Upgrade rowan

Notably, new rowan comes with support for mutable syntax trees.

Cargo.lock

@@ -1,7 +1,5 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
-
 [[package]]
 name = "addr2line"
 version = "0.14.1"
@@ -1326,9 +1324,9 @@ checksum = "b5eb417147ba9860a96cfe72a0b93bf88fee1744b5636ec99ab20c1aa9376581"
 
 [[package]]
 name = "rowan"
-version = "0.12.6"
+version = "0.13.0-pre.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a1b36e449f3702f3b0c821411db1cbdf30fb451726a9456dce5dabcd44420043"
+checksum = "8f300be7fa17c3fa563d2bc6ab5b1a8d5163162f9111599eda4f86a563714724"
 dependencies = [
  "countme",
  "hashbrown",

crates/hir/src/semantics.rs

@@ -143,6 +143,12 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.imp.diagnostics_display_range(diagnostics)
     }
 
+    pub fn token_ancestors_with_macros(
+        &self,
+        token: SyntaxToken,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        token.parent().into_iter().flat_map(move |it| self.ancestors_with_macros(it))
+    }
     pub fn ancestors_with_macros(&self, node: SyntaxNode) -> impl Iterator<Item = SyntaxNode> + '_ {
         self.imp.ancestors_with_macros(node)
     }
@@ -270,8 +276,8 @@ impl<'db, DB: HirDatabase> Semantics<'db, DB> {
         self.imp.scope(node)
     }
 
-    pub fn scope_at_offset(&self, node: &SyntaxNode, offset: TextSize) -> SemanticsScope<'db> {
+    pub fn scope_at_offset(&self, token: &SyntaxToken, offset: TextSize) -> SemanticsScope<'db> {
-        self.imp.scope_at_offset(node, offset)
+        self.imp.scope_at_offset(&token.parent().unwrap(), offset)
     }
 
     pub fn scope_for_def(&self, def: Trait) -> SemanticsScope<'db> {
@@ -341,7 +347,10 @@ impl<'db> SemanticsImpl<'db> {
 
     fn descend_into_macros(&self, token: SyntaxToken) -> SyntaxToken {
         let _p = profile::span("descend_into_macros");
-        let parent = token.parent();
+        let parent = match token.parent() {
+            Some(it) => it,
+            None => return token,
+        };
         let sa = self.analyze(&parent);
 
         let token = successors(Some(InFile::new(sa.file_id, token)), |token| {
@@ -360,7 +369,9 @@ impl<'db> SemanticsImpl<'db> {
                 .as_ref()?
                 .map_token_down(token.as_ref())?;
 
-            self.cache(find_root(&token.value.parent()), token.file_id);
+            if let Some(parent) = token.value.parent() {
+                self.cache(find_root(&parent), token.file_id);
+            }
 
             Some(token)
         })
@@ -378,7 +389,7 @@ impl<'db> SemanticsImpl<'db> {
         // Handle macro token cases
         node.token_at_offset(offset)
             .map(|token| self.descend_into_macros(token))
-            .map(|it| self.ancestors_with_macros(it.parent()))
+            .map(|it| self.token_ancestors_with_macros(it))
             .flatten()
     }
 
@@ -394,6 +405,13 @@ impl<'db> SemanticsImpl<'db> {
         src.with_value(&node).original_file_range(self.db.upcast())
     }
 
+    fn token_ancestors_with_macros(
+        &self,
+        token: SyntaxToken,
+    ) -> impl Iterator<Item = SyntaxNode> + '_ {
+        token.parent().into_iter().flat_map(move |parent| self.ancestors_with_macros(parent))
+    }
+
     fn ancestors_with_macros(&self, node: SyntaxNode) -> impl Iterator<Item = SyntaxNode> + '_ {
         let node = self.find_file(node);
         node.ancestors_with_macros(self.db.upcast()).map(|it| it.value)
@@ -405,7 +423,7 @@ impl<'db> SemanticsImpl<'db> {
         offset: TextSize,
     ) -> impl Iterator<Item = SyntaxNode> + '_ {
         node.token_at_offset(offset)
-            .map(|token| self.ancestors_with_macros(token.parent()))
+            .map(|token| self.token_ancestors_with_macros(token))
             .kmerge_by(|node1, node2| node1.text_range().len() < node2.text_range().len())
     }
 

crates/hir_expand/src/lib.rs

@@ -510,7 +510,10 @@ impl InFile<SyntaxToken> {
         self,
         db: &dyn db::AstDatabase,
     ) -> impl Iterator<Item = InFile<SyntaxNode>> + '_ {
-        self.map(|it| it.parent()).ancestors_with_macros(db)
+        self.value
+            .parent()
+            .into_iter()
+            .flat_map(move |parent| InFile::new(self.file_id, parent).ancestors_with_macros(db))
     }
 }
 

crates/ide/src/call_hierarchy.rs

@@ -53,10 +53,8 @@ pub(crate) fn incoming_calls(db: &RootDatabase, position: FilePosition) -> Optio
         for (r_range, _) in references {
             let token = file.token_at_offset(r_range.start()).next()?;
             let token = sema.descend_into_macros(token);
-            let syntax = token.parent();
-
             // This target is the containing function
-            if let Some(nav) = syntax.ancestors().find_map(|node| {
+            if let Some(nav) = token.ancestors().find_map(|node| {
                 let fn_ = ast::Fn::cast(node)?;
                 let def = sema.to_def(&fn_)?;
                 def.try_to_nav(sema.db)
@@ -77,12 +75,13 @@ pub(crate) fn outgoing_calls(db: &RootDatabase, position: FilePosition) -> Optio
     let file = file.syntax();
     let token = file.token_at_offset(position.offset).next()?;
     let token = sema.descend_into_macros(token);
-    let syntax = token.parent();
 
     let mut calls = CallLocations::default();
 
-    syntax
+    token
-        .descendants()
+        .parent()
+        .into_iter()
+        .flat_map(|it| it.descendants())
         .filter_map(|node| FnCallNode::with_node_exact(&node))
         .filter_map(|call_node| {
             let name_ref = call_node.name_ref()?;

crates/ide/src/doc_links.rs

@@ -279,7 +279,7 @@ pub(crate) fn external_docs(
     let token = pick_best(file.token_at_offset(position.offset))?;
     let token = sema.descend_into_macros(token);
 
