         "Replace impl trait with generic",
         target,
-        |edit| {
-            let mut editor = edit.make_editor(&parent_node);
+        |builder| {
+            let mut editor = builder.make_editor(fn_.syntax());
 
             let existing_names = match fn_.generic_param_list() {
                 Some(generic_param_list) => generic_param_list
@@ -63,11 +54,11 @@ pub(crate) fn introduce_named_generic(acc: &mut Assists, ctx: &AssistContext<'_>
             fn_.syntax_editor_add_generic_param(&mut editor, generic_param.clone());
 
             if let Some(cap) = ctx.config.snippet_cap {
-                editor.add_annotation(generic_param.syntax(), edit.make_tabstop_before(cap));
+                editor.add_annotation(generic_param.syntax(), builder.make_tabstop_before(cap));
             }
 
             editor.add_mappings(make.finish_with_mappings());
-            edit.add_file_edits(ctx.file_id(), editor);
+            builder.add_file_edits(ctx.file_id(), editor);
         },
     )
 }

crates/syntax/src/ast/edit_in_place.rs

@@ -64,40 +64,38 @@ impl ast::Fn {
     ) {
         match self.generic_param_list() {
             Some(generic_param_list) => match generic_param_list.generic_params().last() {
-                Some(_last_param) => {
+                Some(last_param) => {
                     // There exists a generic param list and it's not empty
                     let position = generic_param_list.r_angle_token().map_or_else(
                         || crate::syntax_editor::Position::last_child_of(self.syntax()),
                         crate::syntax_editor::Position::before,
                     );
 
-                    if let Some(last_param) = generic_param_list.generic_params().last() {
-                        if last_param
-                            .syntax()
-                            .next_sibling_or_token()
-                            .map_or(false, |it| it.kind() == SyntaxKind::COMMA)
-                        {
-                            editor.insert(
-                                crate::syntax_editor::Position::after(last_param.syntax()),
-                                new_param.syntax().clone(),
-                            );
-                            editor.insert(
-                                crate::syntax_editor::Position::after(last_param.syntax()),
-                                make::token(SyntaxKind::WHITESPACE),
-                            );
-                            editor.insert(
-                                crate::syntax_editor::Position::after(last_param.syntax()),
-                                make::token(SyntaxKind::COMMA),
-                            );
-                        } else {
-                            let elements = vec![
-                                make::token(SyntaxKind::COMMA).into(),
-                                make::token(SyntaxKind::WHITESPACE).into(),
-                                new_param.syntax().clone().into(),
-                            ];
-                            editor.insert_all(position, elements);
-                        }
-                    };
+                    if last_param
+                        .syntax()
+                        .next_sibling_or_token()
+                        .map_or(false, |it| it.kind() == SyntaxKind::COMMA)
+                    {
+                        editor.insert(
+                            crate::syntax_editor::Position::after(last_param.syntax()),
+                            new_param.syntax().clone(),
+                        );
+                        editor.insert(
+                            crate::syntax_editor::Position::after(last_param.syntax()),
+                            make::token(SyntaxKind::WHITESPACE),
+                        );
+                        editor.insert(
+                            crate::syntax_editor::Position::after(last_param.syntax()),
+                            make::token(SyntaxKind::COMMA),
+                        );
+                    } else {
+                        let elements = vec![
+                            make::token(SyntaxKind::COMMA).into(),
+                            make::token(SyntaxKind::WHITESPACE).into(),
+                            new_param.syntax().clone().into(),
+                        ];
+                        editor.insert_all(position, elements);
+                    }
                 }
                 None => {
                     // There exists a generic param list but it's empty