Migrate assists to format args captures, part 1

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

@@ -69,14 +69,14 @@ pub(crate) fn add_explicit_type(acc: &mut Assists, ctx: &AssistContext<'_>) -> O
     let inferred_type = ty.display_source_code(ctx.db(), module.into()).ok()?;
     acc.add(
         AssistId("add_explicit_type", AssistKind::RefactorRewrite),
-        format!("Insert explicit type `{}`", inferred_type),
+        format!("Insert explicit type `{inferred_type}`"),
         pat_range,
         |builder| match ascribed_ty {
             Some(ascribed_ty) => {
                 builder.replace(ascribed_ty.syntax().text_range(), inferred_type);
             }
             None => {
-                builder.insert(pat_range.end(), format!(": {}", inferred_type));
+                builder.insert(pat_range.end(), format!(": {inferred_type}"));
             }
         },
     )

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

@@ -35,16 +35,16 @@ pub(crate) fn add_return_type(acc: &mut Assists, ctx: &AssistContext<'_>) -> Opt
             match builder_edit_pos {
                 InsertOrReplace::Insert(insert_pos, needs_whitespace) => {
                     let preceeding_whitespace = if needs_whitespace { " " } else { "" };
-                    builder.insert(insert_pos, &format!("{}-> {} ", preceeding_whitespace, ty))
+                    builder.insert(insert_pos, &format!("{preceeding_whitespace}-> {ty} "))
                 }
                 InsertOrReplace::Replace(text_range) => {
-                    builder.replace(text_range, &format!("-> {}", ty))
+                    builder.replace(text_range, &format!("-> {ty}"))
                 }
             }
             if let FnType::Closure { wrap_expr: true } = fn_type {
                 cov_mark::hit!(wrap_closure_non_block_expr);
                 // `|x| x` becomes `|x| -> T x` which is invalid, so wrap it in a block
-                builder.replace(tail_expr.syntax().text_range(), &format!("{{{}}}", tail_expr));
+                builder.replace(tail_expr.syntax().text_range(), &format!("{{{tail_expr}}}"));
             }
         },
     )

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

@@ -93,12 +93,13 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext<'_>) -> Opti
             builder.trigger_signature_help();
             match ctx.config.snippet_cap {
                 Some(cap) => {
-                    let snip = format!("::<{}>", get_snippet_fish_head(number_of_arguments));
+                    let fish_head = get_snippet_fish_head(number_of_arguments);
+                    let snip = format!("::<{fish_head}>");
                     builder.insert_snippet(cap, ident.text_range().end(), snip)
                 }
                 None => {
                     let fish_head = std::iter::repeat("_").take(number_of_arguments).format(", ");
-                    let snip = format!("::<{}>", fish_head);
+                    let snip = format!("::<{fish_head}>");
                     builder.insert(ident.text_range().end(), snip);
                 }
             }
@@ -109,7 +110,7 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext<'_>) -> Opti
 /// This will create a snippet string with tabstops marked
 fn get_snippet_fish_head(number_of_arguments: usize) -> String {
     let mut fish_head = (1..number_of_arguments)
-        .format_with("", |i, f| f(&format_args!("${{{}:_}}, ", i)))
+        .format_with("", |i, f| f(&format_args!("${{{i}:_}}, ")))
         .to_string();
 
     // tabstop 0 is a special case and always the last one

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

@@ -123,20 +123,20 @@ pub(crate) fn apply_demorgan(acc: &mut Assists, ctx: &AssistContext<'_>) -> Opti
                     let lhs_range = lhs.syntax().text_range();
                     let not_lhs = invert_boolean_expression(lhs);
 
-                    edit.replace(lhs_range, format!("!({}", not_lhs.syntax().text()));
+                    edit.replace(lhs_range, format!("!({not_lhs}"));
                 }
 
                 if let Some(rhs) = terms.pop_back() {
                     let rhs_range = rhs.syntax().text_range();
                     let not_rhs = invert_boolean_expression(rhs);
 
-                    edit.replace(rhs_range, format!("{})", not_rhs.syntax().text()));
+                    edit.replace(rhs_range, format!("{not_rhs})"));
                 }
 
                 for term in terms {
                     let term_range = term.syntax().text_range();
                     let not_term = invert_boolean_expression(term);
-                    edit.replace(term_range, not_term.syntax().text());
+                    edit.replace(term_range, not_term.to_string());
                 }
             }
         },