-    let node = token.parent();
+    let node = token.parent()?;
     let definition = match_ast! {
         match node {
             ast::NameRef(name_ref) => NameRefClass::classify(&sema, &name_ref).map(|d| d.referenced(sema.db)),

crates/ide/src/extend_selection.rs

@@ -88,7 +88,7 @@ fn try_extend_selection(
                     return Some(range);
                 }
             }
-            token.parent()
+            token.parent()?
         }
         NodeOrToken::Node(node) => node,
     };
@@ -142,7 +142,8 @@ fn extend_tokens_from_range(
     let extended = {
         let fst_expanded = sema.descend_into_macros(first_token.clone());
         let lst_expanded = sema.descend_into_macros(last_token.clone());
-        let mut lca = algo::least_common_ancestor(&fst_expanded.parent(), &lst_expanded.parent())?;
+        let mut lca =
+            algo::least_common_ancestor(&fst_expanded.parent()?, &lst_expanded.parent()?)?;
         lca = shallowest_node(&lca);
         if lca.first_token() == Some(fst_expanded) && lca.last_token() == Some(lst_expanded) {
             lca = lca.parent()?;
@@ -151,9 +152,13 @@ fn extend_tokens_from_range(
     };
 
     // Compute parent node range
-    let validate = |token: &SyntaxToken| {
+    let validate = |token: &SyntaxToken| -> bool {
         let expanded = sema.descend_into_macros(token.clone());
-        algo::least_common_ancestor(&extended, &expanded.parent()).as_ref() == Some(&extended)
+        let parent = match expanded.parent() {
+            Some(it) => it,
+            None => return false,
+        };
+        algo::least_common_ancestor(&extended, &parent).as_ref() == Some(&extended)
     };
 
     // Find the first and last text range under expanded parent

crates/ide/src/goto_definition.rs

@@ -30,7 +30,7 @@ pub(crate) fn goto_definition(
     let file = sema.parse(position.file_id).syntax().clone();
     let original_token = pick_best(file.token_at_offset(position.offset))?;
     let token = sema.descend_into_macros(original_token.clone());
-    let parent = token.parent();
+    let parent = token.parent()?;
     if let Some(comment) = ast::Comment::cast(token) {
         let nav = def_for_doc_comment(&sema, position, &comment)?.try_to_nav(db)?;
         return Some(RangeInfo::new(original_token.text_range(), vec![nav]));
@@ -63,7 +63,7 @@ fn def_for_doc_comment(
     position: FilePosition,
     doc_comment: &ast::Comment,
 ) -> Option<hir::ModuleDef> {
-    let parent = doc_comment.syntax().parent();
+    let parent = doc_comment.syntax().parent()?;
     let (link, ns) = extract_positioned_link_from_comment(position, doc_comment)?;
 
     let def = doc_owner_to_def(sema, parent)?;

crates/ide/src/goto_type_definition.rs

@@ -22,7 +22,7 @@ pub(crate) fn goto_type_definition(
     let token: SyntaxToken = pick_best(file.syntax().token_at_offset(position.offset))?;
     let token: SyntaxToken = sema.descend_into_macros(token);
 
-    let (ty, node) = sema.ancestors_with_macros(token.parent()).find_map(|node| {
+    let (ty, node) = sema.token_ancestors_with_macros(token).find_map(|node| {
         let ty = match_ast! {
             match node {
                 ast::Expr(it) => sema.type_of_expr(&it)?,

crates/ide/src/hover.rs

@@ -92,7 +92,7 @@ pub(crate) fn hover(
 
     let mut res = HoverResult::default();
 
-    let node = token.parent();
+    let node = token.parent()?;
     let definition = match_ast! {
         match node {
             // we don't use NameClass::referenced_or_defined here as we do not want to resolve
@@ -438,7 +438,7 @@ fn hover_for_keyword(
     if !token.kind().is_keyword() {
         return None;
     }
-    let famous_defs = FamousDefs(&sema, sema.scope(&token.parent()).krate());
+    let famous_defs = FamousDefs(&sema, sema.scope(&token.parent()?).krate());
     // std exposes {}_keyword modules with docstrings on the root to document keywords
     let keyword_mod = format!("{}_keyword", token.text());
     let doc_owner = find_std_module(&famous_defs, &keyword_mod)?;

crates/ide/src/join_lines.rs

@@ -32,29 +32,35 @@ pub(crate) fn join_lines(file: &SourceFile, range: TextRange) -> TextEdit {
         range
     };
 
-    let node = match file.syntax().covering_element(range) {
-        NodeOrToken::Node(node) => node,
-        NodeOrToken::Token(token) => token.parent(),
-    };
     let mut edit = TextEdit::builder();
-    for token in node.descendants_with_tokens().filter_map(|it| it.into_token()) {
+    match file.syntax().covering_element(range) {
-        let range = match range.intersect(token.text_range()) {
+        NodeOrToken::Node(node) => {
-            Some(range) => range,
+            for token in node.descendants_with_tokens().filter_map(|it| it.into_token()) {
-            None => continue,
+                remove_newlines(&mut edit, &token, range)
-        } - token.text_range().start();
-        let text = token.text();
-        for (pos, _) in text[range].bytes().enumerate().filter(|&(_, b)| b == b'\n') {
-            let pos: TextSize = (pos as u32).into();
-            let offset = token.text_range().start() + range.start() + pos;
-            if !edit.invalidates_offset(offset) {
-                remove_newline(&mut edit, &token, offset);
             }
         }
-    }
+        NodeOrToken::Token(token) => remove_newlines(&mut edit, &token, range),
-
+    };
     edit.finish()
 }
 
+fn remove_newlines(edit: &mut TextEditBuilder, token: &SyntaxToken, range: TextRange) {
+    let intersection = match range.intersect(token.text_range()) {
+        Some(range) => range,
+        None => return,
+    };
+
+    let range = intersection - token.text_range().start();
+    let text = token.text();
+    for (pos, _) in text[range].bytes().enumerate().filter(|&(_, b)| b == b'\n') {
+        let pos: TextSize = (pos as u32).into();
+        let offset = token.text_range().start() + range.start() + pos;
+        if !edit.invalidates_offset(offset) {
+            remove_newline(edit, &token, offset);
+        }
+    }
+}
+
 fn remove_newline(edit: &mut TextEditBuilder, token: &SyntaxToken, offset: TextSize) {
     if token.kind() != WHITESPACE || token.text().bytes().filter(|&b| b == b'\n').count() != 1 {
         let mut string_open_quote = false;
@@ -148,7 +154,7 @@ fn has_comma_after(node: &SyntaxNode) -> bool {
 }
 
