2 files changed, 77 insertions, 46 deletions

diff --git a/crates/ra_syntax/src/ast/edit.rs b/crates/ra_syntax/src/ast/edit.rs
index b736098ac..0e78d8b63 100644
--- a/crates/ra_syntax/src/ast/edit.rs
+++ b/crates/ra_syntax/src/ast/edit.rs
@@ -22,9 +22,8 @@ impl ast::BinExpr {
     #[must_use]
     pub fn replace_op(&self, op: SyntaxKind) -> Option<ast::BinExpr> {
         let op_node: SyntaxElement = self.op_details()?.0.into();
-        let to_insert: Option<SyntaxElement> = Some(tokens::op(op).into());
-        let replace_range = RangeInclusive::new(op_node.clone(), op_node);
-        Some(replace_children(self, replace_range, to_insert.into_iter()))
+        let to_insert: Option<SyntaxElement> = Some(make::token(op).into());
+        Some(replace_children(self, single_node(op_node), to_insert))
     }
 }
 
@@ -40,11 +39,10 @@ impl ast::FnDef {
         } else {
             to_insert.push(make::tokens::single_space().into());
             to_insert.push(body.syntax().clone().into());
-            return insert_children(self, InsertPosition::Last, to_insert.into_iter());
+            return insert_children(self, InsertPosition::Last, to_insert);
         };
         to_insert.push(body.syntax().clone().into());
-        let replace_range = RangeInclusive::new(old_body_or_semi.clone(), old_body_or_semi);
-        replace_children(self, replace_range, to_insert.into_iter())
+        replace_children(self, single_node(old_body_or_semi), to_insert)
     }
 }
 
@@ -77,7 +75,7 @@ impl ast::ItemList {
         let ws = tokens::WsBuilder::new(&format!("\n{}", indent));
         let to_insert: ArrayVec<[SyntaxElement; 2]> =
             [ws.ws().into(), item.syntax().clone().into()].into();
-        insert_children(self, position, to_insert.into_iter())
+        insert_children(self, position, to_insert)
     }
 
     fn l_curly(&self) -> Option<SyntaxElement> {
@@ -109,9 +107,7 @@ impl ast::ItemList {
         let to_insert = iter::once(ws.ws().into());
         match existing_ws {
             None => insert_children(self, InsertPosition::After(l_curly), to_insert),
-            Some(ws) => {
-                replace_children(self, RangeInclusive::new(ws.clone().into(), ws.into()), to_insert)
-            }
+            Some(ws) => replace_children(self, single_node(ws), to_insert),
         }
     }
 }
@@ -188,7 +184,7 @@ impl ast::RecordFieldList {
             InsertPosition::After(anchor) => after_field!(anchor),
         };
 
-        insert_children(self, position, to_insert.iter().cloned())
+        insert_children(self, position, to_insert)
     }
 
     fn l_curly(&self) -> Option<SyntaxElement> {
@@ -207,7 +203,49 @@ impl ast::TypeParam {
             Some(it) => it.syntax().clone().into(),
             None => colon.clone().into(),
         };
-        replace_children(self, RangeInclusive::new(colon.into(), end), iter::empty())
+        replace_children(self, colon.into()..=end, iter::empty())
+    }
+}
+
+impl ast::Path {
+    #[must_use]
+    pub fn with_segment(&self, segment: ast::PathSegment) -> ast::Path {
+        if let Some(old) = self.segment() {
+            return replace_children(
+                self,
+                single_node(old.syntax().clone()),
+                iter::once(segment.syntax().clone().into()),
+            );
+        }
+        self.clone()
+    }
+}
+
+impl ast::PathSegment {
+    #[must_use]
+    pub fn with_type_args(&self, type_args: ast::TypeArgList) -> ast::PathSegment {
+        self._with_type_args(type_args, false)
+    }
+
+    #[must_use]
+    pub fn with_turbo_fish(&self, type_args: ast::TypeArgList) -> ast::PathSegment {
+        self._with_type_args(type_args, true)
+    }
+
+    fn _with_type_args(&self, type_args: ast::TypeArgList, turbo: bool) -> ast::PathSegment {
+        if let Some(old) = self.type_arg_list() {
+            return replace_children(
+                self,
+                single_node(old.syntax().clone()),
+                iter::once(type_args.syntax().clone().into()),
+            );
+        }
+        let mut to_insert: ArrayVec<[SyntaxElement; 2]> = ArrayVec::new();
+        if turbo {
+            to_insert.push(make::token(T![::]).into());
+        }
+        to_insert.push(type_args.syntax().clone().into());
+        insert_children(self, InsertPosition::Last, to_insert)
     }
 }
 
