Fix the free-var test in validDerivPred
The free-var test (now documented as (VD3)) was too narrow, affecting only class predicates. #21302 (closed) demonstrated that this wasn't enough!
Fixes #21302 (closed).
The free-var test (now documented as (VD3)) was too narrow, affecting only class predicates. #21302 (closed) demonstrated that this wasn't enough!
Fixes #21302 (closed).