anchor.diff:  
   identifier : Identifier | contextSensitiveKeyword ;
   
  -keyword : 'convenience' | 'class' | 'deinit' | 'enum' | 'extension' | 'func' | 'import' | 'init' | 'let' | 'protocol' | 'static' | 'struct' | 'subscript' | 'typealias' | 'var' | 'break' | 'case' | 'continue' | 'default' | 'do' | 'else' | 'fallthrough' | 'if' | 'in' | 'for' | 'return' | 'switch' | 'where' | 'while' | 'as' | 'dynamicType' | 'is' | 'super' | 'self' | 'Self' | 'Type' | 'repeat' ;
  +keyword :
  + // Keywords used in declarations
  + 'associatedtype' | 'class' | 'deinit' | 'enum' | 'extension' | 'func' | 'import' | 'init' | 'internal'
  + | 'private' | 'protocol' | 'public' | 'static' | 'struct' | 'subscript' | 'typealias'
  + // Keywords used in statements
  + | 'break' | 'case' | 'continue' | 'default' | 'defer' | 'do' | 'else' | 'fallthrough' | 'for' | 'guard' | 'if' | 'in'
  + | 'repeat' | 'return' | 'switch' | 'where' | 'while'
  + // Keywords used in expressions and types
  + | 'as' | 'catch' | 'dynamicType' | 'is' | 'nil' | 'rethrows' | 'super' | 'self' | 'Self' | 'throw'
  + | 'throws' | 'try' | '#column' | '#file' | '#function' | '#line'
  + | BooleanLiteral
  + // Keywords used in patterns
  + | '_'
  + // Keywords that begin with a number sign (#)
  + | '#available' | '#column' | '#else' | '#elseif' | '#endif' | '#file' | '#function' | '#if' | '#line' | '#selector'
  + ;
   
   contextSensitiveKeyword :
    'associativity' | 'convenience' | 'dynamic' | 'didSet' | 'final' | 'get' | 'infix' | 'indirect' |
  
positive.code: parenthesizedExpression : '(' expressionElementList? ')'  ;
  expressionElementList : expressionElement (',' expressionElement)*  ;
  expressionElement : expression | expressionElementIdentifier ':' expression  ;
  expressionElementIdentifier: identifier | keyword ;
  
  // GRAMMAR OF A WILDCARD EXPRESSION
  
negative.code:  | attributes? sType
   | externalParameterName? localParameterName typeAnnotation '...'
   ;
  // Swift Language Reference does not have "keyword"
  externalParameterName : identifier | keyword | '_'  ;
  localParameterName : identifier | '_'  ;
  defaultArgumentClause : '=' expression  ;
  