3 files changed, 124 insertions, 272 deletions

diff --git a/crates/syntax/src/ast/edit.rs b/crates/syntax/src/ast/edit.rs
index cbc75f922..4b5f5c571 100644
--- a/crates/syntax/src/ast/edit.rs
+++ b/crates/syntax/src/ast/edit.rs
@@ -2,20 +2,20 @@
 //! immutable, all function here return a fresh copy of the tree, instead of
 //! doing an in-place modification.
 use std::{
-    array, fmt, iter,
+    fmt, iter,
     ops::{self, RangeInclusive},
 };
 
 use arrayvec::ArrayVec;
 
 use crate::{
-    algo::{self, SyntaxRewriter},
+    algo,
     ast::{
         self,
         make::{self, tokens},
-        AstNode, GenericParamsOwner, NameOwner, TypeBoundsOwner,
+        AstNode,
     },
-    AstToken, Direction, InsertPosition, SmolStr, SyntaxElement, SyntaxKind,
+    ted, AstToken, Direction, InsertPosition, NodeOrToken, SmolStr, SyntaxElement, SyntaxKind,
     SyntaxKind::{ATTR, COMMENT, WHITESPACE},
     SyntaxNode, SyntaxToken, T,
 };
@@ -29,37 +29,6 @@ impl ast::BinExpr {
     }
 }
 
-impl ast::Fn {
-    #[must_use]
-    pub fn with_body(&self, body: ast::BlockExpr) -> ast::Fn {
-        let mut to_insert: ArrayVec<SyntaxElement, 2> = ArrayVec::new();
-        let old_body_or_semi: SyntaxElement = if let Some(old_body) = self.body() {
-            old_body.syntax().clone().into()
-        } else if let Some(semi) = self.semicolon_token() {
-            to_insert.push(make::tokens::single_space().into());
-            semi.into()
-        } else {
-            to_insert.push(make::tokens::single_space().into());
-            to_insert.push(body.syntax().clone().into());
-            return self.insert_children(InsertPosition::Last, to_insert);
-        };
-        to_insert.push(body.syntax().clone().into());
-        self.replace_children(single_node(old_body_or_semi), to_insert)
-    }
-
-    #[must_use]
-    pub fn with_generic_param_list(&self, generic_args: ast::GenericParamList) -> ast::Fn {
-        if let Some(old) = self.generic_param_list() {
-            return self.replace_descendant(old, generic_args);
-        }
-
-        let anchor = self.name().expect("The function must have a name").syntax().clone();
-
-        let to_insert = [generic_args.syntax().clone().into()];
-        self.insert_children(InsertPosition::After(anchor.into()), array::IntoIter::new(to_insert))
-    }
-}
-
 fn make_multiline<N>(node: N) -> N
 where
     N: AstNode + Clone,
@@ -92,81 +61,6 @@ where
     }
 }
 