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

@@ -127,10 +127,12 @@ pub(crate) fn auto_import(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<
         .sort_by_key(|import| Reverse(relevance_score(ctx, import, current_module.as_ref())));
 
     for import in proposed_imports {
+        let import_path = import.import_path;
+
         acc.add_group(
             &group_label,
             AssistId("auto_import", AssistKind::QuickFix),
-            format!("Import `{}`", import.import_path),
+            format!("Import `{import_path}`"),
             range,
             |builder| {
                 let scope = match scope.clone() {
@@ -138,7 +140,7 @@ pub(crate) fn auto_import(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<
                     ImportScope::Module(it) => ImportScope::Module(builder.make_mut(it)),
                     ImportScope::Block(it) => ImportScope::Block(builder.make_mut(it)),
                 };
-                insert_use(&scope, mod_path_to_ast(&import.import_path), &ctx.config.insert_use);
+                insert_use(&scope, mod_path_to_ast(&import_path), &ctx.config.insert_use);
             },
         );
     }

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

@@ -54,16 +54,17 @@ fn block_to_line(acc: &mut Assists, comment: ast::Comment) -> Option<()> {
 
             let indent_spaces = indentation.to_string();
             let output = lines
-                .map(|l| l.trim_start_matches(&indent_spaces))
-                .map(|l| {
+                .map(|line| {
+                    let line = line.trim_start_matches(&indent_spaces);
+
                     // Don't introduce trailing whitespace
-                    if l.is_empty() {
+                    if line.is_empty() {
                         line_prefix.to_string()
                     } else {
-                        format!("{} {}", line_prefix, l.trim_start_matches(&indent_spaces))
+                        format!("{line_prefix} {line}")
                     }
                 })
-                .join(&format!("\n{}", indent_spaces));
+                .join(&format!("\n{indent_spaces}"));
 
             edit.replace(target, output)
         },
@@ -96,7 +97,7 @@ fn line_to_block(acc: &mut Assists, comment: ast::Comment) -> Option<()> {
             let block_prefix =
                 CommentKind { shape: CommentShape::Block, ..comment.kind() }.prefix();
 
-            let output = format!("{}\n{}\n{}*/", block_prefix, block_comment_body, indentation);
+            let output = format!("{block_prefix}\n{block_comment_body}\n{indentation}*/");
 
             edit.replace(target, output)
         },

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

@@ -32,19 +32,19 @@ pub(crate) fn convert_integer_literal(acc: &mut Assists, ctx: &AssistContext<'_>
         }
 
         let mut converted = match target_radix {
-            Radix::Binary => format!("0b{:b}", value),
-            Radix::Octal => format!("0o{:o}", value),
+            Radix::Binary => format!("0b{value:b}"),
+            Radix::Octal => format!("0o{value:o}"),
             Radix::Decimal => value.to_string(),
-            Radix::Hexadecimal => format!("0x{:X}", value),
+            Radix::Hexadecimal => format!("0x{value:X}"),
         };
 
-        let label = format!("Convert {} to {}{}", literal, converted, suffix.unwrap_or_default());
-
         // Appends the type suffix back into the new literal if it exists.
         if let Some(suffix) = suffix {
             converted.push_str(suffix);
         }
 
+        let label = format!("Convert {literal} to {converted}");
+
         acc.add_group(
             &group_id,
             AssistId("convert_integer_literal", AssistKind::RefactorInline),

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

@@ -86,9 +86,9 @@ pub(crate) fn convert_into_to_from(acc: &mut Assists, ctx: &AssistContext<'_>) -
         impl_.syntax().text_range(),
         |builder| {
             builder.replace(src_type.syntax().text_range(), dest_type.to_string());
-            builder.replace(ast_trait.syntax().text_range(), format!("From<{}>", src_type));
+            builder.replace(ast_trait.syntax().text_range(), format!("From<{src_type}>"));
             builder.replace(into_fn_return.syntax().text_range(), "-> Self");
-            builder.replace(into_fn_params.syntax().text_range(), format!("(val: {})", src_type));
+            builder.replace(into_fn_params.syntax().text_range(), format!("(val: {src_type})"));
             builder.replace(into_fn_name.syntax().text_range(), "from");
 
