23 files changed, 301 insertions, 306 deletions

diff --git a/crates/ra_assists/src/add_derive.rs b/crates/ra_assists/src/assists/add_derive.rs
index 9c88644df..9c88644df 100644
--- a/crates/ra_assists/src/add_derive.rs
+++ b/crates/ra_assists/src/assists/add_derive.rs
diff --git a/crates/ra_assists/src/add_explicit_type.rs b/crates/ra_assists/src/assists/add_explicit_type.rs
index 78f0f7f28..78f0f7f28 100644
--- a/crates/ra_assists/src/add_explicit_type.rs
+++ b/crates/ra_assists/src/assists/add_explicit_type.rs
diff --git a/crates/ra_assists/src/add_impl.rs b/crates/ra_assists/src/assists/add_impl.rs
index 4b61f4031..4b61f4031 100644
--- a/crates/ra_assists/src/add_impl.rs
+++ b/crates/ra_assists/src/assists/add_impl.rs
diff --git a/crates/ra_assists/src/add_missing_impl_members.rs b/crates/ra_assists/src/assists/add_missing_impl_members.rs
index cbeb7054f..22d20909d 100644
--- a/crates/ra_assists/src/add_missing_impl_members.rs
+++ b/crates/ra_assists/src/assists/add_missing_impl_members.rs
@@ -4,10 +4,7 @@ use ra_syntax::{
     SmolStr,
 };
 
-use crate::{
-    ast_editor::{AstBuilder, AstEditor},
-    Assist, AssistCtx, AssistId,
-};
+use crate::{ast_builder::Make, ast_editor::AstEditor, Assist, AssistCtx, AssistId};
 
 #[derive(PartialEq)]
 enum AddMissingImplMembersMode {
@@ -105,9 +102,7 @@ fn strip_docstring(item: ast::ImplItem) -> ast::ImplItem {
 fn add_body(fn_def: ast::FnDef) -> ast::FnDef {
     let mut ast_editor = AstEditor::new(fn_def.clone());
     if fn_def.body().is_none() {
-        ast_editor.set_body(&AstBuilder::<ast::Block>::single_expr(
-            &AstBuilder::<ast::Expr>::unimplemented(),
-        ));
+        ast_editor.set_body(&Make::<ast::Block>::single_expr(Make::<ast::Expr>::unimplemented()));
     }
     ast_editor.ast().to_owned()
 }
diff --git a/crates/ra_assists/src/auto_import.rs b/crates/ra_assists/src/assists/auto_import.rs
index 5aae98546..5aae98546 100644
--- a/crates/ra_assists/src/auto_import.rs
+++ b/crates/ra_assists/src/assists/auto_import.rs
diff --git a/crates/ra_assists/src/change_visibility.rs b/crates/ra_assists/src/assists/change_visibility.rs
index 60c74debc..60c74debc 100644
--- a/crates/ra_assists/src/change_visibility.rs
+++ b/crates/ra_assists/src/assists/change_visibility.rs
diff --git a/crates/ra_assists/src/fill_match_arms.rs b/crates/ra_assists/src/assists/fill_match_arms.rs
index f59062bb9..817433526 100644
--- a/crates/ra_assists/src/fill_match_arms.rs
+++ b/crates/ra_assists/src/assists/fill_match_arms.rs
@@ -3,7 +3,7 @@ use std::iter;
 use hir::{db::HirDatabase, Adt, HasSource};
 use ra_syntax::ast::{self, AstNode, NameOwner};
 
-use crate::{ast_editor::AstBuilder, Assist, AssistCtx, AssistId};
+use crate::{ast_builder::Make, Assist, AssistCtx, AssistId};
 
 pub(crate) fn fill_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let match_expr = ctx.node_at_offset::<ast::MatchExpr>()?;
@@ -29,13 +29,10 @@ pub(crate) fn fill_match_arms(mut ctx: AssistCtx<impl HirDatabase>) -> Option<As
 
     ctx.add_action(AssistId("fill_match_arms"), "fill match arms", |edit| {
         let variants = variant_list.variants();
-        let arms = variants.filter_map(build_pat).map(|pat| {
-            AstBuilder::<ast::MatchArm>::from_pieces(
-                iter::once(pat),
-                &AstBuilder::<ast::Expr>::unit(),
-            )
-        });
-        let new_arm_list = AstBuilder::<ast::MatchArmList>::from_arms(arms);
+        let arms = variants
+            .filter_map(build_pat)
+            .map(|pat| Make::<ast::MatchArm>::from(iter::once(pat), Make::<ast::Expr>::unit()));
+        let new_arm_list = Make::<ast::MatchArmList>::from_arms(arms);
 
