Initial commit

venv/Lib/site-packages/blib2to3/Grammar.txt

@@ -0,0 +1,261 @@
+# Grammar for 2to3. This grammar supports Python 2.x and 3.x.
+
+# NOTE WELL: You should also follow all the steps listed at
+# https://devguide.python.org/grammar/
+
+# Start symbols for the grammar:
+#	file_input is a module or sequence of commands read from an input file;
+#	single_input is a single interactive statement;
+#	eval_input is the input for the eval() and input() functions.
+# NB: compound_stmt in single_input is followed by extra NEWLINE!
+file_input: (NEWLINE | stmt)* ENDMARKER
+single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
+eval_input: testlist NEWLINE* ENDMARKER
+
+typevar: NAME [':' expr] ['=' expr]
+paramspec: '**' NAME ['=' expr]
+typevartuple: '*' NAME ['=' (expr|star_expr)]
+typeparam: typevar | paramspec | typevartuple
+typeparams: '[' typeparam (',' typeparam)* [','] ']'
+
+decorator: '@' namedexpr_test NEWLINE
+decorators: decorator+
+decorated: decorators (classdef | funcdef | async_funcdef)
+async_funcdef: ASYNC funcdef
+funcdef: 'def' NAME [typeparams] parameters ['->' test] ':' suite
+parameters: '(' [typedargslist] ')'
+
+# The following definition for typedarglist is equivalent to this set of rules:
+#
+#     arguments = argument (',' argument)*
+#     argument = tfpdef ['=' test]
+#     kwargs = '**' tname [',']
+#     args = '*' [tname_star]
+#     kwonly_kwargs = (',' argument)* [',' [kwargs]]
+#     args_kwonly_kwargs = args kwonly_kwargs | kwargs
+#     poskeyword_args_kwonly_kwargs = arguments [',' [args_kwonly_kwargs]]
+#     typedargslist_no_posonly  = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs
+#     typedarglist = arguments ',' '/' [',' [typedargslist_no_posonly]])|(typedargslist_no_posonly)"
+#
+# It needs to be fully expanded to allow our LL(1) parser to work on it.
+
+typedargslist: tfpdef ['=' test] (',' tfpdef ['=' test])* ',' '/' [
+                     ',' [((tfpdef ['=' test] ',')* ('*' [tname_star] (',' tname ['=' test])*
+                            [',' ['**' tname [',']]] | '**' tname [','])
+                     | tfpdef ['=' test] (',' tfpdef ['=' test])* [','])]
+                ] | ((tfpdef ['=' test] ',')* ('*' [tname_star] (',' tname ['=' test])*
+                     [',' ['**' tname [',']]] | '**' tname [','])
+                     | tfpdef ['=' test] (',' tfpdef ['=' test])* [','])
+
+tname: NAME [':' test]
+tname_star: NAME [':' (test|star_expr)]
+tfpdef: tname | '(' tfplist ')'
+tfplist: tfpdef (',' tfpdef)* [',']
+
+# The following definition for varargslist is equivalent to this set of rules:
+#
+#     arguments = argument (',' argument )*
+#     argument = vfpdef ['=' test]
+#     kwargs = '**' vname [',']
+#     args = '*' [vname]
+#     kwonly_kwargs = (',' argument )* [',' [kwargs]]
+#     args_kwonly_kwargs = args kwonly_kwargs | kwargs
+#     poskeyword_args_kwonly_kwargs = arguments [',' [args_kwonly_kwargs]]
+#     vararglist_no_posonly = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs
+#     varargslist = arguments ',' '/' [','[(vararglist_no_posonly)]] | (vararglist_no_posonly)
+#
+# It needs to be fully expanded to allow our LL(1) parser to work on it.
+
+varargslist: vfpdef ['=' test ](',' vfpdef ['=' test])* ',' '/' [',' [
+                     ((vfpdef ['=' test] ',')* ('*' [vname] (',' vname ['=' test])*
+                            [',' ['**' vname [',']]] | '**' vname [','])
+                            | vfpdef ['=' test] (',' vfpdef ['=' test])* [','])
+                     ]] | ((vfpdef ['=' test] ',')*
+                     ('*' [vname] (',' vname ['=' test])*  [',' ['**' vname [',']]]| '**' vname [','])
+                     | vfpdef ['=' test] (',' vfpdef ['=' test])* [','])
+
+vname: NAME
+vfpdef: vname | '(' vfplist ')'
+vfplist: vfpdef (',' vfpdef)* [',']
+
+stmt: simple_stmt | compound_stmt
+simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
+small_stmt: (type_stmt | expr_stmt | del_stmt | pass_stmt | flow_stmt |
+             import_stmt | global_stmt | assert_stmt)
+expr_stmt: testlist_star_expr (annassign | augassign (yield_expr|testlist) |
+                     ('=' (yield_expr|testlist_star_expr))*)
+annassign: ':' test ['=' (yield_expr|testlist_star_expr)]
+testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
+augassign: ('+=' | '-=' | '*=' | '@=' | '/=' | '%=' | '&=' | '|=' | '^=' |
+            '<<=' | '>>=' | '**=' | '//=')
+# For normal and annotated assignments, additional restrictions enforced by the interpreter
+del_stmt: 'del' exprlist
+pass_stmt: 'pass'
+flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt
+break_stmt: 'break'
+continue_stmt: 'continue'
+return_stmt: 'return' [testlist_star_expr]
+yield_stmt: yield_expr
+raise_stmt: 'raise' [test ['from' test | ',' test [',' test]]]
+import_stmt: import_name | import_from
+import_name: 'import' dotted_as_names
+import_from: ('from' ('.'* dotted_name | '.'+)
+              'import' ('*' | '(' import_as_names ')' | import_as_names))
+import_as_name: NAME ['as' NAME]
+dotted_as_name: dotted_name ['as' NAME]
+import_as_names: import_as_name (',' import_as_name)* [',']
+dotted_as_names: dotted_as_name (',' dotted_as_name)*
+dotted_name: NAME ('.' NAME)*
+global_stmt: ('global' | 'nonlocal') NAME (',' NAME)*
+assert_stmt: 'assert' test [',' test]
+type_stmt: "type" NAME [typeparams] '=' test
+
+compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated | async_stmt | match_stmt
+async_stmt: ASYNC (funcdef | with_stmt | for_stmt)
+if_stmt: 'if' namedexpr_test ':' suite ('elif' namedexpr_test ':' suite)* ['else' ':' suite]
+while_stmt: 'while' namedexpr_test ':' suite ['else' ':' suite]
+for_stmt: 'for' exprlist 'in' testlist_star_expr ':' suite ['else' ':' suite]
+try_stmt: ('try' ':' suite
+           ((except_clause ':' suite)+
+	    ['else' ':' suite]
+	    ['finally' ':' suite] |
+	   'finally' ':' suite))
+with_stmt: 'with' asexpr_test (',' asexpr_test)*  ':' suite
+
+# NB compile.c makes sure that the default except clause is last
+except_clause: 'except' ['*'] [test [(',' | 'as') test]]
+suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT
+
+# Backward compatibility cruft to support:
+# [ x for x in lambda: True, lambda: False if x() ]
+# even while also allowing:
+# lambda x: 5 if x else 2
+# (But not a mix of the two)
+testlist_safe: old_test [(',' old_test)+ [',']]
+old_test: or_test | old_lambdef
+old_lambdef: 'lambda' [varargslist] ':' old_test
+
+namedexpr_test: asexpr_test [':=' asexpr_test]
+
+# This is actually not a real rule, though since the parser is very
+# limited in terms of the strategy about match/case rules, we are inserting
+# a virtual case (<expr> as <expr>) as a valid expression. Unless a better
+# approach is thought, the only side effect of this seem to be just allowing
+# more stuff to be parser (which would fail on the ast).
+asexpr_test: test ['as' test]
+
+test: or_test ['if' or_test 'else' test] | lambdef
+or_test: and_test ('or' and_test)*
+and_test: not_test ('and' not_test)*
+not_test: 'not' not_test | comparison
+comparison: expr (comp_op expr)*
+comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'
+star_expr: '*' expr
+expr: xor_expr ('|' xor_expr)*
+xor_expr: and_expr ('^' and_expr)*
+and_expr: shift_expr ('&' shift_expr)*
+shift_expr: arith_expr (('<<'|'>>') arith_expr)*
+arith_expr: term (('+'|'-') term)*
+term: factor (('*'|'@'|'/'|'%'|'//') factor)*
+factor: ('+'|'-'|'~') factor | power
+power: [AWAIT] atom trailer* ['**' factor]
+atom: ('(' [yield_expr|testlist_gexp] ')' |
+       '[' [listmaker] ']' |
+       '{' [dictsetmaker] '}' |
+       '`' testlist1 '`' |
+       NAME | NUMBER | (STRING | fstring)+ | '.' '.' '.')
+listmaker: (namedexpr_test|star_expr) ( old_comp_for | (',' (namedexpr_test|star_expr))* [','] )
+testlist_gexp: (namedexpr_test|star_expr) ( old_comp_for | (',' (namedexpr_test|star_expr))* [','] )
+lambdef: 'lambda' [varargslist] ':' test
+trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
+subscriptlist: (subscript|star_expr) (',' (subscript|star_expr))* [',']
+subscript: test [':=' test] | [test] ':' [test] [sliceop]
+sliceop: ':' [test]
+exprlist: (expr|star_expr) (',' (expr|star_expr))* [',']
+testlist: test (',' test)* [',']
+dictsetmaker: ( ((test ':' asexpr_test | '**' expr)
+                 (comp_for | (',' (test ':' asexpr_test | '**' expr))* [','])) |
+                ((test [':=' test] | star_expr)
+		 (comp_for | (',' (test [':=' test] | star_expr))* [','])) )
+
+classdef: 'class' NAME [typeparams] ['(' [arglist] ')'] ':' suite
+
+arglist: argument (',' argument)* [',']
+
+# "test '=' test" is really "keyword '=' test", but we have no such token.
+# These need to be in a single rule to avoid grammar that is ambiguous
+# to our LL(1) parser. Even though 'test' includes '*expr' in star_expr,
+# we explicitly match '*' here, too, to give it proper precedence.
+# Illegal combinations and orderings are blocked in ast.c:
+# multiple (test comp_for) arguments are blocked; keyword unpackings
+# that precede iterable unpackings are blocked; etc.
+argument: ( test [comp_for] |
+            test ':=' test [comp_for] |
+            test 'as' test |
+            test '=' asexpr_test |
+	    '**' test |
+            '*' test )
+
+comp_iter: comp_for | comp_if
+comp_for: [ASYNC] 'for' exprlist 'in' or_test [comp_iter]
+comp_if: 'if' old_test [comp_iter]
+
+# As noted above, testlist_safe extends the syntax allowed in list
+# comprehensions and generators. We can't use it indiscriminately in all
+# derivations using a comp_for-like pattern because the testlist_safe derivation
+# contains comma which clashes with trailing comma in arglist.
+#
+# This was an issue because the parser would not follow the correct derivation
+# when parsing syntactically valid Python code. Since testlist_safe was created
+# specifically to handle list comprehensions and generator expressions enclosed
+# with parentheses, it's safe to only use it in those. That avoids the issue; we
+# can parse code like set(x for x in [],).
+#
+# The syntax supported by this set of rules is not a valid Python 3 syntax,
+# hence the prefix "old".
+#
+# See https://bugs.python.org/issue27494
+old_comp_iter: old_comp_for | old_comp_if
+old_comp_for: [ASYNC] 'for' exprlist 'in' testlist_safe [old_comp_iter]
+old_comp_if: 'if' old_test [old_comp_iter]
+
+testlist1: test (',' test)*
+
+# not used in grammar, but may appear in "node" passed from Parser to Compiler
+encoding_decl: NAME
+
+yield_expr: 'yield' [yield_arg]
+yield_arg: 'from' test | testlist_star_expr
+
+
+# 3.10 match statement definition
+
+# PS: normally the grammar is much much more restricted, but
+# at this moment for not trying to bother much with encoding the
+# exact same DSL in a LL(1) parser, we will just accept an expression
+# and let the ast.parse() step of the safe mode to reject invalid
+# grammar.
+
+# The reason why it is more restricted is that, patterns are some
+# sort of a DSL (more advanced than our LHS on assignments, but
+# still in a very limited python subset). They are not really
+# expressions, but who cares. If we can parse them, that is enough
+# to reformat them.
+
+match_stmt: "match" subject_expr ':' NEWLINE INDENT case_block+ DEDENT
+
+# This is more permissive than the actual version. For example it
+# accepts `match *something:`, even though single-item starred expressions
+# are forbidden.
+subject_expr: (namedexpr_test|star_expr) (',' (namedexpr_test|star_expr))* [',']
+
+# cases
+case_block: "case" patterns [guard] ':' suite
+guard: 'if' namedexpr_test
+patterns: pattern (',' pattern)* [',']
+pattern: (expr|star_expr) ['as' expr]
+
+fstring: FSTRING_START fstring_middle* FSTRING_END
+fstring_middle: fstring_replacement_field | FSTRING_MIDDLE
+fstring_replacement_field: '{' (yield_expr | testlist_star_expr) ['='] [ "!" NAME ] [ ':' fstring_format_spec* ] '}'
+fstring_format_spec: FSTRING_MIDDLE | fstring_replacement_field

