Symbol table for type parameter (PEP 695) raises AssertionError on get_type()

[wookayin]

Bug report

Bug description:

Tested with CPython 3.12.0rc3

import symtable

def foo[T]():
    return "bar"

t_mod = symtable.symtable("""\
def foo[T]():
    return "bar"
""", '?', 'exec')

t_T = t_mod.get_children()[0]
print(t_T.get_type())

Traceback (most recent call last):
   File ".../bug_symtable.py", line 12, in <module>
     print(t_T.get_type())
           ^^^^^^^^^^^^^^
   File ".../3.12.0rc3/lib/python3.12/symtable.py", line 74, in get_type
     assert self._table.type in (1, 2, 3), \
 AssertionError: unexpected type: 6
 [Finished in 1 seconds with code 1]

The symbol table for type parameters (generic) seem to have a new type, but it appears that the symtable implementation was not updated accordingly. Also there is no _symtable.TYPE_* constant for type code 6 (see _symtable).

https://github.com/python/cpython/blob/3.12/Lib/symtable.py#L62-L75
https://github.com/python/cpython/blob/main/Lib/symtable.py#L62-L75

There are new block types introduced by PEP 695 https://github.com/python/cpython/blob/3.12/Include/internal/pycore_symtable.h#L13-L23

- 0: FunctionBlock
- 1: ClassBlock
- 2: ModuleBlock

    // Used for annotations 'from __future__ import annotations' 
- 3: AnnotationBlock

    // Used for generics and type aliases. These work mostly like functions
    // (see PEP 695 for details). The three different blocks function identically;
    // they are different enum entries only so that error messages can be more
    // precise.
- 4: TypeVarBoundBlock
- 5: TypeAliasBlock
- 6: TypeParamBlock

https://github.com/python/cpython/blob/3.12/Include/internal/pycore_symtable.h#L13-L23

Hope this can be fixed by the 3.12 GA release.

CPython versions tested on:

3.12.0rc3

Operating systems tested on:

macOS

Linked PRs

• gh-110045: Update symtable module for PEP 695 #110066
• [3.12] gh-110045: Update symtable module for PEP 695 (GH-110066) #110070

[AlexWaygood]

Cc. @JelleZijlstra @carljm

[terryjreedy]

Same error on Windows 10 and main.