 fn join_single_expr_block(edit: &mut TextEditBuilder, token: &SyntaxToken) -> Option<()> {
-    let block_expr = ast::BlockExpr::cast(token.parent())?;
+    let block_expr = ast::BlockExpr::cast(token.parent()?)?;
     if !block_expr.is_standalone() {
         return None;
     }
@@ -170,7 +176,7 @@ fn join_single_expr_block(edit: &mut TextEditBuilder, token: &SyntaxToken) -> Op
 }
 
 fn join_single_use_tree(edit: &mut TextEditBuilder, token: &SyntaxToken) -> Option<()> {
-    let use_tree_list = ast::UseTreeList::cast(token.parent())?;
+    let use_tree_list = ast::UseTreeList::cast(token.parent()?)?;
     let (tree,) = use_tree_list.use_trees().collect_tuple()?;
     edit.replace(use_tree_list.syntax().text_range(), tree.syntax().text().to_string());
     Some(())

crates/ide/src/matching_brace.rs

@@ -25,7 +25,7 @@ pub(crate) fn matching_brace(file: &SourceFile, offset: TextSize) -> Option<Text
             Some((node, idx))
         })
         .next()?;
-    let parent = brace_token.parent();
+    let parent = brace_token.parent()?;
     if brace_token.kind() == T![|] && !ast::ParamList::can_cast(parent.kind()) {
         cov_mark::hit!(pipes_not_braces);
         return None;

crates/ide/src/references.rs

@@ -148,14 +148,15 @@ fn decl_access(def: &Definition, syntax: &SyntaxNode, range: TextRange) -> Optio
 
 fn get_name_of_item_declaration(syntax: &SyntaxNode, position: FilePosition) -> Option<ast::Name> {
     let token = syntax.token_at_offset(position.offset).right_biased()?;
+    let token_parent = token.parent()?;
     let kind = token.kind();
     if kind == T![;] {
-        ast::Struct::cast(token.parent())
+        ast::Struct::cast(token_parent)
             .filter(|struct_| struct_.field_list().is_none())
             .and_then(|struct_| struct_.name())
     } else if kind == T!['{'] {
         match_ast! {
-            match (token.parent()) {
+            match token_parent {
                 ast::RecordFieldList(rfl) => match_ast! {
                     match (rfl.syntax().parent()?) {
                         ast::Variant(it) => it.name(),
@@ -169,7 +170,7 @@ fn get_name_of_item_declaration(syntax: &SyntaxNode, position: FilePosition) ->
             }
         }
     } else if kind == T!['('] {
-        let tfl = ast::TupleFieldList::cast(token.parent())?;
+        let tfl = ast::TupleFieldList::cast(token_parent)?;
         match_ast! {
             match (tfl.syntax().parent()?) {
                 ast::Variant(it) => it.name(),

crates/ide/src/runnables.rs

@@ -167,8 +167,7 @@ fn find_related_tests(
             let functions = refs.iter().filter_map(|(range, _)| {
                 let token = file.token_at_offset(range.start()).next()?;
                 let token = sema.descend_into_macros(token);
-                let syntax = token.parent();
+                token.ancestors().find_map(ast::Fn::cast)
-                syntax.ancestors().find_map(ast::Fn::cast)
             });
 
             for fn_def in functions {

crates/ide/src/syntax_highlighting.rs

@@ -64,7 +64,7 @@ pub(crate) fn highlight(
             Some(range) => {
                 let node = match source_file.syntax().covering_element(range) {
                     NodeOrToken::Node(it) => it,
-                    NodeOrToken::Token(it) => it.parent(),
+                    NodeOrToken::Token(it) => it.parent().unwrap(),
                 };
                 (node, range)
             }
@@ -167,16 +167,19 @@ fn traverse(
         let element_to_highlight = if current_macro_call.is_some() && element.kind() != COMMENT {
             // Inside a macro -- expand it first
             let token = match element.clone().into_token() {
-                Some(it) if it.parent().kind() == TOKEN_TREE => it,
+                Some(it) if it.parent().map_or(false, |it| it.kind() == TOKEN_TREE) => it,
                 _ => continue,
             };
             let token = sema.descend_into_macros(token.clone());
-            let parent = token.parent();
+            match token.parent() {
-
+                Some(parent) => {
-            // We only care Name and Name_ref
+                    // We only care Name and Name_ref
-            match (token.kind(), parent.kind()) {
+                    match (token.kind(), parent.kind()) {
-                (IDENT, NAME) | (IDENT, NAME_REF) => parent.into(),
+                        (IDENT, NAME) | (IDENT, NAME_REF) => parent.into(),
-                _ => token.into(),
+                        _ => token.into(),
+                    }
+                }
+                None => token.into(),
             }
         } else {
             element.clone()

crates/ide/src/syntax_highlighting/format.rs

@@ -28,7 +28,7 @@ pub(super) fn highlight_format_string(
 }
 
 fn is_format_string(string: &ast::String) -> Option<()> {
-    let parent = string.syntax().parent();
+    let parent = string.syntax().parent()?;
 
     let name = parent.parent().and_then(ast::MacroCall::cast)?.path()?.segment()?.name_ref()?;
     if !matches!(name.text(), "format_args" | "format_args_nl") {

crates/ide/src/syntax_tree.rs

@@ -27,7 +27,7 @@ pub(crate) fn syntax_tree(
                 if let Some(tree) = syntax_tree_for_string(&token, text_range) {
                     return tree;
                 }
-                token.parent()
+                token.parent().unwrap()
             }
         };
 

crates/ide/src/typing.rs

@@ -108,7 +108,7 @@ fn on_dot_typed(file: &SourceFile, offset: TextSize) -> Option<TextEdit> {
     };
     let current_indent_len = TextSize::of(current_indent);
 
-    let parent = whitespace.syntax().parent();
+    let parent = whitespace.syntax().parent()?;
     // Make sure dot is a part of call chain
     if !matches!(parent.kind(), FIELD_EXPR | METHOD_CALL_EXPR) {
         return None;

crates/ide_assists/src/handlers/add_turbo_fish.rs

@@ -38,7 +38,7 @@ pub(crate) fn add_turbo_fish(acc: &mut Assists, ctx: &AssistContext) -> Option<(
         cov_mark::hit!(add_turbo_fish_one_fish_is_enough);
         return None;
     }
-    let name_ref = ast::NameRef::cast(ident.parent())?;
+    let name_ref = ast::NameRef::cast(ident.parent()?)?;
     let def = match NameRefClass::classify(&ctx.sema, &name_ref)? {
         NameRefClass::Definition(def) => def,
         NameRefClass::ExternCrate(_) | NameRefClass::FieldShorthand { .. } => return None,

crates/ide_assists/src/handlers/change_visibility.rs

@@ -41,7 +41,7 @@ fn add_vis(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     });
 
     let (offset, target) = if let Some(keyword) = item_keyword {
-        let parent = keyword.parent();
+        let parent = keyword.parent()?;
         let def_kws = vec![CONST, STATIC, TYPE_ALIAS, FN, MODULE, STRUCT, ENUM, TRAIT];
         // Parent is not a definition, can't add visibility
         if !def_kws.iter().any(|&def_kw| def_kw == parent.kind()) {

crates/ide_assists/src/handlers/expand_glob_import.rs

@@ -48,7 +48,7 @@ pub(crate) fn expand_glob_import(acc: &mut Assists, ctx: &AssistContext) -> Opti
         _ => return None,
     };
 