venv/Lib/site-packages/blib2to3/LICENSE

@@ -0,0 +1,254 @@
+A. HISTORY OF THE SOFTWARE
+==========================
+
+Python was created in the early 1990s by Guido van Rossum at Stichting
+Mathematisch Centrum (CWI, see https://www.cwi.nl) in the Netherlands
+as a successor of a language called ABC.  Guido remains Python's
+principal author, although it includes many contributions from others.
+
+In 1995, Guido continued his work on Python at the Corporation for
+National Research Initiatives (CNRI, see https://www.cnri.reston.va.us)
+in Reston, Virginia where he released several versions of the
+software.
+
+In May 2000, Guido and the Python core development team moved to
+BeOpen.com to form the BeOpen PythonLabs team.  In October of the same
+year, the PythonLabs team moved to Digital Creations, which became
+Zope Corporation.  In 2001, the Python Software Foundation (PSF, see
+https://www.python.org/psf/) was formed, a non-profit organization
+created specifically to own Python-related Intellectual Property.
+Zope Corporation was a sponsoring member of the PSF.
+
+All Python releases are Open Source (see https://opensource.org for
+the Open Source Definition).  Historically, most, but not all, Python
+releases have also been GPL-compatible; the table below summarizes
+the various releases.
+
+    Release         Derived     Year        Owner       GPL-
+                    from                                compatible? (1)
+
+    0.9.0 thru 1.2              1991-1995   CWI         yes
+    1.3 thru 1.5.2  1.2         1995-1999   CNRI        yes
+    1.6             1.5.2       2000        CNRI        no
+    2.0             1.6         2000        BeOpen.com  no
+    1.6.1           1.6         2001        CNRI        yes (2)
+    2.1             2.0+1.6.1   2001        PSF         no
+    2.0.1           2.0+1.6.1   2001        PSF         yes
+    2.1.1           2.1+2.0.1   2001        PSF         yes
+    2.1.2           2.1.1       2002        PSF         yes
+    2.1.3           2.1.2       2002        PSF         yes
+    2.2 and above   2.1.1       2001-now    PSF         yes
+
+Footnotes:
+
+(1) GPL-compatible doesn't mean that we're distributing Python under
+    the GPL.  All Python licenses, unlike the GPL, let you distribute
+    a modified version without making your changes open source.  The
+    GPL-compatible licenses make it possible to combine Python with
+    other software that is released under the GPL; the others don't.
+
+(2) According to Richard Stallman, 1.6.1 is not GPL-compatible,
+    because its license has a choice of law clause.  According to
+    CNRI, however, Stallman's lawyer has told CNRI's lawyer that 1.6.1
+    is "not incompatible" with the GPL.
+
+Thanks to the many outside volunteers who have worked under Guido's
+direction to make these releases possible.
+
+
+B. TERMS AND CONDITIONS FOR ACCESSING OR OTHERWISE USING PYTHON
+===============================================================
+
+PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
+--------------------------------------------
+
+1. This LICENSE AGREEMENT is between the Python Software Foundation
+("PSF"), and the Individual or Organization ("Licensee") accessing and
+otherwise using this software ("Python") in source or binary form and
+its associated documentation.
+
+2. Subject to the terms and conditions of this License Agreement, PSF hereby
+grants Licensee a nonexclusive, royalty-free, world-wide license to reproduce,
+analyze, test, perform and/or display publicly, prepare derivative works,
+distribute, and otherwise use Python alone or in any derivative version,
+provided, however, that PSF's License Agreement and PSF's notice of copyright,
+i.e., "Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010,
+2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018 Python Software Foundation; All
+Rights Reserved" are retained in Python alone or in any derivative version
+prepared by Licensee.
+
+3. In the event Licensee prepares a derivative work that is based on
+or incorporates Python or any part thereof, and wants to make
+the derivative work available to others as provided herein, then
+Licensee hereby agrees to include in any such work a brief summary of
+the changes made to Python.
+
+4. PSF is making Python available to Licensee on an "AS IS"
+basis.  PSF MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
+IMPLIED.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, PSF MAKES NO AND
+DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
+FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON WILL NOT
+INFRINGE ANY THIRD PARTY RIGHTS.
+
+5. PSF SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
+FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS
+A RESULT OF MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON,
+OR ANY DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
+
+6. This License Agreement will automatically terminate upon a material
+breach of its terms and conditions.
+
+7. Nothing in this License Agreement shall be deemed to create any
+relationship of agency, partnership, or joint venture between PSF and
+Licensee.  This License Agreement does not grant permission to use PSF
+trademarks or trade name in a trademark sense to endorse or promote
+products or services of Licensee, or any third party.
+
+8. By copying, installing or otherwise using Python, Licensee
+agrees to be bound by the terms and conditions of this License
+Agreement.
+
+
+BEOPEN.COM LICENSE AGREEMENT FOR PYTHON 2.0
+-------------------------------------------
+
+BEOPEN PYTHON OPEN SOURCE LICENSE AGREEMENT VERSION 1
+
+1. This LICENSE AGREEMENT is between BeOpen.com ("BeOpen"), having an
+office at 160 Saratoga Avenue, Santa Clara, CA 95051, and the
+Individual or Organization ("Licensee") accessing and otherwise using
+this software in source or binary form and its associated
+documentation ("the Software").
+
+2. Subject to the terms and conditions of this BeOpen Python License
+Agreement, BeOpen hereby grants Licensee a non-exclusive,
+royalty-free, world-wide license to reproduce, analyze, test, perform
+and/or display publicly, prepare derivative works, distribute, and
+otherwise use the Software alone or in any derivative version,
+provided, however, that the BeOpen Python License is retained in the
+Software, alone or in any derivative version prepared by Licensee.
+
+3. BeOpen is making the Software available to Licensee on an "AS IS"
+basis.  BEOPEN MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
+IMPLIED.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, BEOPEN MAKES NO AND
+DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
+FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF THE SOFTWARE WILL NOT
+INFRINGE ANY THIRD PARTY RIGHTS.
+
+4. BEOPEN SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF THE
+SOFTWARE FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS
+AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THE SOFTWARE, OR ANY
+DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
+
+5. This License Agreement will automatically terminate upon a material
+breach of its terms and conditions.
+
+6. This License Agreement shall be governed by and interpreted in all
+respects by the law of the State of California, excluding conflict of
+law provisions.  Nothing in this License Agreement shall be deemed to
+create any relationship of agency, partnership, or joint venture
+between BeOpen and Licensee.  This License Agreement does not grant
+permission to use BeOpen trademarks or trade names in a trademark
+sense to endorse or promote products or services of Licensee, or any
+third party.  As an exception, the "BeOpen Python" logos available at
+http://www.pythonlabs.com/logos.html may be used according to the
+permissions granted on that web page.
+
+7. By copying, installing or otherwise using the software, Licensee
+agrees to be bound by the terms and conditions of this License
+Agreement.
+
+
+CNRI LICENSE AGREEMENT FOR PYTHON 1.6.1
+---------------------------------------
+
+1. This LICENSE AGREEMENT is between the Corporation for National
+Research Initiatives, having an office at 1895 Preston White Drive,
+Reston, VA 20191 ("CNRI"), and the Individual or Organization
+("Licensee") accessing and otherwise using Python 1.6.1 software in
+source or binary form and its associated documentation.
+
+2. Subject to the terms and conditions of this License Agreement, CNRI
+hereby grants Licensee a nonexclusive, royalty-free, world-wide
+license to reproduce, analyze, test, perform and/or display publicly,
+prepare derivative works, distribute, and otherwise use Python 1.6.1
+alone or in any derivative version, provided, however, that CNRI's
+License Agreement and CNRI's notice of copyright, i.e., "Copyright (c)
+1995-2001 Corporation for National Research Initiatives; All Rights
+Reserved" are retained in Python 1.6.1 alone or in any derivative
+version prepared by Licensee.  Alternately, in lieu of CNRI's License
+Agreement, Licensee may substitute the following text (omitting the
+quotes): "Python 1.6.1 is made available subject to the terms and
+conditions in CNRI's License Agreement.  This Agreement together with
+Python 1.6.1 may be located on the Internet using the following
+unique, persistent identifier (known as a handle): 1895.22/1013.  This
+Agreement may also be obtained from a proxy server on the Internet
+using the following URL: http://hdl.handle.net/1895.22/1013".
+
+3. In the event Licensee prepares a derivative work that is based on
+or incorporates Python 1.6.1 or any part thereof, and wants to make
+the derivative work available to others as provided herein, then
+Licensee hereby agrees to include in any such work a brief summary of
+the changes made to Python 1.6.1.
+
+4. CNRI is making Python 1.6.1 available to Licensee on an "AS IS"
+basis.  CNRI MAKES NO REPRESENTATIONS OR WARRANTIES, EXPRESS OR
+IMPLIED.  BY WAY OF EXAMPLE, BUT NOT LIMITATION, CNRI MAKES NO AND
+DISCLAIMS ANY REPRESENTATION OR WARRANTY OF MERCHANTABILITY OR FITNESS
+FOR ANY PARTICULAR PURPOSE OR THAT THE USE OF PYTHON 1.6.1 WILL NOT
+INFRINGE ANY THIRD PARTY RIGHTS.
+
+5. CNRI SHALL NOT BE LIABLE TO LICENSEE OR ANY OTHER USERS OF PYTHON
+1.6.1 FOR ANY INCIDENTAL, SPECIAL, OR CONSEQUENTIAL DAMAGES OR LOSS AS
+A RESULT OF MODIFYING, DISTRIBUTING, OR OTHERWISE USING PYTHON 1.6.1,
+OR ANY DERIVATIVE THEREOF, EVEN IF ADVISED OF THE POSSIBILITY THEREOF.
+
+6. This License Agreement will automatically terminate upon a material
+breach of its terms and conditions.
+
+7. This License Agreement shall be governed by the federal
+intellectual property law of the United States, including without
+limitation the federal copyright law, and, to the extent such
+U.S. federal law does not apply, by the law of the Commonwealth of
+Virginia, excluding Virginia's conflict of law provisions.
+Notwithstanding the foregoing, with regard to derivative works based
+on Python 1.6.1 that incorporate non-separable material that was
+previously distributed under the GNU General Public License (GPL), the
+law of the Commonwealth of Virginia shall govern this License
+Agreement only as to issues arising under or with respect to
+Paragraphs 4, 5, and 7 of this License Agreement.  Nothing in this
+License Agreement shall be deemed to create any relationship of
+agency, partnership, or joint venture between CNRI and Licensee.  This
+License Agreement does not grant permission to use CNRI trademarks or
+trade name in a trademark sense to endorse or promote products or
+services of Licensee, or any third party.
+
+8. By clicking on the "ACCEPT" button where indicated, or by copying,
+installing or otherwise using Python 1.6.1, Licensee agrees to be
+bound by the terms and conditions of this License Agreement.
+
+        ACCEPT
+
+
+CWI LICENSE AGREEMENT FOR PYTHON 0.9.0 THROUGH 1.2
+--------------------------------------------------
+
+Copyright (c) 1991 - 1995, Stichting Mathematisch Centrum Amsterdam,
+The Netherlands.  All rights reserved.
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose and without fee is hereby granted,
+provided that the above copyright notice appear in all copies and that
+both that copyright notice and this permission notice appear in
+supporting documentation, and that the name of Stichting Mathematisch
+Centrum or CWI not be used in advertising or publicity pertaining to
+distribution of the software without specific, written prior
+permission.
+
+STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
+THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
+FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
+OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

venv/Lib/site-packages/blib2to3/PatternGrammar.txt

@@ -0,0 +1,28 @@
+# Copyright 2006 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+# A grammar to describe tree matching patterns.
+# Not shown here:
+# - 'TOKEN' stands for any token (leaf node)
+# - 'any' stands for any node (leaf or interior)
+# With 'any' we can still specify the sub-structure.
+
+# The start symbol is 'Matcher'.
+
+Matcher: Alternatives ENDMARKER
+
+Alternatives: Alternative ('|' Alternative)*
+
+Alternative: (Unit | NegatedUnit)+
+
+Unit: [NAME '='] ( STRING [Repeater]
+                 | NAME [Details] [Repeater]
+                 | '(' Alternatives ')' [Repeater]
+                 | '[' Alternatives ']'
+		 )
+
+NegatedUnit: 'not' (STRING | NAME [Details] | '(' Alternatives ')')
+
+Repeater: '*' | '+' | '{' NUMBER [',' NUMBER] '}'
+
+Details: '<' Alternatives '>'

venv/Lib/site-packages/blib2to3/README

@@ -0,0 +1,24 @@
+A subset of lib2to3 taken from Python 3.7.0b2. Commit hash:
+9c17e3a1987004b8bcfbe423953aad84493a7984
+
+Reasons for forking:
+
+- consistent handling of f-strings for users of Python < 3.6.2
+- backport of BPO-33064 that fixes parsing files with trailing commas after \*args and
+  \*\*kwargs
+- backport of GH-6143 that restores the ability to reformat legacy usage of `async`
+- support all types of string literals
+- better ability to debug (better reprs)
+- INDENT and DEDENT don't hold whitespace and comment prefixes
+- ability to Cythonize
+
+Change Log:
+
+- Changes default logger used by Driver
+- Backported the following upstream parser changes:
+  - "bpo-42381: Allow walrus in set literals and set comprehensions (GH-23332)"
+    https://github.com/python/cpython/commit/cae60187cf7a7b26281d012e1952fafe4e2e97e9
+  - "bpo-42316: Allow unparenthesized walrus operator in indexes (GH-23317)"
+    https://github.com/python/cpython/commit/b0aba1fcdc3da952698d99aec2334faa79a8b68c
+- Tweaks to help mypyc compile faster code (including inlining type information,
+  "Final-ing", etc.)

venv/Lib/site-packages/blib2to3/__init__.py

@@ -0,0 +1 @@
+# empty

venv/Lib/site-packages/blib2to3/pgen2/__init__.py

@@ -0,0 +1,4 @@
+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""The pgen2 package."""