         edit.target(match_expr.syntax().text_range());
         edit.set_cursor(expr.syntax().text_range().start());
@@ -66,21 +63,21 @@ fn resolve_enum_def(
 }
 
 fn build_pat(var: ast::EnumVariant) -> Option<ast::Pat> {
-    let path = &AstBuilder::<ast::Path>::from_pieces(var.parent_enum().name()?, var.name()?);
+    let path = Make::<ast::Path>::from(var.parent_enum().name()?, var.name()?);
 
     let pat: ast::Pat = match var.kind() {
         ast::StructKind::Tuple(field_list) => {
-            let pats = iter::repeat(AstBuilder::<ast::PlaceholderPat>::placeholder().into())
+            let pats = iter::repeat(Make::<ast::PlaceholderPat>::placeholder().into())
                 .take(field_list.fields().count());
-            AstBuilder::<ast::TupleStructPat>::from_pieces(path, pats).into()
+            Make::<ast::TupleStructPat>::from(path, pats).into()
         }
         ast::StructKind::Named(field_list) => {
             let pats = field_list
                 .fields()
-                .map(|f| AstBuilder::<ast::BindPat>::from_name(&f.name().unwrap()).into());
-            AstBuilder::<ast::RecordPat>::from_pieces(path, pats).into()
+                .map(|f| Make::<ast::BindPat>::from_name(f.name().unwrap()).into());
+            Make::<ast::RecordPat>::from(path, pats).into()
         }
-        ast::StructKind::Unit => AstBuilder::<ast::PathPat>::from_path(path).into(),
+        ast::StructKind::Unit => Make::<ast::PathPat>::from_path(path).into(),
     };
 
     Some(pat)
diff --git a/crates/ra_assists/src/flip_binexpr.rs b/crates/ra_assists/src/assists/flip_binexpr.rs
index b55b36a8e..b55b36a8e 100644
--- a/crates/ra_assists/src/flip_binexpr.rs
+++ b/crates/ra_assists/src/assists/flip_binexpr.rs
diff --git a/crates/ra_assists/src/flip_comma.rs b/crates/ra_assists/src/assists/flip_comma.rs
index 5ee7561bc..5ee7561bc 100644
--- a/crates/ra_assists/src/flip_comma.rs
+++ b/crates/ra_assists/src/assists/flip_comma.rs
diff --git a/crates/ra_assists/src/inline_local_variable.rs b/crates/ra_assists/src/assists/inline_local_variable.rs
index eedb29199..eedb29199 100644
--- a/crates/ra_assists/src/inline_local_variable.rs
+++ b/crates/ra_assists/src/assists/inline_local_variable.rs
diff --git a/crates/ra_assists/src/introduce_variable.rs b/crates/ra_assists/src/assists/introduce_variable.rs
index 470ffe120..470ffe120 100644
--- a/crates/ra_assists/src/introduce_variable.rs
+++ b/crates/ra_assists/src/assists/introduce_variable.rs
diff --git a/crates/ra_assists/src/merge_match_arms.rs b/crates/ra_assists/src/assists/merge_match_arms.rs
index 3b6a99895..3b6a99895 100644
--- a/crates/ra_assists/src/merge_match_arms.rs
+++ b/crates/ra_assists/src/assists/merge_match_arms.rs
diff --git a/crates/ra_assists/src/move_bounds.rs b/crates/ra_assists/src/assists/move_bounds.rs
index 526de1d98..6fd2fb72b 100644
--- a/crates/ra_assists/src/move_bounds.rs
+++ b/crates/ra_assists/src/assists/move_bounds.rs
@@ -6,7 +6,7 @@ use ra_syntax::{
     TextRange,
 };
 
-use crate::{ast_editor::AstBuilder, Assist, AssistCtx, AssistId};
+use crate::{ast_builder::Make, Assist, AssistCtx, AssistId};
 
 pub(crate) fn move_bounds_to_where_clause(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     let type_param_list = ctx.node_at_offset::<ast::TypeParamList>()?;
@@ -52,7 +52,7 @@ pub(crate) fn move_bounds_to_where_clause(mut ctx: AssistCtx<impl HirDatabase>)
             }
 
             let predicates = type_params.iter().filter_map(build_predicate);
-            let where_clause = AstBuilder::<ast::WhereClause>::from_predicates(predicates);
+            let where_clause = Make::<ast::WhereClause>::from_predicates(predicates);
 