-    let current_scope = ctx.sema.scope(&star.parent());
+    let current_scope = ctx.sema.scope(&star.parent()?);
     let current_module = current_scope.module()?;
 
     let refs_in_target = find_refs_in_mod(ctx, target_module, Some(current_module))?;

crates/ide_assists/src/handlers/extract_function.rs

@@ -16,7 +16,6 @@ use syntax::{
         edit::{AstNodeEdit, IndentLevel},
         AstNode,
     },
-    SyntaxElement,
     SyntaxKind::{self, BLOCK_EXPR, BREAK_EXPR, COMMENT, PATH_EXPR, RETURN_EXPR},
     SyntaxNode, SyntaxToken, TextRange, TextSize, TokenAtOffset, WalkEvent, T,
 };
@@ -62,7 +61,10 @@ pub(crate) fn extract_function(acc: &mut Assists, ctx: &AssistContext) -> Option
         return None;
     }
 
-    let node = element_to_node(node);
+    let node = match node {
+        syntax::NodeOrToken::Node(n) => n,
+        syntax::NodeOrToken::Token(t) => t.parent()?,
+    };
 
     let body = extraction_target(&node, ctx.frange.range)?;
 
@@ -560,14 +562,6 @@ impl HasTokenAtOffset for FunctionBody {
     }
 }
 
-/// node or token's parent
-fn element_to_node(node: SyntaxElement) -> SyntaxNode {
-    match node {
-        syntax::NodeOrToken::Node(n) => n,
-        syntax::NodeOrToken::Token(t) => t.parent(),
-    }
-}
-
 /// Try to guess what user wants to extract
 ///
 /// We have basically have two cases:
@@ -1246,7 +1240,7 @@ fn make_body(
             })
         }
         FlowHandler::If { .. } => {
-            let lit_false = ast::Literal::cast(make::tokens::literal("false").parent()).unwrap();
+            let lit_false = make::expr_literal("false");
             with_tail_expr(block, lit_false.into())
         }
         FlowHandler::IfOption { .. } => {
@@ -1420,9 +1414,7 @@ fn update_external_control_flow(handler: &FlowHandler, syntax: &SyntaxNode) -> S
 fn make_rewritten_flow(handler: &FlowHandler, arg_expr: Option<ast::Expr>) -> Option<ast::Expr> {
     let value = match handler {
         FlowHandler::None | FlowHandler::Try { .. } => return None,
-        FlowHandler::If { .. } => {
+        FlowHandler::If { .. } => make::expr_literal("true").into(),
-            ast::Literal::cast(make::tokens::literal("true").parent()).unwrap().into()
-        }
         FlowHandler::IfOption { .. } => {
             let expr = arg_expr.unwrap_or_else(|| make::expr_tuple(Vec::new()));
             let args = make::arg_list(iter::once(expr));

crates/ide_assists/src/handlers/flip_trait_bound.rs

@@ -23,7 +23,7 @@ pub(crate) fn flip_trait_bound(acc: &mut Assists, ctx: &AssistContext) -> Option
     let plus = ctx.find_token_syntax_at_offset(T![+])?;
 
     // Make sure we're in a `TypeBoundList`
-    if ast::TypeBoundList::cast(plus.parent()).is_none() {
+    if ast::TypeBoundList::cast(plus.parent()?).is_none() {
         return None;
     }
 

crates/ide_assists/src/handlers/invert_if.rs

@@ -30,7 +30,7 @@ use crate::{
 
 pub(crate) fn invert_if(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let if_keyword = ctx.find_token_syntax_at_offset(T![if])?;
-    let expr = ast::IfExpr::cast(if_keyword.parent())?;
+    let expr = ast::IfExpr::cast(if_keyword.parent()?)?;
     let if_range = if_keyword.text_range();
     let cursor_in_range = if_range.contains_range(ctx.frange.range);
     if !cursor_in_range {

crates/ide_assists/src/handlers/move_bounds.rs

@@ -1,8 +1,6 @@
 use syntax::{
-    ast::{self, edit::AstNodeEdit, make, AstNode, NameOwner, TypeBoundsOwner},
+    ast::{self, edit_in_place::GenericParamsOwnerEdit, make, AstNode, NameOwner, TypeBoundsOwner},
     match_ast,
-    SyntaxKind::*,
-    T,
 };
 
 use crate::{AssistContext, AssistId, AssistKind, Assists};
@@ -23,7 +21,7 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 // }
 // ```
 pub(crate) fn move_bounds_to_where_clause(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
-    let type_param_list = ctx.find_node_at_offset::<ast::GenericParamList>()?;
+    let type_param_list = ctx.find_node_at_offset::<ast::GenericParamList>()?.clone_for_update();
 
     let mut type_params = type_param_list.type_params();
     if type_params.all(|p| p.type_bound_list().is_none()) {
@@ -31,23 +29,7 @@ pub(crate) fn move_bounds_to_where_clause(acc: &mut Assists, ctx: &AssistContext
     }
 
     let parent = type_param_list.syntax().parent()?;
-    if parent.children_with_tokens().any(|it| it.kind() == WHERE_CLAUSE) {
+    let original_parent_range = parent.text_range();
-        return None;
-    }
-
-    let anchor = match_ast! {
-        match parent {
-            ast::Fn(it) => it.body()?.syntax().clone().into(),
-            ast::Trait(it) => it.assoc_item_list()?.syntax().clone().into(),
-            ast::Impl(it) => it.assoc_item_list()?.syntax().clone().into(),
-            ast::Enum(it) => it.variant_list()?.syntax().clone().into(),
-            ast::Struct(it) => {
-                it.syntax().children_with_tokens()
-                    .find(|it| it.kind() == RECORD_FIELD_LIST || it.kind() == T![;])?
-            },
-            _ => return None
-        }
-    };
 
