AST: add ArgumentList

ql/src/codeql_ruby/ast/Expr.qll

@@ -24,6 +24,23 @@ class Self extends Expr, @token_self {
   final override string getAPrimaryQlClass() { result = "Self" }
 }
 
+/**
+ * A sequence of expressions in the right-hand side of an assignment or
+ * a `return`, `break` or `next` statement.
+ * ```rb
+ * x = 1, *items, 3, *more
+ * return 1, 2
+ * next *list
+ * break **map
+ * return 1, 2, *items, k: 5, **map
+ * ```
+ */
+class ArgumentList extends Expr {
+  override ArgumentList::Range range;
+
+  override string getAPrimaryQlClass() { result = "ArgumentList" }
+}
+
 /** A sequence of expressions. */
 class StmtSequence extends Expr {
   override StmtSequence::Range range;

ql/src/codeql_ruby/ast/internal/Expr.qll

@@ -16,6 +16,36 @@ module Self {
   }
 }
 
+module ArgumentList {
+  private class ValidParent = @break or @return or @next or @assignment or @operator_assignment;
+
+  abstract class Range extends Expr::Range {
+    Range() { generated.getParent() instanceof ValidParent }
+
+    abstract Expr getElement(int i);
+
+    final override string toString() { result = "..., ..." }
+
+    override predicate child(string label, AstNode::Range child) {
+      label = "getElement" and child = getElement(_)
+    }
+  }
+
+  private class ArgArgumentList extends ArgumentList::Range, @argument_list {
+    final override Generated::ArgumentList generated;
+
+    ArgArgumentList() { count(generated.getChild(_)) != 1 }
+
+    final override Expr getElement(int i) { result = generated.getChild(i) }
+  }
+
+  private class AssignmentList extends ArgumentList::Range, @right_assignment_list {
+    final override Generated::RightAssignmentList generated;
+
+    final override Expr getElement(int i) { result = generated.getChild(i) }
+  }
+}
+
 module StmtSequence {
   abstract class Range extends Expr::Range {
     abstract Stmt getStmt(int n);