             for s in selfs {

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

@@ -119,19 +119,19 @@ pub(crate) fn convert_for_loop_with_for_each(
             {
                 // We have either "for x in &col" and col implements a method called iter
                 //             or "for x in &mut col" and col implements a method called iter_mut
-                format_to!(buf, "{}.{}()", expr_behind_ref, method);
+                format_to!(buf, "{expr_behind_ref}.{method}()");
             } else if let ast::Expr::RangeExpr(..) = iterable {
                 // range expressions need to be parenthesized for the syntax to be correct
-                format_to!(buf, "({})", iterable);
+                format_to!(buf, "({iterable})");
             } else if impls_core_iter(&ctx.sema, &iterable) {
-                format_to!(buf, "{}", iterable);
+                format_to!(buf, "{iterable}");
             } else if let ast::Expr::RefExpr(_) = iterable {
-                format_to!(buf, "({}).into_iter()", iterable);
+                format_to!(buf, "({iterable}).into_iter()");
             } else {
-                format_to!(buf, "{}.into_iter()", iterable);
+                format_to!(buf, "{iterable}.into_iter()");
             }
 
-            format_to!(buf, ".for_each(|{}| {});", pat, body);
+            format_to!(buf, ".for_each(|{pat}| {body});");
 
             builder.replace(for_loop.syntax().text_range(), buf)
         },

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

@@ -80,7 +80,7 @@ fn binders_to_str(binders: &[(Name, bool)], addmut: bool) -> String {
         .map(
             |(ident, ismut)| {
                 if *ismut && addmut {
-                    format!("mut {}", ident)
+                    format!("mut {ident}")
                 } else {
                     ident.to_string()
                 }
@@ -93,7 +93,7 @@ fn binders_to_str(binders: &[(Name, bool)], addmut: bool) -> String {
     } else if binders.len() == 1 {
         vars
     } else {
-        format!("({})", vars)
+        format!("({vars})")
     }
 }
 
@@ -153,7 +153,7 @@ pub(crate) fn convert_let_else_to_match(acc: &mut Assists, ctx: &AssistContext<'
 
             let only_expr = let_else_block.statements().next().is_none();
             let branch2 = match &let_else_block.tail_expr() {
-                Some(tail) if only_expr => format!("{},", tail.syntax().text()),
+                Some(tail) if only_expr => format!("{tail},"),
                 _ => let_else_block.syntax().text().to_string(),
             };
             let replace = if binders.is_empty() {

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

@@ -226,7 +226,13 @@ fn edit_field_references(
 }
 
 fn generate_names(fields: impl Iterator<Item = ast::TupleField>) -> Vec<ast::Name> {
-    fields.enumerate().map(|(i, _)| ast::make::name(&format!("field{}", i + 1))).collect()
+    fields
+        .enumerate()
+        .map(|(i, _)| {
+            let idx = i + 1;
+            ast::make::name(&format!("field{idx}"))
+        })
+        .collect()
 }
 
 #[cfg(test)]

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

@@ -58,16 +58,16 @@ pub(crate) fn convert_two_arm_bool_match_to_matches_macro(
         target_range,
         |builder| {
             let mut arm_str = String::new();
-            if let Some(ref pat) = first_arm.pat() {
+            if let Some(pat) = &first_arm.pat() {
                 arm_str += &pat.to_string();
             }
-            if let Some(ref guard) = first_arm.guard() {
-                arm_str += &format!(" {}", &guard.to_string());
+            if let Some(guard) = &first_arm.guard() {
+                arm_str += &format!(" {guard}");
             }
             if invert_matches {
-                builder.replace(target_range, format!("!matches!({}, {})", expr, arm_str));
+                builder.replace(target_range, format!("!matches!({expr}, {arm_str})"));
             } else {
-                builder.replace(target_range, format!("matches!({}, {})", expr, arm_str));
+                builder.replace(target_range, format!("matches!({expr}, {arm_str})"));
             }
         },
     )

