private Expression realizeNas(Expression expr) {
    return createDirectMethodCall(
      new VariableExpression(valueRecorderName),
      resources.getAstNodeCache().ValueRecorder_RealizeNas,
      new ArgumentListExpression(primitiveConstExpression(recordCount), expr));
  }
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