Migrate extract_type_alias to mutable ast

Author: DropDemBits

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

@@ -1,6 +1,9 @@
 use either::Either;
 use ide_db::syntax_helpers::node_ext::walk_ty;
-use syntax::ast::{self, edit::IndentLevel, make, AstNode, HasGenericParams, HasName};
+use syntax::{
+    ast::{self, edit::IndentLevel, make, AstNode, HasGenericParams, HasName},
+    ted,
+};
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
 
@@ -34,14 +37,16 @@ pub(crate) fn extract_type_alias(acc: &mut Assists, ctx: &AssistContext<'_>) ->
         || item.syntax(),
         |impl_| impl_.as_ref().either(AstNode::syntax, AstNode::syntax),
     );
-    let insert_pos = node.text_range().start();
     let target = ty.syntax().text_range();
 
     acc.add(
         AssistId("extract_type_alias", AssistKind::RefactorExtract),
         "Extract type as type alias",
         target,
-        |builder| {
+        |edit| {
+            let node = edit.make_syntax_mut(node.clone());
+            let target_ty = edit.make_mut(ty.clone());
+
             let mut known_generics = match item.generic_param_list() {
                 Some(it) => it.generic_params().collect(),
                 None => Vec::new(),
@@ -56,27 +61,29 @@ pub(crate) fn extract_type_alias(acc: &mut Assists, ctx: &AssistContext<'_>) ->
             let generic_params =
                 generics.map(|it| make::generic_param_list(it.into_iter().cloned()));
 
+            // Replace original type with the alias
             let ty_args = generic_params
                 .as_ref()
                 .map_or(String::new(), |it| it.to_generic_args().to_string());
-            let replacement = format!("Type{ty_args}");
-            builder.replace(target, replacement);
-
-            let indent = IndentLevel::from_node(node);
-            let generic_params = generic_params.map_or(String::new(), |it| it.to_string());
-            match ctx.config.snippet_cap {
-                Some(cap) => {
-                    builder.insert_snippet(
-                        cap,
-                        insert_pos,
-                        format!("type $0Type{generic_params} = {ty};\n\n{indent}"),
-                    );
-                }
-                None => {
-                    builder.insert(
-                        insert_pos,
-                        format!("type Type{generic_params} = {ty};\n\n{indent}"),
-                    );
+            // FIXME: replace with a `ast::make` constructor
+            let new_ty = make::ty(&format!("Type{ty_args}")).clone_for_update();
+            ted::replace(target_ty.syntax(), new_ty.syntax());
+
+            // Insert new alias
+            let indent = IndentLevel::from_node(&node);
+            let ty_alias = make::ty_alias("Type", generic_params, None, None, Some((ty, None)))
+                .clone_for_update();
+            ted::insert_all(
+                ted::Position::before(node),
+                vec![
+                    ty_alias.syntax().clone().into(),
+                    make::tokens::whitespace(&format!("\n\n{indent}")).into(),
+                ],
+            );
+
+            if let Some(cap) = ctx.config.snippet_cap {
+                if let Some(name) = ty_alias.name() {
+                    edit.add_tabstop_before(cap, name);
                 }
             }
         },

crates/syntax/src/ast/make.rs

@@ -166,7 +166,7 @@ pub fn ty_alias(
     assignment: Option<(ast::Type, Option<ast::WhereClause>)>,
 ) -> ast::TypeAlias {
     let mut s = String::new();
-    s.push_str(&format!("type {} ", ident));
+    s.push_str(&format!("type {}", ident));
 
     if let Some(list) = generic_param_list {
         s.push_str(&list.to_string());
@@ -182,9 +182,9 @@ pub fn ty_alias(
 
     if let Some(exp) = assignment {
         if let Some(cl) = exp.1 {
-            s.push_str(&format!("= {} {}", &exp.0.to_string(), &cl.to_string()));
+            s.push_str(&format!(" = {} {}", &exp.0.to_string(), &cl.to_string()));
         } else {
-            s.push_str(&format!("= {}", &exp.0.to_string()));
+            s.push_str(&format!(" = {}", &exp.0.to_string()));
         }
     }