Fix UnicodeDecodeError.object inferred as str instead of bytes (#2358)

Author: JulianJvn

ChangeLog

@@ -22,6 +22,11 @@ What's New in astroid 3.0.3?
 ============================
 Release date: TBA
 
+
+* Fix type of ``UnicodeDecodeError.object`` inferred as ``str`` instead of ``bytes``.
+
+  Closes pylint-dev/pylint#9342
+
 * Fix ``no-member`` false positives for ``args`` and ``kwargs`` on ``ParamSpec`` under Python 3.12.
 
   Closes pylint-dev/pylint#9401

astroid/interpreter/objectmodel.py

@@ -818,7 +818,7 @@ def attr_path(self):
 class UnicodeDecodeErrorInstanceModel(ExceptionInstanceModel):
     @property
     def attr_object(self):
-        return node_classes.Const("")
+        return node_classes.Const(b"")
 
 
 BUILTIN_EXCEPTIONS = {

tests/test_object_model.py

@@ -742,13 +742,14 @@ def test_oserror(self) -> None:
     def test_unicodedecodeerror(self) -> None:
         code = """
         try:
-            raise UnicodeDecodeError("utf-8", "blob", 0, 1, "reason")
+            raise UnicodeDecodeError("utf-8", b"blob", 0, 1, "reason")
         except UnicodeDecodeError as error:
-            error.object[:1] #@
+            error.object #@
         """
         node = builder.extract_node(code)
         inferred = next(node.infer())
         assert isinstance(inferred, astroid.Const)
+        assert inferred.value == b""
 
     def test_import_error(self) -> None:
         ast_nodes = builder.extract_node(