2 files changed, 58 insertions, 23 deletions

diff --git a/crates/syntax/src/ast/edit_in_place.rs b/crates/syntax/src/ast/edit_in_place.rs
index 1788f2a40..7adfe5e16 100644
--- a/crates/syntax/src/ast/edit_in_place.rs
+++ b/crates/syntax/src/ast/edit_in_place.rs
@@ -8,7 +8,7 @@ use parser::T;
 use crate::{
     ast,
     ted::{self, Position},
-    AstNode, Direction, SyntaxKind,
+    AstNode, Direction, SyntaxElement,
 };
 
 use super::NameOwner;
@@ -27,7 +27,7 @@ impl GenericParamsOwnerEdit for ast::Fn {
             } else {
                 Position::last_child_of(self.syntax().clone())
             };
-            create_where_clause(position, true)
+            create_where_clause(position)
         }
         self.where_clause().unwrap()
     }
@@ -41,7 +41,7 @@ impl GenericParamsOwnerEdit for ast::Impl {
             } else {
                 Position::last_child_of(self.syntax().clone())
             };
-            create_where_clause(position, false)
+            create_where_clause(position)
         }
         self.where_clause().unwrap()
     }
@@ -55,7 +55,7 @@ impl GenericParamsOwnerEdit for ast::Trait {
             } else {
                 Position::last_child_of(self.syntax().clone())
             };
-            create_where_clause(position, false)
+            create_where_clause(position)
         }
         self.where_clause().unwrap()
     }
@@ -77,7 +77,7 @@ impl GenericParamsOwnerEdit for ast::Struct {
             } else {
                 Position::last_child_of(self.syntax().clone())
             };
-            create_where_clause(position, true)
+            create_where_clause(position)
         }
         self.where_clause().unwrap()
     }
@@ -93,21 +93,16 @@ impl GenericParamsOwnerEdit for ast::Enum {
             } else {
                 Position::last_child_of(self.syntax().clone())
             };
-            create_where_clause(position, true)
+            create_where_clause(position)
         }
         self.where_clause().unwrap()
     }
 }
 
-fn create_where_clause(position: Position, after: bool) {
-    let mut elements = vec![make::where_clause(empty()).clone_for_update().syntax().clone().into()];
-    let ws = make::tokens::single_space().into();
-    if after {
-        elements.insert(0, ws)
-    } else {
-        elements.push(ws)
-    }
-    ted::insert_all(position, elements);
+fn create_where_clause(position: Position) {
+    let where_clause: SyntaxElement =
+        make::where_clause(empty()).clone_for_update().syntax().clone().into();
+    ted::insert_ws(position, where_clause);
 }
 
 impl ast::WhereClause {
@@ -117,12 +112,7 @@ impl ast::WhereClause {
                 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())
+        ted::append_child_ws(self.syntax().clone(), predicate.syntax().clone())
     }
 }
 
diff --git a/crates/syntax/src/ted.rs b/crates/syntax/src/ted.rs
index 8d6175ed9..f2166bbd3 100644
--- a/crates/syntax/src/ted.rs
+++ b/crates/syntax/src/ted.rs
@@ -1,8 +1,9 @@
 //! Primitive tree editor, ed for trees
-#![allow(unused)]
 use std::ops::RangeInclusive;
 
-use crate::{SyntaxElement, SyntaxNode};
+use parser::T;
+
+use crate::{ast::make, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken};
 
 #[derive(Debug)]
 pub struct Position {
@@ -42,9 +43,25 @@ impl Position {
     }
 }
 
+pub fn insert_ws(position: Position, elem: impl Into<SyntaxElement>) {
+    insert_all_ws(position, vec![elem.into()])
+}
 pub fn insert(position: Position, elem: impl Into<SyntaxElement>) {
     insert_all(position, vec![elem.into()])
 }
+pub fn insert_all_ws(position: Position, mut elements: Vec<SyntaxElement>) {
+    if let Some(first) = elements.first() {
+        if let Some(ws) = ws_before(&position, first) {
+            elements.insert(0, ws.into())
+        }
+    }
+    if let Some(last) = elements.last() {
+        if let Some(ws) = ws_after(&position, last) {
+            elements.push(ws.into())
+        }
+    }
+    insert_all(position, elements)
+}
 pub fn insert_all(position: Position, elements: Vec<SyntaxElement>) {
     let (parent, index) = match position.repr {
         PositionRepr::FirstChild(parent) => (parent, 0),
@@ -72,7 +89,35 @@ pub fn replace_all(range: RangeInclusive<SyntaxElement>, new: Vec<SyntaxElement>
     parent.splice_children(start..end + 1, new)
 }
 
+pub fn append_child_ws(node: impl Into<SyntaxNode>, child: impl Into<SyntaxElement>) {
+    let position = Position::last_child_of(node);
+    insert_ws(position, child)
+}
 pub fn append_child(node: impl Into<SyntaxNode>, child: impl Into<SyntaxElement>) {
     let position = Position::last_child_of(node);
     insert(position, child)
 }
+
+fn ws_before(position: &Position, new: &SyntaxElement) -> Option<SyntaxToken> {
+    let prev = match &position.repr {
+        PositionRepr::FirstChild(_) => return None,
+        PositionRepr::After(it) => it,
+    };
+    ws_between(prev, new)
+}
+fn ws_after(position: &Position, new: &SyntaxElement) -> Option<SyntaxToken> {
+    let next = match &position.repr {
+        PositionRepr::FirstChild(parent) => parent.first_child_or_token()?,
+        PositionRepr::After(sibling) => sibling.next_sibling_or_token()?,
+    };
+    ws_between(new, &next)
+}
+fn ws_between(left: &SyntaxElement, right: &SyntaxElement) -> Option<SyntaxToken> {
+    if left.kind() == SyntaxKind::WHITESPACE || right.kind() == SyntaxKind::WHITESPACE {
+        return None;
+    }
+    if right.kind() == T![;] || right.kind() == T![,] {
+        return None;
+    }
+    Some(make::tokens::single_space().into())
+}