10. 完整的语法规范
******************

这是完整的 Python 语法规范，直接提取自用于生成 CPython 解析器的语法 (
参见 Grammar/python.gram)。 这里显示的版本省略了有关代码生成和错误恢复
的细节。

所用的标记法是 EBNF 和 PEG 的混合体。 特别地，"&" 后跟一个符号、形符或
带括号的分组来表示正向前视（即要求执行匹配但不会被消耗掉），而 "!" 表
示负向前视（即要求 _不_ 执行匹配）。 我们使用 "|" 分隔符来表示 PEG 的“
有序选择” (在传统 PEG 语法中则写为 "/")。

   # PEG grammar for Python

   @trailer '''
   void *
   _PyPegen_parse(Parser *p)
   {
       // Initialize keywords
       p->keywords = reserved_keywords;
       p->n_keyword_lists = n_keyword_lists;

       // Run parser
       void *result = NULL;
       if (p->start_rule == Py_file_input) {
           result = file_rule(p);
       } else if (p->start_rule == Py_single_input) {
           result = interactive_rule(p);
       } else if (p->start_rule == Py_eval_input) {
           result = eval_rule(p);
       } else if (p->start_rule == Py_func_type_input) {
           result = func_type_rule(p);
       } else if (p->start_rule == Py_fstring_input) {
           result = fstring_rule(p);
       }

       return result;
   }

   // The end
   '''
   file[mod_ty]: a=[statements] ENDMARKER { _PyPegen_make_module(p, a) }
   interactive[mod_ty]: a=statement_newline { Interactive(a, p->arena) }
   eval[mod_ty]: a=expressions NEWLINE* ENDMARKER { Expression(a, p->arena) }
   func_type[mod_ty]: '(' a=[type_expressions] ')' '->' b=expression NEWLINE* ENDMARKER { FunctionType(a, b, p->arena) }
   fstring[expr_ty]: star_expressions

   # type_expressions allow */** but ignore them
   type_expressions[asdl_expr_seq*]:
       | a=','.expression+ ',' '*' b=expression ',' '**' c=expression {
           (asdl_expr_seq*)_PyPegen_seq_append_to_end(p, CHECK(_PyPegen_seq_append_to_end(p, a, b)), c) }
       | a=','.expression+ ',' '*' b=expression { (asdl_expr_seq*)_PyPegen_seq_append_to_end(p, a, b) }
       | a=','.expression+ ',' '**' b=expression { (asdl_expr_seq*)_PyPegen_seq_append_to_end(p, a, b) }
       | '*' a=expression ',' '**' b=expression {
           (asdl_expr_seq*)_PyPegen_seq_append_to_end(p, CHECK(_PyPegen_singleton_seq(p, a)), b) }
       | '*' a=expression { (asdl_expr_seq*)_PyPegen_singleton_seq(p, a) }
       | '**' a=expression { (asdl_expr_seq*)_PyPegen_singleton_seq(p, a) }
       | a[asdl_expr_seq*]=','.expression+ {a}

   statements[asdl_stmt_seq*]: a=statement+ { (asdl_stmt_seq*)_PyPegen_seq_flatten(p, a) }
   statement[asdl_stmt_seq*]: a=compound_stmt { (asdl_stmt_seq*)_PyPegen_singleton_seq(p, a) } | a[asdl_stmt_seq*]=simple_stmt { a }
   statement_newline[asdl_stmt_seq*]:
       | a=compound_stmt NEWLINE { (asdl_stmt_seq*)_PyPegen_singleton_seq(p, a) }
       | simple_stmt
       | NEWLINE { (asdl_stmt_seq*)_PyPegen_singleton_seq(p, CHECK(_Py_Pass(EXTRA))) }
       | ENDMARKER { _PyPegen_interactive_exit(p) }
   simple_stmt[asdl_stmt_seq*]:
       | a=small_stmt !';' NEWLINE { (asdl_stmt_seq*)_PyPegen_singleton_seq(p, a) } # Not needed, there for speedup
       | a[asdl_stmt_seq*]=';'.small_stmt+ [';'] NEWLINE { a }
   # NOTE: assignment MUST precede expression, else parsing a simple assignment
   # will throw a SyntaxError.
   small_stmt[stmt_ty] (memo):
       | assignment
       | e=star_expressions { _Py_Expr(e, EXTRA) }
       | &'return' return_stmt
       | &('import' | 'from') import_stmt
       | &'raise' raise_stmt
       | 'pass' { _Py_Pass(EXTRA) }
       | &'del' del_stmt
       | &'yield' yield_stmt
       | &'assert' assert_stmt
       | 'break' { _Py_Break(EXTRA) }
       | 'continue' { _Py_Continue(EXTRA) }
       | &'global' global_stmt
       | &'nonlocal' nonlocal_stmt
   compound_stmt[stmt_ty]:
       | &('def' | '@' | ASYNC) function_def
       | &'if' if_stmt
       | &('class' | '@') class_def
       | &('with' | ASYNC) with_stmt
       | &('for' | ASYNC) for_stmt
       | &'try' try_stmt
       | &'while' while_stmt

