@Override
  public void visitPostfixExpression(PostfixExpression expr) {
    PostfixExpression conversion =
        new PostfixExpression(
            convertAndRecordNa(expr.getExpression()),
            expr.getOperation());

    conversion.setSourcePosition(expr);
    result = record(conversion);
  }
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