bpo-28964: add line number of node (if available) to ast.literal_eval error messages (GH-23677)

Lib/ast.py

@@ -63,7 +63,10 @@ def literal_eval(node_or_string):
     if isinstance(node_or_string, Expression):
         node_or_string = node_or_string.body
     def _raise_malformed_node(node):
-        raise ValueError(f'malformed node or string: {node!r}')
+        msg = "malformed node or string"
+        if lno := getattr(node, 'lineno', None):
+            msg += f' on line {lno}'
+        raise ValueError(msg + f': {node!r}')
     def _convert_num(node):
         if not isinstance(node, Constant) or type(node.value) not in (int, float, complex):
             _raise_malformed_node(node)