   # NOTE: annotated_rhs may start with 'yield'; yield_expr must start with 'yield'
   assignment[stmt_ty]:
       | a=NAME ':' b=expression c=['=' d=annotated_rhs { d }] {
           CHECK_VERSION(
               6,
               "Variable annotation syntax is",
               _Py_AnnAssign(CHECK(_PyPegen_set_expr_context(p, a, Store)), b, c, 1, EXTRA)
           ) }
       | a=('(' b=single_target ')' { b }
            | single_subscript_attribute_target) ':' b=expression c=['=' d=annotated_rhs { d }] {
           CHECK_VERSION(6, "Variable annotations syntax is", _Py_AnnAssign(a, b, c, 0, EXTRA)) }
       | a[asdl_expr_seq*]=(z=star_targets '=' { z })+ b=(yield_expr | star_expressions) !'=' tc=[TYPE_COMMENT] {
            _Py_Assign(a, b, NEW_TYPE_COMMENT(p, tc), EXTRA) }
       | a=single_target b=augassign ~ c=(yield_expr | star_expressions) {
            _Py_AugAssign(a, b->kind, c, EXTRA) }
       | invalid_assignment

   augassign[AugOperator*]:
       | '+=' { _PyPegen_augoperator(p, Add) }
       | '-=' { _PyPegen_augoperator(p, Sub) }
       | '*=' { _PyPegen_augoperator(p, Mult) }
       | '@=' { CHECK_VERSION(5, "The '@' operator is", _PyPegen_augoperator(p, MatMult)) }
       | '/=' { _PyPegen_augoperator(p, Div) }
       | '%=' { _PyPegen_augoperator(p, Mod) }
       | '&=' { _PyPegen_augoperator(p, BitAnd) }
       | '|=' { _PyPegen_augoperator(p, BitOr) }
       | '^=' { _PyPegen_augoperator(p, BitXor) }
       | '<<=' { _PyPegen_augoperator(p, LShift) }
       | '>>=' { _PyPegen_augoperator(p, RShift) }
       | '**=' { _PyPegen_augoperator(p, Pow) }
       | '//=' { _PyPegen_augoperator(p, FloorDiv) }

   global_stmt[stmt_ty]: 'global' a[asdl_expr_seq*]=','.NAME+ {
       _Py_Global(CHECK(_PyPegen_map_names_to_ids(p, a)), EXTRA) }
   nonlocal_stmt[stmt_ty]: 'nonlocal' a[asdl_expr_seq*]=','.NAME+ {
       _Py_Nonlocal(CHECK(_PyPegen_map_names_to_ids(p, a)), EXTRA) }

   yield_stmt[stmt_ty]: y=yield_expr { _Py_Expr(y, EXTRA) }

   assert_stmt[stmt_ty]: 'assert' a=expression b=[',' z=expression { z }] { _Py_Assert(a, b, EXTRA) }

   del_stmt[stmt_ty]:
       | 'del' a=del_targets &(';' | NEWLINE) { _Py_Delete(a, EXTRA) }
       | invalid_del_stmt

   import_stmt[stmt_ty]: import_name | import_from
   import_name[stmt_ty]: 'import' a=dotted_as_names { _Py_Import(a, EXTRA) }
   # note below: the ('.' | '...') is necessary because '...' is tokenized as ELLIPSIS
   import_from[stmt_ty]:
       | 'from' a=('.' | '...')* b=dotted_name 'import' c=import_from_targets {
           _Py_ImportFrom(b->v.Name.id, c, _PyPegen_seq_count_dots(a), EXTRA) }
       | 'from' a=('.' | '...')+ 'import' b=import_from_targets {
           _Py_ImportFrom(NULL, b, _PyPegen_seq_count_dots(a), EXTRA) }
   import_from_targets[asdl_alias_seq*]:
       | '(' a=import_from_as_names [','] ')' { a }
       | import_from_as_names !','
       | '*' { (asdl_alias_seq*)_PyPegen_singleton_seq(p, CHECK(_PyPegen_alias_for_star(p))) }
       | invalid_import_from_targets
   import_from_as_names[asdl_alias_seq*]:
       | a[asdl_alias_seq*]=','.import_from_as_name+ { a }
   import_from_as_name[alias_ty]:
       | a=NAME b=['as' z=NAME { z }] { _Py_alias(a->v.Name.id,
                                                  (b) ? ((expr_ty) b)->v.Name.id : NULL,
                                                  p->arena) }
   dotted_as_names[asdl_alias_seq*]:
       | a[asdl_alias_seq*]=','.dotted_as_name+ { a }
   dotted_as_name[alias_ty]:
       | a=dotted_name b=['as' z=NAME { z }] { _Py_alias(a->v.Name.id,
                                                         (b) ? ((expr_ty) b)->v.Name.id : NULL,
                                                         p->arena) }
   dotted_name[expr_ty]:
       | a=dotted_name '.' b=NAME { _PyPegen_join_names_with_dot(p, a, b) }
       | NAME

   if_stmt[stmt_ty]:
       | 'if' a=named_expression ':' b=block c=elif_stmt { _Py_If(a, b, CHECK((asdl_stmt_seq*)_PyPegen_singleton_seq(p, c)), EXTRA) }
       | 'if' a=named_expression ':' b=block c=[else_block] { _Py_If(a, b, c, EXTRA) }
   elif_stmt[stmt_ty]:
       | 'elif' a=named_expression ':' b=block c=elif_stmt { _Py_If(a, b, CHECK(_PyPegen_singleton_seq(p, c)), EXTRA) }
       | 'elif' a=named_expression ':' b=block c=[else_block] { _Py_If(a, b, c, EXTRA) }
   else_block[asdl_stmt_seq*]: 'else' ':' b=block { b }

   while_stmt[stmt_ty]:
       | 'while' a=named_expression ':' b=block c=[else_block] { _Py_While(a, b, c, EXTRA) }