             let to_insert = match anchor.prev_sibling_or_token() {
                 Some(ref elem) if elem.kind() == WHITESPACE => {
@@ -69,9 +69,8 @@ pub(crate) fn move_bounds_to_where_clause(mut ctx: AssistCtx<impl HirDatabase>)
 }
 
 fn build_predicate(param: &ast::TypeParam) -> Option<ast::WherePred> {
-    let path = AstBuilder::<ast::Path>::from_name(param.name()?);
-    let predicate =
-        AstBuilder::<ast::WherePred>::from_pieces(path, param.type_bound_list()?.bounds());
+    let path = Make::<ast::Path>::from_name(param.name()?);
+    let predicate = Make::<ast::WherePred>::from(path, param.type_bound_list()?.bounds());
     Some(predicate)
 }
 
diff --git a/crates/ra_assists/src/move_guard.rs b/crates/ra_assists/src/assists/move_guard.rs
index 699221e33..699221e33 100644
--- a/crates/ra_assists/src/move_guard.rs
+++ b/crates/ra_assists/src/assists/move_guard.rs
diff --git a/crates/ra_assists/src/raw_string.rs b/crates/ra_assists/src/assists/raw_string.rs
index 965a64c98..965a64c98 100644
--- a/crates/ra_assists/src/raw_string.rs
+++ b/crates/ra_assists/src/assists/raw_string.rs
diff --git a/crates/ra_assists/src/remove_dbg.rs b/crates/ra_assists/src/assists/remove_dbg.rs
index 870133fda..870133fda 100644
--- a/crates/ra_assists/src/remove_dbg.rs
+++ b/crates/ra_assists/src/assists/remove_dbg.rs
diff --git a/crates/ra_assists/src/replace_if_let_with_match.rs b/crates/ra_assists/src/assists/replace_if_let_with_match.rs
index 401835c57..401835c57 100644
--- a/crates/ra_assists/src/replace_if_let_with_match.rs
+++ b/crates/ra_assists/src/assists/replace_if_let_with_match.rs
diff --git a/crates/ra_assists/src/split_import.rs b/crates/ra_assists/src/assists/split_import.rs
index 2c1edddb9..2c1edddb9 100644
--- a/crates/ra_assists/src/split_import.rs
+++ b/crates/ra_assists/src/assists/split_import.rs
diff --git a/crates/ra_assists/src/ast_builder.rs b/crates/ra_assists/src/ast_builder.rs
new file mode 100644
index 000000000..9a62b96b3
--- /dev/null
+++ b/crates/ra_assists/src/ast_builder.rs
@@ -0,0 +1,218 @@
+use itertools::Itertools;
+
+use ra_syntax::{ast, AstNode, SourceFile};
+
+pub struct Make<N: AstNode> {
+    _phantom: std::marker::PhantomData<N>,
+}
+
+impl Make<ast::RecordField> {
+    pub fn from(name: ast::NameRef, expr: Option<ast::Expr>) -> ast::RecordField {
+        match expr {
+            Some(expr) => Self::from_text(&format!("{}: {}", name.syntax(), expr.syntax())),
+            None => Self::from_text(&name.syntax().to_string()),
+        }
+    }
+
+    fn from_text(text: &str) -> ast::RecordField {
+        ast_node_from_file_text(&format!("fn f() {{ S {{ {}, }} }}", text))
+    }
+}
+
+impl Make<ast::Block> {
+    pub fn single_expr(e: ast::Expr) -> ast::Block {
+        Self::from_text(&format!("{{ {} }}", e.syntax()))
+    }
+
+    fn from_text(text: &str) -> ast::Block {
+        ast_node_from_file_text(&format!("fn f() {}", text))
+    }
+}
+
+impl Make<ast::Expr> {
+    pub fn unit() -> ast::Expr {
+        Self::from_text("()")
+    }
+
+    pub fn unimplemented() -> ast::Expr {
+        Self::from_text("unimplemented!()")
+    }
+
+    fn from_text(text: &str) -> ast::Expr {
+        ast_node_from_file_text(&format!("const C: () = {};", text))
+    }
+}
+
+impl Make<ast::NameRef> {
+    pub fn from(text: &str) -> ast::NameRef {
+        ast_node_from_file_text(&format!("fn f() {{ {}; }}", text))
+    }
+}
+
+impl Make<ast::Path> {
+    pub fn from_name(name: ast::Name) -> ast::Path {
+        let name = name.syntax().to_string();
+        Self::from_text(name.as_str())
+    }
+
+    pub fn from(enum_name: ast::Name, var_name: ast::Name) -> ast::Path {
+        Self::from_text(&format!("{}::{}", enum_name.syntax(), var_name.syntax()))
+    }
+
+    fn from_text(text: &str) -> ast::Path {
+        ast_node_from_file_text(text)
+    }
+}
+
+impl Make<ast::BindPat> {
+    pub fn from_name(name: ast::Name) -> ast::BindPat {
+        Self::from_text(name.text())
+    }
+
+    fn from_text(text: &str) -> ast::BindPat {
+        ast_node_from_file_text(&format!("fn f({}: ())", text))
+    }
+}
+
+impl Make<ast::PlaceholderPat> {
+    pub fn placeholder() -> ast::PlaceholderPat {
+        Self::from_text("_")
+    }
+
+    fn from_text(text: &str) -> ast::PlaceholderPat {
+        ast_node_from_file_text(&format!("fn f({}: ())", text))
+    }
+}
+
+impl Make<ast::TupleStructPat> {