-impl ast::Impl {
-    #[must_use]
-    pub fn with_assoc_item_list(&self, items: ast::AssocItemList) -> ast::Impl {
-        let mut to_insert: ArrayVec<SyntaxElement, 2> = ArrayVec::new();
-        if let Some(old_items) = self.assoc_item_list() {
-            let to_replace: SyntaxElement = old_items.syntax().clone().into();
-            to_insert.push(items.syntax().clone().into());
-            self.replace_children(single_node(to_replace), to_insert)
-        } else {
-            to_insert.push(make::tokens::single_space().into());
-            to_insert.push(items.syntax().clone().into());
-            self.insert_children(InsertPosition::Last, to_insert)
-        }
-    }
-}
-
-impl ast::AssocItemList {
-    #[must_use]
-    pub fn append_items(
-        &self,
-        items: impl IntoIterator<Item = ast::AssocItem>,
-    ) -> ast::AssocItemList {
-        let mut res = self.clone();
-        if !self.syntax().text().contains_char('\n') {
-            res = make_multiline(res);
-        }
-        items.into_iter().for_each(|it| res = res.append_item(it));
-        res.fixup_trailing_whitespace().unwrap_or(res)
-    }
-
-    #[must_use]
-    pub fn append_item(&self, item: ast::AssocItem) -> ast::AssocItemList {
-        let (indent, position, whitespace) = match self.assoc_items().last() {
-            Some(it) => (
-                leading_indent(it.syntax()).unwrap_or_default().to_string(),
-                InsertPosition::After(it.syntax().clone().into()),
-                "\n\n",
-            ),
-            None => match self.l_curly_token() {
-                Some(it) => (
-                    "    ".to_string() + &leading_indent(self.syntax()).unwrap_or_default(),
-                    InsertPosition::After(it.into()),
-                    "\n",
-                ),
-                None => return self.clone(),
-            },
-        };
-        let ws = tokens::WsBuilder::new(&format!("{}{}", whitespace, indent));
-        let to_insert: ArrayVec<SyntaxElement, 2> =
-            [ws.ws().into(), item.syntax().clone().into()].into();
-        self.insert_children(position, to_insert)
-    }
-
-    /// Remove extra whitespace between last item and closing curly brace.
-    fn fixup_trailing_whitespace(&self) -> Option<ast::AssocItemList> {
-        let first_token_after_items =
-            self.assoc_items().last()?.syntax().next_sibling_or_token()?;
-        let last_token_before_curly = self.r_curly_token()?.prev_sibling_or_token()?;
-        if last_token_before_curly != first_token_after_items {
-            // there is something more between last item and
-            // right curly than just whitespace - bail out
-            return None;
-        }
-        let whitespace =
-            last_token_before_curly.clone().into_token().and_then(ast::Whitespace::cast)?;
-        let text = whitespace.syntax().text();
-        let newline = text.rfind('\n')?;
-        let keep = tokens::WsBuilder::new(&text[newline..]);
-        Some(self.replace_children(
-            first_token_after_items..=last_token_before_curly,
-            std::iter::once(keep.ws().into()),
-        ))
-    }
-}
-
 impl ast::RecordExprFieldList {
     #[must_use]
     pub fn append_field(&self, field: &ast::RecordExprField) -> ast::RecordExprFieldList {
@@ -243,36 +137,6 @@ impl ast::RecordExprFieldList {
     }
 }
 
-impl ast::TypeAlias {
-    #[must_use]
-    pub fn remove_bounds(&self) -> ast::TypeAlias {
-        let colon = match self.colon_token() {
-            Some(it) => it,
-            None => return self.clone(),
-        };
-        let end = match self.type_bound_list() {
-            Some(it) => it.syntax().clone().into(),
-            None => colon.clone().into(),
-        };
-        self.replace_children(colon.into()..=end, iter::empty())
-    }
-}
-
-impl ast::TypeParam {
-    #[must_use]
-    pub fn remove_bounds(&self) -> ast::TypeParam {
-        let colon = match self.colon_token() {
-            Some(it) => it,
-            None => return self.clone(),
-        };
-        let end = match self.type_bound_list() {
-            Some(it) => it.syntax().clone().into(),
-            None => colon.clone().into(),
-        };
-        self.replace_children(colon.into()..=end, iter::empty())
-    }
-}
-
 impl ast::Path {
     #[must_use]
     pub fn with_segment(&self, segment: ast::PathSegment) -> ast::Path {
@@ -313,33 +177,7 @@ impl ast::PathSegment {
     }
 }
 
-impl ast::Use {
-    #[must_use]
-    pub fn with_use_tree(&self, use_tree: ast::UseTree) -> ast::Use {
-        if let Some(old) = self.use_tree() {
-            return self.replace_descendant(old, use_tree);
-        }
-        self.clone()
-    }
-}
-
 impl ast::UseTree {
-    #[must_use]
-    pub fn with_path(&self, path: ast::Path) -> ast::UseTree {
-        if let Some(old) = self.path() {
-            return self.replace_descendant(old, path);
-        }
-        self.clone()
-    }
-
-    #[must_use]
-    pub fn with_use_tree_list(&self, use_tree_list: ast::UseTreeList) -> ast::UseTree {
-        if let Some(old) = self.use_tree_list() {
-            return self.replace_descendant(old, use_tree_list);
-        }
-        self.clone()
-    }
-
     /// Splits off the given prefix, making it the path component of the use tree, appending the rest of the path to all UseTreeList items.
     #[must_use]
     pub fn split_prefix(&self, prefix: &ast::Path) -> ast::UseTree {
@@ -449,61 +287,6 @@ impl ast::MatchArmList {
     }
 }
 
