Simplify

crates/syntax/src/ast/expr_ext.rs

@@ -48,7 +48,7 @@ impl ast::Expr {
     }
 
     /// Preorder walk all the expression's child expressions preserving events.
-    /// If the callback returns true the subtree of the expression will be skipped.
+    /// If the callback returns true on an [`WalkEvent::Enter`], the subtree of the expression will be skipped.
     /// Note that the subtree may already be skipped due to the context analysis this function does.
     pub fn preorder(&self, cb: &mut dyn FnMut(WalkEvent<ast::Expr>) -> bool) {
         let mut preorder = self.syntax().preorder();

crates/syntax/src/ast/make.rs

@@ -304,12 +304,20 @@ pub fn expr_prefix(op: SyntaxKind, expr: ast::Expr) -> ast::Expr {
 pub fn expr_call(f: ast::Expr, arg_list: ast::ArgList) -> ast::Expr {
     expr_from_text(&format!("{}{}", f, arg_list))
 }
-pub fn expr_method_call(receiver: ast::Expr, method: &str, arg_list: ast::ArgList) -> ast::Expr {
+pub fn expr_method_call(
+    receiver: ast::Expr,
+    method: ast::NameRef,
+    arg_list: ast::ArgList,
+) -> ast::Expr {
     expr_from_text(&format!("{}.{}{}", receiver, method, arg_list))
 }
 pub fn expr_ref(expr: ast::Expr, exclusive: bool) -> ast::Expr {
     expr_from_text(&if exclusive { format!("&mut {}", expr) } else { format!("&{}", expr) })
 }
+pub fn expr_closure(pats: impl IntoIterator<Item = ast::Param>, expr: ast::Expr) -> ast::Expr {
+    let params = pats.into_iter().join(", ");
+    expr_from_text(&format!("|{}| {}", params, expr))
+}
 pub fn expr_paren(expr: ast::Expr) -> ast::Expr {
     expr_from_text(&format!("({})", expr))
 }

crates/syntax/src/ast/node_ext.rs

@@ -611,6 +611,12 @@ impl ast::Item {
     }
 }
 
+impl ast::Condition {
+    pub fn is_pattern_cond(&self) -> bool {
+        self.let_token().is_some()
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum FieldKind {
     Name(ast::NameRef),