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

@@ -133,7 +133,7 @@ fn generate_name(
     _usages: &Option<UsageSearchResult>,
 ) -> String {
     // FIXME: detect if name already used
-    format!("_{}", index)
+    format!("_{index}")
 }
 
 enum RefType {
@@ -168,12 +168,12 @@ fn edit_tuple_assignment(
     let add_cursor = |text: &str| {
         // place cursor on first tuple item
         let first_tuple = &data.field_names[0];
-        text.replacen(first_tuple, &format!("$0{}", first_tuple), 1)
+        text.replacen(first_tuple, &format!("$0{first_tuple}"), 1)
     };
 
     // with sub_pattern: keep original tuple and add subpattern: `tup @ (_0, _1)`
     if in_sub_pattern {
-        let text = format!(" @ {}", tuple_pat);
+        let text = format!(" @ {tuple_pat}");
         match ctx.config.snippet_cap {
             Some(cap) => {
                 let snip = add_cursor(&text);
@@ -314,9 +314,9 @@ struct RefData {
 impl RefData {
     fn format(&self, field_name: &str) -> String {
         match (self.needs_deref, self.needs_parentheses) {
-            (true, true) => format!("(*{})", field_name),
-            (true, false) => format!("*{}", field_name),
-            (false, true) => format!("({})", field_name),
+            (true, true) => format!("(*{field_name})"),
+            (true, false) => format!("*{field_name}"),
+            (false, true) => format!("({field_name})"),
             (false, false) => field_name.to_string(),
         }
     }

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

@@ -181,7 +181,7 @@ fn make_function_name(semantics_scope: &hir::SemanticsScope<'_>) -> ast::NameRef
     let mut counter = 0;
     while names_in_scope.contains(&name) {
         counter += 1;
-        name = format!("{}{}", &default_name, counter)
+        name = format!("{default_name}{counter}")
     }
     make::name_ref(&name)
 }
@@ -1291,19 +1291,23 @@ fn make_call(ctx: &AssistContext<'_>, fun: &Function, indent: IndentLevel) -> St
     match fun.outliving_locals.as_slice() {
         [] => {}
         [var] => {
-            format_to!(buf, "let {}{} = ", mut_modifier(var), var.local.name(ctx.db()))
+            let modifier = mut_modifier(var);
+            let name = var.local.name(ctx.db());
+            format_to!(buf, "let {modifier}{name} = ")
         }
         vars => {
             buf.push_str("let (");
             let bindings = vars.iter().format_with(", ", |local, f| {
-                f(&format_args!("{}{}", mut_modifier(local), local.local.name(ctx.db())))
+                let modifier = mut_modifier(local);
+                let name = local.local.name(ctx.db());
+                f(&format_args!("{modifier}{name}"))
             });
-            format_to!(buf, "{}", bindings);
+            format_to!(buf, "{bindings}");
             buf.push_str(") = ");
         }
     }
 
-    format_to!(buf, "{}", expr);
+    format_to!(buf, "{expr}");
     let insert_comma = fun
         .body
         .parent()
@@ -1447,6 +1451,8 @@ fn format_function(
     new_indent: IndentLevel,
 ) -> String {
     let mut fn_def = String::new();
+
+    let fun_name = &fun.name;
     let params = fun.make_param_list(ctx, module);
     let ret_ty = fun.make_ret_ty(ctx, module);
     let body = make_body(ctx, old_indent, new_indent, fun);
@@ -1454,42 +1460,28 @@ fn format_function(
     let async_kw = if fun.control_flow.is_async { "async " } else { "" };
     let unsafe_kw = if fun.control_flow.is_unsafe { "unsafe " } else { "" };
     let (generic_params, where_clause) = make_generic_params_and_where_clause(ctx, fun);
+
+    format_to!(fn_def, "\n\n{new_indent}{const_kw}{async_kw}{unsafe_kw}");
     match ctx.config.snippet_cap {
-        Some(_) => format_to!(
-            fn_def,
-            "\n\n{}{}{}{}fn $0{}",
-            new_indent,
-            const_kw,
-            async_kw,
-            unsafe_kw,
-            fun.name,
-        ),
-        None => format_to!(
-            fn_def,
-            "\n\n{}{}{}{}fn {}",
-            new_indent,
-            const_kw,
-            async_kw,
-            unsafe_kw,
-            fun.name,
-        ),
+        Some(_) => format_to!(fn_def, "fn $0{fun_name}"),
+        None => format_to!(fn_def, "fn {fun_name}"),
     }
 
     if let Some(generic_params) = generic_params {
-        format_to!(fn_def, "{}", generic_params);
+        format_to!(fn_def, "{generic_params}");
     }
 
