An approach is provided for completing a decision logic. For statements in a syntax tree of the decision logic and using a symbolic execution technique, path expression(s) that refer to respective input object(s) are identified. A statement in the decision logic is detected that modifies an attribute value of a path expression included in the path expression(s) and that refers to an input object included in the input object(s). A copy instruction is inserted as a new node in the syntax tree so that the attribute value of the path expression is a copy of the input object. Responsive to inserting the copy instruction, the path expression is prevented from modifying the input object.