JetFile: PredicateExpression.jet
  NAMESPACE_HEADER
    <empty list>
  FUN
    PsiElement(fun)('fun')
    PsiWhiteSpace(' ')
    PsiElement(IDENTIFIER)('foo')
    VALUE_PARAMETER_LIST
      PsiElement(LPAR)('(')
      PsiElement(RPAR)(')')
    PsiWhiteSpace(' ')
    BLOCK
      PsiElement(LBRACE)('{')
      PsiWhiteSpace('\n  ')
      DOT_QUALIFIED_EXPRESSION
        PREDICATE_EXPRESSION
          REFERENCE_EXPRESSION
            PsiElement(IDENTIFIER)('a')
          PsiElement(QUEST)('?')
          REFERENCE_EXPRESSION
            PsiElement(IDENTIFIER)('f')
        PsiElement(DOT)('.')
        REFERENCE_EXPRESSION
          PsiElement(IDENTIFIER)('foo')
      PsiWhiteSpace('\n')
      PsiElement(RBRACE)('}')