   for_stmt[stmt_ty]:
       | 'for' t=star_targets 'in' ~ ex=star_expressions ':' tc=[TYPE_COMMENT] b=block el=[else_block] {
           _Py_For(t, ex, b, el, NEW_TYPE_COMMENT(p, tc), EXTRA) }
       | ASYNC 'for' t=star_targets 'in' ~ ex=star_expressions ':' tc=[TYPE_COMMENT] b=block el=[else_block] {
           CHECK_VERSION(5, "Async for loops are", _Py_AsyncFor(t, ex, b, el, NEW_TYPE_COMMENT(p, tc), EXTRA)) }
       | invalid_for_target

   with_stmt[stmt_ty]:
       | 'with' '(' a[asdl_withitem_seq*]=','.with_item+ ','? ')' ':' b=block {
           _Py_With(a, b, NULL, EXTRA) }
       | 'with' a[asdl_withitem_seq*]=','.with_item+ ':' tc=[TYPE_COMMENT] b=block {
           _Py_With(a, b, NEW_TYPE_COMMENT(p, tc), EXTRA) }
       | ASYNC 'with' '(' a[asdl_withitem_seq*]=','.with_item+ ','? ')' ':' b=block {
          CHECK_VERSION(5, "Async with statements are", _Py_AsyncWith(a, b, NULL, EXTRA)) }
       | ASYNC 'with' a[asdl_withitem_seq*]=','.with_item+ ':' tc=[TYPE_COMMENT] b=block {
          CHECK_VERSION(5, "Async with statements are", _Py_AsyncWith(a, b, NEW_TYPE_COMMENT(p, tc), EXTRA)) }
   with_item[withitem_ty]:
       | e=expression 'as' t=target &(',' | ')' | ':') { _Py_withitem(e, t, p->arena) }
       | invalid_with_item
       | e=expression { _Py_withitem(e, NULL, p->arena) }

   try_stmt[stmt_ty]:
       | 'try' ':' b=block f=finally_block { _Py_Try(b, NULL, NULL, f, EXTRA) }
       | 'try' ':' b=block ex[asdl_excepthandler_seq*]=except_block+ el=[else_block] f=[finally_block] { _Py_Try(b, ex, el, f, EXTRA) }
   except_block[excepthandler_ty]:
       | 'except' e=expression t=['as' z=NAME { z }] ':' b=block {
           _Py_ExceptHandler(e, (t) ? ((expr_ty) t)->v.Name.id : NULL, b, EXTRA) }
       | 'except' ':' b=block { _Py_ExceptHandler(NULL, NULL, b, EXTRA) }
   finally_block[asdl_stmt_seq*]: 'finally' ':' a=block { a }

   return_stmt[stmt_ty]:
       | 'return' a=[star_expressions] { _Py_Return(a, EXTRA) }

   raise_stmt[stmt_ty]:
       | 'raise' a=expression b=['from' z=expression { z }] { _Py_Raise(a, b, EXTRA) }
       | 'raise' { _Py_Raise(NULL, NULL, EXTRA) }

   function_def[stmt_ty]:
       | d=decorators f=function_def_raw { _PyPegen_function_def_decorators(p, d, f) }
       | function_def_raw

   function_def_raw[stmt_ty]:
       | 'def' n=NAME '(' params=[params] ')' a=['->' z=expression { z }] ':' tc=[func_type_comment] b=block {
           _Py_FunctionDef(n->v.Name.id,
                           (params) ? params : CHECK(_PyPegen_empty_arguments(p)),
                           b, NULL, a, NEW_TYPE_COMMENT(p, tc), EXTRA) }
       | ASYNC 'def' n=NAME '(' params=[params] ')' a=['->' z=expression { z }] ':' tc=[func_type_comment] b=block {
           CHECK_VERSION(
               5,
               "Async functions are",
               _Py_AsyncFunctionDef(n->v.Name.id,
                               (params) ? params : CHECK(_PyPegen_empty_arguments(p)),
                               b, NULL, a, NEW_TYPE_COMMENT(p, tc), EXTRA)
           ) }
   func_type_comment[Token*]:
       | NEWLINE t=TYPE_COMMENT &(NEWLINE INDENT) { t }  # Must be followed by indented block
       | invalid_double_type_comments
       | TYPE_COMMENT

   params[arguments_ty]:
       | invalid_parameters
       | parameters

   parameters[arguments_ty]:
       | a=slash_no_default b[asdl_arg_seq*]=param_no_default* c=param_with_default* d=[star_etc] {
           _PyPegen_make_arguments(p, a, NULL, b, c, d) }
       | a=slash_with_default b=param_with_default* c=[star_etc] {
           _PyPegen_make_arguments(p, NULL, a, NULL, b, c) }
       | a[asdl_arg_seq*]=param_no_default+ b=param_with_default* c=[star_etc] {
           _PyPegen_make_arguments(p, NULL, NULL, a, b, c) }
       | a=param_with_default+ b=[star_etc] { _PyPegen_make_arguments(p, NULL, NULL, NULL, a, b)}
       | a=star_etc { _PyPegen_make_arguments(p, NULL, NULL, NULL, NULL, a) }

