4 files changed, 29 insertions, 37 deletions

diff --git a/crates/ra_assists/src/handlers/add_custom_impl.rs b/crates/ra_assists/src/handlers/add_custom_impl.rs
index dd2bed25a..15f9b216b 100644
--- a/crates/ra_assists/src/handlers/add_custom_impl.rs
+++ b/crates/ra_assists/src/handlers/add_custom_impl.rs
@@ -1,17 +1,13 @@
-//! FIXME: write short doc here
-
-use join_to_string::join;
 use ra_syntax::{
     ast::{self, AstNode},
     Direction, SmolStr,
     SyntaxKind::{IDENT, WHITESPACE},
     TextRange, TextUnit,
 };
+use stdx::SepBy;
 
 use crate::{Assist, AssistCtx, AssistId};
 
-const DERIVE_TRAIT: &str = "derive";
-
 // Assist: add_custom_impl
 //
 // Adds impl block for derived trait.
@@ -38,7 +34,7 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
         .descendants_with_tokens()
         .filter(|t| t.kind() == IDENT)
         .find_map(|i| i.into_token())
-        .filter(|t| *t.text() == DERIVE_TRAIT)?
+        .filter(|t| *t.text() == "derive")?
         .text()
         .clone();
 
@@ -63,8 +59,7 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
             .filter(|t| t != trait_token.text())
             .collect::<Vec<SmolStr>>();
         let has_more_derives = !new_attr_input.is_empty();
-        let new_attr_input =
-            join(new_attr_input.iter()).separator(", ").surround_with("(", ")").to_string();
+        let new_attr_input = new_attr_input.iter().sep_by(", ").surround_with("(", ")").to_string();
         let new_attr_input_len = new_attr_input.len();
 
         let mut buf = String::new();
@@ -100,9 +95,10 @@ pub(crate) fn add_custom_impl(ctx: AssistCtx) -> Option<Assist> {
 
 #[cfg(test)]
 mod tests {
-    use super::*;
     use crate::helpers::{check_assist, check_assist_not_applicable};
 
+    use super::*;
+
     #[test]
     fn add_custom_impl_for_unique_input() {
         check_assist(
diff --git a/crates/ra_assists/src/handlers/add_impl.rs b/crates/ra_assists/src/handlers/add_impl.rs
index afae7d385..6622eadb2 100644
--- a/crates/ra_assists/src/handlers/add_impl.rs
+++ b/crates/ra_assists/src/handlers/add_impl.rs
@@ -1,9 +1,8 @@
-use format_buf::format;
-use join_to_string::join;
 use ra_syntax::{
     ast::{self, AstNode, NameOwner, TypeParamsOwner},
     TextUnit,
 };
+use stdx::{format_to, SepBy};
 
 use crate::{Assist, AssistCtx, AssistId};
 
@@ -36,7 +35,7 @@ pub(crate) fn add_impl(ctx: AssistCtx) -> Option<Assist> {
         let mut buf = String::new();
         buf.push_str("\n\nimpl");
         if let Some(type_params) = &type_params {
-            format!(buf, "{}", type_params.syntax());
+            format_to!(buf, "{}", type_params.syntax());
         }
         buf.push_str(" ");
         buf.push_str(name.text().as_str());
@@ -47,7 +46,9 @@ pub(crate) fn add_impl(ctx: AssistCtx) -> Option<Assist> {
                 .map(|it| it.text().clone());
             let type_params =
                 type_params.type_params().filter_map(|it| it.name()).map(|it| it.text().clone());
-            join(lifetime_params.chain(type_params)).surround_with("<", ">").to_buf(&mut buf);
+
+            let generic_params = lifetime_params.chain(type_params).sep_by(", ");
+            format_to!(buf, "<{}>", generic_params)
         }
         buf.push_str(" {\n");
         edit.set_cursor(start_offset + TextUnit::of_str(&buf));
diff --git a/crates/ra_assists/src/handlers/add_new.rs b/crates/ra_assists/src/handlers/add_new.rs
index 729a223e0..240b19fa3 100644
--- a/crates/ra_assists/src/handlers/add_new.rs
+++ b/crates/ra_assists/src/handlers/add_new.rs
@@ -1,14 +1,11 @@
-use std::fmt::Write;
-
-use format_buf::format;
 use hir::Adt;
-use join_to_string::join;
 use ra_syntax::{
     ast::{
         self, AstNode, NameOwner, StructKind, TypeAscriptionOwner, TypeParamsOwner, VisibilityOwner,
     },
     TextUnit, T,
 };
+use stdx::{format_to, SepBy};
 
 use crate::{Assist, AssistCtx, AssistId};
 
