SHELL_SCRIPT
  COMMANDS_LIST
    GENERIC_COMMAND_DIRECTIVE
      PsiElement($)('$')
      SUBSHELL_COMMAND
        PsiElement(()('(')
        COMPOUND_LIST
          SIMPLE_COMMAND
            GENERIC_COMMAND_DIRECTIVE
              LITERAL
                PsiElement(word)('echo')
            PsiWhiteSpace(' ')
            LITERAL
              PsiElement(word)('a')
        PsiElement())(')')