-    format_to!(fn_def, "{}", params);
+    format_to!(fn_def, "{params}");
 
     if let Some(ret_ty) = ret_ty {
-        format_to!(fn_def, " {}", ret_ty);
+        format_to!(fn_def, " {ret_ty}");
     }
 
     if let Some(where_clause) = where_clause {
-        format_to!(fn_def, " {}", where_clause);
+        format_to!(fn_def, " {where_clause}");
     }
 
-    format_to!(fn_def, " {}", body);
+    format_to!(fn_def, " {body}");
 
     fn_def
 }

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

@@ -127,7 +127,7 @@ pub(crate) fn extract_module(acc: &mut Assists, ctx: &AssistContext<'_>) -> Opti
             for item in items_to_be_processed {
                 let item = item.indent(IndentLevel(1));
                 let mut indented_item = String::new();
-                format_to!(indented_item, "{}{}", new_item_indent, item.to_string());
+                format_to!(indented_item, "{new_item_indent}{item}");
                 body_items.push(indented_item);
             }
 
@@ -137,30 +137,28 @@ pub(crate) fn extract_module(acc: &mut Assists, ctx: &AssistContext<'_>) -> Opti
                 let mut impl_body_def = String::new();
 
                 if let Some(self_ty) = impl_.self_ty() {
-                    format_to!(
-                        impl_body_def,
-                        "{}impl {} {{\n{}\n{}}}",
-                        old_item_indent + 1,
-                        self_ty.to_string(),
-                        body,
-                        old_item_indent + 1
-                    );
-
+                    {
+                        let impl_indent = old_item_indent + 1;
+                        format_to!(
+                            impl_body_def,
+                            "{impl_indent}impl {self_ty} {{\n{body}\n{impl_indent}}}",
+                        );
+                    }
                     body = impl_body_def;
 
                     // Add the import for enum/struct corresponding to given impl block
                     module.make_use_stmt_of_node_with_super(self_ty.syntax());
                     for item in module.use_items {
-                        let mut indented_item = String::new();
-                        format_to!(indented_item, "{}{}", old_item_indent + 1, item.to_string());
-                        body = format!("{}\n\n{}", indented_item, body);
+                        let item_indent = old_item_indent + 1;
+                        body = format!("{item_indent}{item}\n\n{body}");
                     }
                 }
             }
 
             let mut module_def = String::new();
 
-            format_to!(module_def, "mod {} {{\n{}\n{}}}", module.name, body, old_item_indent);
+            let module_name = module.name;
+            format_to!(module_def, "mod {module_name} {{\n{body}\n{old_item_indent}}}");
 
             let mut usages_to_be_updated_for_curr_file = vec![];
             for usages_to_be_updated_for_file in usages_to_be_processed {
@@ -199,7 +197,7 @@ pub(crate) fn extract_module(acc: &mut Assists, ctx: &AssistContext<'_>) -> Opti
                     builder.delete(range);
                 }
 
-                builder.insert(impl_.syntax().text_range().end(), format!("\n\n{}", module_def));
+                builder.insert(impl_.syntax().text_range().end(), format!("\n\n{module_def}"));
             } else {
                 builder.replace(module.text_range, module_def)
             }
@@ -343,9 +341,10 @@ impl Module {
                 && !self.text_range.contains_range(desc.text_range())
             {
                 if let Some(name_ref) = ast::NameRef::cast(desc) {
+                    let mod_name = self.name;
                     return Some((
                         name_ref.syntax().text_range(),
-                        format!("{}::{}", self.name, name_ref),
+                        format!("{mod_name}::{name_ref}"),
                     ));
                 }
             }