   # Some duplication here because we can't write (',' | &')'),
   # which is because we don't support empty alternatives (yet).
   #
   slash_no_default[asdl_arg_seq*]:
       | a[asdl_arg_seq*]=param_no_default+ '/' ',' { a }
       | a[asdl_arg_seq*]=param_no_default+ '/' &')' { a }
   slash_with_default[SlashWithDefault*]:
       | a=param_no_default* b=param_with_default+ '/' ',' { _PyPegen_slash_with_default(p, (asdl_arg_seq *)a, b) }
       | a=param_no_default* b=param_with_default+ '/' &')' { _PyPegen_slash_with_default(p, (asdl_arg_seq *)a, b) }

   star_etc[StarEtc*]:
       | '*' a=param_no_default b=param_maybe_default* c=[kwds] {
           _PyPegen_star_etc(p, a, b, c) }
       | '*' ',' b=param_maybe_default+ c=[kwds] {
           _PyPegen_star_etc(p, NULL, b, c) }
       | a=kwds { _PyPegen_star_etc(p, NULL, NULL, a) }
       | invalid_star_etc

   kwds[arg_ty]: '**' a=param_no_default { a }

   # One parameter.  This *includes* a following comma and type comment.
   #
   # There are three styles:
   # - No default
   # - With default
   # - Maybe with default
   #
   # There are two alternative forms of each, to deal with type comments:
   # - Ends in a comma followed by an optional type comment
   # - No comma, optional type comment, must be followed by close paren
   # The latter form is for a final parameter without trailing comma.
   #
   param_no_default[arg_ty]:
       | a=param ',' tc=TYPE_COMMENT? { _PyPegen_add_type_comment_to_arg(p, a, tc) }
       | a=param tc=TYPE_COMMENT? &')' { _PyPegen_add_type_comment_to_arg(p, a, tc) }
   param_with_default[NameDefaultPair*]:
       | a=param c=default ',' tc=TYPE_COMMENT? { _PyPegen_name_default_pair(p, a, c, tc) }
       | a=param c=default tc=TYPE_COMMENT? &')' { _PyPegen_name_default_pair(p, a, c, tc) }
   param_maybe_default[NameDefaultPair*]:
       | a=param c=default? ',' tc=TYPE_COMMENT? { _PyPegen_name_default_pair(p, a, c, tc) }
       | a=param c=default? tc=TYPE_COMMENT? &')' { _PyPegen_name_default_pair(p, a, c, tc) }
   param[arg_ty]: a=NAME b=annotation? { _Py_arg(a->v.Name.id, b, NULL, EXTRA) }

   annotation[expr_ty]: ':' a=expression { a }
   default[expr_ty]: '=' a=expression { a }

   decorators[asdl_expr_seq*]: a[asdl_expr_seq*]=('@' f=named_expression NEWLINE { f })+ { a }

   class_def[stmt_ty]:
       | a=decorators b=class_def_raw { _PyPegen_class_def_decorators(p, a, b) }
       | class_def_raw
   class_def_raw[stmt_ty]:
       | 'class' a=NAME b=['(' z=[arguments] ')' { z }] ':' c=block {
           _Py_ClassDef(a->v.Name.id,
                        (b) ? ((expr_ty) b)->v.Call.args : NULL,
                        (b) ? ((expr_ty) b)->v.Call.keywords : NULL,
                        c, NULL, EXTRA) }

   block[asdl_stmt_seq*] (memo):
       | NEWLINE INDENT a=statements DEDENT { a }
       | simple_stmt
       | invalid_block

   expressions_list[asdl_expr_seq*]: a[asdl_expr_seq*]=','.star_expression+ [','] { a }
   star_expressions[expr_ty]:
       | a=star_expression b=(',' c=star_expression { c })+ [','] {
           _Py_Tuple(CHECK(_PyPegen_seq_insert_in_front(p, a, b)), Load, EXTRA) }
       | a=star_expression ',' { _Py_Tuple(CHECK(_PyPegen_singleton_seq(p, a)), Load, EXTRA) }
       | star_expression
   star_expression[expr_ty] (memo):
       | '*' a=bitwise_or { _Py_Starred(a, Load, EXTRA) }
       | expression

   star_named_expressions[asdl_expr_seq*]: a[asdl_expr_seq*]=','.star_named_expression+ [','] { a }
   star_named_expression[expr_ty]:
       | '*' a=bitwise_or { _Py_Starred(a, Load, EXTRA) }
       | named_expression
   named_expression[expr_ty]:
       | a=NAME ':=' ~ b=expression { _Py_NamedExpr(CHECK(_PyPegen_set_expr_context(p, a, Store)), b, EXTRA) }
       | expression !':='
       | invalid_named_expression

   annotated_rhs[expr_ty]: yield_expr | star_expressions

   expressions[expr_ty]:
       | a=expression b=(',' c=expression { c })+ [','] {
           _Py_Tuple(CHECK(_PyPegen_seq_insert_in_front(p, a, b)), Load, EXTRA) }
       | a=expression ',' { _Py_Tuple(CHECK(_PyPegen_singleton_seq(p, a)), Load, EXTRA) }
       | expression
   expression[expr_ty] (memo):
       | a=disjunction 'if' b=disjunction 'else' c=expression { _Py_IfExp(b, a, c, EXTRA) }
       | disjunction
       | lambdef

   lambdef[expr_ty]:
       | 'lambda' a=[lambda_params] ':' b=expression { _Py_Lambda((a) ? a : CHECK(_PyPegen_empty_arguments(p)), b, EXTRA) }

   lambda_params[arguments_ty]:
       | invalid_lambda_parameters
       | lambda_parameters

