anchor.diff:  isCaseCondition
       : 'is' type
       -> ^(IS_EXPR type)
  +    ;
  +
  +satisfiesCaseCondition
  +    : 'satisfies' type
       ;
   
   forFail
  
positive.code: // Control structures.
  
  condition
      : expression | existsCondition | nonemptyCondition | isCondition
      ;
  
  existsCondition
  
negative.code:     ;
  
  typeConstraint
      : 'given' typeName typeArguments? formalParameters? caseTypes? metatypes? satisfiedTypes? abstractedType?
      -> ^(TYPE_CONSTRAINT typeName formalParameters? satisfiedTypes? abstractedType?)
      ;
      
  