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

@@ -296,10 +296,14 @@ fn create_struct_def(
 
 fn update_variant(variant: &ast::Variant, generics: Option<ast::GenericParamList>) -> Option<()> {
     let name = variant.name()?;
-    let ty = generics
+    let generic_args = generics
         .filter(|generics| generics.generic_params().count() > 0)
-        .map(|generics| make::ty(&format!("{}{}", &name.text(), generics.to_generic_args())))
-        .unwrap_or_else(|| make::ty(&name.text()));
+        .map(|generics| generics.to_generic_args());
+    // FIXME: replace with a `ast::make` constructor
+    let ty = match generic_args {
+        Some(generic_args) => make::ty(&format!("{name}{generic_args}")),
+        None => make::ty(&name.text()),
+    };
 
     // change from a record to a tuple field list
     let tuple_field = make::tuple_field(None, ty);

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

@@ -1,8 +1,7 @@
 use either::Either;
 use ide_db::syntax_helpers::node_ext::walk_ty;
-use itertools::Itertools;
 use syntax::{
-    ast::{self, edit::IndentLevel, AstNode, HasGenericParams, HasName},
+    ast::{self, edit::IndentLevel, make, AstNode, HasGenericParams, HasName},
     match_ast,
 };
 
@@ -64,41 +63,29 @@ pub(crate) fn extract_type_alias(acc: &mut Assists, ctx: &AssistContext<'_>) ->
                 known_generics.extend(it.generic_params());
             }
             let generics = collect_used_generics(&ty, &known_generics);
+            let generic_params =
+                generics.map(|it| make::generic_param_list(it.into_iter().cloned()));
 
-            let replacement = if !generics.is_empty() {
-                format!(
-                    "Type<{}>",
-                    generics.iter().format_with(", ", |generic, f| {
-                        match generic {
-                            ast::GenericParam::ConstParam(cp) => f(&cp.name().unwrap()),
-                            ast::GenericParam::LifetimeParam(lp) => f(&lp.lifetime().unwrap()),
-                            ast::GenericParam::TypeParam(tp) => f(&tp.name().unwrap()),
-                        }
-                    })
-                )
-            } else {
-                String::from("Type")
-            };
+            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 generics = if !generics.is_empty() {
-                format!("<{}>", generics.iter().format(", "))
-            } else {
-                String::new()
-            };
+            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{} = {};\n\n{}", generics, ty, indent),
+                        format!("type $0Type{generic_params} = {ty};\n\n{indent}"),
                     );
                 }
                 None => {
                     builder.insert(
                         insert_pos,
-                        format!("type Type{} = {};\n\n{}", generics, ty, indent),
+                        format!("type Type{generic_params} = {ty};\n\n{indent}"),
                     );
                 }
             }
@@ -109,7 +96,7 @@ pub(crate) fn extract_type_alias(acc: &mut Assists, ctx: &AssistContext<'_>) ->
 fn collect_used_generics<'gp>(
     ty: &ast::Type,
     known_generics: &'gp [ast::GenericParam],
-) -> Vec<&'gp ast::GenericParam> {
+) -> Option<Vec<&'gp ast::GenericParam>> {
     // can't use a closure -> closure here cause lifetime inference fails for that
     fn find_lifetime(text: &str) -> impl Fn(&&ast::GenericParam) -> bool + '_ {
         move |gp: &&ast::GenericParam| match gp {
@@ -198,7 +185,8 @@ fn collect_used_generics<'gp>(
         ast::GenericParam::LifetimeParam(_) => 0,
         ast::GenericParam::TypeParam(_) => 1,
     });
-    generics
+
+    Some(generics).filter(|it| it.len() > 0)
 }
 
 #[cfg(test)]

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

@@ -91,13 +91,13 @@ pub(crate) fn extract_variable(acc: &mut Assists, ctx: &AssistContext<'_>) -> Op
 
             match anchor {
                 Anchor::Before(_) | Anchor::Replace(_) => {
-                    format_to!(buf, "let {}{} = {}", var_modifier, var_name, reference_modifier)
+                    format_to!(buf, "let {var_modifier}{var_name} = {reference_modifier}")
                 }
                 Anchor::WrapInBlock(_) => {
-                    format_to!(buf, "{{ let {} = {}", var_name, reference_modifier)
+                    format_to!(buf, "{{ let {var_name} = {reference_modifier}")
                 }
             };
-            format_to!(buf, "{}", to_extract.syntax());
+            format_to!(buf, "{to_extract}");
 