     let target = type_param_list.syntax().text_range();
     acc.add(
@@ -55,29 +37,27 @@ pub(crate) fn move_bounds_to_where_clause(acc: &mut Assists, ctx: &AssistContext
         "Move to where clause",
         target,
         |edit| {
-            let new_params = type_param_list
+            let where_clause: ast::WhereClause = match_ast! {
-                .type_params()
+                match parent {
-                .filter(|it| it.type_bound_list().is_some())
+                    ast::Fn(it) => it.get_or_create_where_clause(),
-                .map(|type_param| {
+                    // ast::Trait(it) => it.get_or_create_where_clause(),
-                    let without_bounds = type_param.remove_bounds();
+                    ast::Impl(it) => it.get_or_create_where_clause(),
-                    (type_param, without_bounds)
+                    // ast::Enum(it) => it.get_or_create_where_clause(),
-                });
+                    ast::Struct(it) => it.get_or_create_where_clause(),
-
+                    _ => return,
-            let new_type_param_list = type_param_list.replace_descendants(new_params);
-            edit.replace_ast(type_param_list.clone(), new_type_param_list);
-
-            let where_clause = {
-                let predicates = type_param_list.type_params().filter_map(build_predicate);
-                make::where_clause(predicates)
-            };
-
-            let to_insert = match anchor.prev_sibling_or_token() {
-                Some(ref elem) if elem.kind() == WHITESPACE => {
-                    format!("{} ", where_clause.syntax())
                 }
-                _ => format!(" {}", where_clause.syntax()),
             };
-            edit.insert(anchor.text_range().start(), to_insert);
+
+            for type_param in type_param_list.type_params() {
+                if let Some(tbl) = type_param.type_bound_list() {
+                    if let Some(predicate) = build_predicate(type_param.clone()) {
+                        where_clause.add_predicate(predicate.clone_for_update())
+                    }
+                    tbl.remove()
+                }
+            }
+
+            edit.replace(original_parent_range, parent.to_string())
         },
     )
 }

crates/ide_assists/src/handlers/split_import.rs

@@ -17,7 +17,7 @@ use crate::{AssistContext, AssistId, AssistKind, Assists};
 // ```
 pub(crate) fn split_import(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let colon_colon = ctx.find_token_syntax_at_offset(T![::])?;
-    let path = ast::Path::cast(colon_colon.parent())?.qualifier()?;
+    let path = ast::Path::cast(colon_colon.parent()?)?.qualifier()?;
     let top_path = successors(Some(path.clone()), |it| it.parent_path()).last()?;
 
     let use_tree = top_path.syntax().ancestors().find_map(ast::UseTree::cast)?;

crates/ide_assists/src/handlers/unwrap_block.rs

@@ -30,7 +30,7 @@ pub(crate) fn unwrap_block(acc: &mut Assists, ctx: &AssistContext) -> Option<()>
     let assist_label = "Unwrap block";
 
     let l_curly_token = ctx.find_token_syntax_at_offset(T!['{'])?;
-    let mut block = ast::BlockExpr::cast(l_curly_token.parent())?;
+    let mut block = ast::BlockExpr::cast(l_curly_token.parent()?)?;
     let target = block.syntax().text_range();
     let mut parent = block.syntax().parent()?;
     if ast::MatchArm::can_cast(parent.kind()) {

crates/ide_completion/src/completions/fn_param.rs

@@ -33,7 +33,7 @@ pub(crate) fn complete_fn_param(acc: &mut Completions, ctx: &CompletionContext)
         });
     };
 
-    for node in ctx.token.parent().ancestors() {
+    for node in ctx.token.ancestors() {
         match_ast! {
             match node {
                 ast::SourceFile(it) => it.items().filter_map(|item| match item {

crates/ide_completion/src/completions/trait_impl.rs

@@ -82,13 +82,14 @@ pub(crate) fn complete_trait_impl(acc: &mut Completions, ctx: &CompletionContext
 
 fn completion_match(ctx: &CompletionContext) -> Option<(ImplCompletionKind, SyntaxNode, Impl)> {
     let mut token = ctx.token.clone();
-    // For keywork without name like `impl .. { fn $0 }`, the current position is inside
+    // For keyword without name like `impl .. { fn $0 }`, the current position is inside
     // the whitespace token, which is outside `FN` syntax node.
     // We need to follow the previous token in this case.
     if token.kind() == SyntaxKind::WHITESPACE {
         token = token.prev_token()?;
     }
 
+    let parent_kind = token.parent().map_or(SyntaxKind::EOF, |it| it.kind());
     let impl_item_offset = match token.kind() {
         // `impl .. { const $0 }`
         // ERROR      0
@@ -102,14 +103,14 @@ fn completion_match(ctx: &CompletionContext) -> Option<(ImplCompletionKind, Synt
         // FN/TYPE_ALIAS/CONST  1
         //  NAME                0
         //    IDENT             <- *
-        SyntaxKind::IDENT if token.parent().kind() == SyntaxKind::NAME => 1,
+        SyntaxKind::IDENT if parent_kind == SyntaxKind::NAME => 1,
         // `impl .. { foo$0 }`
         // MACRO_CALL       3
         //  PATH            2
         //    PATH_SEGMENT  1
         //      NAME_REF    0
         //        IDENT     <- *
-        SyntaxKind::IDENT if token.parent().kind() == SyntaxKind::NAME_REF => 3,
+        SyntaxKind::IDENT if parent_kind == SyntaxKind::NAME_REF => 3,
         _ => return None,
     };
 

crates/ide_completion/src/context.rs

@@ -120,7 +120,7 @@ impl<'a> CompletionContext<'a> {
         let original_token =
             original_file.syntax().token_at_offset(position.offset).left_biased()?;
         let token = sema.descend_into_macros(original_token.clone());
-        let scope = sema.scope_at_offset(&token.parent(), position.offset);
+        let scope = sema.scope_at_offset(&token, position.offset);
         let mut locals = vec![];
         scope.process_all_names(&mut |name, scope| {
             if let ScopeDef::Local(local) = scope {
@@ -281,7 +281,7 @@ impl<'a> CompletionContext<'a> {
     fn fill_impl_def(&mut self) {
         self.impl_def = self
             .sema
-            .ancestors_with_macros(self.token.parent())
+            .token_ancestors_with_macros(self.token.clone())
             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
             .find_map(ast::Impl::cast);
     }
@@ -293,7 +293,10 @@ impl<'a> CompletionContext<'a> {
         offset: TextSize,
     ) {
         let expected = {
-            let mut node = self.token.parent();
+            let mut node = match self.token.parent() {
+                Some(it) => it,
+                None => return,
+            };
             loop {
                 let ret = match_ast! {
                     match node {
@@ -474,17 +477,17 @@ impl<'a> CompletionContext<'a> {
         }
 
