3 files changed, 7 insertions, 154 deletions

diff --git a/crates/ide_db/src/helpers/merge_imports.rs b/crates/ide_db/src/helpers/merge_imports.rs
index 475ef99b5..8fb40e837 100644
--- a/crates/ide_db/src/helpers/merge_imports.rs
+++ b/crates/ide_db/src/helpers/merge_imports.rs
@@ -42,10 +42,12 @@ pub fn try_merge_imports(
         return None;
     }
 
+    let lhs = lhs.clone_subtree().clone_for_update();
     let lhs_tree = lhs.use_tree()?;
     let rhs_tree = rhs.use_tree()?;
     let merged = try_merge_trees(&lhs_tree, &rhs_tree, merge_behavior)?;
-    Some(lhs.with_use_tree(merged).clone_for_update())
+    ted::replace(lhs_tree.syntax(), merged.syntax());
+    Some(lhs)
 }
 
 pub fn try_merge_trees(
diff --git a/crates/syntax/src/algo.rs b/crates/syntax/src/algo.rs
index 825ea3185..241713c48 100644
--- a/crates/syntax/src/algo.rs
+++ b/crates/syntax/src/algo.rs
@@ -1,6 +1,6 @@
 //! FIXME: write short doc here
 
-use std::{fmt, hash::BuildHasherDefault, ops::RangeInclusive};
+use std::{hash::BuildHasherDefault, ops::RangeInclusive};
 
 use indexmap::IndexMap;
 use itertools::Itertools;
@@ -330,110 +330,6 @@ fn _replace_children(
     with_children(parent, new_children)
 }
 
-#[derive(Debug, PartialEq, Eq, Hash)]
-enum InsertPos {
-    FirstChildOf(SyntaxNode),
-    After(SyntaxElement),
-}
-
-#[derive(Default)]
-pub(crate) struct SyntaxRewriter<'a> {
-    //FIXME: add debug_assertions that all elements are in fact from the same file.
-    replacements: FxHashMap<SyntaxElement, Replacement>,
-    insertions: IndexMap<InsertPos, Vec<SyntaxElement>>,
-    _pd: std::marker::PhantomData<&'a ()>,
-}
-
-impl fmt::Debug for SyntaxRewriter<'_> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_struct("SyntaxRewriter")
-            .field("replacements", &self.replacements)
-            .field("insertions", &self.insertions)
-            .finish()
-    }
-}
-
-impl SyntaxRewriter<'_> {
-    pub(crate) fn replace<T: Clone + Into<SyntaxElement>>(&mut self, what: &T, with: &T) {
-        let what = what.clone().into();
-        let replacement = Replacement::Single(with.clone().into());
-        self.replacements.insert(what, replacement);
-    }
-
-    pub(crate) fn rewrite(&self, node: &SyntaxNode) -> SyntaxNode {
-        let _p = profile::span("rewrite");
-
-        if self.replacements.is_empty() && self.insertions.is_empty() {
-            return node.clone();
-        }
-        let green = self.rewrite_children(node);
-        with_green(node, green)
-    }
-
-    pub(crate) fn rewrite_ast<N: AstNode>(self, node: &N) -> N {
-        N::cast(self.rewrite(node.syntax())).unwrap()
-    }
-
-    fn replacement(&self, element: &SyntaxElement) -> Option<Replacement> {
-        self.replacements.get(element).cloned()
-    }
-
-    fn insertions(&self, pos: &InsertPos) -> Option<impl Iterator<Item = SyntaxElement> + '_> {
-        self.insertions.get(pos).map(|insertions| insertions.iter().cloned())
-    }
-
-    fn rewrite_children(&self, node: &SyntaxNode) -> rowan::GreenNode {
-        let _p = profile::span("rewrite_children");
-
-        //  FIXME: this could be made much faster.
-        let mut new_children = Vec::new();
-        if let Some(elements) = self.insertions(&InsertPos::FirstChildOf(node.clone())) {
-            new_children.extend(elements.map(element_to_green));
-        }
-        for child in node.children_with_tokens() {
-            self.rewrite_self(&mut new_children, &child);
-        }
-
-        rowan::GreenNode::new(rowan::SyntaxKind(node.kind() as u16), new_children)
-    }
-
-    fn rewrite_self(
-        &self,
-        acc: &mut Vec<NodeOrToken<rowan::GreenNode, rowan::GreenToken>>,
-        element: &SyntaxElement,
-    ) {
-        let _p = profile::span("rewrite_self");
-
-        if let Some(replacement) = self.replacement(&element) {
-            match replacement {
-                Replacement::Single(element) => acc.push(element_to_green(element)),
-            };
-        } else {
-            match element {
-                NodeOrToken::Token(it) => acc.push(NodeOrToken::Token(it.green().to_owned())),
-                NodeOrToken::Node(it) => {
-                    acc.push(NodeOrToken::Node(self.rewrite_children(it)));
-                }
-            }
-        }
-        if let Some(elements) = self.insertions(&InsertPos::After(element.clone())) {
-            acc.extend(elements.map(element_to_green));
-        }
-    }
-}
-
-fn element_to_green(element: SyntaxElement) -> NodeOrToken<rowan::GreenNode, rowan::GreenToken> {
-    match element {
-        NodeOrToken::Node(it) => NodeOrToken::Node(it.green().into_owned()),
-        NodeOrToken::Token(it) => NodeOrToken::Token(it.green().to_owned()),
-    }
-}
-
-#[derive(Clone, Debug)]
-enum Replacement {
-    Single(SyntaxElement),
-}
-
 fn with_children(
     parent: &SyntaxNode,
     new_children: Vec<NodeOrToken<rowan::GreenNode, rowan::GreenToken>>,
diff --git a/crates/syntax/src/ast/edit.rs b/crates/syntax/src/ast/edit.rs
index 78c0dc102..10ec94cd2 100644
--- a/crates/syntax/src/ast/edit.rs
+++ b/crates/syntax/src/ast/edit.rs
@@ -2,18 +2,18 @@
 //! 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, TypeBoundsOwner,
     },
     ted, AstToken, Direction, InsertPosition, NodeOrToken, SmolStr, SyntaxElement, SyntaxKind,
     SyntaxKind::{ATTR, COMMENT, WHITESPACE},
@@ -46,18 +46,6 @@ impl ast::Fn {
         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
@@ -313,33 +301,7 @@ 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 {
@@ -664,13 +626,6 @@ 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())
     }