-impl ast::GenericParamList {
-    #[must_use]
-    pub fn append_params(
-        &self,
-        params: impl IntoIterator<Item = ast::GenericParam>,
-    ) -> ast::GenericParamList {
-        let mut res = self.clone();
-        params.into_iter().for_each(|it| res = res.append_param(it));
-        res
-    }
-
-    #[must_use]
-    pub fn append_param(&self, item: ast::GenericParam) -> ast::GenericParamList {
-        let space = tokens::single_space();
-
-        let mut to_insert: ArrayVec<SyntaxElement, 4> = ArrayVec::new();
-        if self.generic_params().next().is_some() {
-            to_insert.push(space.into());
-        }
-        to_insert.push(item.syntax().clone().into());
-
-        macro_rules! after_l_angle {
-            () => {{
-                let anchor = match self.l_angle_token() {
-                    Some(it) => it.into(),
-                    None => return self.clone(),
-                };
-                InsertPosition::After(anchor)
-            }};
-        }
-
-        macro_rules! after_field {
-            ($anchor:expr) => {
-                if let Some(comma) = $anchor
-                    .syntax()
-                    .siblings_with_tokens(Direction::Next)
-                    .find(|it| it.kind() == T![,])
-                {
-                    InsertPosition::After(comma)
-                } else {
-                    to_insert.insert(0, make::token(T![,]).into());
-                    InsertPosition::After($anchor.syntax().clone().into())
-                }
-            };
-        }
-
-        let position = match self.generic_params().last() {
-            Some(it) => after_field!(it),
-            None => after_l_angle!(),
-        };
-
-        self.insert_children(position, to_insert)
-    }
-}
-
 #[must_use]
 pub fn remove_attrs_and_docs<N: ast::AttrsOwner>(node: &N) -> N {
     N::cast(remove_attrs_and_docs_inner(node.syntax().clone())).unwrap()
@@ -554,6 +337,12 @@ impl ops::Add<u8> for IndentLevel {
 }
 
 impl IndentLevel {
+    pub fn single() -> IndentLevel {
+        IndentLevel(0)
+    }
+    pub fn is_zero(&self) -> bool {
+        self.0 == 0
+    }
     pub fn from_element(element: &SyntaxElement) -> IndentLevel {
         match element {
             rowan::NodeOrToken::Node(it) => IndentLevel::from_node(it),
@@ -588,37 +377,39 @@ impl IndentLevel {
     /// ```
     /// if you indent the block, the `{` token would stay put.
     fn increase_indent(self, node: SyntaxNode) -> SyntaxNode {
-        let mut rewriter = SyntaxRewriter::default();
-        node.descendants_with_tokens()
-            .filter_map(|el| el.into_token())
-            .filter_map(ast::Whitespace::cast)
-            .filter(|ws| {
-                let text = ws.syntax().text();
-                text.contains('\n')
-            })
-            .for_each(|ws| {
-                let new_ws = make::tokens::whitespace(&format!("{}{}", ws.syntax(), self,));
-                rewriter.replace(ws.syntax(), &new_ws)
-            });
-        rewriter.rewrite(&node)
+        let res = node.clone_subtree().clone_for_update();
+        let tokens = res.preorder_with_tokens().filter_map(|event| match event {
+            rowan::WalkEvent::Leave(NodeOrToken::Token(it)) => Some(it),
+            _ => None,
+        });
+        for token in tokens {
+            if let Some(ws) = ast::Whitespace::cast(token) {
+                if ws.text().contains('\n') {
+                    let new_ws = make::tokens::whitespace(&format!("{}{}", ws.syntax(), self));
+                    ted::replace(ws.syntax(), &new_ws)
+                }
+            }
+        }
+        res.clone_subtree()
     }
 
