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.