venv/Lib/site-packages/blib2to3/pgen2/conv.py

@@ -0,0 +1,256 @@
+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+# mypy: ignore-errors
+
+"""Convert graminit.[ch] spit out by pgen to Python code.
+
+Pgen is the Python parser generator.  It is useful to quickly create a
+parser from a grammar file in Python's grammar notation.  But I don't
+want my parsers to be written in C (yet), so I'm translating the
+parsing tables to Python data structures and writing a Python parse
+engine.
+
+Note that the token numbers are constants determined by the standard
+Python tokenizer.  The standard token module defines these numbers and
+their names (the names are not used much).  The token numbers are
+hardcoded into the Python tokenizer and into pgen.  A Python
+implementation of the Python tokenizer is also available, in the
+standard tokenize module.
+
+On the other hand, symbol numbers (representing the grammar's
+non-terminals) are assigned by pgen based on the actual grammar
+input.
+
+Note: this module is pretty much obsolete; the pgen module generates
+equivalent grammar tables directly from the Grammar.txt input file
+without having to invoke the Python pgen C program.
+
+"""
+
+# Python imports
+import re
+
+# Local imports
+from pgen2 import grammar, token
+
+
+class Converter(grammar.Grammar):
+    """Grammar subclass that reads classic pgen output files.
+
+    The run() method reads the tables as produced by the pgen parser
+    generator, typically contained in two C files, graminit.h and
+    graminit.c.  The other methods are for internal use only.
+
+    See the base class for more documentation.
+
+    """
+
+    def run(self, graminit_h, graminit_c):
+        """Load the grammar tables from the text files written by pgen."""
+        self.parse_graminit_h(graminit_h)
+        self.parse_graminit_c(graminit_c)
+        self.finish_off()
+
+    def parse_graminit_h(self, filename):
+        """Parse the .h file written by pgen.  (Internal)
+
+        This file is a sequence of #define statements defining the
+        nonterminals of the grammar as numbers.  We build two tables
+        mapping the numbers to names and back.
+
+        """
+        try:
+            f = open(filename)
+        except OSError as err:
+            print(f"Can't open {filename}: {err}")
+            return False
+        self.symbol2number = {}
+        self.number2symbol = {}
+        lineno = 0
+        for line in f:
+            lineno += 1
+            mo = re.match(r"^#define\s+(\w+)\s+(\d+)$", line)
+            if not mo and line.strip():
+                print(f"{filename}({lineno}): can't parse {line.strip()}")
+            else:
+                symbol, number = mo.groups()
+                number = int(number)
+                assert symbol not in self.symbol2number
+                assert number not in self.number2symbol
+                self.symbol2number[symbol] = number
+                self.number2symbol[number] = symbol
+        return True
+
+    def parse_graminit_c(self, filename):
+        """Parse the .c file written by pgen.  (Internal)
+
+        The file looks as follows.  The first two lines are always this:
+
+        #include "pgenheaders.h"
+        #include "grammar.h"
+
+        After that come four blocks:
+
+        1) one or more state definitions
+        2) a table defining dfas
+        3) a table defining labels
+        4) a struct defining the grammar
+
+        A state definition has the following form:
+        - one or more arc arrays, each of the form:
+          static arc arcs_<n>_<m>[<k>] = {
+                  {<i>, <j>},
+                  ...
+          };
+        - followed by a state array, of the form:
+          static state states_<s>[<t>] = {
+                  {<k>, arcs_<n>_<m>},
+                  ...
+          };
+
+        """
+        try:
+            f = open(filename)
+        except OSError as err:
+            print(f"Can't open {filename}: {err}")
+            return False
+        # The code below essentially uses f's iterator-ness!
+        lineno = 0
+
+        # Expect the two #include lines
+        lineno, line = lineno + 1, next(f)
+        assert line == '#include "pgenheaders.h"\n', (lineno, line)
+        lineno, line = lineno + 1, next(f)
+        assert line == '#include "grammar.h"\n', (lineno, line)
+
+        # Parse the state definitions
+        lineno, line = lineno + 1, next(f)
+        allarcs = {}
+        states = []
+        while line.startswith("static arc "):
+            while line.startswith("static arc "):
+                mo = re.match(r"static arc arcs_(\d+)_(\d+)\[(\d+)\] = {$", line)
+                assert mo, (lineno, line)
+                n, m, k = list(map(int, mo.groups()))
+                arcs = []
+                for _ in range(k):
+                    lineno, line = lineno + 1, next(f)
+                    mo = re.match(r"\s+{(\d+), (\d+)},$", line)
+                    assert mo, (lineno, line)
+                    i, j = list(map(int, mo.groups()))
+                    arcs.append((i, j))
+                lineno, line = lineno + 1, next(f)
+                assert line == "};\n", (lineno, line)
+                allarcs[(n, m)] = arcs
+                lineno, line = lineno + 1, next(f)
+            mo = re.match(r"static state states_(\d+)\[(\d+)\] = {$", line)
+            assert mo, (lineno, line)
+            s, t = list(map(int, mo.groups()))
+            assert s == len(states), (lineno, line)
+            state = []
+            for _ in range(t):
+                lineno, line = lineno + 1, next(f)
+                mo = re.match(r"\s+{(\d+), arcs_(\d+)_(\d+)},$", line)
+                assert mo, (lineno, line)
+                k, n, m = list(map(int, mo.groups()))
+                arcs = allarcs[n, m]
+                assert k == len(arcs), (lineno, line)
+                state.append(arcs)
+            states.append(state)
+            lineno, line = lineno + 1, next(f)
+            assert line == "};\n", (lineno, line)
+            lineno, line = lineno + 1, next(f)
+        self.states = states
+
+        # Parse the dfas
+        dfas = {}
+        mo = re.match(r"static dfa dfas\[(\d+)\] = {$", line)
+        assert mo, (lineno, line)
+        ndfas = int(mo.group(1))
+        for i in range(ndfas):
+            lineno, line = lineno + 1, next(f)
+            mo = re.match(r'\s+{(\d+), "(\w+)", (\d+), (\d+), states_(\d+),$', line)
+            assert mo, (lineno, line)
+            symbol = mo.group(2)
+            number, x, y, z = list(map(int, mo.group(1, 3, 4, 5)))
+            assert self.symbol2number[symbol] == number, (lineno, line)
+            assert self.number2symbol[number] == symbol, (lineno, line)
+            assert x == 0, (lineno, line)
+            state = states[z]
+            assert y == len(state), (lineno, line)
+            lineno, line = lineno + 1, next(f)
+            mo = re.match(r'\s+("(?:\\\d\d\d)*")},$', line)
+            assert mo, (lineno, line)
+            first = {}
+            rawbitset = eval(mo.group(1))
+            for i, c in enumerate(rawbitset):
+                byte = ord(c)
+                for j in range(8):
+                    if byte & (1 << j):
+                        first[i * 8 + j] = 1
+            dfas[number] = (state, first)
+        lineno, line = lineno + 1, next(f)
+        assert line == "};\n", (lineno, line)
+        self.dfas = dfas
+
+        # Parse the labels
+        labels = []
+        lineno, line = lineno + 1, next(f)
+        mo = re.match(r"static label labels\[(\d+)\] = {$", line)
+        assert mo, (lineno, line)
+        nlabels = int(mo.group(1))
+        for i in range(nlabels):
+            lineno, line = lineno + 1, next(f)
+            mo = re.match(r'\s+{(\d+), (0|"\w+")},$', line)
+            assert mo, (lineno, line)
+            x, y = mo.groups()
+            x = int(x)
+            if y == "0":
+                y = None
+            else:
+                y = eval(y)
+            labels.append((x, y))
+        lineno, line = lineno + 1, next(f)
+        assert line == "};\n", (lineno, line)
+        self.labels = labels
+
+        # Parse the grammar struct
+        lineno, line = lineno + 1, next(f)
+        assert line == "grammar _PyParser_Grammar = {\n", (lineno, line)
+        lineno, line = lineno + 1, next(f)
+        mo = re.match(r"\s+(\d+),$", line)
+        assert mo, (lineno, line)
+        ndfas = int(mo.group(1))
+        assert ndfas == len(self.dfas)
+        lineno, line = lineno + 1, next(f)
+        assert line == "\tdfas,\n", (lineno, line)
+        lineno, line = lineno + 1, next(f)
+        mo = re.match(r"\s+{(\d+), labels},$", line)
+        assert mo, (lineno, line)
+        nlabels = int(mo.group(1))
+        assert nlabels == len(self.labels), (lineno, line)
+        lineno, line = lineno + 1, next(f)
+        mo = re.match(r"\s+(\d+)$", line)
+        assert mo, (lineno, line)
+        start = int(mo.group(1))
+        assert start in self.number2symbol, (lineno, line)
+        self.start = start
+        lineno, line = lineno + 1, next(f)
+        assert line == "};\n", (lineno, line)
+        try:
+            lineno, line = lineno + 1, next(f)
+        except StopIteration:
+            pass
+        else:
+            assert 0, (lineno, line)
+
+    def finish_off(self):
+        """Create additional useful structures.  (Internal)."""
+        self.keywords = {}  # map from keyword strings to arc labels
+        self.tokens = {}  # map from numeric token values to arc labels
+        for ilabel, (type, value) in enumerate(self.labels):
+            if type == token.NAME and value is not None:
+                self.keywords[value] = ilabel
+            elif value is None:
+                self.tokens[type] = ilabel

venv/Lib/site-packages/blib2to3/pgen2/driver.py

@@ -0,0 +1,318 @@
+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+# Modifications:
+# Copyright 2006 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Parser driver.
+
+This provides a high-level interface to parse a file into a syntax tree.
+
+"""
+
+__author__ = "Guido van Rossum <guido@python.org>"
+
+__all__ = ["Driver", "load_grammar"]
+
+# Python imports
+import io
+import logging
+import os
+import pkgutil
+import sys
+from contextlib import contextmanager
+from dataclasses import dataclass, field
+from logging import Logger
+from typing import IO, Any, Iterable, Iterator, Optional, Union, cast
+
+from blib2to3.pgen2.grammar import Grammar
+from blib2to3.pgen2.tokenize import GoodTokenInfo
+from blib2to3.pytree import NL
+
+# Pgen imports
+from . import grammar, parse, pgen, token, tokenize
+
+Path = Union[str, "os.PathLike[str]"]
+
+
+@dataclass
+class ReleaseRange:
+    start: int
+    end: Optional[int] = None
+    tokens: list[Any] = field(default_factory=list)
+
+    def lock(self) -> None:
+        total_eaten = len(self.tokens)
+        self.end = self.start + total_eaten
+
+
+class TokenProxy:
+    def __init__(self, generator: Any) -> None:
+        self._tokens = generator
+        self._counter = 0
+        self._release_ranges: list[ReleaseRange] = []
+
+    @contextmanager
+    def release(self) -> Iterator["TokenProxy"]:
+        release_range = ReleaseRange(self._counter)
+        self._release_ranges.append(release_range)
+        try:
+            yield self
+        finally:
+            # Lock the last release range to the final position that
+            # has been eaten.
+            release_range.lock()
+
+    def eat(self, point: int) -> Any:
+        eaten_tokens = self._release_ranges[-1].tokens
+        if point < len(eaten_tokens):
+            return eaten_tokens[point]
+        else:
+            while point >= len(eaten_tokens):
+                token = next(self._tokens)
+                eaten_tokens.append(token)
+            return token
+
+    def __iter__(self) -> "TokenProxy":
+        return self
+
+    def __next__(self) -> Any:
+        # If the current position is already compromised (looked up)
+        # return the eaten token, if not just go further on the given
+        # token producer.
+        for release_range in self._release_ranges:
+            assert release_range.end is not None
+
+            start, end = release_range.start, release_range.end
+            if start <= self._counter < end:
+                token = release_range.tokens[self._counter - start]
+                break
+        else:
+            token = next(self._tokens)
+        self._counter += 1
+        return token
+
+    def can_advance(self, to: int) -> bool:
+        # Try to eat, fail if it can't. The eat operation is cached
+        # so there won't be any additional cost of eating here
+        try:
+            self.eat(to)
+        except StopIteration:
+            return False
+        else:
+            return True
+
+
+class Driver:
+    def __init__(self, grammar: Grammar, logger: Optional[Logger] = None) -> None:
+        self.grammar = grammar
+        if logger is None:
+            logger = logging.getLogger(__name__)
+        self.logger = logger
+
+    def parse_tokens(self, tokens: Iterable[GoodTokenInfo], debug: bool = False) -> NL:
+        """Parse a series of tokens and return the syntax tree."""
+        # XXX Move the prefix computation into a wrapper around tokenize.
+        proxy = TokenProxy(tokens)
+
+        p = parse.Parser(self.grammar)
+        p.setup(proxy=proxy)
+
+        lineno = 1
+        column = 0
+        indent_columns: list[int] = []
+        type = value = start = end = line_text = None
+        prefix = ""
+
+        for quintuple in proxy:
+            type, value, start, end, line_text = quintuple
+            if start != (lineno, column):
+                assert (lineno, column) <= start, ((lineno, column), start)
+                s_lineno, s_column = start
+                if lineno < s_lineno:
+                    prefix += "\n" * (s_lineno - lineno)
+                    lineno = s_lineno
+                    column = 0
+                if column < s_column:
+                    prefix += line_text[column:s_column]
+                    column = s_column
+            if type in (tokenize.COMMENT, tokenize.NL):
+                prefix += value
+                lineno, column = end
+                if value.endswith("\n"):
+                    lineno += 1
+                    column = 0
+                continue
+            if type == token.OP:
+                type = grammar.opmap[value]
+            if debug:
+                assert type is not None
+                self.logger.debug(
+                    "%s %r (prefix=%r)", token.tok_name[type], value, prefix
+                )
+            if type == token.INDENT:
+                indent_columns.append(len(value))
+                _prefix = prefix + value
+                prefix = ""
+                value = ""
+            elif type == token.DEDENT:
+                _indent_col = indent_columns.pop()
+                prefix, _prefix = self._partially_consume_prefix(prefix, _indent_col)
+            if p.addtoken(cast(int, type), value, (prefix, start)):
+                if debug:
+                    self.logger.debug("Stop.")
+                break
+            prefix = ""
+            if type in {token.INDENT, token.DEDENT}:
+                prefix = _prefix
+            lineno, column = end
+            # FSTRING_MIDDLE is the only token that can end with a newline, and
+            # `end` will point to the next line. For that case, don't increment lineno.
+            if value.endswith("\n") and type != token.FSTRING_MIDDLE:
+                lineno += 1
+                column = 0
+        else:
+            # We never broke out -- EOF is too soon (how can this happen???)
+            assert start is not None
+            raise parse.ParseError("incomplete input", type, value, (prefix, start))
+        assert p.rootnode is not None
+        return p.rootnode
+
+    def parse_stream_raw(self, stream: IO[str], debug: bool = False) -> NL:
+        """Parse a stream and return the syntax tree."""
+        tokens = tokenize.generate_tokens(stream.readline, grammar=self.grammar)
+        return self.parse_tokens(tokens, debug)
+
+    def parse_stream(self, stream: IO[str], debug: bool = False) -> NL:
+        """Parse a stream and return the syntax tree."""
+        return self.parse_stream_raw(stream, debug)
+
+    def parse_file(
+        self, filename: Path, encoding: Optional[str] = None, debug: bool = False
+    ) -> NL:
+        """Parse a file and return the syntax tree."""
+        with open(filename, encoding=encoding) as stream:
+            return self.parse_stream(stream, debug)
+
+    def parse_string(self, text: str, debug: bool = False) -> NL:
+        """Parse a string and return the syntax tree."""
+        tokens = tokenize.generate_tokens(
+            io.StringIO(text).readline, grammar=self.grammar
+        )
+        return self.parse_tokens(tokens, debug)
+
+    def _partially_consume_prefix(self, prefix: str, column: int) -> tuple[str, str]:
+        lines: list[str] = []
+        current_line = ""
+        current_column = 0
+        wait_for_nl = False
+        for char in prefix:
+            current_line += char
+            if wait_for_nl:
+                if char == "\n":
+                    if current_line.strip() and current_column < column:
+                        res = "".join(lines)
+                        return res, prefix[len(res) :]
+
+                    lines.append(current_line)
+                    current_line = ""
+                    current_column = 0
+                    wait_for_nl = False
+            elif char in " \t":
+                current_column += 1
+            elif char == "\n":
+                # unexpected empty line
+                current_column = 0
+            elif char == "\f":
+                current_column = 0
+            else:
+                # indent is finished
+                wait_for_nl = True
+        return "".join(lines), current_line
+
+
+def _generate_pickle_name(gt: Path, cache_dir: Optional[Path] = None) -> str:
+    head, tail = os.path.splitext(gt)
+    if tail == ".txt":
+        tail = ""
+    name = head + tail + ".".join(map(str, sys.version_info)) + ".pickle"
+    if cache_dir:
+        return os.path.join(cache_dir, os.path.basename(name))
+    else:
+        return name
+
+
+def load_grammar(
+    gt: str = "Grammar.txt",
+    gp: Optional[str] = None,
+    save: bool = True,
+    force: bool = False,
+    logger: Optional[Logger] = None,
+) -> Grammar:
+    """Load the grammar (maybe from a pickle)."""
+    if logger is None:
+        logger = logging.getLogger(__name__)
+    gp = _generate_pickle_name(gt) if gp is None else gp
+    if force or not _newer(gp, gt):
+        g: grammar.Grammar = pgen.generate_grammar(gt)
+        if save:
+            try:
+                g.dump(gp)
+            except OSError:
+                # Ignore error, caching is not vital.
+                pass
+    else:
+        g = grammar.Grammar()
+        g.load(gp)
+    return g
+
+
+def _newer(a: str, b: str) -> bool:
+    """Inquire whether file a was written since file b."""
+    if not os.path.exists(a):
+        return False
+    if not os.path.exists(b):
+        return True
+    return os.path.getmtime(a) >= os.path.getmtime(b)
+
+
+def load_packaged_grammar(
+    package: str, grammar_source: str, cache_dir: Optional[Path] = None
+) -> grammar.Grammar:
+    """Normally, loads a pickled grammar by doing
+        pkgutil.get_data(package, pickled_grammar)
+    where *pickled_grammar* is computed from *grammar_source* by adding the
+    Python version and using a ``.pickle`` extension.
+
+    However, if *grammar_source* is an extant file, load_grammar(grammar_source)
+    is called instead. This facilitates using a packaged grammar file when needed
+    but preserves load_grammar's automatic regeneration behavior when possible.
+
+    """
+    if os.path.isfile(grammar_source):
+        gp = _generate_pickle_name(grammar_source, cache_dir) if cache_dir else None
+        return load_grammar(grammar_source, gp=gp)
+    pickled_name = _generate_pickle_name(os.path.basename(grammar_source), cache_dir)
+    data = pkgutil.get_data(package, pickled_name)
+    assert data is not None
+    g = grammar.Grammar()
+    g.loads(data)
+    return g
+
+
+def main(*args: str) -> bool:
+    """Main program, when run as a script: produce grammar pickle files.
+
+    Calls load_grammar for each argument, a path to a grammar text file.
+    """
+    if not args:
+        args = tuple(sys.argv[1:])
+    logging.basicConfig(level=logging.INFO, stream=sys.stdout, format="%(message)s")
+    for gt in args:
+        load_grammar(gt, save=True, force=True)
+    return True
+
+
+if __name__ == "__main__":
+    sys.exit(int(not main()))

