make ast object safe

crates/ra_assists/src/ast_editor.rs

@@ -19,7 +19,10 @@ pub struct AstEditor<N: AstNode> {
 }
 
 impl<N: AstNode> AstEditor<N> {
-    pub fn new(node: N) -> AstEditor<N> {
+    pub fn new(node: N) -> AstEditor<N>
+    where
+        N: Clone,
+    {
         AstEditor { original_ast: node.clone(), ast: node }
     }
 
@@ -379,7 +382,7 @@ impl AstBuilder<ast::MatchArmList> {
 
 fn ast_node_from_file_text<N: AstNode>(text: &str) -> N {
     let parse = SourceFile::parse(text);
-    let res = parse.tree().syntax().descendants().find_map(N::cast).unwrap().to_owned();
+    let res = parse.tree().syntax().descendants().find_map(N::cast).unwrap();
     res
 }
 

crates/ra_syntax/src/ast.rs

@@ -25,15 +25,23 @@ pub use self::{
 /// conversion itself has zero runtime cost: ast and syntax nodes have exactly
 /// the same representation: a pointer to the tree root and a pointer to the
 /// node itself.
-pub trait AstNode: Clone {
+pub trait AstNode {
-    fn can_cast(kind: SyntaxKind) -> bool;
+    fn can_cast(kind: SyntaxKind) -> bool
+    where
+        Self: Sized;
 
     fn cast(syntax: SyntaxNode) -> Option<Self>
     where
         Self: Sized;
+
     fn syntax(&self) -> &SyntaxNode;
 }
 
+#[test]
+fn assert_ast_is_object_safe() {
+    fn _f(_: &dyn AstNode, _: &dyn NameOwner) {}
+}
+
 /// Like `AstNode`, but wraps tokens rather than interior nodes.
 pub trait AstToken {
     fn cast(token: SyntaxToken) -> Option<Self>