+    pub fn from(path: ast::Path, pats: impl Iterator<Item = ast::Pat>) -> ast::TupleStructPat {
+        let pats_str = pats.map(|p| p.syntax().to_string()).collect::<Vec<_>>().join(", ");
+        Self::from_text(&format!("{}({})", path.syntax(), pats_str))
+    }
+
+    fn from_text(text: &str) -> ast::TupleStructPat {
+        ast_node_from_file_text(&format!("fn f({}: ())", text))
+    }
+}
+
+impl Make<ast::RecordPat> {
+    pub fn from(path: ast::Path, pats: impl Iterator<Item = ast::Pat>) -> ast::RecordPat {
+        let pats_str = pats.map(|p| p.syntax().to_string()).collect::<Vec<_>>().join(", ");
+        Self::from_text(&format!("{}{{ {} }}", path.syntax(), pats_str))
+    }
+
+    fn from_text(text: &str) -> ast::RecordPat {
+        ast_node_from_file_text(&format!("fn f({}: ())", text))
+    }
+}
+
+impl Make<ast::PathPat> {
+    pub fn from_path(path: ast::Path) -> ast::PathPat {
+        let path_str = path.syntax().text().to_string();
+        Self::from_text(path_str.as_str())
+    }
+
+    fn from_text(text: &str) -> ast::PathPat {
+        ast_node_from_file_text(&format!("fn f({}: ())", text))
+    }
+}
+
+impl Make<ast::MatchArm> {
+    pub fn from(pats: impl Iterator<Item = ast::Pat>, expr: ast::Expr) -> ast::MatchArm {
+        let pats_str = pats.map(|p| p.syntax().to_string()).join(" | ");
+        Self::from_text(&format!("{} => {}", pats_str, expr.syntax()))
+    }
+
+    fn from_text(text: &str) -> ast::MatchArm {
+        ast_node_from_file_text(&format!("fn f() {{ match () {{{}}} }}", text))
+    }
+}
+
+impl Make<ast::MatchArmList> {
+    pub fn from_arms(arms: impl Iterator<Item = ast::MatchArm>) -> ast::MatchArmList {
+        let arms_str = arms.map(|arm| format!("\n    {}", arm.syntax())).join(",");
+        Self::from_text(&format!("{},\n", arms_str))
+    }
+
+    fn from_text(text: &str) -> ast::MatchArmList {
+        ast_node_from_file_text(&format!("fn f() {{ match () {{{}}} }}", text))
+    }
+}
+
+impl Make<ast::WherePred> {
+    pub fn from(path: ast::Path, bounds: impl Iterator<Item = ast::TypeBound>) -> ast::WherePred {
+        let bounds = bounds.map(|b| b.syntax().to_string()).collect::<Vec<_>>().join(" + ");
+        Self::from_text(&format!("{}: {}", path.syntax(), bounds))
+    }
+
+    fn from_text(text: &str) -> ast::WherePred {
+        ast_node_from_file_text(&format!("fn f() where {} {{ }}", text))
+    }
+}
+
+impl Make<ast::WhereClause> {
+    pub fn from_predicates(preds: impl Iterator<Item = ast::WherePred>) -> ast::WhereClause {
+        let preds = preds.map(|p| p.syntax().to_string()).collect::<Vec<_>>().join(", ");
+        Self::from_text(preds.as_str())
+    }
+
+    fn from_text(text: &str) -> ast::WhereClause {
+        ast_node_from_file_text(&format!("fn f() where {} {{ }}", text))
+    }
+}
+
+fn ast_node_from_file_text<N: AstNode>(text: &str) -> N {
+    let parse = SourceFile::parse(text);
+    let res = parse.tree().syntax().descendants().find_map(N::cast).unwrap();
+    res
+}
+
+pub(crate) mod tokens {
+    use once_cell::sync::Lazy;
+    use ra_syntax::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
+
+    static SOURCE_FILE: Lazy<Parse<SourceFile>> = Lazy::new(|| SourceFile::parse(",\n; ;"));
+
+    pub(crate) fn comma() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == T![,])
+            .unwrap()
+    }
+
+    pub(crate) fn single_space() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == " ")
+            .unwrap()
+    }
+
+    #[allow(unused)]
+    pub(crate) fn single_newline() -> SyntaxToken {
+        SOURCE_FILE
+            .tree()
+            .syntax()
+            .descendants_with_tokens()
+            .filter_map(|it| it.into_token())
+            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == "\n")
+            .unwrap()
+    }
+
+    pub(crate) struct WsBuilder(SourceFile);
+
+    impl WsBuilder {
+        pub(crate) fn new(text: &str) -> WsBuilder {
+            WsBuilder(SourceFile::parse(text).ok().unwrap())
+        }
+        pub(crate) fn ws(&self) -> SyntaxToken {
+            self.0.syntax().first_child_or_token().unwrap().into_token().unwrap()
+        }
+    }
+
+}
diff --git a/crates/ra_assists/src/ast_editor.rs b/crates/ra_assists/src/ast_editor.rs
index cf32ea52d..55c0aa59f 100644
--- a/crates/ra_assists/src/ast_editor.rs
+++ b/crates/ra_assists/src/ast_editor.rs
@@ -1,18 +1,18 @@
 use std::{iter, ops::RangeInclusive};
 