   # lambda_parameters etc. duplicates parameters but without annotations
   # or type comments, and if there's no comma after a parameter, we expect
   # a colon, not a close parenthesis.  (For more, see parameters above.)
   #
   lambda_parameters[arguments_ty]:
       | a=lambda_slash_no_default b[asdl_arg_seq*]=lambda_param_no_default* c=lambda_param_with_default* d=[lambda_star_etc] {
           _PyPegen_make_arguments(p, a, NULL, b, c, d) }
       | a=lambda_slash_with_default b=lambda_param_with_default* c=[lambda_star_etc] {
           _PyPegen_make_arguments(p, NULL, a, NULL, b, c) }
       | a[asdl_arg_seq*]=lambda_param_no_default+ b=lambda_param_with_default* c=[lambda_star_etc] {
           _PyPegen_make_arguments(p, NULL, NULL, a, b, c) }
       | a=lambda_param_with_default+ b=[lambda_star_etc] { _PyPegen_make_arguments(p, NULL, NULL, NULL, a, b)}
       | a=lambda_star_etc { _PyPegen_make_arguments(p, NULL, NULL, NULL, NULL, a) }

   lambda_slash_no_default[asdl_arg_seq*]:
       | a[asdl_arg_seq*]=lambda_param_no_default+ '/' ',' { a }
       | a[asdl_arg_seq*]=lambda_param_no_default+ '/' &':' { a }
   lambda_slash_with_default[SlashWithDefault*]:
       | a=lambda_param_no_default* b=lambda_param_with_default+ '/' ',' { _PyPegen_slash_with_default(p, (asdl_arg_seq *)a, b) }
       | a=lambda_param_no_default* b=lambda_param_with_default+ '/' &':' { _PyPegen_slash_with_default(p, (asdl_arg_seq *)a, b) }

   lambda_star_etc[StarEtc*]:
       | '*' a=lambda_param_no_default b=lambda_param_maybe_default* c=[lambda_kwds] {
           _PyPegen_star_etc(p, a, b, c) }
       | '*' ',' b=lambda_param_maybe_default+ c=[lambda_kwds] {
           _PyPegen_star_etc(p, NULL, b, c) }
       | a=lambda_kwds { _PyPegen_star_etc(p, NULL, NULL, a) }
       | invalid_lambda_star_etc

   lambda_kwds[arg_ty]: '**' a=lambda_param_no_default { a }

   lambda_param_no_default[arg_ty]:
       | a=lambda_param ',' { a }
       | a=lambda_param &':' { a }
   lambda_param_with_default[NameDefaultPair*]:
       | a=lambda_param c=default ',' { _PyPegen_name_default_pair(p, a, c, NULL) }
       | a=lambda_param c=default &':' { _PyPegen_name_default_pair(p, a, c, NULL) }
   lambda_param_maybe_default[NameDefaultPair*]:
       | a=lambda_param c=default? ',' { _PyPegen_name_default_pair(p, a, c, NULL) }
       | a=lambda_param c=default? &':' { _PyPegen_name_default_pair(p, a, c, NULL) }
   lambda_param[arg_ty]: a=NAME { _Py_arg(a->v.Name.id, NULL, NULL, EXTRA) }

   disjunction[expr_ty] (memo):
       | a=conjunction b=('or' c=conjunction { c })+ { _Py_BoolOp(
           Or,
           CHECK(_PyPegen_seq_insert_in_front(p, a, b)),
           EXTRA) }
       | conjunction
   conjunction[expr_ty] (memo):
       | a=inversion b=('and' c=inversion { c })+ { _Py_BoolOp(
           And,
           CHECK(_PyPegen_seq_insert_in_front(p, a, b)),
           EXTRA) }
       | inversion
   inversion[expr_ty] (memo):
       | 'not' a=inversion { _Py_UnaryOp(Not, a, EXTRA) }
       | comparison
   comparison[expr_ty]:
       | a=bitwise_or b=compare_op_bitwise_or_pair+ {
           _Py_Compare(a, CHECK(_PyPegen_get_cmpops(p, b)), CHECK(_PyPegen_get_exprs(p, b)), EXTRA) }
       | bitwise_or
   compare_op_bitwise_or_pair[CmpopExprPair*]:
       | eq_bitwise_or
       | noteq_bitwise_or
       | lte_bitwise_or
       | lt_bitwise_or
       | gte_bitwise_or
       | gt_bitwise_or
       | notin_bitwise_or
       | in_bitwise_or
       | isnot_bitwise_or
       | is_bitwise_or
   eq_bitwise_or[CmpopExprPair*]: '==' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, Eq, a) }
   noteq_bitwise_or[CmpopExprPair*]:
       | (tok='!=' {_PyPegen_check_barry_as_flufl(p) ? NULL : tok}) a=bitwise_or {_PyPegen_cmpop_expr_pair(p, NotEq, a) }
   lte_bitwise_or[CmpopExprPair*]: '<=' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, LtE, a) }
   lt_bitwise_or[CmpopExprPair*]: '<' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, Lt, a) }
   gte_bitwise_or[CmpopExprPair*]: '>=' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, GtE, a) }
   gt_bitwise_or[CmpopExprPair*]: '>' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, Gt, a) }
   notin_bitwise_or[CmpopExprPair*]: 'not' 'in' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, NotIn, a) }
   in_bitwise_or[CmpopExprPair*]: 'in' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, In, a) }
   isnot_bitwise_or[CmpopExprPair*]: 'is' 'not' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, IsNot, a) }
   is_bitwise_or[CmpopExprPair*]: 'is' a=bitwise_or { _PyPegen_cmpop_expr_pair(p, Is, a) }

   bitwise_or[expr_ty]:
       | a=bitwise_or '|' b=bitwise_xor { _Py_BinOp(a, BitOr, b, EXTRA) }
       | bitwise_xor
   bitwise_xor[expr_ty]:
       | a=bitwise_xor '^' b=bitwise_and { _Py_BinOp(a, BitXor, b, EXTRA) }
       | bitwise_and
   bitwise_and[expr_ty]:
       | a=bitwise_and '&' b=shift_expr { _Py_BinOp(a, BitAnd, b, EXTRA) }
       | shift_expr
   shift_expr[expr_ty]:
       | a=shift_expr '<<' b=sum { _Py_BinOp(a, LShift, b, EXTRA) }
       | a=shift_expr '>>' b=sum { _Py_BinOp(a, RShift, b, EXTRA) }
       | sum