     fn decrease_indent(self, node: SyntaxNode) -> SyntaxNode {
-        let mut rewriter = SyntaxRewriter::default();
-        node.descendants_with_tokens()
-            .filter_map(|el| el.into_token())
-            .filter_map(ast::Whitespace::cast)
-            .filter(|ws| {
-                let text = ws.syntax().text();
-                text.contains('\n')
-            })
-            .for_each(|ws| {
-                let new_ws = make::tokens::whitespace(
-                    &ws.syntax().text().replace(&format!("\n{}", self), "\n"),
-                );
-                rewriter.replace(ws.syntax(), &new_ws)
-            });
-        rewriter.rewrite(&node)
+        let res = node.clone_subtree().clone_for_update();
+        let tokens = res.preorder_with_tokens().filter_map(|event| match event {
+            rowan::WalkEvent::Leave(NodeOrToken::Token(it)) => Some(it),
+            _ => None,
+        });
+        for token in tokens {
+            if let Some(ws) = ast::Whitespace::cast(token) {
+                if ws.text().contains('\n') {
+                    let new_ws = make::tokens::whitespace(
+                        &ws.syntax().text().replace(&format!("\n{}", self), "\n"),
+                    );
+                    ted::replace(ws.syntax(), &new_ws)
+                }
+            }
+        }
+        res.clone_subtree()
     }
 }
 
@@ -662,13 +453,6 @@ pub trait AstNodeEdit: AstNode + Clone + Sized {
         let new_syntax = algo::replace_children(self.syntax(), to_replace, to_insert);
         Self::cast(new_syntax).unwrap()
     }
-
-    #[must_use]
-    fn replace_descendant<D: AstNode>(&self, old: D, new: D) -> Self {
-        let mut rewriter = SyntaxRewriter::default();
-        rewriter.replace(old.syntax(), new.syntax());
-        rewriter.rewrite_ast(self)
-    }
     fn indent_level(&self) -> IndentLevel {
         IndentLevel::from_node(self.syntax())
     }
diff --git a/crates/syntax/src/ast/edit_in_place.rs b/crates/syntax/src/ast/edit_in_place.rs
index 168355555..ca777d057 100644
--- a/crates/syntax/src/ast/edit_in_place.rs
+++ b/crates/syntax/src/ast/edit_in_place.rs
@@ -2,11 +2,16 @@
 
 use std::iter::empty;
 
-use parser::T;
+use parser::{SyntaxKind, T};
+use rowan::SyntaxElement;
 
 use crate::{
     algo::neighbor,
-    ast::{self, edit::AstNodeEdit, make, GenericParamsOwner, WhereClause},
+    ast::{
+        self,
+        edit::{AstNodeEdit, IndentLevel},
+        make, GenericParamsOwner,
+    },
     ted::{self, Position},
     AstNode, AstToken, Direction,
 };
@@ -37,7 +42,7 @@ impl GenericParamsOwnerEdit for ast::Fn {
         }
     }
 
-    fn get_or_create_where_clause(&self) -> WhereClause {
+    fn get_or_create_where_clause(&self) -> ast::WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(ty) = self.ret_type() {
                 Position::after(ty.syntax())
@@ -67,7 +72,7 @@ impl GenericParamsOwnerEdit for ast::Impl {
         }
     }
 
-    fn get_or_create_where_clause(&self) -> WhereClause {
+    fn get_or_create_where_clause(&self) -> ast::WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(items) = self.assoc_item_list() {
                 Position::before(items.syntax())
@@ -97,7 +102,7 @@ impl GenericParamsOwnerEdit for ast::Trait {
         }
     }
 
-    fn get_or_create_where_clause(&self) -> WhereClause {
+    fn get_or_create_where_clause(&self) -> ast::WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(items) = self.assoc_item_list() {
                 Position::before(items.syntax())
@@ -127,7 +132,7 @@ impl GenericParamsOwnerEdit for ast::Struct {
         }
     }
 
-    fn get_or_create_where_clause(&self) -> WhereClause {
+    fn get_or_create_where_clause(&self) -> ast::WhereClause {
         if self.where_clause().is_none() {
             let tfl = self.field_list().and_then(|fl| match fl {
                 ast::FieldList::RecordFieldList(_) => None,
@@ -165,7 +170,7 @@ impl GenericParamsOwnerEdit for ast::Enum {
         }
     }
 
-    fn get_or_create_where_clause(&self) -> WhereClause {
+    fn get_or_create_where_clause(&self) -> ast::WhereClause {
         if self.where_clause().is_none() {
             let position = if let Some(gpl) = self.generic_param_list() {
                 Position::after(gpl.syntax())
@@ -272,6 +277,75 @@ impl ast::Use {
     }
 }
 