         self.use_item_syntax =
-            self.sema.ancestors_with_macros(self.token.parent()).find_map(ast::Use::cast);
+            self.sema.token_ancestors_with_macros(self.token.clone()).find_map(ast::Use::cast);
 
         self.function_syntax = self
             .sema
-            .ancestors_with_macros(self.token.parent())
+            .token_ancestors_with_macros(self.token.clone())
             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
             .find_map(ast::Fn::cast);
 
         self.record_field_syntax = self
             .sema
-            .ancestors_with_macros(self.token.parent())
+            .token_ancestors_with_macros(self.token.clone())
             .take_while(|it| {
                 it.kind() != SOURCE_FILE && it.kind() != MODULE && it.kind() != CALL_EXPR
             })

crates/ide_completion/src/patterns.rs

@@ -184,11 +184,7 @@ fn test_has_impl_as_prev_sibling() {
 }
 
 pub(crate) fn is_in_loop_body(element: SyntaxElement) -> bool {
-    let leaf = match element {
+    for node in element.ancestors() {
-        NodeOrToken::Node(node) => node,
-        NodeOrToken::Token(token) => token.parent(),
-    };
-    for node in leaf.ancestors() {
         if node.kind() == FN || node.kind() == CLOSURE_EXPR {
             break;
         }
@@ -201,7 +197,7 @@ pub(crate) fn is_in_loop_body(element: SyntaxElement) -> bool {
             }
         };
         if let Some(body) = loop_body {
-            if body.syntax().text_range().contains_range(leaf.text_range()) {
+            if body.syntax().text_range().contains_range(element.text_range()) {
                 return true;
             }
         }
@@ -235,12 +231,8 @@ fn previous_sibling_or_ancestor_sibling(element: SyntaxElement) -> Option<Syntax
         Some(sibling)
     } else {
         // if not trying to find first ancestor which has such a sibling
-        let node = match element {
+        let range = element.text_range();
-            NodeOrToken::Node(node) => node,
+        let top_node = element.ancestors().take_while(|it| it.text_range() == range).last()?;
-            NodeOrToken::Token(token) => token.parent(),
-        };
-        let range = node.text_range();
-        let top_node = node.ancestors().take_while(|it| it.text_range() == range).last()?;
         let prev_sibling_node = top_node.ancestors().find(|it| {
             non_trivia_sibling(NodeOrToken::Node(it.to_owned()), Direction::Prev).is_some()
         })?;

crates/ide_db/src/call_info.rs

@@ -109,7 +109,7 @@ fn call_info_impl(
     token: SyntaxToken,
 ) -> Option<(hir::Callable, Option<usize>)> {
     // Find the calling expression and it's NameRef
-    let calling_node = FnCallNode::with_node(&token.parent())?;
+    let calling_node = FnCallNode::with_node(&token.parent()?)?;
 
     let callable = match &calling_node {
         FnCallNode::CallExpr(call) => sema.type_of_expr(&call.expr()?)?.as_callable(sema.db)?,

crates/ide_ssr/src/resolving.rs

@@ -195,7 +195,7 @@ impl<'db> ResolutionScope<'db> {
             .syntax()
             .token_at_offset(resolve_context.offset)
             .left_biased()
-            .map(|token| token.parent())
+            .and_then(|token| token.parent())
             .unwrap_or_else(|| file.syntax().clone());
         let node = pick_node_for_resolution(node);
         let scope = sema.scope(&node);

crates/syntax/Cargo.toml

@@ -13,7 +13,7 @@ doctest = false
 [dependencies]
 cov-mark = { version = "1.1", features = ["thread-local"] }
 itertools = "0.10.0"
-rowan = "0.12.2"
+rowan = "0.13.0-pre.2"
 rustc_lexer = { version = "710.0.0", package = "rustc-ap-rustc_lexer" }
 rustc-hash = "1.1.0"
 arrayvec = "0.5.1"

crates/syntax/src/algo.rs

@@ -4,7 +4,6 @@ use std::{
     fmt,
     hash::BuildHasherDefault,
     ops::{self, RangeInclusive},
-    ptr,
 };
 
 use indexmap::IndexMap;
@@ -27,7 +26,7 @@ pub fn ancestors_at_offset(
     offset: TextSize,
 ) -> impl Iterator<Item = SyntaxNode> {
     node.token_at_offset(offset)
-        .map(|token| token.parent().ancestors())
+        .map(|token| token.ancestors())
         .kmerge_by(|node1, node2| node1.text_range().len() < node2.text_range().len())
 }
 
@@ -171,7 +170,7 @@ pub fn diff(from: &SyntaxNode, to: &SyntaxNode) -> TreeDiff {
             && lhs.text_range().len() == rhs.text_range().len()
             && match (&lhs, &rhs) {
                 (NodeOrToken::Node(lhs), NodeOrToken::Node(rhs)) => {
-                    ptr::eq(lhs.green(), rhs.green()) || lhs.text() == rhs.text()
+                    lhs == rhs || lhs.text() == rhs.text()
                 }
                 (NodeOrToken::Token(lhs), NodeOrToken::Token(rhs)) => lhs.text() == rhs.text(),
                 _ => false,
@@ -280,9 +279,10 @@ fn _insert_children(
         to_green_element(element)
     });
 
-    let mut old_children = parent.green().children().map(|it| match it {
+    let parent_green = parent.green();
-        NodeOrToken::Token(it) => NodeOrToken::Token(it.clone()),
+    let mut old_children = parent_green.children().map(|it| match it {
-        NodeOrToken::Node(it) => NodeOrToken::Node(it.clone()),
+        NodeOrToken::Token(it) => NodeOrToken::Token(it.to_owned()),
+        NodeOrToken::Node(it) => NodeOrToken::Node(it.to_owned()),
     });
 
     let new_children = match &position {
@@ -319,9 +319,10 @@ fn _replace_children(
 ) -> SyntaxNode {
     let start = position_of_child(parent, to_delete.start().clone());
     let end = position_of_child(parent, to_delete.end().clone());
-    let mut old_children = parent.green().children().map(|it| match it {
+    let parent_green = parent.green();
-        NodeOrToken::Token(it) => NodeOrToken::Token(it.clone()),
+    let mut old_children = parent_green.children().map(|it| match it {
-        NodeOrToken::Node(it) => NodeOrToken::Node(it.clone()),
+        NodeOrToken::Token(it) => NodeOrToken::Token(it.to_owned()),
+        NodeOrToken::Node(it) => NodeOrToken::Node(it.to_owned()),
     });
 