 use arrayvec::ArrayVec;
-use itertools::Itertools;
 
-use hir::Name;
 use ra_fmt::leading_indent;
 use ra_syntax::{
     algo::{insert_children, replace_children},
-    ast, AstNode, Direction, InsertPosition, SourceFile, SyntaxElement,
+    ast, AstNode, Direction, InsertPosition, SyntaxElement,
     SyntaxKind::*,
     T,
 };
 use ra_text_edit::TextEditBuilder;
 
+use crate::ast_builder::tokens;
+
 pub struct AstEditor<N: AstNode> {
     original_ast: N,
     ast: N,
@@ -240,228 +240,3 @@ impl AstEditor<ast::FnDef> {
         self.ast = self.replace_children(replace_range, to_insert.into_iter())
     }
 }
-
-pub struct AstBuilder<N: AstNode> {
-    _phantom: std::marker::PhantomData<N>,
-}
-
-impl AstBuilder<ast::RecordField> {
-    pub fn from_name(name: &Name) -> ast::RecordField {
-        ast_node_from_file_text(&format!("fn f() {{ S {{ {}: (), }} }}", name))
-    }
-
-    fn from_text(text: &str) -> ast::RecordField {
-        ast_node_from_file_text(&format!("fn f() {{ S {{ {}, }} }}", text))
-    }
-
-    pub fn from_pieces(name: &ast::NameRef, expr: Option<&ast::Expr>) -> ast::RecordField {
-        match expr {
-            Some(expr) => Self::from_text(&format!("{}: {}", name.syntax(), expr.syntax())),
-            None => Self::from_text(&name.syntax().to_string()),
-        }
-    }
-}
-
-impl AstBuilder<ast::Block> {
-    fn from_text(text: &str) -> ast::Block {
-        ast_node_from_file_text(&format!("fn f() {}", text))
-    }
-
-    pub fn single_expr(e: &ast::Expr) -> ast::Block {
-        Self::from_text(&format!("{{ {} }}", e.syntax()))
-    }
-}
-
-impl AstBuilder<ast::Expr> {
-    fn from_text(text: &str) -> ast::Expr {
-        ast_node_from_file_text(&format!("const C: () = {};", text))
-    }
-
-    pub fn unit() -> ast::Expr {
-        Self::from_text("()")
-    }
-
-    pub fn unimplemented() -> ast::Expr {
-        Self::from_text("unimplemented!()")
-    }
-}
-
-impl AstBuilder<ast::NameRef> {
-    pub fn new(text: &str) -> ast::NameRef {
-        ast_node_from_file_text(&format!("fn f() {{ {}; }}", text))
-    }
-}
-
-impl AstBuilder<ast::Path> {
-    fn from_text(text: &str) -> ast::Path {
-        ast_node_from_file_text(text)
-    }
-
-    pub fn from_name(name: ast::Name) -> ast::Path {
-        let name = name.syntax().to_string();
-        Self::from_text(name.as_str())
-    }
-
-    pub fn from_pieces(enum_name: ast::Name, var_name: ast::Name) -> ast::Path {
-        Self::from_text(&format!("{}::{}", enum_name.syntax(), var_name.syntax()))
-    }
-}
-
-impl AstBuilder<ast::BindPat> {
-    fn from_text(text: &str) -> ast::BindPat {
-        ast_node_from_file_text(&format!("fn f({}: ())", text))
-    }
-
-    pub fn from_name(name: &ast::Name) -> ast::BindPat {
-        Self::from_text(name.text())
-    }
-}
-
-impl AstBuilder<ast::PlaceholderPat> {
-    fn from_text(text: &str) -> ast::PlaceholderPat {
-        ast_node_from_file_text(&format!("fn f({}: ())", text))
-    }
-
-    pub fn placeholder() -> ast::PlaceholderPat {
-        Self::from_text("_")
-    }
-}
-
-impl AstBuilder<ast::TupleStructPat> {
-    fn from_text(text: &str) -> ast::TupleStructPat {
-        ast_node_from_file_text(&format!("fn f({}: ())", text))
-    }
-
-    pub fn from_pieces(
-        path: &ast::Path,
-        pats: impl Iterator<Item = ast::Pat>,
-    ) -> ast::TupleStructPat {
-        let pats_str = pats.map(|p| p.syntax().to_string()).collect::<Vec<_>>().join(", ");
-        Self::from_text(&format!("{}({})", path.syntax(), pats_str))
-    }
-}
-
-impl AstBuilder<ast::RecordPat> {
-    fn from_text(text: &str) -> ast::RecordPat {
-        ast_node_from_file_text(&format!("fn f({}: ())", text))
-    }
-
-    pub fn from_pieces(path: &ast::Path, pats: impl Iterator<Item = ast::Pat>) -> ast::RecordPat {