+impl ast::Impl {
+    pub fn get_or_create_assoc_item_list(&self) -> ast::AssocItemList {
+        if self.assoc_item_list().is_none() {
+            let assoc_item_list = make::assoc_item_list().clone_for_update();
+            ted::append_child(self.syntax(), assoc_item_list.syntax());
+        }
+        self.assoc_item_list().unwrap()
+    }
+}
+
+impl ast::AssocItemList {
+    pub fn add_item(&self, item: ast::AssocItem) {
+        let (indent, position, whitespace) = match self.assoc_items().last() {
+            Some(last_item) => (
+                IndentLevel::from_node(last_item.syntax()),
+                Position::after(last_item.syntax()),
+                "\n\n",
+            ),
+            None => match self.l_curly_token() {
+                Some(l_curly) => {
+                    self.normalize_ws_between_braces();
+                    (IndentLevel::from_token(&l_curly) + 1, Position::after(&l_curly), "\n")
+                }
+                None => (IndentLevel::single(), Position::last_child_of(self.syntax()), "\n"),
+            },
+        };
+        let elements: Vec<SyntaxElement<_>> = vec![
+            make::tokens::whitespace(&format!("{}{}", whitespace, indent)).into(),
+            item.syntax().clone().into(),
+        ];
+        ted::insert_all(position, elements);
+    }
+
+    fn normalize_ws_between_braces(&self) -> Option<()> {
+        let l = self.l_curly_token()?;
+        let r = self.r_curly_token()?;
+        let indent = IndentLevel::from_node(self.syntax());
+
+        match l.next_sibling_or_token() {
+            Some(ws) if ws.kind() == SyntaxKind::WHITESPACE => {
+                if ws.next_sibling_or_token()?.into_token()? == r {
+                    ted::replace(ws, make::tokens::whitespace(&format!("\n{}", indent)));
+                }
+            }
+            Some(ws) if ws.kind() == T!['}'] => {
+                ted::insert(Position::after(l), make::tokens::whitespace(&format!("\n{}", indent)));
+            }
+            _ => (),
+        }
+        Some(())
+    }
+}
+
+impl ast::Fn {
+    pub fn get_or_create_body(&self) -> ast::BlockExpr {
+        if self.body().is_none() {
+            let body = make::ext::empty_block_expr().clone_for_update();
+            match self.semicolon_token() {
+                Some(semi) => {
+                    ted::replace(semi, body.syntax());
+                    ted::insert(Position::before(body.syntax), make::tokens::single_space());
+                }
+                None => ted::append_child(self.syntax(), body.syntax()),
+            }
+        }
+        self.body().unwrap()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use std::fmt;
diff --git a/crates/syntax/src/ast/make.rs b/crates/syntax/src/ast/make.rs
index 1998ad1f6..d13926ded 100644
--- a/crates/syntax/src/ast/make.rs
+++ b/crates/syntax/src/ast/make.rs
@@ -12,7 +12,7 @@
 use itertools::Itertools;
 use stdx::{format_to, never};
 
-use crate::{ast, AstNode, SourceFile, SyntaxKind, SyntaxNode, SyntaxToken};
+use crate::{ast, AstNode, SourceFile, SyntaxKind, SyntaxToken};
 
 /// While the parent module defines basic atomic "constructors", the `ext`
 /// module defines shortcuts for common things.
@@ -99,7 +99,7 @@ fn ty_from_text(text: &str) -> ast::Type {
 }
 
 pub fn assoc_item_list() -> ast::AssocItemList {
-    ast_from_text("impl C for D {};")
+    ast_from_text("impl C for D {}")
 }
 
 pub fn impl_trait(trait_: ast::Path, ty: ast::Path) -> ast::Impl {
@@ -601,17 +601,11 @@ fn ast_from_text<N: AstNode>(text: &str) -> N {
             panic!("Failed to make ast node `{}` from text {}", std::any::type_name::<N>(), text)
         }
     };
-    let node = node.syntax().clone();
-    let node = unroot(node);
-    let node = N::cast(node).unwrap();
+    let node = node.clone_subtree();
     assert_eq!(node.syntax().text_range().start(), 0.into());
     node
 }
 
-fn unroot(n: SyntaxNode) -> SyntaxNode {
-    SyntaxNode::new_root(n.green().into())
-}
-
 pub fn token(kind: SyntaxKind) -> SyntaxToken {
     tokens::SOURCE_FILE
         .tree()