     let before = old_children.by_ref().take(start).collect::<Vec<_>>();
@@ -487,9 +488,9 @@ impl<'a> SyntaxRewriter<'a> {
     /// Returns `None` when there are no replacements.
     pub fn rewrite_root(&self) -> Option<SyntaxNode> {
         let _p = profile::span("rewrite_root");
-        fn element_to_node_or_parent(element: &SyntaxElement) -> SyntaxNode {
+        fn element_to_node_or_parent(element: &SyntaxElement) -> Option<SyntaxNode> {
             match element {
-                SyntaxElement::Node(it) => it.clone(),
+                SyntaxElement::Node(it) => Some(it.clone()),
                 SyntaxElement::Token(it) => it.parent(),
             }
         }
@@ -497,9 +498,9 @@ impl<'a> SyntaxRewriter<'a> {
         assert!(self.f.is_none());
         self.replacements
             .keys()
-            .map(element_to_node_or_parent)
+            .filter_map(element_to_node_or_parent)
-            .chain(self.insertions.keys().map(|pos| match pos {
+            .chain(self.insertions.keys().filter_map(|pos| match pos {
-                InsertPos::FirstChildOf(it) => it.clone(),
+                InsertPos::FirstChildOf(it) => Some(it.clone()),
                 InsertPos::After(it) => element_to_node_or_parent(it),
             }))
             // If we only have one replacement/insertion, we must return its parent node, since `rewrite` does
@@ -552,7 +553,7 @@ impl<'a> SyntaxRewriter<'a> {
             };
         } else {
             match element {
-                NodeOrToken::Token(it) => acc.push(NodeOrToken::Token(it.green().clone())),
+                NodeOrToken::Token(it) => acc.push(NodeOrToken::Token(it.green().to_owned())),
                 NodeOrToken::Node(it) => {
                     acc.push(NodeOrToken::Node(self.rewrite_children(it)));
                 }
@@ -567,7 +568,7 @@ impl<'a> SyntaxRewriter<'a> {
 fn element_to_green(element: SyntaxElement) -> NodeOrToken<rowan::GreenNode, rowan::GreenToken> {
     match element {
         NodeOrToken::Node(it) => NodeOrToken::Node(it.green().to_owned()),
-        NodeOrToken::Token(it) => NodeOrToken::Token(it.green().clone()),
+        NodeOrToken::Token(it) => NodeOrToken::Token(it.green().to_owned()),
     }
 }
 
@@ -625,7 +626,7 @@ fn position_of_child(parent: &SyntaxNode, child: SyntaxElement) -> usize {
 fn to_green_element(element: SyntaxElement) -> NodeOrToken<rowan::GreenNode, rowan::GreenToken> {
     match element {
         NodeOrToken::Node(it) => it.green().to_owned().into(),
-        NodeOrToken::Token(it) => it.green().clone().into(),
+        NodeOrToken::Token(it) => it.green().to_owned().into(),
     }
 }
 

crates/syntax/src/ast.rs

@@ -6,6 +6,7 @@ mod token_ext;
 mod node_ext;
 mod expr_ext;
 pub mod edit;
+pub mod edit_in_place;
 pub mod make;
 
 use std::marker::PhantomData;
@@ -40,6 +41,12 @@ pub trait AstNode {
         Self: Sized;
 
     fn syntax(&self) -> &SyntaxNode;
+    fn clone_for_update(&self) -> Self
+    where
+        Self: Sized,
+    {
+        Self::cast(self.syntax().clone_for_update()).unwrap()
+    }
 }
 
 /// Like `AstNode`, but wraps tokens rather than interior nodes.

crates/syntax/src/ast/edit_in_place.rs

@@ -0,0 +1,105 @@
+//! Structural editing for ast.
+
+use std::iter::empty;
+
+use ast::{edit::AstNodeEdit, make, GenericParamsOwner, WhereClause};
+use parser::T;
+
+use crate::{
+    ast,
+    ted::{self, Position},
+    AstNode, Direction, SyntaxKind,
+};
+
+use super::NameOwner;
+
+pub trait GenericParamsOwnerEdit: ast::GenericParamsOwner + AstNodeEdit {
+    fn get_or_create_where_clause(&self) -> ast::WhereClause;
+}
+
+impl GenericParamsOwnerEdit for ast::Fn {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let position = if let Some(ty) = self.ret_type() {
+                Position::after(ty.syntax().clone())
+            } else if let Some(param_list) = self.param_list() {
+                Position::after(param_list.syntax().clone())
+            } else {
+                Position::last_child_of(self.syntax().clone())
+            };
+            create_where_clause(position)
+        }
+        self.where_clause().unwrap()
+    }
+}
+
+impl GenericParamsOwnerEdit for ast::Impl {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let position = if let Some(ty) = self.self_ty() {
+                Position::after(ty.syntax().clone())
+            } else {
+                Position::last_child_of(self.syntax().clone())
+            };
+            create_where_clause(position)
+        }
+        self.where_clause().unwrap()
+    }
+}
+impl GenericParamsOwnerEdit for ast::Struct {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let tfl = self.field_list().and_then(|fl| match fl {
+                ast::FieldList::RecordFieldList(_) => None,
+                ast::FieldList::TupleFieldList(it) => Some(it),
+            });
+            let position = if let Some(tfl) = tfl {
+                Position::after(tfl.syntax().clone())
+            } else if let Some(gpl) = self.generic_param_list() {
+                Position::after(gpl.syntax().clone())
+            } else if let Some(name) = self.name() {
+                Position::after(name.syntax().clone())
+            } else {
+                Position::last_child_of(self.syntax().clone())
+            };
+            create_where_clause(position)
+        }
+        self.where_clause().unwrap()
+    }
+}
+
+fn create_where_clause(position: Position) {
+    let elements = vec![
+        make::tokens::single_space().into(),
+        make::where_clause(empty()).clone_for_update().syntax().clone().into(),
+    ];
+    ted::insert_all(position, elements);
+}
+
+impl ast::WhereClause {
+    pub fn add_predicate(&self, predicate: ast::WherePred) {
+        if let Some(pred) = self.predicates().last() {
+            if !pred.syntax().siblings_with_tokens(Direction::Next).any(|it| it.kind() == T![,]) {
+                ted::append_child(self.syntax().clone(), make::token(T![,]));
+            }
+        }
+        if self.syntax().children_with_tokens().last().map(|it| it.kind())
+            != Some(SyntaxKind::WHITESPACE)
+        {
+            ted::append_child(self.syntax().clone(), make::tokens::single_space());
+        }
+        ted::append_child(self.syntax().clone(), predicate.syntax().clone())
+    }
+}
+
+impl ast::TypeBoundList {
+    pub fn remove(&self) {
+        if let Some(colon) =
+            self.syntax().siblings_with_tokens(Direction::Prev).find(|it| it.kind() == T![:])
+        {
+            ted::remove_all(colon..=self.syntax().clone().into())
+        } else {
+            ted::remove(self.syntax().clone())
+        }
+    }
+}