-        let pats_str = pats.map(|p| p.syntax().to_string()).collect::<Vec<_>>().join(", ");
-        Self::from_text(&format!("{}{{ {} }}", path.syntax(), pats_str))
-    }
-}
-
-impl AstBuilder<ast::PathPat> {
-    fn from_text(text: &str) -> ast::PathPat {
-        ast_node_from_file_text(&format!("fn f({}: ())", text))
-    }
-
-    pub fn from_path(path: &ast::Path) -> ast::PathPat {
-        let path_str = path.syntax().text().to_string();
-        Self::from_text(path_str.as_str())
-    }
-}
-
-impl AstBuilder<ast::MatchArm> {
-    fn from_text(text: &str) -> ast::MatchArm {
-        ast_node_from_file_text(&format!("fn f() {{ match () {{{}}} }}", text))
-    }
-
-    pub fn from_pieces(pats: impl Iterator<Item = ast::Pat>, expr: &ast::Expr) -> ast::MatchArm {
-        let pats_str = pats.map(|p| p.syntax().to_string()).join(" | ");
-        Self::from_text(&format!("{} => {}", pats_str, expr.syntax()))
-    }
-}
-
-impl AstBuilder<ast::MatchArmList> {
-    fn from_text(text: &str) -> ast::MatchArmList {
-        ast_node_from_file_text(&format!("fn f() {{ match () {{{}}} }}", text))
-    }
-
-    pub fn from_arms(arms: impl Iterator<Item = ast::MatchArm>) -> ast::MatchArmList {
-        let arms_str = arms.map(|arm| format!("\n    {}", arm.syntax())).join(",");
-        Self::from_text(&format!("{},\n", arms_str))
-    }
-}
-
-impl AstBuilder<ast::WherePred> {
-    fn from_text(text: &str) -> ast::WherePred {
-        ast_node_from_file_text(&format!("fn f() where {} {{ }}", text))
-    }
-
-    pub fn from_pieces(
-        path: ast::Path,
-        bounds: impl Iterator<Item = ast::TypeBound>,
-    ) -> ast::WherePred {
-        let bounds = bounds.map(|b| b.syntax().to_string()).collect::<Vec<_>>().join(" + ");
-        Self::from_text(&format!("{}: {}", path.syntax(), bounds))
-    }
-}
-
-impl AstBuilder<ast::WhereClause> {
-    fn from_text(text: &str) -> ast::WhereClause {
-        ast_node_from_file_text(&format!("fn f() where {} {{ }}", text))
-    }
-
-    pub fn from_predicates(preds: impl Iterator<Item = ast::WherePred>) -> ast::WhereClause {
-        let preds = preds.map(|p| p.syntax().to_string()).collect::<Vec<_>>().join(", ");
-        Self::from_text(preds.as_str())
-    }
-}
-
-fn ast_node_from_file_text<N: AstNode>(text: &str) -> N {
-    let parse = SourceFile::parse(text);
-    let res = parse.tree().syntax().descendants().find_map(N::cast).unwrap();
-    res
-}
-
-mod tokens {
-    use once_cell::sync::Lazy;
-    use ra_syntax::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
-
-    static SOURCE_FILE: Lazy<Parse<SourceFile>> = Lazy::new(|| SourceFile::parse(",\n; ;"));
-
-    pub(crate) fn comma() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == T![,])
-            .unwrap()
-    }
-
-    pub(crate) fn single_space() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == " ")
-            .unwrap()
-    }
-
-    #[allow(unused)]
-    pub(crate) fn single_newline() -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == WHITESPACE && it.text().as_str() == "\n")
-            .unwrap()
-    }
-
-    pub(crate) struct WsBuilder(SourceFile);
-
-    impl WsBuilder {
-        pub(crate) fn new(text: &str) -> WsBuilder {
-            WsBuilder(SourceFile::parse(text).ok().unwrap())
-        }
-        pub(crate) fn ws(&self) -> SyntaxToken {
-            self.0.syntax().first_child_or_token().unwrap().into_token().unwrap()
-        }
-    }
-
-}
diff --git a/crates/ra_assists/src/lib.rs b/crates/ra_assists/src/lib.rs
index 756acf415..71b017076 100644
--- a/crates/ra_assists/src/lib.rs
+++ b/crates/ra_assists/src/lib.rs
@@ -8,6 +8,7 @@
 mod assist_ctx;
 mod marks;
 pub mod ast_editor;
+pub mod ast_builder;
 