             if let Anchor::Replace(stmt) = anchor {
                 cov_mark::hit!(test_extract_var_expr_stmt);
@@ -107,8 +107,8 @@ pub(crate) fn extract_variable(acc: &mut Assists, ctx: &AssistContext<'_>) -> Op
                 match ctx.config.snippet_cap {
                     Some(cap) => {
                         let snip = buf.replace(
-                            &format!("let {}{}", var_modifier, var_name),
-                            &format!("let {}$0{}", var_modifier, var_name),
+                            &format!("let {var_modifier}{var_name}"),
+                            &format!("let {var_modifier}$0{var_name}"),
                         );
                         edit.replace_snippet(cap, expr_range, snip)
                     }
@@ -135,8 +135,8 @@ pub(crate) fn extract_variable(acc: &mut Assists, ctx: &AssistContext<'_>) -> Op
             match ctx.config.snippet_cap {
                 Some(cap) => {
                     let snip = buf.replace(
-                        &format!("let {}{}", var_modifier, var_name),
-                        &format!("let {}$0{}", var_modifier, var_name),
+                        &format!("let {var_modifier}{var_name}"),
+                        &format!("let {var_modifier}$0{var_name}"),
                     );
                     edit.insert_snippet(cap, offset, snip)
                 }

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

@@ -57,8 +57,8 @@ fn add_vis_to_referenced_module_def(acc: &mut Assists, ctx: &AssistContext<'_>)
         if current_module.krate() == target_module.krate() { "pub(crate)" } else { "pub" };
 
     let assist_label = match target_name {
-        None => format!("Change visibility to {}", missing_visibility),
-        Some(name) => format!("Change visibility of {} to {}", name, missing_visibility),
+        None => format!("Change visibility to {missing_visibility}"),
+        Some(name) => format!("Change visibility of {name} to {missing_visibility}"),
     };
 
     acc.add(AssistId("fix_visibility", AssistKind::QuickFix), assist_label, target, |builder| {
@@ -68,15 +68,15 @@ fn add_vis_to_referenced_module_def(acc: &mut Assists, ctx: &AssistContext<'_>)
                 Some(current_visibility) => builder.replace_snippet(
                     cap,
                     current_visibility.syntax().text_range(),
-                    format!("$0{}", missing_visibility),
+                    format!("$0{missing_visibility}"),
                 ),
-                None => builder.insert_snippet(cap, offset, format!("$0{} ", missing_visibility)),
+                None => builder.insert_snippet(cap, offset, format!("$0{missing_visibility} ")),
             },
             None => match current_visibility {
                 Some(current_visibility) => {
                     builder.replace(current_visibility.syntax().text_range(), missing_visibility)
                 }
-                None => builder.insert(offset, format!("{} ", missing_visibility)),
+                None => builder.insert(offset, format!("{missing_visibility} ")),
             },
         }
     })
@@ -114,7 +114,7 @@ fn add_vis_to_referenced_record_field(acc: &mut Assists, ctx: &AssistContext<'_>
 
     let target_name = record_field_def.name(ctx.db());
     let assist_label =
-        format!("Change visibility of {}.{} to {}", parent_name, target_name, missing_visibility);
+        format!("Change visibility of {parent_name}.{target_name} to {missing_visibility}");
 
     acc.add(AssistId("fix_visibility", AssistKind::QuickFix), assist_label, target, |builder| {
         builder.edit_file(target_file);
@@ -123,15 +123,15 @@ fn add_vis_to_referenced_record_field(acc: &mut Assists, ctx: &AssistContext<'_>
                 Some(current_visibility) => builder.replace_snippet(
                     cap,
                     current_visibility.syntax().text_range(),
-                    format!("$0{}", missing_visibility),
+                    format!("$0{missing_visibility}"),
                 ),
-                None => builder.insert_snippet(cap, offset, format!("$0{} ", missing_visibility)),
+                None => builder.insert_snippet(cap, offset, format!("$0{missing_visibility} ")),
             },
             None => match current_visibility {
                 Some(current_visibility) => {
                     builder.replace(current_visibility.syntax().text_range(), missing_visibility)
                 }
-                None => builder.insert(offset, format!("{} ", missing_visibility)),
+                None => builder.insert(offset, format!("{missing_visibility} ")),
             },
         }
     })