   sum[expr_ty]:
       | a=sum '+' b=term { _Py_BinOp(a, Add, b, EXTRA) }
       | a=sum '-' b=term { _Py_BinOp(a, Sub, b, EXTRA) }
       | term
   term[expr_ty]:
       | a=term '*' b=factor { _Py_BinOp(a, Mult, b, EXTRA) }
       | a=term '/' b=factor { _Py_BinOp(a, Div, b, EXTRA) }
       | a=term '//' b=factor { _Py_BinOp(a, FloorDiv, b, EXTRA) }
       | a=term '%' b=factor { _Py_BinOp(a, Mod, b, EXTRA) }
       | a=term '@' b=factor { CHECK_VERSION(5, "The '@' operator is", _Py_BinOp(a, MatMult, b, EXTRA)) }
       | factor
   factor[expr_ty] (memo):
       | '+' a=factor { _Py_UnaryOp(UAdd, a, EXTRA) }
       | '-' a=factor { _Py_UnaryOp(USub, a, EXTRA) }
       | '~' a=factor { _Py_UnaryOp(Invert, a, EXTRA) }
       | power
   power[expr_ty]:
       | a=await_primary '**' b=factor { _Py_BinOp(a, Pow, b, EXTRA) }
       | await_primary
   await_primary[expr_ty] (memo):
       | AWAIT a=primary { CHECK_VERSION(5, "Await expressions are", _Py_Await(a, EXTRA)) }
       | primary
   primary[expr_ty]:
       | a=primary '.' b=NAME { _Py_Attribute(a, b->v.Name.id, Load, EXTRA) }
       | a=primary b=genexp { _Py_Call(a, CHECK(_PyPegen_singleton_seq(p, b)), NULL, EXTRA) }
       | a=primary '(' b=[arguments] ')' {
           _Py_Call(a,
                    (b) ? ((expr_ty) b)->v.Call.args : NULL,
                    (b) ? ((expr_ty) b)->v.Call.keywords : NULL,
                    EXTRA) }
       | a=primary '[' b=slices ']' { _Py_Subscript(a, b, Load, EXTRA) }
       | atom

   slices[expr_ty]:
       | a=slice !',' { a }
       | a[asdl_expr_seq*]=','.slice+ [','] { _Py_Tuple(a, Load, EXTRA) }
   slice[expr_ty]:
       | a=[expression] ':' b=[expression] c=[':' d=[expression] { d }] { _Py_Slice(a, b, c, EXTRA) }
       | a=expression { a }
   atom[expr_ty]:
       | NAME
       | 'True' { _Py_Constant(Py_True, NULL, EXTRA) }
       | 'False' { _Py_Constant(Py_False, NULL, EXTRA) }
       | 'None' { _Py_Constant(Py_None, NULL, EXTRA) }
       | &STRING strings
       | NUMBER
       | &'(' (tuple | group | genexp)
       | &'[' (list | listcomp)
       | &'{' (dict | set | dictcomp | setcomp)
       | '...' { _Py_Constant(Py_Ellipsis, NULL, EXTRA) }

   strings[expr_ty] (memo): a=STRING+ { _PyPegen_concatenate_strings(p, a) }
   list[expr_ty]:
       | '[' a=[star_named_expressions] ']' { _Py_List(a, Load, EXTRA) }
   listcomp[expr_ty]:
       | '[' a=named_expression ~ b=for_if_clauses ']' { _Py_ListComp(a, b, EXTRA) }
       | invalid_comprehension
   tuple[expr_ty]:
       | '(' a=[y=star_named_expression ',' z=[star_named_expressions] { _PyPegen_seq_insert_in_front(p, y, z) } ] ')' {
           _Py_Tuple(a, Load, EXTRA) }
   group[expr_ty]:
       | '(' a=(yield_expr | named_expression) ')' { a }
       | invalid_group
   genexp[expr_ty]:
       | '(' a=expression ~ b=for_if_clauses ')' { _Py_GeneratorExp(a, b, EXTRA) }
       | invalid_comprehension
   set[expr_ty]: '{' a=expressions_list '}' { _Py_Set(a, EXTRA) }
   setcomp[expr_ty]:
       | '{' a=expression ~ b=for_if_clauses '}' { _Py_SetComp(a, b, EXTRA) }
       | invalid_comprehension
   dict[expr_ty]:
       | '{' a=[double_starred_kvpairs] '}' {
           _Py_Dict(CHECK(_PyPegen_get_keys(p, a)), CHECK(_PyPegen_get_values(p, a)), EXTRA) }
   dictcomp[expr_ty]:
       | '{' a=kvpair b=for_if_clauses '}' { _Py_DictComp(a->key, a->value, b, EXTRA) }
       | invalid_dict_comprehension
   double_starred_kvpairs[asdl_seq*]: a=','.double_starred_kvpair+ [','] { a }
   double_starred_kvpair[KeyValuePair*]:
       | '**' a=bitwise_or { _PyPegen_key_value_pair(p, NULL, a) }
       | kvpair
   kvpair[KeyValuePair*]: a=expression ':' b=expression { _PyPegen_key_value_pair(p, a, b) }
   for_if_clauses[asdl_comprehension_seq*]:
       | a[asdl_comprehension_seq*]=for_if_clause+ { a }
   for_if_clause[comprehension_ty]:
       | ASYNC 'for' a=star_targets 'in' ~ b=disjunction c[asdl_expr_seq*]=('if' z=disjunction { z })* {
           CHECK_VERSION(6, "Async comprehensions are", _Py_comprehension(a, b, c, 1, p->arena)) }
       | 'for' a=star_targets 'in' ~ b=disjunction c[asdl_expr_seq*]=('if' z=disjunction { z })* {
           _Py_comprehension(a, b, c, 0, p->arena) }
       | invalid_for_target

