* Add new capability to the PEG parser to type variable assignments. For instance:
```
| a[asdl_stmt_seq*]=';'.small_stmt+ [';'] NEWLINE { a }
```
* Add new sequence types from the asdl definition (automatically generated)
* Make `asdl_seq` type a generic aliasing pointer type.
* Create a new `asdl_generic_seq` for the generic case using `void*`.
* The old `asdl_seq_GET`/`ast_seq_SET` macros now are typed.
* New `asdl_seq_GET_UNTYPED`/`ast_seq_SET_UNTYPED` macros for dealing with generic sequences.
* Changes all possible `asdl_seq` types to use specific versions everywhere.
GCC says
```
../cpython/Parser/string_parser.c: In function ‘fstring_find_expr’:
../cpython/Parser/string_parser.c:404:93: warning: ‘cols’ may be used uninitialized in this function [-Wmaybe-uninitialized]
404 | p2->starting_col_offset = p->tok->first_lineno == p->tok->lineno ? t->col_offset + cols : cols;
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
../cpython/Parser/string_parser.c:384:16: note: ‘cols’ was declared here
384 | int lines, cols;
| ^~~~
../cpython/Parser/string_parser.c:403:45: warning: ‘lines’ may be used uninitialized in this function [-Wmaybe-uninitialized]
403 | p2->starting_lineno = t->lineno + lines - 1;
| ~~~~~~~~~~~~~~~~~~^~~
../cpython/Parser/string_parser.c:384:9: note: ‘lines’ was declared here
384 | int lines, cols;
| ^~~~~
```
and, indeed, if `PyBytes_AsString` somehow fails, lines & cols will not be initialized.
This commit changes the parsing of f-string expressions with the new parser. The parser gets pre-fed with the location of the expression itself (not the f-string, which was what we were doing before). This allows us to completely skip the shifting of the AST nodes after the parsing is completed.
This commit removes the old parser, the deprecated parser module, the old parser compatibility flags and environment variables and all associated support code and documentation.
Pablo Galindo
Eric V. Smith
Benjamin Peterson
Lysandros Nikolaou