anchor.diff:  They could be added instead at a later stage.
   
   *Example*
  -`RETURN [1, "Yo"] :: LIST OF STRING | LIST OF NUMBER`
  +`RETURN [1, "Yo"] :: LIST OF (STRING | NUMBER)`
  
positive.code: ==== Material and nullable types
  
  The type system provides a way to track nullability, i.e. a type may express if a given expression may be `NULL` or not.
  Tracking (non-)nullability helps an implementation to detect and warn about possible user errors during compile time and  it also enables optimizations that rely on values not being `NULL`.
  
  Material types are all types that do not permit `NULL` as a valid result of evaluating the underlying expression.
  In the sections below, generally only the material variants of each type are given.
  
negative.code: [abstract]
  .Abstract
  
  This CIP specifies the Public Type System of Cypher and introduces literal syntax for writing down types as well as new syntax for type annotations. The proposed type annotation syntax does not change the Cypher grammar right now but rather is intended as a template to be used by future CIPs. This CIP also informatively discusses future syntax that might use the introduced literal type syntax.
  
  toc::[]
  
  