Add ast.Constant

Issue #26146: Add a new kind of AST node: ast.Constant. It can be used by
external AST optimizers, but the compiler does not emit directly such node.

An optimizer can replace the following AST nodes with ast.Constant:

* ast.NameConstant: None, False, True
* ast.Num: int, float, complex
* ast.Str: str
* ast.Bytes: bytes
* ast.Tuple if items are constants too: tuple
* frozenset

Update code to accept ast.Constant instead of ast.Num and/or ast.Str:

* compiler
* docstrings
* ast.literal_eval()
* Tools/parser/unparse.py

1 files changed, 4 insertions, 0 deletions

diff --git a/Misc/NEWS b/Misc/NEWS
index 676f2ca..6e1a5a0 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,10 @@ Release date: tba
 Core and Builtins
 -----------------
 
+- Issue #26146: Add a new kind of AST node: ``ast.Constant``. It can be used
+  by external AST optimizers, but the compiler does not emit directly such
+  node.
+
 - Issue #18018: Import raises ImportError instead of SystemError if a relative
   import is attempted without a known parent package.