3 files changed, 91 insertions, 19 deletions

diff --git a/crates/syntax/src/ast/edit.rs b/crates/syntax/src/ast/edit.rs
index 0b3b76d4a..64fac13a7 100644
--- a/crates/syntax/src/ast/edit.rs
+++ b/crates/syntax/src/ast/edit.rs
@@ -479,7 +479,7 @@ impl ast::MatchArmList {
             Some(t) => t,
             None => return self.clone(),
         };
-        let position = InsertPosition::Before(r_curly.into());
+        let position = InsertPosition::Before(r_curly);
         let arm_ws = tokens::WsBuilder::new("    ");
         let match_indent = &leading_indent(self.syntax()).unwrap_or_default();
         let match_ws = tokens::WsBuilder::new(&format!("\n{}", match_indent));
diff --git a/crates/syntax/src/ast/edit_in_place.rs b/crates/syntax/src/ast/edit_in_place.rs
index 06cde591d..449b058fb 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;
@@ -36,8 +36,8 @@ impl GenericParamsOwnerEdit for ast::Fn {
 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())
+            let position = if let Some(items) = self.assoc_item_list() {
+                Position::before(items.syntax().clone())
             } else {
                 Position::last_child_of(self.syntax().clone())
             };
@@ -46,6 +46,21 @@ impl GenericParamsOwnerEdit for ast::Impl {
         self.where_clause().unwrap()
     }
 }
+
+impl GenericParamsOwnerEdit for ast::Trait {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let position = if let Some(items) = self.assoc_item_list() {
+                Position::before(items.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() {
@@ -68,26 +83,35 @@ impl GenericParamsOwnerEdit for ast::Struct {
     }
 }
 
+impl GenericParamsOwnerEdit for ast::Enum {
+    fn get_or_create_where_clause(&self) -> WhereClause {
+        if self.where_clause().is_none() {
+            let position = 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);
+    let where_clause: SyntaxElement =
+        make::where_clause(empty()).clone_for_update().syntax().clone().into();
+    ted::insert(position, where_clause);
 }
 
 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![,]));
+                ted::append_child_raw(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())
     }
 }
diff --git a/crates/syntax/src/ted.rs b/crates/syntax/src/ted.rs
index 8d6175ed9..442dfa14a 100644
--- a/crates/syntax/src/ted.rs
+++ b/crates/syntax/src/ted.rs
@@ -1,8 +1,12 @@
-//! Primitive tree editor, ed for trees
-#![allow(unused)]
+//! Primitive tree editor, ed for trees.
+//!
+//! The `_raw`-suffixed functions insert elements as is, unsuffixed versions fix
+//! up elements around the edges.
 use std::ops::RangeInclusive;
 
-use crate::{SyntaxElement, SyntaxNode};
+use parser::T;
+
+use crate::{ast::make, SyntaxElement, SyntaxKind, SyntaxNode, SyntaxToken};
 
 #[derive(Debug)]
 pub struct Position {
@@ -45,7 +49,23 @@ impl Position {
 pub fn insert(position: Position, elem: impl Into<SyntaxElement>) {
     insert_all(position, vec![elem.into()])
 }
-pub fn insert_all(position: Position, elements: Vec<SyntaxElement>) {
+pub fn insert_raw(position: Position, elem: impl Into<SyntaxElement>) {
+    insert_all_raw(position, vec![elem.into()])
+}
+pub fn insert_all(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_raw(position, elements)
+}
+pub fn insert_all_raw(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),
@@ -76,3 +96,31 @@ pub fn append_child(node: impl Into<SyntaxNode>, child: impl Into<SyntaxElement>
     let position = Position::last_child_of(node);
     insert(position, child)
 }
+pub fn append_child_raw(node: impl Into<SyntaxNode>, child: impl Into<SyntaxElement>) {
+    let position = Position::last_child_of(node);
+    insert_raw(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())
+}