venv/Lib/site-packages/blib2to3/pgen2/grammar.py

@@ -0,0 +1,228 @@
+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""This module defines the data structures used to represent a grammar.
+
+These are a bit arcane because they are derived from the data
+structures used by Python's 'pgen' parser generator.
+
+There's also a table here mapping operators to their names in the
+token module; the Python tokenize module reports all operators as the
+fallback token code OP, but the parser needs the actual token code.
+
+"""
+
+# Python imports
+import os
+import pickle
+import tempfile
+from typing import Any, Optional, TypeVar, Union
+
+# Local imports
+from . import token
+
+_P = TypeVar("_P", bound="Grammar")
+Label = tuple[int, Optional[str]]
+DFA = list[list[tuple[int, int]]]
+DFAS = tuple[DFA, dict[int, int]]
+Path = Union[str, "os.PathLike[str]"]
+
+
+class Grammar:
+    """Pgen parsing tables conversion class.
+
+    Once initialized, this class supplies the grammar tables for the
+    parsing engine implemented by parse.py.  The parsing engine
+    accesses the instance variables directly.  The class here does not
+    provide initialization of the tables; several subclasses exist to
+    do this (see the conv and pgen modules).
+
+    The load() method reads the tables from a pickle file, which is
+    much faster than the other ways offered by subclasses.  The pickle
+    file is written by calling dump() (after loading the grammar
+    tables using a subclass).  The report() method prints a readable
+    representation of the tables to stdout, for debugging.
+
+    The instance variables are as follows:
+
+    symbol2number -- a dict mapping symbol names to numbers.  Symbol
+                     numbers are always 256 or higher, to distinguish
+                     them from token numbers, which are between 0 and
+                     255 (inclusive).
+
+    number2symbol -- a dict mapping numbers to symbol names;
+                     these two are each other's inverse.
+
+    states        -- a list of DFAs, where each DFA is a list of
+                     states, each state is a list of arcs, and each
+                     arc is a (i, j) pair where i is a label and j is
+                     a state number.  The DFA number is the index into
+                     this list.  (This name is slightly confusing.)
+                     Final states are represented by a special arc of
+                     the form (0, j) where j is its own state number.
+
+    dfas          -- a dict mapping symbol numbers to (DFA, first)
+                     pairs, where DFA is an item from the states list
+                     above, and first is a set of tokens that can
+                     begin this grammar rule (represented by a dict
+                     whose values are always 1).
+
+    labels        -- a list of (x, y) pairs where x is either a token
+                     number or a symbol number, and y is either None
+                     or a string; the strings are keywords.  The label
+                     number is the index in this list; label numbers
+                     are used to mark state transitions (arcs) in the
+                     DFAs.
+
+    start         -- the number of the grammar's start symbol.
+
+    keywords      -- a dict mapping keyword strings to arc labels.
+
+    tokens        -- a dict mapping token numbers to arc labels.
+
+    """
+
+    def __init__(self) -> None:
+        self.symbol2number: dict[str, int] = {}
+        self.number2symbol: dict[int, str] = {}
+        self.states: list[DFA] = []
+        self.dfas: dict[int, DFAS] = {}
+        self.labels: list[Label] = [(0, "EMPTY")]
+        self.keywords: dict[str, int] = {}
+        self.soft_keywords: dict[str, int] = {}
+        self.tokens: dict[int, int] = {}
+        self.symbol2label: dict[str, int] = {}
+        self.version: tuple[int, int] = (0, 0)
+        self.start = 256
+        # Python 3.7+ parses async as a keyword, not an identifier
+        self.async_keywords = False
+
+    def dump(self, filename: Path) -> None:
+        """Dump the grammar tables to a pickle file."""
+
+        # mypyc generates objects that don't have a __dict__, but they
+        # do have __getstate__ methods that will return an equivalent
+        # dictionary
+        if hasattr(self, "__dict__"):
+            d = self.__dict__
+        else:
+            d = self.__getstate__()  # type: ignore
+
+        with tempfile.NamedTemporaryFile(
+            dir=os.path.dirname(filename), delete=False
+        ) as f:
+            pickle.dump(d, f, pickle.HIGHEST_PROTOCOL)
+        os.replace(f.name, filename)
+
+    def _update(self, attrs: dict[str, Any]) -> None:
+        for k, v in attrs.items():
+            setattr(self, k, v)
+
+    def load(self, filename: Path) -> None:
+        """Load the grammar tables from a pickle file."""
+        with open(filename, "rb") as f:
+            d = pickle.load(f)
+        self._update(d)
+
+    def loads(self, pkl: bytes) -> None:
+        """Load the grammar tables from a pickle bytes object."""
+        self._update(pickle.loads(pkl))
+
+    def copy(self: _P) -> _P:
+        """
+        Copy the grammar.
+        """
+        new = self.__class__()
+        for dict_attr in (
+            "symbol2number",
+            "number2symbol",
+            "dfas",
+            "keywords",
+            "soft_keywords",
+            "tokens",
+            "symbol2label",
+        ):
+            setattr(new, dict_attr, getattr(self, dict_attr).copy())
+        new.labels = self.labels[:]
+        new.states = self.states[:]
+        new.start = self.start
+        new.version = self.version
+        new.async_keywords = self.async_keywords
+        return new
+
+    def report(self) -> None:
+        """Dump the grammar tables to standard output, for debugging."""
+        from pprint import pprint
+
+        print("s2n")
+        pprint(self.symbol2number)
+        print("n2s")
+        pprint(self.number2symbol)
+        print("states")
+        pprint(self.states)
+        print("dfas")
+        pprint(self.dfas)
+        print("labels")
+        pprint(self.labels)
+        print("start", self.start)
+
+
+# Map from operator to number (since tokenize doesn't do this)
+
+opmap_raw = """
+( LPAR
+) RPAR
+[ LSQB
+] RSQB
+: COLON
+, COMMA
+; SEMI
++ PLUS
+- MINUS
+* STAR
+/ SLASH
+| VBAR
+& AMPER
+< LESS
+> GREATER
+= EQUAL
+. DOT
+% PERCENT
+` BACKQUOTE
+{ LBRACE
+} RBRACE
+@ AT
+@= ATEQUAL
+== EQEQUAL
+!= NOTEQUAL
+<> NOTEQUAL
+<= LESSEQUAL
+>= GREATEREQUAL
+~ TILDE
+^ CIRCUMFLEX
+<< LEFTSHIFT
+>> RIGHTSHIFT
+** DOUBLESTAR
++= PLUSEQUAL
+-= MINEQUAL
+*= STAREQUAL
+/= SLASHEQUAL
+%= PERCENTEQUAL
+&= AMPEREQUAL
+|= VBAREQUAL
+^= CIRCUMFLEXEQUAL
+<<= LEFTSHIFTEQUAL
+>>= RIGHTSHIFTEQUAL
+**= DOUBLESTAREQUAL
+// DOUBLESLASH
+//= DOUBLESLASHEQUAL
+-> RARROW
+:= COLONEQUAL
+! BANG
+"""
+
+opmap = {}
+for line in opmap_raw.splitlines():
+    if line:
+        op, name = line.split()
+        opmap[op] = getattr(token, name)

venv/Lib/site-packages/blib2to3/pgen2/literals.py

@@ -0,0 +1,66 @@
+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Safely evaluate Python string literals without using eval()."""
+
+import re
+from typing import Match
+
+simple_escapes: dict[str, str] = {
+    "a": "\a",
+    "b": "\b",
+    "f": "\f",
+    "n": "\n",
+    "r": "\r",
+    "t": "\t",
+    "v": "\v",
+    "'": "'",
+    '"': '"',
+    "\\": "\\",
+}
+
+
+def escape(m: Match[str]) -> str:
+    all, tail = m.group(0, 1)
+    assert all.startswith("\\")
+    esc = simple_escapes.get(tail)
+    if esc is not None:
+        return esc
+    if tail.startswith("x"):
+        hexes = tail[1:]
+        if len(hexes) < 2:
+            raise ValueError("invalid hex string escape ('\\%s')" % tail)
+        try:
+            i = int(hexes, 16)
+        except ValueError:
+            raise ValueError("invalid hex string escape ('\\%s')" % tail) from None
+    else:
+        try:
+            i = int(tail, 8)
+        except ValueError:
+            raise ValueError("invalid octal string escape ('\\%s')" % tail) from None
+    return chr(i)
+
+
+def evalString(s: str) -> str:
+    assert s.startswith("'") or s.startswith('"'), repr(s[:1])
+    q = s[0]
+    if s[:3] == q * 3:
+        q = q * 3
+    assert s.endswith(q), repr(s[-len(q) :])
+    assert len(s) >= 2 * len(q)
+    s = s[len(q) : -len(q)]
+    return re.sub(r"\\(\'|\"|\\|[abfnrtv]|x.{0,2}|[0-7]{1,3})", escape, s)
+
+
+def test() -> None:
+    for i in range(256):
+        c = chr(i)
+        s = repr(c)
+        e = evalString(s)
+        if e != c:
+            print(i, c, s, e)
+
+
+if __name__ == "__main__":
+    test()