 use itertools::Itertools;
 
@@ -17,6 +18,7 @@ use ra_syntax::{TextRange, TextUnit};
 use ra_text_edit::TextEdit;
 
 pub(crate) use crate::assist_ctx::{Assist, AssistCtx};
+pub use crate::assists::auto_import::auto_import_text_edit;
 
 /// Unique identifier of the assist, should not be shown to the user
 /// directly.
@@ -46,7 +48,7 @@ where
     H: HirDatabase + 'static,
 {
     AssistCtx::with_ctx(db, range, false, |ctx| {
-        all_assists()
+        assists::all()
             .iter()
             .filter_map(|f| f(ctx.clone()))
             .map(|a| match a {
@@ -68,7 +70,7 @@ where
     use std::cmp::Ordering;
 
     AssistCtx::with_ctx(db, range, true, |ctx| {
-        let mut a = all_assists()
+        let mut a = assists::all()
             .iter()
             .filter_map(|f| f(ctx.clone()))
             .map(|a| match a {
@@ -86,51 +88,56 @@ where
     })
 }
 
-mod add_derive;
-mod add_explicit_type;
-mod add_impl;
-mod flip_comma;
-mod flip_binexpr;
-mod change_visibility;
-mod fill_match_arms;
-mod merge_match_arms;
-mod introduce_variable;
-mod inline_local_variable;
-mod raw_string;
-mod replace_if_let_with_match;
-mod split_import;
-mod remove_dbg;
-pub mod auto_import;
-mod add_missing_impl_members;
-mod move_guard;
-mod move_bounds;
-
-fn all_assists<DB: HirDatabase>() -> &'static [fn(AssistCtx<DB>) -> Option<Assist>] {
-    &[
-        add_derive::add_derive,
-        add_explicit_type::add_explicit_type,
-        add_impl::add_impl,
-        change_visibility::change_visibility,
-        fill_match_arms::fill_match_arms,
-        merge_match_arms::merge_match_arms,
-        flip_comma::flip_comma,
-        flip_binexpr::flip_binexpr,
-        introduce_variable::introduce_variable,
-        replace_if_let_with_match::replace_if_let_with_match,
-        split_import::split_import,
-        remove_dbg::remove_dbg,
-        auto_import::auto_import,
-        add_missing_impl_members::add_missing_impl_members,
-        add_missing_impl_members::add_missing_default_members,
-        inline_local_variable::inline_local_varialbe,
-        move_guard::move_guard_to_arm_body,
-        move_guard::move_arm_cond_to_match_guard,
-        move_bounds::move_bounds_to_where_clause,
-        raw_string::add_hash,
-        raw_string::make_raw_string,
-        raw_string::make_usual_string,
-        raw_string::remove_hash,
-    ]
+mod assists {
+    use crate::{Assist, AssistCtx};
+    use hir::db::HirDatabase;
+
+    mod add_derive;
+    mod add_explicit_type;
+    mod add_impl;
+    mod flip_comma;
+    mod flip_binexpr;
+    mod change_visibility;
+    mod fill_match_arms;
+    mod merge_match_arms;
+    mod introduce_variable;
+    mod inline_local_variable;
+    mod raw_string;
+    mod replace_if_let_with_match;
+    mod split_import;
+    mod remove_dbg;
+    pub(crate) mod auto_import;
+    mod add_missing_impl_members;
+    mod move_guard;
+    mod move_bounds;
+
+    pub(crate) fn all<DB: HirDatabase>() -> &'static [fn(AssistCtx<DB>) -> Option<Assist>] {
+        &[
+            add_derive::add_derive,
+            add_explicit_type::add_explicit_type,
+            add_impl::add_impl,
+            change_visibility::change_visibility,
