As I found when writing the class decorator patch PEP 306 hasn't been updated since the new AST was added. Here is a suggested replacement block for the Checklist section. AST hackers feel free to make suggestions. Checklist __ Grammar/Grammar: OK, you'd probably worked this one out :) __ Parser/Python.asdl may need changes to match the Grammar. Use Parser/asdl_c.py to regenerate Include/Python-ast.h __ Python/Python-ast.c may need changes to create the AST objects involved with the Grammar change. Lib/compiler/ast.py will need matching changes to the pure-python AST objects. __ Parser/pgen needs to be rerun to regenerate Include/graminit.h and Include/graminit.c __ Python/compile.c: You will need to create or modify the compiler_* functions for your productions. __ You may need to regenerate Lib/symbol.py and/or Lib/token.py and/or Lib/keyword.py __ The parser module. Add some of your new syntax to test_parser, bang on parsermodule.c until it passes. __ The compiler package. A good test is to compile the standard library and test suite with the compiler package and then check it runs. You did add some of your new syntax to the test suite, didn't you? There's a script in Tools/compiler that does this. __ If you've gone so far as to change the token structure of Python, then the tokenizer library module will need to be changed. __ Certain changes may require tweaks to the library module pyclbr. __ Documentation must be written!