address isinstance false negative when provided too many arguments

Author: rogersheu

doc/whatsnew/fragments/9847.false_negative

@@ -0,0 +1,4 @@
+Fix a false negative when `isinstance` has too many arguments.
+Change now provides a `too-many-arguments` output with behavior similar to other `too-many-arguments` calls.
+
+Closes #9847

pylint/checkers/typecheck.py

@@ -1420,8 +1420,16 @@ def _check_argument_order(
             self.add_message("arguments-out-of-order", node=node, args=())
 
     def _check_isinstance_args(self, node: nodes.Call) -> None:
-        if len(node.args) != 2:
-            # isinstance called with wrong number of args
+        if len(node.args) > 2:
+            # for when isinstance called with too many args
+            self.add_message(
+                "too-many-arguments",
+                node=node,
+                args=(len(node.args), 2),
+                confidence=HIGH,
+            )
+        elif len(node.args) < 2:
+            # not currently handling the too few args case
             return
 
         second_arg = node.args[1]

tests/functional/t/too/too_many_arguments.py

@@ -36,3 +36,8 @@ def func_call():
 # +1: [too-many-arguments]
 def name1(param1, param2, param3, /, param4, param5, *args, param6="apple", **kwargs):
     return param1, param2, param3, param4, param5, param6, args, kwargs
+
+
+# Negative case, see `_check_isinstance_args` in `./pylint/checkers/typecheck.py`
+isinstance(1, int, int) # [too-many-arguments]
+isinstance(1, 1, int) # [too-many-arguments, isinstance-second-argument-not-valid-type]

tests/functional/t/too/too_many_arguments.txt

@@ -1,3 +1,6 @@
 too-many-arguments:4:0:4:19:stupid_function:Too many arguments (9/5):UNDEFINED
 too-many-positional-arguments:4:0:4:19:stupid_function:Too many positional arguments (9/5):HIGH
 too-many-arguments:37:0:37:9:name1:Too many arguments (6/5):UNDEFINED
+too-many-arguments:42:0:42:23::Too many arguments (3/2):HIGH
+isinstance-second-argument-not-valid-type:43:0:43:21::Second argument of isinstance is not a type:INFERENCE
+too-many-arguments:43:0:43:21::Too many arguments (3/2):HIGH