@@ -53,24 +50,22 @@ pub(crate) fn add_new(ctx: AssistCtx) -> Option<Assist> {
             buf.push('\n');
         }
 
-        let vis = strukt.visibility().map(|v| format!("{} ", v.syntax()));
+        let vis = strukt.visibility().map(|v| format!("{} ", v));
         let vis = vis.as_deref().unwrap_or("");
-        write!(&mut buf, "    {}fn new(", vis).unwrap();
-
-        join(field_list.fields().filter_map(|f| {
-            Some(format!("{}: {}", f.name()?.syntax().text(), f.ascribed_type()?.syntax().text()))
-        }))
-        .separator(", ")
-        .to_buf(&mut buf);
 
-        buf.push_str(") -> Self { Self {");
-
-        join(field_list.fields().filter_map(|f| Some(f.name()?.syntax().text())))
-            .separator(", ")
-            .surround_with(" ", " ")
-            .to_buf(&mut buf);
+        let params = field_list
+            .fields()
+            .filter_map(|f| {
+                Some(format!(
+                    "{}: {}",
+                    f.name()?.syntax().text(),
+                    f.ascribed_type()?.syntax().text()
+                ))
+            })
+            .sep_by(", ");
+        let fields = field_list.fields().filter_map(|f| f.name()).sep_by(", ");
 
-        buf.push_str("} }");
+        format_to!(buf, "    {}fn new({}) -> Self {{ Self {{ {} }} }}", vis, params, fields);
 
         let (start_offset, end_offset) = impl_def
             .and_then(|impl_def| {
@@ -103,7 +98,7 @@ fn generate_impl_text(strukt: &ast::StructDef, code: &str) -> String {
     let mut buf = String::with_capacity(code.len());
     buf.push_str("\n\nimpl");
     if let Some(type_params) = &type_params {
-        format!(buf, "{}", type_params.syntax());
+        format_to!(buf, "{}", type_params.syntax());
     }
     buf.push_str(" ");
     buf.push_str(strukt.name().unwrap().text().as_str());
@@ -114,10 +109,10 @@ fn generate_impl_text(strukt: &ast::StructDef, code: &str) -> String {
             .map(|it| it.text().clone());
         let type_params =
             type_params.type_params().filter_map(|it| it.name()).map(|it| it.text().clone());
-        join(lifetime_params.chain(type_params)).surround_with("<", ">").to_buf(&mut buf);
+        format_to!(buf, "<{}>", lifetime_params.chain(type_params).sep_by(", "))
     }
 
-    format!(&mut buf, " {{\n{}\n}}\n", code);
+    format_to!(buf, " {{\n{}\n}}\n", code);
 
     buf
 }
diff --git a/crates/ra_assists/src/handlers/introduce_variable.rs b/crates/ra_assists/src/handlers/introduce_variable.rs
index b453c51fb..1edbdc14c 100644
--- a/crates/ra_assists/src/handlers/introduce_variable.rs
+++ b/crates/ra_assists/src/handlers/introduce_variable.rs
@@ -1,4 +1,3 @@
-use format_buf::format;
 use ra_syntax::{
     ast::{self, AstNode},
     SyntaxKind::{
@@ -7,6 +6,7 @@ use ra_syntax::{
     },
     SyntaxNode, TextUnit,
 };
+use stdx::format_to;
 use test_utils::tested_by;
 
 use crate::{Assist, AssistCtx, AssistId};
@@ -52,7 +52,7 @@ pub(crate) fn introduce_variable(ctx: AssistCtx) -> Option<Assist> {
             buf.push_str("let var_name = ");
             TextUnit::of_str("let ")
         };
-        format!(buf, "{}", expr.syntax());
+        format_to!(buf, "{}", expr.syntax());
         let full_stmt = ast::ExprStmt::cast(anchor_stmt.clone());
         let is_full_stmt = if let Some(expr_stmt) = &full_stmt {
             Some(expr.syntax().clone()) == expr_stmt.expr().map(|e| e.syntax().clone())