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

2 files changed, 11 insertions, 3 deletions

diff --git a/Include/Python-ast.h b/Include/Python-ast.h
index 175e380..1ab376a 100644
--- a/Include/Python-ast.h
+++ b/Include/Python-ast.h
@@ -202,9 +202,9 @@ enum _expr_kind {BoolOp_kind=1, BinOp_kind=2, UnaryOp_kind=3, Lambda_kind=4,
                   Await_kind=12, Yield_kind=13, YieldFrom_kind=14,
                   Compare_kind=15, Call_kind=16, Num_kind=17, Str_kind=18,
                   FormattedValue_kind=19, JoinedStr_kind=20, Bytes_kind=21,
-                  NameConstant_kind=22, Ellipsis_kind=23, Attribute_kind=24,
-                  Subscript_kind=25, Starred_kind=26, Name_kind=27,
-                  List_kind=28, Tuple_kind=29};
+                  NameConstant_kind=22, Ellipsis_kind=23, Constant_kind=24,
+                  Attribute_kind=25, Subscript_kind=26, Starred_kind=27,
+                  Name_kind=28, List_kind=29, Tuple_kind=30};
 struct _expr {
     enum _expr_kind kind;
     union {
@@ -316,6 +316,10 @@ struct _expr {
         } NameConstant;
         
         struct {
+            constant value;
+        } Constant;
+        
+        struct {
             expr_ty value;
             identifier attr;
             expr_context_ty ctx;
@@ -567,6 +571,9 @@ expr_ty _Py_NameConstant(singleton value, int lineno, int col_offset, PyArena
                          *arena);
 #define Ellipsis(a0, a1, a2) _Py_Ellipsis(a0, a1, a2)
 expr_ty _Py_Ellipsis(int lineno, int col_offset, PyArena *arena);
+#define Constant(a0, a1, a2, a3) _Py_Constant(a0, a1, a2, a3)
+expr_ty _Py_Constant(constant value, int lineno, int col_offset, PyArena
+                     *arena);
 #define Attribute(a0, a1, a2, a3, a4, a5) _Py_Attribute(a0, a1, a2, a3, a4, a5)
 expr_ty _Py_Attribute(expr_ty value, identifier attr, expr_context_ty ctx, int
                       lineno, int col_offset, PyArena *arena);
diff --git a/Include/asdl.h b/Include/asdl.h
index 495153c..35e9fa1 100644
--- a/Include/asdl.h
+++ b/Include/asdl.h
@@ -6,6 +6,7 @@ typedef PyObject * string;
 typedef PyObject * bytes;
 typedef PyObject * object;
 typedef PyObject * singleton;
+typedef PyObject * constant;
 
 /* It would be nice if the code generated by asdl_c.py was completely
    independent of Python, but it is a goal the requires too much work