   yield_expr[expr_ty]:
       | 'yield' 'from' a=expression { _Py_YieldFrom(a, EXTRA) }
       | 'yield' a=[star_expressions] { _Py_Yield(a, EXTRA) }

   arguments[expr_ty] (memo):
       | a=args [','] &')' { a }
       | incorrect_arguments
   args[expr_ty]:
       | a[asdl_expr_seq*]=','.(starred_expression | named_expression !'=')+ b=[',' k=kwargs {k}] { _PyPegen_collect_call_seqs(p, a, b, EXTRA) }
       | a=kwargs { _Py_Call(_PyPegen_dummy_name(p),
                             CHECK_NULL_ALLOWED(_PyPegen_seq_extract_starred_exprs(p, a)),
                             CHECK_NULL_ALLOWED(_PyPegen_seq_delete_starred_exprs(p, a)),
                             EXTRA) }
   kwargs[asdl_seq*]:
       | a=','.kwarg_or_starred+ ',' b=','.kwarg_or_double_starred+ { _PyPegen_join_sequences(p, a, b) }
       | ','.kwarg_or_starred+
       | ','.kwarg_or_double_starred+
   starred_expression[expr_ty]:
       | '*' a=expression { _Py_Starred(a, Load, EXTRA) }
   kwarg_or_starred[KeywordOrStarred*]:
       | a=NAME '=' b=expression {
           _PyPegen_keyword_or_starred(p, CHECK(_Py_keyword(a->v.Name.id, b, EXTRA)), 1) }
       | a=starred_expression { _PyPegen_keyword_or_starred(p, a, 0) }
       | invalid_kwarg
   kwarg_or_double_starred[KeywordOrStarred*]:
       | a=NAME '=' b=expression {
           _PyPegen_keyword_or_starred(p, CHECK(_Py_keyword(a->v.Name.id, b, EXTRA)), 1) }
       | '**' a=expression { _PyPegen_keyword_or_starred(p, CHECK(_Py_keyword(NULL, a, EXTRA)), 1) }
       | invalid_kwarg

   # NOTE: star_targets may contain *bitwise_or, targets may not.
   star_targets[expr_ty]:
       | a=star_target !',' { a }
       | a=star_target b=(',' c=star_target { c })* [','] {
           _Py_Tuple(CHECK(_PyPegen_seq_insert_in_front(p, a, b)), Store, EXTRA) }
   star_targets_seq[asdl_expr_seq*]: a[asdl_expr_seq*]=','.star_target+ [','] { a }
   star_target[expr_ty] (memo):
       | '*' a=(!'*' star_target) {
           _Py_Starred(CHECK(_PyPegen_set_expr_context(p, a, Store)), Store, EXTRA) }
       | a=t_primary '.' b=NAME !t_lookahead { _Py_Attribute(a, b->v.Name.id, Store, EXTRA) }
       | a=t_primary '[' b=slices ']' !t_lookahead { _Py_Subscript(a, b, Store, EXTRA) }
       | star_atom
   star_atom[expr_ty]:
       | a=NAME { _PyPegen_set_expr_context(p, a, Store) }
       | '(' a=star_target ')' { _PyPegen_set_expr_context(p, a, Store) }
       | '(' a=[star_targets_seq] ')' { _Py_Tuple(a, Store, EXTRA) }
       | '[' a=[star_targets_seq] ']' { _Py_List(a, Store, EXTRA) }

   single_target[expr_ty]:
       | single_subscript_attribute_target
       | a=NAME { _PyPegen_set_expr_context(p, a, Store) }
       | '(' a=single_target ')' { a }
   single_subscript_attribute_target[expr_ty]:
       | a=t_primary '.' b=NAME !t_lookahead { _Py_Attribute(a, b->v.Name.id, Store, EXTRA) }
       | a=t_primary '[' b=slices ']' !t_lookahead { _Py_Subscript(a, b, Store, EXTRA) }

   del_targets[asdl_expr_seq*]: a[asdl_expr_seq*]=','.del_target+ [','] { a }
   del_target[expr_ty] (memo):
       | a=t_primary '.' b=NAME !t_lookahead { _Py_Attribute(a, b->v.Name.id, Del, EXTRA) }
       | a=t_primary '[' b=slices ']' !t_lookahead { _Py_Subscript(a, b, Del, EXTRA) }
       | del_t_atom
   del_t_atom[expr_ty]:
       | a=NAME { _PyPegen_set_expr_context(p, a, Del) }
       | '(' a=del_target ')' { _PyPegen_set_expr_context(p, a, Del) }
       | '(' a=[del_targets] ')' { _Py_Tuple(a, Del, EXTRA) }
       | '[' a=[del_targets] ']' { _Py_List(a, Del, EXTRA) }