venv/Lib/site-packages/blib2to3/pgen2/parse.py

@@ -0,0 +1,399 @@
+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Parser engine for the grammar tables generated by pgen.
+
+The grammar table must be loaded first.
+
+See Parser/parser.c in the Python distribution for additional info on
+how this parsing engine works.
+
+"""
+from contextlib import contextmanager
+from typing import TYPE_CHECKING, Any, Callable, Iterator, Optional, Union, cast
+
+from blib2to3.pgen2.grammar import Grammar
+from blib2to3.pytree import NL, Context, Leaf, Node, RawNode, convert
+
+# Local imports
+from . import grammar, token, tokenize
+
+if TYPE_CHECKING:
+    from blib2to3.pgen2.driver import TokenProxy
+
+
+Results = dict[str, NL]
+Convert = Callable[[Grammar, RawNode], Union[Node, Leaf]]
+DFA = list[list[tuple[int, int]]]
+DFAS = tuple[DFA, dict[int, int]]
+
+
+def lam_sub(grammar: Grammar, node: RawNode) -> NL:
+    assert node[3] is not None
+    return Node(type=node[0], children=node[3], context=node[2])
+
+
+# A placeholder node, used when parser is backtracking.
+DUMMY_NODE = (-1, None, None, None)
+
+
+def stack_copy(
+    stack: list[tuple[DFAS, int, RawNode]],
+) -> list[tuple[DFAS, int, RawNode]]:
+    """Nodeless stack copy."""
+    return [(dfa, label, DUMMY_NODE) for dfa, label, _ in stack]
+
+
+class Recorder:
+    def __init__(self, parser: "Parser", ilabels: list[int], context: Context) -> None:
+        self.parser = parser
+        self._ilabels = ilabels
+        self.context = context  # not really matter
+
+        self._dead_ilabels: set[int] = set()
+        self._start_point = self.parser.stack
+        self._points = {ilabel: stack_copy(self._start_point) for ilabel in ilabels}
+
+    @property
+    def ilabels(self) -> set[int]:
+        return self._dead_ilabels.symmetric_difference(self._ilabels)
+
+    @contextmanager
+    def switch_to(self, ilabel: int) -> Iterator[None]:
+        with self.backtrack():
+            self.parser.stack = self._points[ilabel]
+            try:
+                yield
+            except ParseError:
+                self._dead_ilabels.add(ilabel)
+            finally:
+                self.parser.stack = self._start_point
+
+    @contextmanager
+    def backtrack(self) -> Iterator[None]:
+        """
+        Use the node-level invariant ones for basic parsing operations (push/pop/shift).
+        These still will operate on the stack; but they won't create any new nodes, or
+        modify the contents of any other existing nodes.
+
+        This saves us a ton of time when we are backtracking, since we
+        want to restore to the initial state as quick as possible, which
+        can only be done by having as little mutatations as possible.
+        """
+        is_backtracking = self.parser.is_backtracking
+        try:
+            self.parser.is_backtracking = True
+            yield
+        finally:
+            self.parser.is_backtracking = is_backtracking
+
+    def add_token(self, tok_type: int, tok_val: str, raw: bool = False) -> None:
+        func: Callable[..., Any]
+        if raw:
+            func = self.parser._addtoken
+        else:
+            func = self.parser.addtoken
+
+        for ilabel in self.ilabels:
+            with self.switch_to(ilabel):
+                args = [tok_type, tok_val, self.context]
+                if raw:
+                    args.insert(0, ilabel)
+                func(*args)
+
+    def determine_route(
+        self, value: Optional[str] = None, force: bool = False
+    ) -> Optional[int]:
+        alive_ilabels = self.ilabels
+        if len(alive_ilabels) == 0:
+            *_, most_successful_ilabel = self._dead_ilabels
+            raise ParseError("bad input", most_successful_ilabel, value, self.context)
+
+        ilabel, *rest = alive_ilabels
+        if force or not rest:
+            return ilabel
+        else:
+            return None
+
+
+class ParseError(Exception):
+    """Exception to signal the parser is stuck."""
+
+    def __init__(
+        self, msg: str, type: Optional[int], value: Optional[str], context: Context
+    ) -> None:
+        Exception.__init__(
+            self, f"{msg}: type={type!r}, value={value!r}, context={context!r}"
+        )
+        self.msg = msg
+        self.type = type
+        self.value = value
+        self.context = context
+
+
+class Parser:
+    """Parser engine.
+
+    The proper usage sequence is:
+
+    p = Parser(grammar, [converter])  # create instance
+    p.setup([start])                  # prepare for parsing
+    <for each input token>:
+        if p.addtoken(...):           # parse a token; may raise ParseError
+            break
+    root = p.rootnode                 # root of abstract syntax tree
+
+    A Parser instance may be reused by calling setup() repeatedly.
+
+    A Parser instance contains state pertaining to the current token
+    sequence, and should not be used concurrently by different threads
+    to parse separate token sequences.
+
+    See driver.py for how to get input tokens by tokenizing a file or
+    string.
+
+    Parsing is complete when addtoken() returns True; the root of the
+    abstract syntax tree can then be retrieved from the rootnode
+    instance variable.  When a syntax error occurs, addtoken() raises
+    the ParseError exception.  There is no error recovery; the parser
+    cannot be used after a syntax error was reported (but it can be
+    reinitialized by calling setup()).
+
+    """
+
+    def __init__(self, grammar: Grammar, convert: Optional[Convert] = None) -> None:
+        """Constructor.
+
+        The grammar argument is a grammar.Grammar instance; see the
+        grammar module for more information.
+
+        The parser is not ready yet for parsing; you must call the
+        setup() method to get it started.
+
+        The optional convert argument is a function mapping concrete
+        syntax tree nodes to abstract syntax tree nodes.  If not
+        given, no conversion is done and the syntax tree produced is
+        the concrete syntax tree.  If given, it must be a function of
+        two arguments, the first being the grammar (a grammar.Grammar
+        instance), and the second being the concrete syntax tree node
+        to be converted.  The syntax tree is converted from the bottom
+        up.
+
+        **post-note: the convert argument is ignored since for Black's
+        usage, convert will always be blib2to3.pytree.convert. Allowing
+        this to be dynamic hurts mypyc's ability to use early binding.
+        These docs are left for historical and informational value.
+
+        A concrete syntax tree node is a (type, value, context, nodes)
+        tuple, where type is the node type (a token or symbol number),
+        value is None for symbols and a string for tokens, context is
+        None or an opaque value used for error reporting (typically a
+        (lineno, offset) pair), and nodes is a list of children for
+        symbols, and None for tokens.
+
+        An abstract syntax tree node may be anything; this is entirely
+        up to the converter function.
+
+        """
+        self.grammar = grammar
+        # See note in docstring above. TL;DR this is ignored.
+        self.convert = convert or lam_sub
+        self.is_backtracking = False
+        self.last_token: Optional[int] = None
+
+    def setup(self, proxy: "TokenProxy", start: Optional[int] = None) -> None:
+        """Prepare for parsing.
+
+        This *must* be called before starting to parse.
+
+        The optional argument is an alternative start symbol; it
+        defaults to the grammar's start symbol.
+
+        You can use a Parser instance to parse any number of programs;
+        each time you call setup() the parser is reset to an initial
+        state determined by the (implicit or explicit) start symbol.
+
+        """
+        if start is None:
+            start = self.grammar.start
+        # Each stack entry is a tuple: (dfa, state, node).
+        # A node is a tuple: (type, value, context, children),
+        # where children is a list of nodes or None, and context may be None.
+        newnode: RawNode = (start, None, None, [])
+        stackentry = (self.grammar.dfas[start], 0, newnode)
+        self.stack: list[tuple[DFAS, int, RawNode]] = [stackentry]
+        self.rootnode: Optional[NL] = None
+        self.used_names: set[str] = set()
+        self.proxy = proxy
+        self.last_token = None
+
+    def addtoken(self, type: int, value: str, context: Context) -> bool:
+        """Add a token; return True iff this is the end of the program."""
+        # Map from token to label
+        ilabels = self.classify(type, value, context)
+        assert len(ilabels) >= 1
+
+        # If we have only one state to advance, we'll directly
+        # take it as is.
+        if len(ilabels) == 1:
+            [ilabel] = ilabels
+            return self._addtoken(ilabel, type, value, context)
+
+        # If there are multiple states which we can advance (only
+        # happen under soft-keywords), then we will try all of them
+        # in parallel and as soon as one state can reach further than
+        # the rest, we'll choose that one. This is a pretty hacky
+        # and hopefully temporary algorithm.
+        #
+        # For a more detailed explanation, check out this post:
+        # https://tree.science/what-the-backtracking.html
+
+        with self.proxy.release() as proxy:
+            counter, force = 0, False
+            recorder = Recorder(self, ilabels, context)
+            recorder.add_token(type, value, raw=True)
+
+            next_token_value = value
+            while recorder.determine_route(next_token_value) is None:
+                if not proxy.can_advance(counter):
+                    force = True
+                    break
+
+                next_token_type, next_token_value, *_ = proxy.eat(counter)
+                if next_token_type in (tokenize.COMMENT, tokenize.NL):
+                    counter += 1
+                    continue
+
+                if next_token_type == tokenize.OP:
+                    next_token_type = grammar.opmap[next_token_value]
+
+                recorder.add_token(next_token_type, next_token_value)
+                counter += 1
+
+            ilabel = cast(int, recorder.determine_route(next_token_value, force=force))
+            assert ilabel is not None
+
+        return self._addtoken(ilabel, type, value, context)
+
+    def _addtoken(self, ilabel: int, type: int, value: str, context: Context) -> bool:
+        # Loop until the token is shifted; may raise exceptions
+        while True:
+            dfa, state, node = self.stack[-1]
+            states, first = dfa
+            arcs = states[state]
+            # Look for a state with this label
+            for i, newstate in arcs:
+                t = self.grammar.labels[i][0]
+                if t >= 256:
+                    # See if it's a symbol and if we're in its first set
+                    itsdfa = self.grammar.dfas[t]
+                    itsstates, itsfirst = itsdfa
+                    if ilabel in itsfirst:
+                        # Push a symbol
+                        self.push(t, itsdfa, newstate, context)
+                        break  # To continue the outer while loop
+
+                elif ilabel == i:
+                    # Look it up in the list of labels
+                    # Shift a token; we're done with it
+                    self.shift(type, value, newstate, context)
+                    # Pop while we are in an accept-only state
+                    state = newstate
+                    while states[state] == [(0, state)]:
+                        self.pop()
+                        if not self.stack:
+                            # Done parsing!
+                            return True
+                        dfa, state, node = self.stack[-1]
+                        states, first = dfa
+                    # Done with this token
+                    self.last_token = type
+                    return False
+
+            else:
+                if (0, state) in arcs:
+                    # An accepting state, pop it and try something else
+                    self.pop()
+                    if not self.stack:
+                        # Done parsing, but another token is input
+                        raise ParseError("too much input", type, value, context)
+                else:
+                    # No success finding a transition
+                    raise ParseError("bad input", type, value, context)
+
+    def classify(self, type: int, value: str, context: Context) -> list[int]:
+        """Turn a token into a label.  (Internal)
+
+        Depending on whether the value is a soft-keyword or not,
+        this function may return multiple labels to choose from."""
+        if type == token.NAME:
+            # Keep a listing of all used names
+            self.used_names.add(value)
+            # Check for reserved words
+            if value in self.grammar.keywords:
+                return [self.grammar.keywords[value]]
+            elif value in self.grammar.soft_keywords:
+                assert type in self.grammar.tokens
+                # Current soft keywords (match, case, type) can only appear at the
+                # beginning of a statement. So as a shortcut, don't try to treat them
+                # like keywords in any other context.
+                # ('_' is also a soft keyword in the real grammar, but for our grammar
+                # it's just an expression, so we don't need to treat it specially.)
+                if self.last_token not in (
+                    None,
+                    token.INDENT,
+                    token.DEDENT,
+                    token.NEWLINE,
+                    token.SEMI,
+                    token.COLON,
+                ):
+                    return [self.grammar.tokens[type]]
+                return [
+                    self.grammar.tokens[type],
+                    self.grammar.soft_keywords[value],
+                ]
+
+        ilabel = self.grammar.tokens.get(type)
+        if ilabel is None:
+            raise ParseError("bad token", type, value, context)
+        return [ilabel]
+
+    def shift(self, type: int, value: str, newstate: int, context: Context) -> None:
+        """Shift a token.  (Internal)"""
+        if self.is_backtracking:
+            dfa, state, _ = self.stack[-1]
+            self.stack[-1] = (dfa, newstate, DUMMY_NODE)
+        else:
+            dfa, state, node = self.stack[-1]
+            rawnode: RawNode = (type, value, context, None)
+            newnode = convert(self.grammar, rawnode)
+            assert node[-1] is not None
+            node[-1].append(newnode)
+            self.stack[-1] = (dfa, newstate, node)
+
+    def push(self, type: int, newdfa: DFAS, newstate: int, context: Context) -> None:
+        """Push a nonterminal.  (Internal)"""
+        if self.is_backtracking:
+            dfa, state, _ = self.stack[-1]
+            self.stack[-1] = (dfa, newstate, DUMMY_NODE)
+            self.stack.append((newdfa, 0, DUMMY_NODE))
+        else:
+            dfa, state, node = self.stack[-1]
+            newnode: RawNode = (type, None, context, [])
+            self.stack[-1] = (dfa, newstate, node)
+            self.stack.append((newdfa, 0, newnode))
+
+    def pop(self) -> None:
+        """Pop a nonterminal.  (Internal)"""
+        if self.is_backtracking:
+            self.stack.pop()
+        else:
+            popdfa, popstate, popnode = self.stack.pop()
+            newnode = convert(self.grammar, popnode)
+            if self.stack:
+                dfa, state, node = self.stack[-1]
+                assert node[-1] is not None
+                node[-1].append(newnode)
+            else:
+                self.rootnode = newnode
+                self.rootnode.used_names = self.used_names