crates/syntax/src/ast/make.rs

@@ -174,6 +174,11 @@ pub fn block_expr(
 pub fn expr_unit() -> ast::Expr {
     expr_from_text("()")
 }
+pub fn expr_literal(text: &str) -> ast::Literal {
+    assert_eq!(text.trim(), text);
+    ast_from_text(&format!("fn f() {{ let _ = {}; }}", text))
+}
+
 pub fn expr_empty_block() -> ast::Expr {
     expr_from_text("{}")
 }
@@ -390,6 +395,7 @@ pub fn token(kind: SyntaxKind) -> SyntaxToken {
     tokens::SOURCE_FILE
         .tree()
         .syntax()
+        .clone_for_update()
         .descendants_with_tokens()
         .filter_map(|it| it.into_token())
         .find(|it| it.kind() == kind)
@@ -544,6 +550,7 @@ pub mod tokens {
         SOURCE_FILE
             .tree()
             .syntax()
+            .clone_for_update()
             .descendants_with_tokens()
             .filter_map(|it| it.into_token())
             .find(|it| it.kind() == WHITESPACE && it.text() == " ")
@@ -569,13 +576,16 @@ pub mod tokens {
     }
 
     pub fn single_newline() -> SyntaxToken {
-        SOURCE_FILE
+        let res = SOURCE_FILE
             .tree()
             .syntax()
+            .clone_for_update()
             .descendants_with_tokens()
             .filter_map(|it| it.into_token())
             .find(|it| it.kind() == WHITESPACE && it.text() == "\n")
-            .unwrap()
+            .unwrap();
+        res.detach();
+        res
     }
 
     pub fn blank_line() -> SyntaxToken {

crates/syntax/src/ast/node_ext.rs

@@ -34,7 +34,9 @@ impl ast::NameRef {
 }
 
 fn text_of_first_token(node: &SyntaxNode) -> &str {
-    node.green().children().next().and_then(|it| it.into_token()).unwrap().text()
+    let t =
+        node.green().children().next().and_then(|it| it.into_token()).unwrap().text().to_string();
+    Box::leak(Box::new(t))
 }
 
 pub enum Macro {

crates/syntax/src/lib.rs

@@ -38,6 +38,7 @@ pub mod ast;
 #[doc(hidden)]
 pub mod fuzz;
 pub mod utils;
+pub mod ted;
 
 use std::{marker::PhantomData, sync::Arc};
 

crates/syntax/src/parsing/reparsing.rs

@@ -124,11 +124,7 @@ fn is_contextual_kw(text: &str) -> bool {
 fn find_reparsable_node(node: &SyntaxNode, range: TextRange) -> Option<(SyntaxNode, Reparser)> {
     let node = node.covering_element(range);
 
-    let mut ancestors = match node {
+    node.ancestors().find_map(|node| {
-        NodeOrToken::Token(it) => it.parent().ancestors(),
-        NodeOrToken::Node(it) => it.ancestors(),
-    };
-    ancestors.find_map(|node| {
         let first_child = node.first_child_or_token().map(|it| it.kind());
         let parent = node.parent().map(|it| it.kind());
         Reparser::for_node(node.kind(), first_child, parent).map(|r| (node, r))

crates/syntax/src/ted.rs

@@ -0,0 +1,78 @@
+//! Primitive tree editor, ed for trees
+#![allow(unused)]
+use std::ops::RangeInclusive;
+
+use crate::{SyntaxElement, SyntaxNode};
+
+#[derive(Debug)]
+pub struct Position {
+    repr: PositionRepr,
+}
+
+#[derive(Debug)]
+enum PositionRepr {
+    FirstChild(SyntaxNode),
+    After(SyntaxElement),
+}
+
+impl Position {
+    pub fn after(elem: impl Into<SyntaxElement>) -> Position {
+        let repr = PositionRepr::After(elem.into());
+        Position { repr }
+    }
+    pub fn before(elem: impl Into<SyntaxElement>) -> Position {
+        let elem = elem.into();
+        let repr = match elem.prev_sibling_or_token() {
+            Some(it) => PositionRepr::After(it),
+            None => PositionRepr::FirstChild(elem.parent().unwrap()),
+        };
+        Position { repr }
+    }
+    pub fn first_child_of(node: impl Into<SyntaxNode>) -> Position {
+        let repr = PositionRepr::FirstChild(node.into());
+        Position { repr }
+    }
+    pub fn last_child_of(node: impl Into<SyntaxNode>) -> Position {
+        let node = node.into();
+        let repr = match node.last_child_or_token() {
+            Some(it) => PositionRepr::After(it),
+            None => PositionRepr::FirstChild(node),
+        };
+        Position { repr }
+    }
+}
+
+pub fn insert(position: Position, elem: impl Into<SyntaxElement>) {
+    insert_all(position, vec![elem.into()])
+}
+pub fn insert_all(position: Position, elements: Vec<SyntaxElement>) {
+    let (parent, index) = match position.repr {
+        PositionRepr::FirstChild(parent) => (parent, 0),
+        PositionRepr::After(child) => (child.parent().unwrap(), child.index() + 1),
+    };
+    parent.splice_children(index..index, elements);
+}
+
+pub fn remove(elem: impl Into<SyntaxElement>) {
+    let elem = elem.into();
+    remove_all(elem.clone()..=elem)
+}
+pub fn remove_all(range: RangeInclusive<SyntaxElement>) {
+    replace_all(range, Vec::new())
+}
+
+pub fn replace(old: impl Into<SyntaxElement>, new: impl Into<SyntaxElement>) {
+    let old = old.into();
+    replace_all(old.clone()..=old, vec![new.into()])
+}
+pub fn replace_all(range: RangeInclusive<SyntaxElement>, new: Vec<SyntaxElement>) {
+    let start = range.start().index();
+    let end = range.end().index();
+    let parent = range.start().parent().unwrap();
+    parent.splice_children(start..end + 1, new)
+}
+
+pub fn append_child(node: impl Into<SyntaxNode>, child: impl Into<SyntaxElement>) {
+    let position = Position::last_child_of(node);
+    insert(position, child)
+}