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>

Author: 5 people

Doc/library/ast.rst

@@ -1724,6 +1724,7 @@ Function and class definitions
  body=[
  FunctionDef(
  name='f',
+ typeparams=[],
  args=arguments(
  posonlyargs=[],
  args=[
@@ -1847,6 +1848,7 @@ Function and class definitions
  body=[
  ClassDef(
  name='Foo',
+ typeparams=[],
  bases=[
  Name(id='base1', ctx=Load()),
  Name(id='base2', ctx=Load())],
@@ -1885,6 +1887,7 @@ Async and await
  body=[
  AsyncFunctionDef(
  name='f',
+ typeparams=[],
  args=arguments(
  posonlyargs=[],
  args=[],

Grammar/python.gram

@@ -112,6 +112,7 @@ simple_stmts[asdl_stmt_seq*]:
 # will throw a SyntaxError.
 simple_stmt[stmt_ty] (memo):
  | assignment
+ | &"type" type_alias
  | e=star_expressions { _PyAST_Expr(e, EXTRA) }
  | &'return' return_stmt
  | &('import' | 'from') import_stmt
@@ -252,8 +253,8 @@ class_def[stmt_ty]:
 
 class_def_raw[stmt_ty]:
  | invalid_class_def_raw
- | 'class' a=NAME b=['(' z=[arguments] ')' { z }] ':' c=block {
- _PyAST_ClassDef(a->v.Name.id,
+ | 'class' a=NAME t=[type_params] b=['(' z=[arguments] ')' { z }] ':' c=block {
+ _PyAST_ClassDef(a->v.Name.id, t,
  (b) ? ((expr_ty) b)->v.Call.args : NULL,
  (b) ? ((expr_ty) b)->v.Call.keywords : NULL,
  c, NULL, EXTRA) }
@@ -267,16 +268,16 @@ function_def[stmt_ty]:
 
 function_def_raw[stmt_ty]:
  | invalid_def_raw
- | 'def' n=NAME &&'(' params=[params] ')' a=['->' z=expression { z }] &&':' tc=[func_type_comment] b=block {
- _PyAST_FunctionDef(n->v.Name.id,
+ | 'def' n=NAME t=[type_params] &&'(' params=[params] ')' a=['->' z=expression { z }] &&':' tc=[func_type_comment] b=block {
+ _PyAST_FunctionDef(n->v.Name.id, t,
  (params) ? params : CHECK(arguments_ty, _PyPegen_empty_arguments(p)),
  b, NULL, a, NEW_TYPE_COMMENT(p, tc), EXTRA) }
- | ASYNC 'def' n=NAME &&'(' params=[params] ')' a=['->' z=expression { z }] &&':' tc=[func_type_comment] b=block {
+ | ASYNC 'def' n=NAME t=[type_params] &&'(' params=[params] ')' a=['->' z=expression { z }] &&':' tc=[func_type_comment] b=block {
  CHECK_VERSION(
  stmt_ty,
  5,
  "Async functions are",
- _PyAST_AsyncFunctionDef(n->v.Name.id,
+ _PyAST_AsyncFunctionDef(n->v.Name.id, t,
  (params) ? params : CHECK(arguments_ty, _PyPegen_empty_arguments(p)),
  b, NULL, a, NEW_TYPE_COMMENT(p, tc), EXTRA)
  ) }
@@ -628,6 +629,39 @@ keyword_patterns[asdl_seq*]:
 keyword_pattern[KeyPatternPair*]:
  | arg=NAME '=' value=pattern { _PyPegen_key_pattern_pair(p, arg, value) }
 
+# Type statement
+# ---------------
+
+type_alias[stmt_ty]:
+ | "type" n=NAME t=[type_params] '=' b=expression {
+ CHECK_VERSION(stmt_ty, 12, "Type statement is",
+ _PyAST_TypeAlias(CHECK(expr_ty, _PyPegen_set_expr_context(p, n, Store)), t, b, EXTRA)) }
+
+# Type parameter declaration
+# --------------------------
+
+type_params[asdl_typeparam_seq*]: '[' t=type_param_seq ']' {
+ CHECK_VERSION(asdl_typeparam_seq *, 12, "Type parameter lists are", t) }
+
+type_param_seq[asdl_typeparam_seq*]: a[asdl_typeparam_seq*]=','.type_param+ [','] { a }
+
+type_param[typeparam_ty] (memo):
+ | a=NAME b=[type_param_bound] { _PyAST_TypeVar(a->v.Name.id, b, EXTRA) }
+ | '*' a=NAME colon=":" e=expression {
+ RAISE_SYNTAX_ERROR_STARTING_FROM(colon, e->kind == Tuple_kind
+ ? "cannot use constraints with TypeVarTuple"
+ : "cannot use bound with TypeVarTuple")
+ }
+ | '*' a=NAME { _PyAST_TypeVarTuple(a->v.Name.id, EXTRA) }
+ | '**' a=NAME colon=":" e=expression {
+ RAISE_SYNTAX_ERROR_STARTING_FROM(colon, e->kind == Tuple_kind
+ ? "cannot use constraints with ParamSpec"
+ : "cannot use bound with ParamSpec")
+ }
+ | '**' a=NAME { _PyAST_ParamSpec(a->v.Name.id, EXTRA) }
+
+type_param_bound[expr_ty]: ":" e=expression { e }
+
 # EXPRESSIONS
 # -----------
 

Include/cpython/funcobject.h

@@ -41,6 +41,7 @@ typedef struct {
  PyObject *func_weakreflist; /* List of weak references */
  PyObject *func_module; /* The __module__ attribute, can be anything */
  PyObject *func_annotations; /* Annotations, a dict or NULL */
+ PyObject *func_typeparams; /* Tuple of active type variables or NULL */
  vectorcallfunc vectorcall;
  /* Version number for use by specializer.
  * Can set to non-zero when we want to specialize.

Include/internal/pycore_ast.h

@@ -17,6 +17,8 @@ struct _py_func_state {
 extern PyFunctionObject* _PyFunction_FromConstructor(PyFrameConstructor *constr);
 
 extern uint32_t _PyFunction_GetVersionForCurrentState(PyFunctionObject *func);
+extern PyObject *_Py_set_function_type_params(
+ PyThreadState* unused, PyObject *func, PyObject *type_params);
 
 #ifdef __cplusplus
 }

Include/internal/pycore_ast_state.h

@@ -68,6 +68,14 @@ struct _Py_interp_cached_objects {
  PyObject *type_slots_pname;
  pytype_slotdef *type_slots_ptrs[MAX_EQUIV];
 
+ /* TypeVar and related types */
+ PyTypeObject *generic_type;
+ PyTypeObject *typevar_type;
+ PyTypeObject *typevartuple_type;
+ PyTypeObject *paramspec_type;
+ PyTypeObject *paramspecargs_type;
+ PyTypeObject *paramspeckwargs_type;
+ PyTypeObject *typealias_type;
 };
 
 #define _Py_INTERP_STATIC_OBJECT(interp, NAME) \