gh-103763: Implement PEP 695 (#103764)

This implements PEP 695, Type Parameter Syntax. It adds support for:

- Generic functions (def func[T](): ...)
- Generic classes (class X[T](): ...)
- Type aliases (type X = ...)
- New scoping when the new syntax is used within a class body
- Compiler and interpreter changes to support the new syntax and scoping rules 

Co-authored-by: Marc Mueller <30130371+cdce8p@users.noreply.github.com>
Co-authored-by: Eric Traut <eric@traut.com>
Co-authored-by: Larry Hastings <larry@hastings.org>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

1 files changed, 18 insertions, 3 deletions

diff --git a/Include/internal/pycore_symtable.h b/Include/internal/pycore_symtable.h
index 9a005be..3fa825d 100644
--- a/Include/internal/pycore_symtable.h
+++ b/Include/internal/pycore_symtable.h
@@ -10,8 +10,17 @@ extern "C" {
 
 struct _mod;   // Type defined in pycore_ast.h
 
-typedef enum _block_type { FunctionBlock, ClassBlock, ModuleBlock, AnnotationBlock }
-    _Py_block_ty;
+typedef enum _block_type {
+    FunctionBlock, ClassBlock, ModuleBlock,
+    // Used for annotations if 'from __future__ import annotations' is active.
+    // Annotation blocks cannot bind names and are not evaluated.
+    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.
+    TypeVarBoundBlock, TypeAliasBlock, TypeParamBlock
+} _Py_block_ty;
 
 typedef enum _comprehension_type {
     NoComprehension = 0,
@@ -49,7 +58,7 @@ typedef struct _symtable_entry {
     PyObject *ste_varnames;  /* list of function parameters */
     PyObject *ste_children;  /* list of child blocks */
     PyObject *ste_directives;/* locations of global and nonlocal statements */
-    _Py_block_ty ste_type;   /* module, class, function or annotation */
+    _Py_block_ty ste_type;
     int ste_nested;      /* true if block is nested */
     unsigned ste_free : 1;        /* true if block has free variables */
     unsigned ste_child_free : 1;  /* true if a child block has free vars,
@@ -64,8 +73,12 @@ typedef struct _symtable_entry {
     unsigned ste_needs_class_closure : 1; /* for class scopes, true if a
                                              closure over __class__
                                              should be created */
+    unsigned ste_needs_classdict : 1; /* for class scopes, true if a closure
+                                         over the class dict should be created */
     unsigned ste_comp_inlined : 1; /* true if this comprehension is inlined */
     unsigned ste_comp_iter_target : 1; /* true if visiting comprehension target */
+    unsigned ste_can_see_class_scope : 1; /* true if this block can see names bound in an
+                                             enclosing class scope */
     int ste_comp_iter_expr; /* non-zero if visiting a comprehension range expression */
     int ste_lineno;          /* first line of block */
     int ste_col_offset;      /* offset of first line of block */
@@ -82,6 +95,7 @@ extern PyTypeObject PySTEntry_Type;
 
 extern long _PyST_GetSymbol(PySTEntryObject *, PyObject *);
 extern int _PyST_GetScope(PySTEntryObject *, PyObject *);
+extern int _PyST_IsFunctionLike(PySTEntryObject *);
 
 extern struct symtable* _PySymtable_Build(
     struct _mod *mod,
@@ -105,6 +119,7 @@ extern PyObject* _Py_Mangle(PyObject *p, PyObject *name);
 #define DEF_IMPORT 2<<6        /* assignment occurred via import */
 #define DEF_ANNOT 2<<7         /* this name is annotated */
 #define DEF_COMP_ITER 2<<8     /* this name is a comprehension iteration variable */
+#define DEF_TYPE_PARAM 2<<9    /* this name is a type parameter */
 
 #define DEF_BOUND (DEF_LOCAL | DEF_PARAM | DEF_IMPORT)