private List<Expression> convertAllAndRecordNa(List<Expression> expressions) {
    List<Expression> conversions = new ArrayList<>(expressions.size());
    for (Expression expr : expressions) conversions.add(convertAndRecordNa(expr));
    return conversions;
  }
Rewrites explicit ("assert x > 3") and implicit ("x > 3") condition
statements. Replacing the original statement with the rewritten one is up
to clients.

@author Peter Niederwieser
spock-core/src/main/java/org/spockframework/compiler/ConditionRewriter.java