venv/Lib/site-packages/blib2to3/pgen2/pgen.py

@@ -0,0 +1,417 @@
+# Copyright 2004-2005 Elemental Security, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+import os
+from typing import IO, Any, Iterator, NoReturn, Optional, Sequence, Union
+
+from blib2to3.pgen2 import grammar, token, tokenize
+from blib2to3.pgen2.tokenize import GoodTokenInfo
+
+Path = Union[str, "os.PathLike[str]"]
+
+
+class PgenGrammar(grammar.Grammar):
+    pass
+
+
+class ParserGenerator:
+    filename: Path
+    stream: IO[str]
+    generator: Iterator[GoodTokenInfo]
+    first: dict[str, Optional[dict[str, int]]]
+
+    def __init__(self, filename: Path, stream: Optional[IO[str]] = None) -> None:
+        close_stream = None
+        if stream is None:
+            stream = open(filename, encoding="utf-8")
+            close_stream = stream.close
+        self.filename = filename
+        self.stream = stream
+        self.generator = tokenize.generate_tokens(stream.readline)
+        self.gettoken()  # Initialize lookahead
+        self.dfas, self.startsymbol = self.parse()
+        if close_stream is not None:
+            close_stream()
+        self.first = {}  # map from symbol name to set of tokens
+        self.addfirstsets()
+
+    def make_grammar(self) -> PgenGrammar:
+        c = PgenGrammar()
+        names = list(self.dfas.keys())
+        names.sort()
+        names.remove(self.startsymbol)
+        names.insert(0, self.startsymbol)
+        for name in names:
+            i = 256 + len(c.symbol2number)
+            c.symbol2number[name] = i
+            c.number2symbol[i] = name
+        for name in names:
+            dfa = self.dfas[name]
+            states = []
+            for state in dfa:
+                arcs = []
+                for label, next in sorted(state.arcs.items()):
+                    arcs.append((self.make_label(c, label), dfa.index(next)))
+                if state.isfinal:
+                    arcs.append((0, dfa.index(state)))
+                states.append(arcs)
+            c.states.append(states)
+            c.dfas[c.symbol2number[name]] = (states, self.make_first(c, name))
+        c.start = c.symbol2number[self.startsymbol]
+        return c
+
+    def make_first(self, c: PgenGrammar, name: str) -> dict[int, int]:
+        rawfirst = self.first[name]
+        assert rawfirst is not None
+        first = {}
+        for label in sorted(rawfirst):
+            ilabel = self.make_label(c, label)
+            ##assert ilabel not in first # XXX failed on <> ... !=
+            first[ilabel] = 1
+        return first
+
+    def make_label(self, c: PgenGrammar, label: str) -> int:
+        # XXX Maybe this should be a method on a subclass of converter?
+        ilabel = len(c.labels)
+        if label[0].isalpha():
+            # Either a symbol name or a named token
+            if label in c.symbol2number:
+                # A symbol name (a non-terminal)
+                if label in c.symbol2label:
+                    return c.symbol2label[label]
+                else:
+                    c.labels.append((c.symbol2number[label], None))
+                    c.symbol2label[label] = ilabel
+                    return ilabel
+            else:
+                # A named token (NAME, NUMBER, STRING)
+                itoken = getattr(token, label, None)
+                assert isinstance(itoken, int), label
+                assert itoken in token.tok_name, label
+                if itoken in c.tokens:
+                    return c.tokens[itoken]
+                else:
+                    c.labels.append((itoken, None))
+                    c.tokens[itoken] = ilabel
+                    return ilabel
+        else:
+            # Either a keyword or an operator
+            assert label[0] in ('"', "'"), label
+            value = eval(label)
+            if value[0].isalpha():
+                if label[0] == '"':
+                    keywords = c.soft_keywords
+                else:
+                    keywords = c.keywords
+
+                # A keyword
+                if value in keywords:
+                    return keywords[value]
+                else:
+                    c.labels.append((token.NAME, value))
+                    keywords[value] = ilabel
+                    return ilabel
+            else:
+                # An operator (any non-numeric token)
+                itoken = grammar.opmap[value]  # Fails if unknown token
+                if itoken in c.tokens:
+                    return c.tokens[itoken]
+                else:
+                    c.labels.append((itoken, None))
+                    c.tokens[itoken] = ilabel
+                    return ilabel
+
+    def addfirstsets(self) -> None:
+        names = list(self.dfas.keys())
+        names.sort()
+        for name in names:
+            if name not in self.first:
+                self.calcfirst(name)
+            # print name, self.first[name].keys()
+
+    def calcfirst(self, name: str) -> None:
+        dfa = self.dfas[name]
+        self.first[name] = None  # dummy to detect left recursion
+        state = dfa[0]
+        totalset: dict[str, int] = {}
+        overlapcheck = {}
+        for label in state.arcs:
+            if label in self.dfas:
+                if label in self.first:
+                    fset = self.first[label]
+                    if fset is None:
+                        raise ValueError("recursion for rule %r" % name)
+                else:
+                    self.calcfirst(label)
+                    fset = self.first[label]
+                    assert fset is not None
+                totalset.update(fset)
+                overlapcheck[label] = fset
+            else:
+                totalset[label] = 1
+                overlapcheck[label] = {label: 1}
+        inverse: dict[str, str] = {}
+        for label, itsfirst in overlapcheck.items():
+            for symbol in itsfirst:
+                if symbol in inverse:
+                    raise ValueError(
+                        "rule %s is ambiguous; %s is in the first sets of %s as well"
+                        " as %s" % (name, symbol, label, inverse[symbol])
+                    )
+                inverse[symbol] = label
+        self.first[name] = totalset
+
+    def parse(self) -> tuple[dict[str, list["DFAState"]], str]:
+        dfas = {}
+        startsymbol: Optional[str] = None
+        # MSTART: (NEWLINE | RULE)* ENDMARKER
+        while self.type != token.ENDMARKER:
+            while self.type == token.NEWLINE:
+                self.gettoken()
+            # RULE: NAME ':' RHS NEWLINE
+            name = self.expect(token.NAME)
+            self.expect(token.OP, ":")
+            a, z = self.parse_rhs()
+            self.expect(token.NEWLINE)
+            # self.dump_nfa(name, a, z)
+            dfa = self.make_dfa(a, z)
+            # self.dump_dfa(name, dfa)
+            # oldlen = len(dfa)
+            self.simplify_dfa(dfa)
+            # newlen = len(dfa)
+            dfas[name] = dfa
+            # print name, oldlen, newlen
+            if startsymbol is None:
+                startsymbol = name
+        assert startsymbol is not None
+        return dfas, startsymbol
+
+    def make_dfa(self, start: "NFAState", finish: "NFAState") -> list["DFAState"]:
+        # To turn an NFA into a DFA, we define the states of the DFA
+        # to correspond to *sets* of states of the NFA.  Then do some
+        # state reduction.  Let's represent sets as dicts with 1 for
+        # values.
+        assert isinstance(start, NFAState)
+        assert isinstance(finish, NFAState)
+
+        def closure(state: NFAState) -> dict[NFAState, int]:
+            base: dict[NFAState, int] = {}
+            addclosure(state, base)
+            return base
+
+        def addclosure(state: NFAState, base: dict[NFAState, int]) -> None:
+            assert isinstance(state, NFAState)
+            if state in base:
+                return
+            base[state] = 1
+            for label, next in state.arcs:
+                if label is None:
+                    addclosure(next, base)
+
+        states = [DFAState(closure(start), finish)]
+        for state in states:  # NB states grows while we're iterating
+            arcs: dict[str, dict[NFAState, int]] = {}
+            for nfastate in state.nfaset:
+                for label, next in nfastate.arcs:
+                    if label is not None:
+                        addclosure(next, arcs.setdefault(label, {}))
+            for label, nfaset in sorted(arcs.items()):
+                for st in states:
+                    if st.nfaset == nfaset:
+                        break
+                else:
+                    st = DFAState(nfaset, finish)
+                    states.append(st)
+                state.addarc(st, label)
+        return states  # List of DFAState instances; first one is start
+
+    def dump_nfa(self, name: str, start: "NFAState", finish: "NFAState") -> None:
+        print("Dump of NFA for", name)
+        todo = [start]
+        for i, state in enumerate(todo):
+            print("  State", i, state is finish and "(final)" or "")
+            for label, next in state.arcs:
+                if next in todo:
+                    j = todo.index(next)
+                else:
+                    j = len(todo)
+                    todo.append(next)
+                if label is None:
+                    print("    -> %d" % j)
+                else:
+                    print("    %s -> %d" % (label, j))
+
+    def dump_dfa(self, name: str, dfa: Sequence["DFAState"]) -> None:
+        print("Dump of DFA for", name)
+        for i, state in enumerate(dfa):
+            print("  State", i, state.isfinal and "(final)" or "")
+            for label, next in sorted(state.arcs.items()):
+                print("    %s -> %d" % (label, dfa.index(next)))
+
+    def simplify_dfa(self, dfa: list["DFAState"]) -> None:
+        # This is not theoretically optimal, but works well enough.
+        # Algorithm: repeatedly look for two states that have the same
+        # set of arcs (same labels pointing to the same nodes) and
+        # unify them, until things stop changing.
+
+        # dfa is a list of DFAState instances
+        changes = True
+        while changes:
+            changes = False
+            for i, state_i in enumerate(dfa):
+                for j in range(i + 1, len(dfa)):
+                    state_j = dfa[j]
+                    if state_i == state_j:
+                        # print "  unify", i, j
+                        del dfa[j]
+                        for state in dfa:
+                            state.unifystate(state_j, state_i)
+                        changes = True
+                        break
+
+    def parse_rhs(self) -> tuple["NFAState", "NFAState"]:
+        # RHS: ALT ('|' ALT)*
+        a, z = self.parse_alt()
+        if self.value != "|":
+            return a, z
+        else:
+            aa = NFAState()
+            zz = NFAState()
+            aa.addarc(a)
+            z.addarc(zz)
+            while self.value == "|":
+                self.gettoken()
+                a, z = self.parse_alt()
+                aa.addarc(a)
+                z.addarc(zz)
+            return aa, zz
+
+    def parse_alt(self) -> tuple["NFAState", "NFAState"]:
+        # ALT: ITEM+
+        a, b = self.parse_item()
+        while self.value in ("(", "[") or self.type in (token.NAME, token.STRING):
+            c, d = self.parse_item()
+            b.addarc(c)
+            b = d
+        return a, b
+
+    def parse_item(self) -> tuple["NFAState", "NFAState"]:
+        # ITEM: '[' RHS ']' | ATOM ['+' | '*']
+        if self.value == "[":
+            self.gettoken()
+            a, z = self.parse_rhs()
+            self.expect(token.OP, "]")
+            a.addarc(z)
+            return a, z
+        else:
+            a, z = self.parse_atom()
+            value = self.value
+            if value not in ("+", "*"):
+                return a, z
+            self.gettoken()
+            z.addarc(a)
+            if value == "+":
+                return a, z
+            else:
+                return a, a
+
+    def parse_atom(self) -> tuple["NFAState", "NFAState"]:
+        # ATOM: '(' RHS ')' | NAME | STRING
+        if self.value == "(":
+            self.gettoken()
+            a, z = self.parse_rhs()
+            self.expect(token.OP, ")")
+            return a, z
+        elif self.type in (token.NAME, token.STRING):
+            a = NFAState()
+            z = NFAState()
+            a.addarc(z, self.value)
+            self.gettoken()
+            return a, z
+        else:
+            self.raise_error(
+                "expected (...) or NAME or STRING, got %s/%s", self.type, self.value
+            )
+            raise AssertionError
+
+    def expect(self, type: int, value: Optional[Any] = None) -> str:
+        if self.type != type or (value is not None and self.value != value):
+            self.raise_error(
+                "expected %s/%s, got %s/%s", type, value, self.type, self.value
+            )
+        value = self.value
+        self.gettoken()
+        return value
+
+    def gettoken(self) -> None:
+        tup = next(self.generator)
+        while tup[0] in (tokenize.COMMENT, tokenize.NL):
+            tup = next(self.generator)
+        self.type, self.value, self.begin, self.end, self.line = tup
+        # print token.tok_name[self.type], repr(self.value)
+
+    def raise_error(self, msg: str, *args: Any) -> NoReturn:
+        if args:
+            try:
+                msg = msg % args
+            except Exception:
+                msg = " ".join([msg] + list(map(str, args)))
+        raise SyntaxError(msg, (self.filename, self.end[0], self.end[1], self.line))
+
+
+class NFAState:
+    arcs: list[tuple[Optional[str], "NFAState"]]
+
+    def __init__(self) -> None:
+        self.arcs = []  # list of (label, NFAState) pairs
+
+    def addarc(self, next: "NFAState", label: Optional[str] = None) -> None:
+        assert label is None or isinstance(label, str)
+        assert isinstance(next, NFAState)
+        self.arcs.append((label, next))
+
+
+class DFAState:
+    nfaset: dict[NFAState, Any]
+    isfinal: bool
+    arcs: dict[str, "DFAState"]
+
+    def __init__(self, nfaset: dict[NFAState, Any], final: NFAState) -> None:
+        assert isinstance(nfaset, dict)
+        assert isinstance(next(iter(nfaset)), NFAState)
+        assert isinstance(final, NFAState)
+        self.nfaset = nfaset
+        self.isfinal = final in nfaset
+        self.arcs = {}  # map from label to DFAState
+
+    def addarc(self, next: "DFAState", label: str) -> None:
+        assert isinstance(label, str)
+        assert label not in self.arcs
+        assert isinstance(next, DFAState)
+        self.arcs[label] = next
+
+    def unifystate(self, old: "DFAState", new: "DFAState") -> None:
+        for label, next in self.arcs.items():
+            if next is old:
+                self.arcs[label] = new
+
+    def __eq__(self, other: Any) -> bool:
+        # Equality test -- ignore the nfaset instance variable
+        assert isinstance(other, DFAState)
+        if self.isfinal != other.isfinal:
+            return False
+        # Can't just return self.arcs == other.arcs, because that
+        # would invoke this method recursively, with cycles...
+        if len(self.arcs) != len(other.arcs):
+            return False
+        for label, next in self.arcs.items():
+            if next is not other.arcs.get(label):
+                return False
+        return True
+
+    __hash__: Any = None  # For Py3 compatibility.
+
+
+def generate_grammar(filename: Path = "Grammar.txt") -> PgenGrammar:
+    p = ParserGenerator(filename)
+    return p.make_grammar()

venv/Lib/site-packages/blib2to3/pgen2/token.py

@@ -0,0 +1,92 @@
+"""Token constants (from "token.h")."""
+
+from typing import Final
+
+#  Taken from Python (r53757) and modified to include some tokens
+#   originally monkeypatched in by pgen2.tokenize
+
+# --start constants--
+ENDMARKER: Final = 0
+NAME: Final = 1
+NUMBER: Final = 2
+STRING: Final = 3
+NEWLINE: Final = 4
+INDENT: Final = 5
+DEDENT: Final = 6
+LPAR: Final = 7
+RPAR: Final = 8
+LSQB: Final = 9
+RSQB: Final = 10
+COLON: Final = 11
+COMMA: Final = 12
+SEMI: Final = 13
+PLUS: Final = 14
+MINUS: Final = 15
+STAR: Final = 16
+SLASH: Final = 17
+VBAR: Final = 18
+AMPER: Final = 19
+LESS: Final = 20
+GREATER: Final = 21
+EQUAL: Final = 22
+DOT: Final = 23
+PERCENT: Final = 24
+BACKQUOTE: Final = 25
+LBRACE: Final = 26
+RBRACE: Final = 27
+EQEQUAL: Final = 28
+NOTEQUAL: Final = 29
+LESSEQUAL: Final = 30
+GREATEREQUAL: Final = 31
+TILDE: Final = 32
+CIRCUMFLEX: Final = 33
+LEFTSHIFT: Final = 34
+RIGHTSHIFT: Final = 35
+DOUBLESTAR: Final = 36
+PLUSEQUAL: Final = 37
+MINEQUAL: Final = 38
+STAREQUAL: Final = 39
+SLASHEQUAL: Final = 40
+PERCENTEQUAL: Final = 41
+AMPEREQUAL: Final = 42
+VBAREQUAL: Final = 43
+CIRCUMFLEXEQUAL: Final = 44
+LEFTSHIFTEQUAL: Final = 45
+RIGHTSHIFTEQUAL: Final = 46
+DOUBLESTAREQUAL: Final = 47
+DOUBLESLASH: Final = 48
+DOUBLESLASHEQUAL: Final = 49
+AT: Final = 50
+ATEQUAL: Final = 51
+OP: Final = 52
+COMMENT: Final = 53
+NL: Final = 54
+RARROW: Final = 55
+AWAIT: Final = 56
+ASYNC: Final = 57
+ERRORTOKEN: Final = 58
+COLONEQUAL: Final = 59
+FSTRING_START: Final = 60
+FSTRING_MIDDLE: Final = 61
+FSTRING_END: Final = 62
+BANG: Final = 63
+N_TOKENS: Final = 64
+NT_OFFSET: Final = 256
+# --end constants--
+
+tok_name: Final[dict[int, str]] = {}
+for _name, _value in list(globals().items()):
+    if type(_value) is int:
+        tok_name[_value] = _name
+
+
+def ISTERMINAL(x: int) -> bool:
+    return x < NT_OFFSET
+
+
+def ISNONTERMINAL(x: int) -> bool:
+    return x >= NT_OFFSET
+
+
+def ISEOF(x: int) -> bool:
+    return x == ENDMARKER

venv/Lib/site-packages/blib2to3/pygram.py

@@ -0,0 +1,204 @@
+# Copyright 2006 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""Export the Python grammar and symbols."""
+
+# Python imports
+import os
+from typing import Union
+
+# Local imports
+from .pgen2 import driver
+from .pgen2.grammar import Grammar
+
+# Moved into initialize because mypyc can't handle __file__ (XXX bug)
+# # The grammar file
+# _GRAMMAR_FILE = os.path.join(os.path.dirname(__file__), "Grammar.txt")
+# _PATTERN_GRAMMAR_FILE = os.path.join(os.path.dirname(__file__),
+#                                      "PatternGrammar.txt")
+
+
+class Symbols:
+    def __init__(self, grammar: Grammar) -> None:
+        """Initializer.
+
+        Creates an attribute for each grammar symbol (nonterminal),
+        whose value is the symbol's type (an int >= 256).
+        """
+        for name, symbol in grammar.symbol2number.items():
+            setattr(self, name, symbol)
+
+
+class _python_symbols(Symbols):
+    and_expr: int
+    and_test: int
+    annassign: int
+    arglist: int
+    argument: int
+    arith_expr: int
+    asexpr_test: int
+    assert_stmt: int
+    async_funcdef: int
+    async_stmt: int
+    atom: int
+    augassign: int
+    break_stmt: int
+    case_block: int
+    classdef: int
+    comp_for: int
+    comp_if: int
+    comp_iter: int
+    comp_op: int
+    comparison: int
+    compound_stmt: int
+    continue_stmt: int
+    decorated: int
+    decorator: int
+    decorators: int
+    del_stmt: int
+    dictsetmaker: int
+    dotted_as_name: int
+    dotted_as_names: int
+    dotted_name: int
+    encoding_decl: int
+    eval_input: int
+    except_clause: int
+    expr: int
+    expr_stmt: int
+    exprlist: int
+    factor: int
+    file_input: int
+    flow_stmt: int
+    for_stmt: int
+    fstring: int
+    fstring_format_spec: int
+    fstring_middle: int
+    fstring_replacement_field: int
+    funcdef: int
+    global_stmt: int
+    guard: int
+    if_stmt: int
+    import_as_name: int
+    import_as_names: int
+    import_from: int
+    import_name: int
+    import_stmt: int
+    lambdef: int
+    listmaker: int
+    match_stmt: int
+    namedexpr_test: int
+    not_test: int
+    old_comp_for: int
+    old_comp_if: int
+    old_comp_iter: int
+    old_lambdef: int
+    old_test: int
+    or_test: int
+    parameters: int
+    paramspec: int
+    pass_stmt: int
+    pattern: int
+    patterns: int
+    power: int
+    raise_stmt: int
+    return_stmt: int
+    shift_expr: int
+    simple_stmt: int
+    single_input: int
+    sliceop: int
+    small_stmt: int
+    subject_expr: int
+    star_expr: int
+    stmt: int
+    subscript: int
+    subscriptlist: int
+    suite: int
+    term: int
+    test: int
+    testlist: int
+    testlist1: int
+    testlist_gexp: int
+    testlist_safe: int
+    testlist_star_expr: int
+    tfpdef: int
+    tfplist: int
+    tname: int
+    tname_star: int
+    trailer: int
+    try_stmt: int
+    type_stmt: int
+    typedargslist: int
+    typeparam: int
+    typeparams: int
+    typevar: int
+    typevartuple: int
+    varargslist: int
+    vfpdef: int
+    vfplist: int
+    vname: int
+    while_stmt: int
+    with_stmt: int
+    xor_expr: int
+    yield_arg: int
+    yield_expr: int
+    yield_stmt: int
+
+
+class _pattern_symbols(Symbols):
+    Alternative: int
+    Alternatives: int
+    Details: int
+    Matcher: int
+    NegatedUnit: int
+    Repeater: int
+    Unit: int
+
+
+python_grammar: Grammar
+python_grammar_async_keywords: Grammar
+python_grammar_soft_keywords: Grammar
+pattern_grammar: Grammar
+python_symbols: _python_symbols
+pattern_symbols: _pattern_symbols
+
+
+def initialize(cache_dir: Union[str, "os.PathLike[str]", None] = None) -> None:
+    global python_grammar
+    global python_grammar_async_keywords
+    global python_grammar_soft_keywords
+    global python_symbols
+    global pattern_grammar
+    global pattern_symbols
+
+    # The grammar file
+    _GRAMMAR_FILE = os.path.join(os.path.dirname(__file__), "Grammar.txt")
+    _PATTERN_GRAMMAR_FILE = os.path.join(
+        os.path.dirname(__file__), "PatternGrammar.txt"
+    )
+
+    python_grammar = driver.load_packaged_grammar("blib2to3", _GRAMMAR_FILE, cache_dir)
+    assert "print" not in python_grammar.keywords
+    assert "exec" not in python_grammar.keywords
+
+    soft_keywords = python_grammar.soft_keywords.copy()
+    python_grammar.soft_keywords.clear()
+
+    python_symbols = _python_symbols(python_grammar)
+
+    # Python 3.0-3.6
+    python_grammar.version = (3, 0)
+
+    # Python 3.7+
+    python_grammar_async_keywords = python_grammar.copy()
+    python_grammar_async_keywords.async_keywords = True
+    python_grammar_async_keywords.version = (3, 7)
+
+    # Python 3.10+
+    python_grammar_soft_keywords = python_grammar_async_keywords.copy()
+    python_grammar_soft_keywords.soft_keywords = soft_keywords
+    python_grammar_soft_keywords.version = (3, 10)
+
+    pattern_grammar = driver.load_packaged_grammar(
+        "blib2to3", _PATTERN_GRAMMAR_FILE, cache_dir
+    )
+    pattern_symbols = _pattern_symbols(pattern_grammar)