+            fill_match_arms::fill_match_arms,
+            merge_match_arms::merge_match_arms,
+            flip_comma::flip_comma,
+            flip_binexpr::flip_binexpr,
+            introduce_variable::introduce_variable,
+            replace_if_let_with_match::replace_if_let_with_match,
+            split_import::split_import,
+            remove_dbg::remove_dbg,
+            auto_import::auto_import,
+            add_missing_impl_members::add_missing_impl_members,
+            add_missing_impl_members::add_missing_default_members,
+            inline_local_variable::inline_local_varialbe,
+            move_guard::move_guard_to_arm_body,
+            move_guard::move_arm_cond_to_match_guard,
+            move_bounds::move_bounds_to_where_clause,
+            raw_string::add_hash,
+            raw_string::make_raw_string,
+            raw_string::make_usual_string,
+            raw_string::remove_hash,
+        ]
+    }
 }
 
 #[cfg(test)]
diff --git a/crates/ra_ide_api/src/completion/complete_scope.rs b/crates/ra_ide_api/src/completion/complete_scope.rs
index c1f48b026..cb70a1f21 100644
--- a/crates/ra_ide_api/src/completion/complete_scope.rs
+++ b/crates/ra_ide_api/src/completion/complete_scope.rs
@@ -1,4 +1,4 @@
-use ra_assists::auto_import;
+use ra_assists::auto_import_text_edit;
 use ra_syntax::{ast, AstNode, SmolStr};
 use ra_text_edit::TextEditBuilder;
 use rustc_hash::FxHashMap;
@@ -23,7 +23,7 @@ pub(super) fn complete_scope(acc: &mut Completions, ctx: &CompletionContext) {
             let edit = {
                 let mut builder = TextEditBuilder::default();
                 builder.replace(ctx.source_range(), name.to_string());
-                auto_import::auto_import_text_edit(
+                auto_import_text_edit(
                     &ctx.token.parent(),
                     &ctx.token.parent(),
                     &path,
diff --git a/crates/ra_ide_api/src/diagnostics.rs b/crates/ra_ide_api/src/diagnostics.rs
index 93e1e7c2d..f07061e99 100644
--- a/crates/ra_ide_api/src/diagnostics.rs
+++ b/crates/ra_ide_api/src/diagnostics.rs
@@ -2,11 +2,11 @@ use std::cell::RefCell;
 
 use hir::diagnostics::{AstDiagnostic, Diagnostic as _, DiagnosticSink};
 use itertools::Itertools;
-use ra_assists::ast_editor::{AstBuilder, AstEditor};
+use ra_assists::{ast_builder::Make, ast_editor::AstEditor};
 use ra_db::SourceDatabase;
 use ra_prof::profile;
 use ra_syntax::{
-    ast::{self, AstNode, RecordField},
+    ast::{self, AstNode},
     Location, SyntaxNode, TextRange, T,
 };
 use ra_text_edit::{TextEdit, TextEditBuilder};
@@ -59,7 +59,11 @@ pub(crate) fn diagnostics(db: &RootDatabase, file_id: FileId) -> Vec<Diagnostic>
         let node = d.ast(db);
         let mut ast_editor = AstEditor::new(node);
         for f in d.missed_fields.iter() {
-            ast_editor.append_field(&AstBuilder::<RecordField>::from_name(f));
+            let field = Make::<ast::RecordField>::from(
+                Make::<ast::NameRef>::from(&f.to_string()),
+                Some(Make::<ast::Expr>::unit()),
+            );
+            ast_editor.append_field(&field);
         }
 
         let mut builder = TextEditBuilder::default();