   targets[asdl_expr_seq*]: a[asdl_expr_seq*]=','.target+ [','] { a }
   target[expr_ty] (memo):
       | a=t_primary '.' b=NAME !t_lookahead { _Py_Attribute(a, b->v.Name.id, Store, EXTRA) }
       | a=t_primary '[' b=slices ']' !t_lookahead { _Py_Subscript(a, b, Store, EXTRA) }
       | t_atom
   t_primary[expr_ty]:
       | a=t_primary '.' b=NAME &t_lookahead { _Py_Attribute(a, b->v.Name.id, Load, EXTRA) }
       | a=t_primary '[' b=slices ']' &t_lookahead { _Py_Subscript(a, b, Load, EXTRA) }
       | a=t_primary b=genexp &t_lookahead { _Py_Call(a, CHECK(_PyPegen_singleton_seq(p, b)), NULL, EXTRA) }
       | a=t_primary '(' b=[arguments] ')' &t_lookahead {
           _Py_Call(a,
                    (b) ? ((expr_ty) b)->v.Call.args : NULL,
                    (b) ? ((expr_ty) b)->v.Call.keywords : NULL,
                    EXTRA) }
       | a=atom &t_lookahead { a }
   t_lookahead: '(' | '[' | '.'
   t_atom[expr_ty]:
       | a=NAME { _PyPegen_set_expr_context(p, a, Store) }
       | '(' a=target ')' { _PyPegen_set_expr_context(p, a, Store) }
       | '(' b=[targets] ')' { _Py_Tuple(b, Store, EXTRA) }
       | '[' b=[targets] ']' { _Py_List(b, Store, EXTRA) }


   # From here on, there are rules for invalid syntax with specialised error messages
   incorrect_arguments:
       | args ',' '*' { RAISE_SYNTAX_ERROR("iterable argument unpacking follows keyword argument unpacking") }
       | a=expression for_if_clauses ',' [args | expression for_if_clauses] {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "Generator expression must be parenthesized") }
       | a=args for_if_clauses { _PyPegen_nonparen_genexp_in_call(p, a) }
       | args ',' a=expression for_if_clauses {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "Generator expression must be parenthesized") }
       | a=args ',' args { _PyPegen_arguments_parsing_error(p, a) }
   invalid_kwarg:
       | a=expression '=' {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
               a, "expression cannot contain assignment, perhaps you meant \"==\"?") }
   invalid_named_expression:
       | a=expression ':=' expression {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
               a, "cannot use assignment expressions with %s", _PyPegen_get_expr_name(a)) }
   invalid_assignment:
       | a=invalid_ann_assign_target ':' expression {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(
               a,
               "only single target (not %s) can be annotated",
               _PyPegen_get_expr_name(a)
           )}
       | a=star_named_expression ',' star_named_expressions* ':' expression {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "only single target (not tuple) can be annotated") }
       | a=expression ':' expression {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "illegal target for annotation") }
       | (star_targets '=')* a=star_expressions '=' {
           RAISE_SYNTAX_ERROR_INVALID_TARGET(STAR_TARGETS, a) }
       | (star_targets '=')* a=yield_expr '=' { RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "assignment to yield expression not possible") }
       | a=star_expressions augassign (yield_expr | star_expressions) {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION( 
               a,
               "'%s' is an illegal expression for augmented assignment",
               _PyPegen_get_expr_name(a)
           )}
   invalid_ann_assign_target[expr_ty]:
       | list
       | tuple
       | '(' a=invalid_ann_assign_target ')' { a }
   invalid_del_stmt:
       | 'del' a=star_expressions {
           RAISE_SYNTAX_ERROR_INVALID_TARGET(DEL_TARGETS, a) }
   invalid_block:
       | NEWLINE !INDENT { RAISE_INDENTATION_ERROR("expected an indented block") }
   invalid_comprehension:
       | ('[' | '(' | '{') a=starred_expression for_if_clauses {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "iterable unpacking cannot be used in comprehension") }
   invalid_dict_comprehension:
       | '{' a='**' bitwise_or for_if_clauses '}' {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "dict unpacking cannot be used in dict comprehension") }
   invalid_parameters:
       | param_no_default* (slash_with_default | param_with_default+) param_no_default {
           RAISE_SYNTAX_ERROR("non-default argument follows default argument") }
   invalid_lambda_parameters:
       | lambda_param_no_default* (lambda_slash_with_default | lambda_param_with_default+) lambda_param_no_default {
           RAISE_SYNTAX_ERROR("non-default argument follows default argument") }
   invalid_star_etc:
       | '*' (')' | ',' (')' | '**')) { RAISE_SYNTAX_ERROR("named arguments must follow bare *") }
       | '*' ',' TYPE_COMMENT { RAISE_SYNTAX_ERROR("bare * has associated type comment") }
   invalid_lambda_star_etc:
       | '*' (':' | ',' (':' | '**')) { RAISE_SYNTAX_ERROR("named arguments must follow bare *") }
   invalid_double_type_comments:
       | TYPE_COMMENT NEWLINE TYPE_COMMENT NEWLINE INDENT {
           RAISE_SYNTAX_ERROR("Cannot have two type comments on def") }
   invalid_with_item:
       | expression 'as' a=expression {
           RAISE_SYNTAX_ERROR_INVALID_TARGET(STAR_TARGETS, a) }

   invalid_for_target:
       | ASYNC? 'for' a=star_expressions {
           RAISE_SYNTAX_ERROR_INVALID_TARGET(FOR_TARGETS, a) }

   invalid_group:
       | '(' a=starred_expression ')' {
           RAISE_SYNTAX_ERROR_KNOWN_LOCATION(a, "can't use starred expression here") }
   invalid_import_from_targets:
       | import_from_as_names ',' {
           RAISE_SYNTAX_ERROR("trailing comma not allowed without surrounding parentheses") }
