diff --git a/crates/ra_assists/src/ast_transform.rs b/crates/ra_assists/src/ast_transform.rs
index 7846e97981..a74ac42d5d 100644
--- a/crates/ra_assists/src/ast_transform.rs
+++ b/crates/ra_assists/src/ast_transform.rs
@@ -157,7 +157,7 @@ impl<'a> QualifyPaths<'a> {
 
 pub fn apply<'a, N: AstNode>(transformer: &dyn AstTransform<'a>, node: N) -> N {
     let syntax = node.syntax();
-    let result = ra_syntax::algo::replace_descendants(syntax, &|element| match element {
+    let result = ra_syntax::algo::replace_descendants(syntax, |element| match element {
         ra_syntax::SyntaxElement::Node(n) => {
             let replacement = transformer.get_substitution(&n)?;
             Some(replacement.into())
diff --git a/crates/ra_ide/src/expand_macro.rs b/crates/ra_ide/src/expand_macro.rs
index f2814e6842..5a079de270 100644
--- a/crates/ra_ide/src/expand_macro.rs
+++ b/crates/ra_ide/src/expand_macro.rs
@@ -52,7 +52,7 @@ fn expand_macro_recur(
         }
     }
 
-    Some(replace_descendants(&expanded, &|n| replaces.get(n).cloned()))
+    Some(replace_descendants(&expanded, |n| replaces.get(n).cloned()))
 }
 
 // FIXME: It would also be cool to share logic here and in the mbe tests,
diff --git a/crates/ra_mbe/src/syntax_bridge.rs b/crates/ra_mbe/src/syntax_bridge.rs
index ea2cac069e..2aaf0215fa 100644
--- a/crates/ra_mbe/src/syntax_bridge.rs
+++ b/crates/ra_mbe/src/syntax_bridge.rs
@@ -570,7 +570,7 @@ mod tests {
         let token_tree = insert_children(
             &rbrace.parent().unwrap(),
             InsertPosition::Last,
-            &mut std::iter::once(space),
+            std::iter::once(space),
         );
 
         // Token Tree now is :
diff --git a/crates/ra_syntax/src/algo.rs b/crates/ra_syntax/src/algo.rs
index ebf59288a3..b87c7084e6 100644
--- a/crates/ra_syntax/src/algo.rs
+++ b/crates/ra_syntax/src/algo.rs
@@ -142,6 +142,15 @@ pub fn diff(from: &SyntaxNode, to: &SyntaxNode) -> TreeDiff {
 /// This is a type-unsafe low-level editing API, if you need to use it,
 /// prefer to create a type-safe abstraction on top of it instead.
 pub fn insert_children(
+    parent: &SyntaxNode,
+    position: InsertPosition<SyntaxElement>,
+    to_insert: impl IntoIterator<Item = SyntaxElement>,
+) -> SyntaxNode {
+    let mut to_insert = to_insert.into_iter();
+    _insert_children(parent, position, &mut to_insert)
+}
+
+fn _insert_children(
     parent: &SyntaxNode,
     position: InsertPosition<SyntaxElement>,
     to_insert: &mut dyn Iterator<Item = SyntaxElement>,
@@ -176,6 +185,15 @@ pub fn insert_children(
 /// This is a type-unsafe low-level editing API, if you need to use it,
 /// prefer to create a type-safe abstraction on top of it instead.
 pub fn replace_children(
+    parent: &SyntaxNode,
+    to_delete: RangeInclusive<SyntaxElement>,
+    to_insert: impl IntoIterator<Item = SyntaxElement>,
+) -> SyntaxNode {
+    let mut to_insert = to_insert.into_iter();
+    _replace_children(parent, to_delete, &mut to_insert)
+}
+
+fn _replace_children(
     parent: &SyntaxNode,
     to_delete: RangeInclusive<SyntaxElement>,
     to_insert: &mut dyn Iterator<Item = SyntaxElement>,
@@ -202,14 +220,21 @@ pub fn replace_children(
 /// to create a type-safe abstraction on top of it instead.
 pub fn replace_descendants(
     parent: &SyntaxNode,
-    map: &impl Fn(&SyntaxElement) -> Option<SyntaxElement>,
+    map: impl Fn(&SyntaxElement) -> Option<SyntaxElement>,
+) -> SyntaxNode {
+    _replace_descendants(parent, &map)
+}
+
+fn _replace_descendants(
+    parent: &SyntaxNode,
+    map: &dyn Fn(&SyntaxElement) -> Option<SyntaxElement>,
 ) -> SyntaxNode {
     //  FIXME: this could be made much faster.
     let new_children = parent.children_with_tokens().map(|it| go(map, it)).collect::<Vec<_>>();
     return with_children(parent, new_children);
 