venv/Lib/site-packages/blib2to3/pytree.py

@@ -0,0 +1,975 @@
+# Copyright 2006 Google, Inc. All Rights Reserved.
+# Licensed to PSF under a Contributor Agreement.
+
+"""
+Python parse tree definitions.
+
+This is a very concrete parse tree; we need to keep every token and
+even the comments and whitespace between tokens.
+
+There's also a pattern matching implementation here.
+"""
+
+# mypy: allow-untyped-defs, allow-incomplete-defs
+
+from typing import Any, Iterable, Iterator, Optional, TypeVar, Union
+
+from blib2to3.pgen2.grammar import Grammar
+
+__author__ = "Guido van Rossum <guido@python.org>"
+
+import sys
+from io import StringIO
+
+HUGE: int = 0x7FFFFFFF  # maximum repeat count, default max
+
+_type_reprs: dict[int, Union[str, int]] = {}
+
+
+def type_repr(type_num: int) -> Union[str, int]:
+    global _type_reprs
+    if not _type_reprs:
+        from . import pygram
+
+        if not hasattr(pygram, "python_symbols"):
+            pygram.initialize(cache_dir=None)
+
+        # printing tokens is possible but not as useful
+        # from .pgen2 import token // token.__dict__.items():
+        for name in dir(pygram.python_symbols):
+            val = getattr(pygram.python_symbols, name)
+            if type(val) == int:
+                _type_reprs[val] = name
+    return _type_reprs.setdefault(type_num, type_num)
+
+
+_P = TypeVar("_P", bound="Base")
+
+NL = Union["Node", "Leaf"]
+Context = tuple[str, tuple[int, int]]
+RawNode = tuple[int, Optional[str], Optional[Context], Optional[list[NL]]]
+
+
+class Base:
+    """
+    Abstract base class for Node and Leaf.
+
+    This provides some default functionality and boilerplate using the
+    template pattern.
+
+    A node may be a subnode of at most one parent.
+    """
+
+    # Default values for instance variables
+    type: int  # int: token number (< 256) or symbol number (>= 256)
+    parent: Optional["Node"] = None  # Parent node pointer, or None
+    children: list[NL]  # List of subnodes
+    was_changed: bool = False
+    was_checked: bool = False
+
+    def __new__(cls, *args, **kwds):
+        """Constructor that prevents Base from being instantiated."""
+        assert cls is not Base, "Cannot instantiate Base"
+        return object.__new__(cls)
+
+    def __eq__(self, other: Any) -> bool:
+        """
+        Compare two nodes for equality.
+
+        This calls the method _eq().
+        """
+        if self.__class__ is not other.__class__:
+            return NotImplemented
+        return self._eq(other)
+
+    @property
+    def prefix(self) -> str:
+        raise NotImplementedError
+
+    def _eq(self: _P, other: _P) -> bool:
+        """
+        Compare two nodes for equality.
+
+        This is called by __eq__ and __ne__.  It is only called if the two nodes
+        have the same type.  This must be implemented by the concrete subclass.
+        Nodes should be considered equal if they have the same structure,
+        ignoring the prefix string and other context information.
+        """
+        raise NotImplementedError
+
+    def __deepcopy__(self: _P, memo: Any) -> _P:
+        return self.clone()
+
+    def clone(self: _P) -> _P:
+        """
+        Return a cloned (deep) copy of self.
+
+        This must be implemented by the concrete subclass.
+        """
+        raise NotImplementedError
+
+    def post_order(self) -> Iterator[NL]:
+        """
+        Return a post-order iterator for the tree.
+
+        This must be implemented by the concrete subclass.
+        """
+        raise NotImplementedError
+
+    def pre_order(self) -> Iterator[NL]:
+        """
+        Return a pre-order iterator for the tree.
+
+        This must be implemented by the concrete subclass.
+        """
+        raise NotImplementedError
+
+    def replace(self, new: Union[NL, list[NL]]) -> None:
+        """Replace this node with a new one in the parent."""
+        assert self.parent is not None, str(self)
+        assert new is not None
+        if not isinstance(new, list):
+            new = [new]
+        l_children = []
+        found = False
+        for ch in self.parent.children:
+            if ch is self:
+                assert not found, (self.parent.children, self, new)
+                if new is not None:
+                    l_children.extend(new)
+                found = True
+            else:
+                l_children.append(ch)
+        assert found, (self.children, self, new)
+        self.parent.children = l_children
+        self.parent.changed()
+        self.parent.invalidate_sibling_maps()
+        for x in new:
+            x.parent = self.parent
+        self.parent = None
+
+    def get_lineno(self) -> Optional[int]:
+        """Return the line number which generated the invocant node."""
+        node = self
+        while not isinstance(node, Leaf):
+            if not node.children:
+                return None
+            node = node.children[0]
+        return node.lineno
+
+    def changed(self) -> None:
+        if self.was_changed:
+            return
+        if self.parent:
+            self.parent.changed()
+        self.was_changed = True
+
+    def remove(self) -> Optional[int]:
+        """
+        Remove the node from the tree. Returns the position of the node in its
+        parent's children before it was removed.
+        """
+        if self.parent:
+            for i, node in enumerate(self.parent.children):
+                if node is self:
+                    del self.parent.children[i]
+                    self.parent.changed()
+                    self.parent.invalidate_sibling_maps()
+                    self.parent = None
+                    return i
+        return None
+
+    @property
+    def next_sibling(self) -> Optional[NL]:
+        """
+        The node immediately following the invocant in their parent's children
+        list. If the invocant does not have a next sibling, it is None
+        """
+        if self.parent is None:
+            return None
+
+        if self.parent.next_sibling_map is None:
+            self.parent.update_sibling_maps()
+        assert self.parent.next_sibling_map is not None
+        return self.parent.next_sibling_map[id(self)]
+
+    @property
+    def prev_sibling(self) -> Optional[NL]:
+        """
+        The node immediately preceding the invocant in their parent's children
+        list. If the invocant does not have a previous sibling, it is None.
+        """
+        if self.parent is None:
+            return None
+
+        if self.parent.prev_sibling_map is None:
+            self.parent.update_sibling_maps()
+        assert self.parent.prev_sibling_map is not None
+        return self.parent.prev_sibling_map[id(self)]
+
+    def leaves(self) -> Iterator["Leaf"]:
+        for child in self.children:
+            yield from child.leaves()
+
+    def depth(self) -> int:
+        if self.parent is None:
+            return 0
+        return 1 + self.parent.depth()
+
+    def get_suffix(self) -> str:
+        """
+        Return the string immediately following the invocant node. This is
+        effectively equivalent to node.next_sibling.prefix
+        """
+        next_sib = self.next_sibling
+        if next_sib is None:
+            return ""
+        prefix = next_sib.prefix
+        return prefix
+
+
+class Node(Base):
+    """Concrete implementation for interior nodes."""
+
+    fixers_applied: Optional[list[Any]]
+    used_names: Optional[set[str]]
+
+    def __init__(
+        self,
+        type: int,
+        children: list[NL],
+        context: Optional[Any] = None,
+        prefix: Optional[str] = None,
+        fixers_applied: Optional[list[Any]] = None,
+    ) -> None:
+        """
+        Initializer.
+
+        Takes a type constant (a symbol number >= 256), a sequence of
+        child nodes, and an optional context keyword argument.
+
+        As a side effect, the parent pointers of the children are updated.
+        """
+        assert type >= 256, type
+        self.type = type
+        self.children = list(children)
+        for ch in self.children:
+            assert ch.parent is None, repr(ch)
+            ch.parent = self
+        self.invalidate_sibling_maps()
+        if prefix is not None:
+            self.prefix = prefix
+        if fixers_applied:
+            self.fixers_applied = fixers_applied[:]
+        else:
+            self.fixers_applied = None
+
+    def __repr__(self) -> str:
+        """Return a canonical string representation."""
+        assert self.type is not None
+        return "{}({}, {!r})".format(
+            self.__class__.__name__,
+            type_repr(self.type),
+            self.children,
+        )
+
+    def __str__(self) -> str:
+        """
+        Return a pretty string representation.
+
+        This reproduces the input source exactly.
+        """
+        return "".join(map(str, self.children))
+
+    def _eq(self, other: Base) -> bool:
+        """Compare two nodes for equality."""
+        return (self.type, self.children) == (other.type, other.children)
+
+    def clone(self) -> "Node":
+        assert self.type is not None
+        """Return a cloned (deep) copy of self."""
+        return Node(
+            self.type,
+            [ch.clone() for ch in self.children],
+            fixers_applied=self.fixers_applied,
+        )
+
+    def post_order(self) -> Iterator[NL]:
+        """Return a post-order iterator for the tree."""
+        for child in self.children:
+            yield from child.post_order()
+        yield self
+
+    def pre_order(self) -> Iterator[NL]:
+        """Return a pre-order iterator for the tree."""
+        yield self
+        for child in self.children:
+            yield from child.pre_order()
+
+    @property
+    def prefix(self) -> str:
+        """
+        The whitespace and comments preceding this node in the input.
+        """
+        if not self.children:
+            return ""
+        return self.children[0].prefix
+
+    @prefix.setter
+    def prefix(self, prefix: str) -> None:
+        if self.children:
+            self.children[0].prefix = prefix
+
+    def set_child(self, i: int, child: NL) -> None:
+        """
+        Equivalent to 'node.children[i] = child'. This method also sets the
+        child's parent attribute appropriately.
+        """
+        child.parent = self
+        self.children[i].parent = None
+        self.children[i] = child
+        self.changed()
+        self.invalidate_sibling_maps()
+
+    def insert_child(self, i: int, child: NL) -> None:
+        """
+        Equivalent to 'node.children.insert(i, child)'. This method also sets
+        the child's parent attribute appropriately.
+        """
+        child.parent = self
+        self.children.insert(i, child)
+        self.changed()
+        self.invalidate_sibling_maps()
+
+    def append_child(self, child: NL) -> None:
+        """
+        Equivalent to 'node.children.append(child)'. This method also sets the
+        child's parent attribute appropriately.
+        """
+        child.parent = self
+        self.children.append(child)
+        self.changed()
+        self.invalidate_sibling_maps()
+
+    def invalidate_sibling_maps(self) -> None:
+        self.prev_sibling_map: Optional[dict[int, Optional[NL]]] = None
+        self.next_sibling_map: Optional[dict[int, Optional[NL]]] = None
+
+    def update_sibling_maps(self) -> None:
+        _prev: dict[int, Optional[NL]] = {}
+        _next: dict[int, Optional[NL]] = {}
+        self.prev_sibling_map = _prev
+        self.next_sibling_map = _next
+        previous: Optional[NL] = None
+        for current in self.children:
+            _prev[id(current)] = previous
+            _next[id(previous)] = current
+            previous = current
+        _next[id(current)] = None
+
+
+class Leaf(Base):
+    """Concrete implementation for leaf nodes."""
+
+    # Default values for instance variables
+    value: str
+    fixers_applied: list[Any]
+    bracket_depth: int
+    # Changed later in brackets.py
+    opening_bracket: Optional["Leaf"] = None
+    used_names: Optional[set[str]]
+    _prefix = ""  # Whitespace and comments preceding this token in the input
+    lineno: int = 0  # Line where this token starts in the input
+    column: int = 0  # Column where this token starts in the input
+    # If not None, this Leaf is created by converting a block of fmt off/skip
+    # code, and `fmt_pass_converted_first_leaf` points to the first Leaf in the
+    # converted code.
+    fmt_pass_converted_first_leaf: Optional["Leaf"] = None
+
+    def __init__(
+        self,
+        type: int,
+        value: str,
+        context: Optional[Context] = None,
+        prefix: Optional[str] = None,
+        fixers_applied: list[Any] = [],
+        opening_bracket: Optional["Leaf"] = None,
+        fmt_pass_converted_first_leaf: Optional["Leaf"] = None,
+    ) -> None:
+        """
+        Initializer.
+
+        Takes a type constant (a token number < 256), a string value, and an
+        optional context keyword argument.
+        """
+
+        assert 0 <= type < 256, type
+        if context is not None:
+            self._prefix, (self.lineno, self.column) = context
+        self.type = type
+        self.value = value
+        if prefix is not None:
+            self._prefix = prefix
+        self.fixers_applied: Optional[list[Any]] = fixers_applied[:]
+        self.children = []
+        self.opening_bracket = opening_bracket
+        self.fmt_pass_converted_first_leaf = fmt_pass_converted_first_leaf
+
+    def __repr__(self) -> str:
+        """Return a canonical string representation."""
+        from .pgen2.token import tok_name
+
+        assert self.type is not None
+        return "{}({}, {!r})".format(
+            self.__class__.__name__,
+            tok_name.get(self.type, self.type),
+            self.value,
+        )
+
+    def __str__(self) -> str:
+        """
+        Return a pretty string representation.
+
+        This reproduces the input source exactly.
+        """
+        return self._prefix + str(self.value)
+
+    def _eq(self, other: "Leaf") -> bool:
+        """Compare two nodes for equality."""
+        return (self.type, self.value) == (other.type, other.value)
+
+    def clone(self) -> "Leaf":
+        assert self.type is not None
+        """Return a cloned (deep) copy of self."""
+        return Leaf(
+            self.type,
+            self.value,
+            (self.prefix, (self.lineno, self.column)),
+            fixers_applied=self.fixers_applied,
+        )
+
+    def leaves(self) -> Iterator["Leaf"]:
+        yield self
+
+    def post_order(self) -> Iterator["Leaf"]:
+        """Return a post-order iterator for the tree."""
+        yield self
+
+    def pre_order(self) -> Iterator["Leaf"]:
+        """Return a pre-order iterator for the tree."""
+        yield self
+
+    @property
+    def prefix(self) -> str:
+        """
+        The whitespace and comments preceding this token in the input.
+        """
+        return self._prefix
+
+    @prefix.setter
+    def prefix(self, prefix: str) -> None:
+        self.changed()
+        self._prefix = prefix
+
+
+def convert(gr: Grammar, raw_node: RawNode) -> NL:
+    """
+    Convert raw node information to a Node or Leaf instance.
+
+    This is passed to the parser driver which calls it whenever a reduction of a
+    grammar rule produces a new complete node, so that the tree is build
+    strictly bottom-up.
+    """
+    type, value, context, children = raw_node
+    if children or type in gr.number2symbol:
+        # If there's exactly one child, return that child instead of
+        # creating a new node.
+        assert children is not None
+        if len(children) == 1:
+            return children[0]
+        return Node(type, children, context=context)
+    else:
+        return Leaf(type, value or "", context=context)
+
+
+_Results = dict[str, NL]
+
+
+class BasePattern:
+    """
+    A pattern is a tree matching pattern.
+
+    It looks for a specific node type (token or symbol), and
+    optionally for a specific content.
+
+    This is an abstract base class.  There are three concrete
+    subclasses:
+
+    - LeafPattern matches a single leaf node;
+    - NodePattern matches a single node (usually non-leaf);
+    - WildcardPattern matches a sequence of nodes of variable length.
+    """
+
+    # Defaults for instance variables
+    type: Optional[int]
+    type = None  # Node type (token if < 256, symbol if >= 256)
+    content: Any = None  # Optional content matching pattern
+    name: Optional[str] = None  # Optional name used to store match in results dict
+
+    def __new__(cls, *args, **kwds):
+        """Constructor that prevents BasePattern from being instantiated."""
