anchor.diff:  	|	LeftArrowElement Identifier
   	;
   
  +/* - Blocks  - */
  +/* - - - - - - */
  +
  +block
  +	//	{ ... }
  +	:	LeftBraceElement
  +		statement*
  +		RightBraceElement
  +	;
  +
   /* - Types - */
   /* - - - - - */
   
  +typeStatement
  +	//	name = type { ... }
  +	:	Identifier EqualsOperator
  +		typeDeclaration
  +	;
  +
   typeDeclaration
  +	//	type { ... }
   	:	TypeKeyword LeftBraceElement
   		RightBraceElement
   	;
  
positive.code: /* - Interface Types - */
  /* - - - - - - - - - - */
  
  iTypeDeclaration
  	:	ITypeKeyword LeftBraceElement
  		RightBraceElement
  	;
  
  /* - Expressions - */
  /* - - - - - - - - */
  
  expression
  	//	Literals.
  
negative.code: 
  statement
  	//	Declarations.
  	:	typeStatement SemicolonElement?
  	|	iTypeStatement SemicolonElement?
  
  	//	Language elements.
  	|	keywordStatement SemicolonElement
  