bpo-46042: Improve SyntaxError locations in the symbol table (GH-30059)

Author: pablogsal

Include/internal/pycore_symtable.h

@@ -13,6 +13,13 @@ struct _mod; // Type defined in pycore_ast.h
 typedef enum _block_type { FunctionBlock, ClassBlock, ModuleBlock, AnnotationBlock }
  _Py_block_ty;
 
+typedef enum _comprehension_type {
+ NoComprehension = 0,
+ ListComprehension = 1,
+ DictComprehension = 2,
+ SetComprehension = 3,
+ GeneratorExpression = 4 } _Py_comprehension_ty;
+
 struct _symtable_entry;
 
 struct symtable {
@@ -42,14 +49,14 @@ 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, or function */
+ _Py_block_ty ste_type; /* module, class or function */
  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,
  including free refs to globals */
  unsigned ste_generator : 1; /* true if namespace is a generator */
  unsigned ste_coroutine : 1; /* true if namespace is a coroutine */
- unsigned ste_comprehension : 1; /* true if namespace is a list comprehension */
+ _Py_comprehension_ty ste_comprehension; /* Kind of comprehension (if any) */
  unsigned ste_varargs : 1; /* true if block has varargs */
  unsigned ste_varkeywords : 1; /* true if block has varkeywords */
  unsigned ste_returns_value : 1; /* true if namespace uses return with

Lib/test/test_exceptions.py

@@ -268,9 +268,10 @@ def baz():
  check(b"\xef\xbb\xbf#coding: utf8\nprint('\xe6\x88\x91')\n", 0, -1)
 
  # Errors thrown by symtable.c
- check('x = [(yield i) for i in range(3)]', 1, 5)
- check('def f():\n from _ import *', 1, 1)
- check('def f(x, x):\n pass', 1, 1)
+ check('x = [(yield i) for i in range(3)]', 1, 7)
+ check('def f():\n from _ import *', 2, 17)
+ check('def f(x, x):\n pass', 1, 10)
+ check('{i for i in range(5) if (j := 0) for j in range(5)}', 1, 38)
  check('def f(x):\n nonlocal x', 2, 3)
  check('def f(x):\n x = 1\n global x', 3, 3)
  check('nonlocal x', 1, 1)

Misc/NEWS.d/next/Core and Builtins/2021-12-11-17-40-34.bpo-46042.aqYxku.rst

@@ -0,0 +1,2 @@
+Improve the location of the caret in :exc:`SyntaxError` exceptions emitted
+by the symbol table. Patch by Pablo Galindo.