@@ -224,7 +262,7 @@ fn strip_attrs_and_docs_inner(mut node: SyntaxNode) -> SyntaxNode {
             Some(el) if el.kind() == WHITESPACE => el.clone(),
             Some(_) | None => start.clone(),
         };
-        node = algo::replace_children(&node, RangeInclusive::new(start, end), &mut iter::empty());
+        node = algo::replace_children(&node, start..=end, &mut iter::empty());
     }
     node
 }
@@ -232,9 +270,10 @@ fn strip_attrs_and_docs_inner(mut node: SyntaxNode) -> SyntaxNode {
 #[must_use]
 pub fn replace_descendants<N: AstNode, D: AstNode>(
     parent: &N,
-    replacement_map: impl Iterator<Item = (D, D)>,
+    replacement_map: impl IntoIterator<Item = (D, D)>,
 ) -> N {
     let map = replacement_map
+        .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());
@@ -348,19 +387,25 @@ fn prev_tokens(token: SyntaxToken) -> impl Iterator<Item = SyntaxToken> {
 fn insert_children<N: AstNode>(
     parent: &N,
     position: InsertPosition<SyntaxElement>,
-    mut to_insert: impl Iterator<Item = SyntaxElement>,
+    to_insert: impl IntoIterator<Item = SyntaxElement>,
 ) -> N {
-    let new_syntax = algo::insert_children(parent.syntax(), position, &mut to_insert);
+    let new_syntax = algo::insert_children(parent.syntax(), position, &mut to_insert.into_iter());
     N::cast(new_syntax).unwrap()
 }
 
+fn single_node(element: impl Into<SyntaxElement>) -> RangeInclusive<SyntaxElement> {
+    let element = element.into();
+    element.clone()..=element
+}
+
 #[must_use]
 fn replace_children<N: AstNode>(
     parent: &N,
     to_replace: RangeInclusive<SyntaxElement>,
-    mut to_insert: impl Iterator<Item = SyntaxElement>,
+    to_insert: impl IntoIterator<Item = SyntaxElement>,
 ) -> N {
-    let new_syntax = algo::replace_children(parent.syntax(), to_replace, &mut to_insert);
+    let new_syntax =
+        algo::replace_children(parent.syntax(), to_replace, &mut to_insert.into_iter());
     N::cast(new_syntax).unwrap()
 }
 
diff --git a/crates/ra_syntax/src/ast/make.rs b/crates/ra_syntax/src/ast/make.rs
index eef45090d..36e648180 100644
--- a/crates/ra_syntax/src/ast/make.rs
+++ b/crates/ra_syntax/src/ast/make.rs
@@ -2,7 +2,7 @@
 //! of smaller pieces.
 use itertools::Itertools;
 
-use crate::{algo, ast, AstNode, SourceFile};
+use crate::{ast, AstNode, SourceFile, SyntaxKind, SyntaxToken};
 
 pub fn name(text: &str) -> ast::Name {
     ast_from_text(&format!("mod {};", text))
@@ -21,20 +21,6 @@ pub fn path_qualified(qual: ast::Path, name_ref: ast::NameRef) -> ast::Path {
 fn path_from_text(text: &str) -> ast::Path {
     ast_from_text(text)
 }
-pub fn path_with_type_arg_list(path: ast::Path, args: Option<ast::TypeArgList>) -> ast::Path {
-    if let Some(args) = args {
-        let syntax = path.syntax();
-        // FIXME: remove existing type args
-        let new_syntax = algo::insert_children(
-            syntax,
-            crate::algo::InsertPosition::Last,
-            &mut Some(args).into_iter().map(|n| n.syntax().clone().into()),
-        );
-        ast::Path::cast(new_syntax).unwrap()
-    } else {
-        path
-    }
-}
 
 pub fn record_field(name: ast::NameRef, expr: Option<ast::Expr>) -> ast::RecordField {
     return match expr {
@@ -181,27 +167,27 @@ pub fn let_stmt(pattern: ast::Pat, initializer: Option<ast::Expr>) -> ast::LetSt
     ast_from_text(&format!("fn f() {{ {} }}", text))
 }
 
+pub fn token(kind: SyntaxKind) -> SyntaxToken {
+    tokens::SOURCE_FILE
+        .tree()
+        .syntax()
+        .descendants_with_tokens()
+        .filter_map(|it| it.into_token())
+        .find(|it| it.kind() == kind)
+        .unwrap_or_else(|| panic!("unhandled token: {:?}", kind))
+}
+
 fn ast_from_text<N: AstNode>(text: &str) -> N {
     let parse = SourceFile::parse(text);
     parse.tree().syntax().descendants().find_map(N::cast).unwrap()
 }
 
 pub mod tokens {
-    use crate::{AstNode, Parse, SourceFile, SyntaxKind, SyntaxKind::*, SyntaxToken, T};
+    use crate::{AstNode, Parse, SourceFile, SyntaxKind::*, SyntaxToken, T};
     use once_cell::sync::Lazy;
 
-    static SOURCE_FILE: Lazy<Parse<SourceFile>> =
-        Lazy::new(|| SourceFile::parse("const C: () = (1 != 1, 2 == 2)\n;"));
-
-    pub fn op(op: SyntaxKind) -> SyntaxToken {
-        SOURCE_FILE
-            .tree()
-            .syntax()
-            .descendants_with_tokens()
-            .filter_map(|it| it.into_token())
-            .find(|it| it.kind() == op)
-            .unwrap()
-    }
+    pub(super) static SOURCE_FILE: Lazy<Parse<SourceFile>> =
+        Lazy::new(|| SourceFile::parse("const C: <()>::Item = (1 != 1, 2 == 2)\n;"));
 
     pub fn comma() -> SyntaxToken {
         SOURCE_FILE