+        assert cls is not BasePattern, "Cannot instantiate BasePattern"
+        return object.__new__(cls)
+
+    def __repr__(self) -> str:
+        assert self.type is not None
+        args = [type_repr(self.type), self.content, self.name]
+        while args and args[-1] is None:
+            del args[-1]
+        return "{}({})".format(self.__class__.__name__, ", ".join(map(repr, args)))
+
+    def _submatch(self, node, results=None) -> bool:
+        raise NotImplementedError
+
+    def optimize(self) -> "BasePattern":
+        """
+        A subclass can define this as a hook for optimizations.
+
+        Returns either self or another node with the same effect.
+        """
+        return self
+
+    def match(self, node: NL, results: Optional[_Results] = None) -> bool:
+        """
+        Does this pattern exactly match a node?
+
+        Returns True if it matches, False if not.
+
+        If results is not None, it must be a dict which will be
+        updated with the nodes matching named subpatterns.
+
+        Default implementation for non-wildcard patterns.
+        """
+        if self.type is not None and node.type != self.type:
+            return False
+        if self.content is not None:
+            r: Optional[_Results] = None
+            if results is not None:
+                r = {}
+            if not self._submatch(node, r):
+                return False
+            if r:
+                assert results is not None
+                results.update(r)
+        if results is not None and self.name:
+            results[self.name] = node
+        return True
+
+    def match_seq(self, nodes: list[NL], results: Optional[_Results] = None) -> bool:
+        """
+        Does this pattern exactly match a sequence of nodes?
+
+        Default implementation for non-wildcard patterns.
+        """
+        if len(nodes) != 1:
+            return False
+        return self.match(nodes[0], results)
+
+    def generate_matches(self, nodes: list[NL]) -> Iterator[tuple[int, _Results]]:
+        """
+        Generator yielding all matches for this pattern.
+
+        Default implementation for non-wildcard patterns.
+        """
+        r: _Results = {}
+        if nodes and self.match(nodes[0], r):
+            yield 1, r
+
+
+class LeafPattern(BasePattern):
+    def __init__(
+        self,
+        type: Optional[int] = None,
+        content: Optional[str] = None,
+        name: Optional[str] = None,
+    ) -> None:
+        """
+        Initializer.  Takes optional type, content, and name.
+
+        The type, if given must be a token type (< 256).  If not given,
+        this matches any *leaf* node; the content may still be required.
+
+        The content, if given, must be a string.
+
+        If a name is given, the matching node is stored in the results
+        dict under that key.
+        """
+        if type is not None:
+            assert 0 <= type < 256, type
+        if content is not None:
+            assert isinstance(content, str), repr(content)
+        self.type = type
+        self.content = content
+        self.name = name
+
+    def match(self, node: NL, results=None) -> bool:
+        """Override match() to insist on a leaf node."""
+        if not isinstance(node, Leaf):
+            return False
+        return BasePattern.match(self, node, results)
+
+    def _submatch(self, node, results=None):
+        """
+        Match the pattern's content to the node's children.
+
+        This assumes the node type matches and self.content is not None.
+
+        Returns True if it matches, False if not.
+
+        If results is not None, it must be a dict which will be
+        updated with the nodes matching named subpatterns.
+
+        When returning False, the results dict may still be updated.
+        """
+        return self.content == node.value
+
+
+class NodePattern(BasePattern):
+    wildcards: bool = False
+
+    def __init__(
+        self,
+        type: Optional[int] = None,
+        content: Optional[Iterable[str]] = None,
+        name: Optional[str] = None,
+    ) -> None:
+        """
+        Initializer.  Takes optional type, content, and name.
+
+        The type, if given, must be a symbol type (>= 256).  If the
+        type is None this matches *any* single node (leaf or not),
+        except if content is not None, in which it only matches
+        non-leaf nodes that also match the content pattern.
+
+        The content, if not None, must be a sequence of Patterns that
+        must match the node's children exactly.  If the content is
+        given, the type must not be None.
+
+        If a name is given, the matching node is stored in the results
+        dict under that key.
+        """
+        if type is not None:
+            assert type >= 256, type
+        if content is not None:
+            assert not isinstance(content, str), repr(content)
+            newcontent = list(content)
+            for i, item in enumerate(newcontent):
+                assert isinstance(item, BasePattern), (i, item)
+                # I don't even think this code is used anywhere, but it does cause
+                # unreachable errors from mypy. This function's signature does look
+                # odd though *shrug*.
+                if isinstance(item, WildcardPattern):  # type: ignore[unreachable]
+                    self.wildcards = True  # type: ignore[unreachable]
+        self.type = type
+        self.content = newcontent  # TODO: this is unbound when content is None
+        self.name = name
+
+    def _submatch(self, node, results=None) -> bool:
+        """
+        Match the pattern's content to the node's children.
+
+        This assumes the node type matches and self.content is not None.
+
+        Returns True if it matches, False if not.
+
+        If results is not None, it must be a dict which will be
+        updated with the nodes matching named subpatterns.
+
+        When returning False, the results dict may still be updated.
+        """
+        if self.wildcards:
+            for c, r in generate_matches(self.content, node.children):
+                if c == len(node.children):
+                    if results is not None:
+                        results.update(r)
+                    return True
+            return False
+        if len(self.content) != len(node.children):
+            return False
+        for subpattern, child in zip(self.content, node.children):
+            if not subpattern.match(child, results):
+                return False
+        return True
+
+
+class WildcardPattern(BasePattern):
+    """
+    A wildcard pattern can match zero or more nodes.
+
+    This has all the flexibility needed to implement patterns like:
+
+    .*      .+      .?      .{m,n}
+    (a b c | d e | f)
+    (...)*  (...)+  (...)?  (...){m,n}
+
+    except it always uses non-greedy matching.
+    """
+
+    min: int
+    max: int
+
+    def __init__(
+        self,
+        content: Optional[str] = None,
+        min: int = 0,
+        max: int = HUGE,
+        name: Optional[str] = None,
+    ) -> None:
+        """
+        Initializer.
+
+        Args:
+            content: optional sequence of subsequences of patterns;
+                     if absent, matches one node;
+                     if present, each subsequence is an alternative [*]
+            min: optional minimum number of times to match, default 0
+            max: optional maximum number of times to match, default HUGE
+            name: optional name assigned to this match
+
+        [*] Thus, if content is [[a, b, c], [d, e], [f, g, h]] this is
+            equivalent to (a b c | d e | f g h); if content is None,
+            this is equivalent to '.' in regular expression terms.
+            The min and max parameters work as follows:
+                min=0, max=maxint: .*
+                min=1, max=maxint: .+
+                min=0, max=1: .?
+                min=1, max=1: .
+            If content is not None, replace the dot with the parenthesized
+            list of alternatives, e.g. (a b c | d e | f g h)*
+        """
+        assert 0 <= min <= max <= HUGE, (min, max)
+        if content is not None:
+            f = lambda s: tuple(s)
+            wrapped_content = tuple(map(f, content))  # Protect against alterations
+            # Check sanity of alternatives
+            assert len(wrapped_content), repr(
+                wrapped_content
+            )  # Can't have zero alternatives
+            for alt in wrapped_content:
+                assert len(alt), repr(alt)  # Can have empty alternatives
+        self.content = wrapped_content
+        self.min = min
+        self.max = max
+        self.name = name
+
+    def optimize(self) -> Any:
+        """Optimize certain stacked wildcard patterns."""
+        subpattern = None
+        if (
+            self.content is not None
+            and len(self.content) == 1
+            and len(self.content[0]) == 1
+        ):
+            subpattern = self.content[0][0]
+        if self.min == 1 and self.max == 1:
+            if self.content is None:
+                return NodePattern(name=self.name)
+            if subpattern is not None and self.name == subpattern.name:
+                return subpattern.optimize()
+        if (
+            self.min <= 1
+            and isinstance(subpattern, WildcardPattern)
+            and subpattern.min <= 1
+            and self.name == subpattern.name
+        ):
+            return WildcardPattern(
+                subpattern.content,
+                self.min * subpattern.min,
+                self.max * subpattern.max,
+                subpattern.name,
+            )
+        return self
+
+    def match(self, node, results=None) -> bool:
+        """Does this pattern exactly match a node?"""
+        return self.match_seq([node], results)
+
+    def match_seq(self, nodes, results=None) -> bool:
+        """Does this pattern exactly match a sequence of nodes?"""
+        for c, r in self.generate_matches(nodes):
+            if c == len(nodes):
+                if results is not None:
+                    results.update(r)
+                    if self.name:
+                        results[self.name] = list(nodes)
+                return True
+        return False
+
+    def generate_matches(self, nodes) -> Iterator[tuple[int, _Results]]:
+        """
+        Generator yielding matches for a sequence of nodes.
+
+        Args:
+            nodes: sequence of nodes
+
+        Yields:
+            (count, results) tuples where:
+            count: the match comprises nodes[:count];
+            results: dict containing named submatches.
+        """
+        if self.content is None:
+            # Shortcut for special case (see __init__.__doc__)
+            for count in range(self.min, 1 + min(len(nodes), self.max)):
+                r = {}
+                if self.name:
+                    r[self.name] = nodes[:count]
+                yield count, r
+        elif self.name == "bare_name":
+            yield self._bare_name_matches(nodes)
+        else:
+            # The reason for this is that hitting the recursion limit usually
+            # results in some ugly messages about how RuntimeErrors are being
+            # ignored. We only have to do this on CPython, though, because other
+            # implementations don't have this nasty bug in the first place.
+            if hasattr(sys, "getrefcount"):
+                save_stderr = sys.stderr
+                sys.stderr = StringIO()
+            try:
+                for count, r in self._recursive_matches(nodes, 0):
+                    if self.name:
+                        r[self.name] = nodes[:count]
+                    yield count, r
+            except RuntimeError:
+                # We fall back to the iterative pattern matching scheme if the recursive
+                # scheme hits the recursion limit.
+                for count, r in self._iterative_matches(nodes):
+                    if self.name:
+                        r[self.name] = nodes[:count]
+                    yield count, r
+            finally:
+                if hasattr(sys, "getrefcount"):
+                    sys.stderr = save_stderr
+
+    def _iterative_matches(self, nodes) -> Iterator[tuple[int, _Results]]:
+        """Helper to iteratively yield the matches."""
+        nodelen = len(nodes)
+        if 0 >= self.min:
+            yield 0, {}
+
+        results = []
+        # generate matches that use just one alt from self.content
+        for alt in self.content:
+            for c, r in generate_matches(alt, nodes):
+                yield c, r
+                results.append((c, r))
+
+        # for each match, iterate down the nodes
+        while results:
+            new_results = []
+            for c0, r0 in results:
+                # stop if the entire set of nodes has been matched
+                if c0 < nodelen and c0 <= self.max:
+                    for alt in self.content:
+                        for c1, r1 in generate_matches(alt, nodes[c0:]):
+                            if c1 > 0:
+                                r = {}
+                                r.update(r0)
+                                r.update(r1)
+                                yield c0 + c1, r
+                                new_results.append((c0 + c1, r))
+            results = new_results
+
+    def _bare_name_matches(self, nodes) -> tuple[int, _Results]:
+        """Special optimized matcher for bare_name."""
+        count = 0
+        r = {}  # type: _Results
+        done = False
+        max = len(nodes)
+        while not done and count < max:
+            done = True
+            for leaf in self.content:
+                if leaf[0].match(nodes[count], r):
+                    count += 1
+                    done = False
+                    break
+        assert self.name is not None
+        r[self.name] = nodes[:count]
+        return count, r
+
+    def _recursive_matches(self, nodes, count) -> Iterator[tuple[int, _Results]]:
+        """Helper to recursively yield the matches."""
+        assert self.content is not None
+        if count >= self.min:
+            yield 0, {}
+        if count < self.max:
+            for alt in self.content:
+                for c0, r0 in generate_matches(alt, nodes):
+                    for c1, r1 in self._recursive_matches(nodes[c0:], count + 1):
+                        r = {}
+                        r.update(r0)
+                        r.update(r1)
+                        yield c0 + c1, r
+
+
+class NegatedPattern(BasePattern):
+    def __init__(self, content: Optional[BasePattern] = None) -> None:
+        """
+        Initializer.
+
+        The argument is either a pattern or None.  If it is None, this
+        only matches an empty sequence (effectively '$' in regex
+        lingo).  If it is not None, this matches whenever the argument
+        pattern doesn't have any matches.
+        """
+        if content is not None:
+            assert isinstance(content, BasePattern), repr(content)
+        self.content = content
+
+    def match(self, node, results=None) -> bool:
+        # We never match a node in its entirety
+        return False
+
+    def match_seq(self, nodes, results=None) -> bool:
+        # We only match an empty sequence of nodes in its entirety
+        return len(nodes) == 0
+
+    def generate_matches(self, nodes: list[NL]) -> Iterator[tuple[int, _Results]]:
+        if self.content is None:
+            # Return a match if there is an empty sequence
+            if len(nodes) == 0:
+                yield 0, {}
+        else:
+            # Return a match if the argument pattern has no matches
+            for c, r in self.content.generate_matches(nodes):
+                return
+            yield 0, {}
+
+
+def generate_matches(
+    patterns: list[BasePattern], nodes: list[NL]
+) -> Iterator[tuple[int, _Results]]:
+    """
+    Generator yielding matches for a sequence of patterns and nodes.
+
+    Args:
+        patterns: a sequence of patterns
+        nodes: a sequence of nodes
+
+    Yields:
+        (count, results) tuples where:
+        count: the entire sequence of patterns matches nodes[:count];
+        results: dict containing named submatches.
+    """
+    if not patterns:
+        yield 0, {}
+    else:
+        p, rest = patterns[0], patterns[1:]
+        for c0, r0 in p.generate_matches(nodes):
+            if not rest:
+                yield c0, r0
+            else:
+                for c1, r1 in generate_matches(rest, nodes[c0:]):
+                    r = {}
+                    r.update(r0)
+                    r.update(r1)
+                    yield c0 + c1, r