     fn go(
-        map: &impl Fn(&SyntaxElement) -> Option<SyntaxElement>,
+        map: &dyn Fn(&SyntaxElement) -> Option<SyntaxElement>,
         element: SyntaxElement,
     ) -> NodeOrToken<rowan::GreenNode, rowan::GreenToken> {
         if let Some(replacement) = map(&element) {
@@ -221,7 +246,7 @@ pub fn replace_descendants(
         match element {
             NodeOrToken::Token(it) => NodeOrToken::Token(it.green().clone()),
             NodeOrToken::Node(it) => {
-                NodeOrToken::Node(replace_descendants(&it, map).green().clone())
+                NodeOrToken::Node(_replace_descendants(&it, map).green().clone())
             }
         }
     }
diff --git a/crates/ra_syntax/src/ast/edit.rs b/crates/ra_syntax/src/ast/edit.rs
index 0e78d8b637..d2630e9e99 100644
--- a/crates/ra_syntax/src/ast/edit.rs
+++ b/crates/ra_syntax/src/ast/edit.rs
@@ -276,7 +276,7 @@ pub fn replace_descendants<N: AstNode, D: AstNode>(
         .into_iter()
         .map(|(from, to)| (from.syntax().clone().into(), to.syntax().clone().into()))
         .collect::<FxHashMap<SyntaxElement, _>>();
-    let new_syntax = algo::replace_descendants(parent.syntax(), &|n| map.get(n).cloned());
+    let new_syntax = algo::replace_descendants(parent.syntax(), |n| map.get(n).cloned());
     N::cast(new_syntax).unwrap()
 }
 
@@ -331,7 +331,7 @@ impl IndentLevel {
                 )
             })
             .collect();
-        algo::replace_descendants(&node, &|n| replacements.get(n).cloned())
+        algo::replace_descendants(&node, |n| replacements.get(n).cloned())
     }
 
     pub fn decrease_indent<N: AstNode>(self, node: N) -> N {
@@ -359,7 +359,7 @@ impl IndentLevel {
                 )
             })
             .collect();
-        algo::replace_descendants(&node, &|n| replacements.get(n).cloned())
+        algo::replace_descendants(&node, |n| replacements.get(n).cloned())
     }
 }
 
@@ -389,7 +389,7 @@ fn insert_children<N: AstNode>(
     position: InsertPosition<SyntaxElement>,
     to_insert: impl IntoIterator<Item = SyntaxElement>,
 ) -> N {
-    let new_syntax = algo::insert_children(parent.syntax(), position, &mut to_insert.into_iter());
+    let new_syntax = algo::insert_children(parent.syntax(), position, to_insert);
     N::cast(new_syntax).unwrap()
 }
 
@@ -404,8 +404,7 @@ fn replace_children<N: AstNode>(
     to_replace: RangeInclusive<SyntaxElement>,
     to_insert: impl IntoIterator<Item = SyntaxElement>,
 ) -> N {
-    let new_syntax =
-        algo::replace_children(parent.syntax(), to_replace, &mut to_insert.into_iter());
+    let new_syntax = algo::replace_children(parent.syntax(), to_replace, to_insert);
     N::cast(new_syntax).unwrap()
 }