Issue #22364: Improved some re error messages using regex for hints.

Lib/re.py

@@ -286,7 +286,7 @@ def _compile(pattern, flags):
     if isinstance(pattern, _pattern_type):
         if flags:
             raise ValueError(
-                "Cannot process flags argument with a compiled pattern")
+                "cannot process flags argument with a compiled pattern")
         return pattern
     if not sre_compile.isstring(pattern):
         raise TypeError("first argument must be string or compiled pattern")

Lib/sre_compile.py

@@ -113,7 +113,7 @@ def _compile(code, pattern, flags):
                 emit(ANY)
         elif op in REPEATING_CODES:
             if flags & SRE_FLAG_TEMPLATE:
-                raise error("internal: unsupported template operator")
+                raise error("internal: unsupported template operator %r" % (op,))
             elif _simple(av) and op is not REPEAT:
                 if op is MAX_REPEAT:
                     emit(REPEAT_ONE)
@@ -216,7 +216,7 @@ def _compile(code, pattern, flags):
             else:
                 code[skipyes] = _len(code) - skipyes + 1
         else:
-            raise ValueError("unsupported operand type", op)
+            raise error("internal: unsupported operand type %r" % (op,))
 
 def _compile_charset(charset, flags, code, fixup=None, fixes=None):
     # compile charset subprogram
@@ -242,7 +242,7 @@ def _compile_charset(charset, flags, code, fixup=None, fixes=None):
             else:
                 emit(av)
         else:
-            raise error("internal: unsupported set operator")
+            raise error("internal: unsupported set operator %r" % (op,))
     emit(FAILURE)
 
 def _optimize_charset(charset, fixup, fixes):

Misc/NEWS

@@ -30,6 +30,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #22364: Improved some re error messages using regex for hints.
+
 - Issue #23742: ntpath.expandvars() no longer loses unbalanced single quotes.
 
 - Issue #21717: The zipfile.ZipFile.open function now supports 'x' (exclusive

Modules/_sre.c

@@ -315,7 +315,7 @@ getstring(PyObject* string, Py_ssize_t* p_length,
 
     /* get pointer to byte string buffer */
     if (PyObject_GetBuffer(string, view, PyBUF_SIMPLE) != 0) {
-        PyErr_SetString(PyExc_TypeError, "expected string or buffer");
+        PyErr_SetString(PyExc_TypeError, "expected string or bytes-like object");
         return NULL;
     }
 
@@ -359,12 +359,12 @@ state_init(SRE_STATE* state, PatternObject* pattern, PyObject* string,
 
     if (isbytes && pattern->isbytes == 0) {
         PyErr_SetString(PyExc_TypeError,
-                        "can't use a string pattern on a bytes-like object");
+                        "cannot use a string pattern on a bytes-like object");
         goto err;
     }
     if (!isbytes && pattern->isbytes > 0) {
         PyErr_SetString(PyExc_TypeError,
-                        "can't use a bytes pattern on a string-like object");
+                        "cannot use a bytes pattern on a string-like object");
         goto err;
     }