Fix a crash on psycopg2 for elif used

ChangeLog

@@ -17,6 +17,11 @@ Release date: TBA
 
 * Fix ``install graphiz`` message which isn't needed for puml output format.
 
+* Fix a crash in the ``check_elif`` extensions where an undetected if in a comprehension
+  with an if statement within a f-string resulted in an out of range error. The checker no
+  longer relies on counting if statements anymore and uses known if statements locations instead.
+  It should not crash on badly parsed if statements anymore.
+
 * Fix ``simplify-boolean-expression`` when condition can be inferred as False.
 
   Closes #5200

pylint/checkers/classes.py

@@ -1848,20 +1848,18 @@ def _check_first_arg_for_type(self, node, metaclass=0):
                     "bad-mcs-method-argument",
                     node.name,
                 )
-        # regular class
-        else:  # pylint: disable=else-if-used
-            # class method
-            if node.type == "classmethod" or node.name == "__class_getitem__":
-                self._check_first_arg_config(
-                    first,
-                    self.config.valid_classmethod_first_arg,
-                    node,
-                    "bad-classmethod-argument",
-                    node.name,
-                )
-            # regular method without self as argument
-            elif first != "self":
-                self.add_message("no-self-argument", node=node)
+        # regular class with class method
+        elif node.type == "classmethod" or node.name == "__class_getitem__":
+            self._check_first_arg_config(
+                first,
+                self.config.valid_classmethod_first_arg,
+                node,
+                "bad-classmethod-argument",
+                node.name,
+            )
+        # regular class with regular method without self as argument
+        elif first != "self":
+            self.add_message("no-self-argument", node=node)
 
     def _check_first_arg_config(self, first, config, node, message, method_name):
         if first not in config:

pylint/extensions/check_elif.py

@@ -15,7 +15,7 @@
 
 from pylint.checkers import BaseTokenChecker
 from pylint.checkers.utils import check_messages
-from pylint.interfaces import IAstroidChecker, ITokenChecker
+from pylint.interfaces import HIGH, IAstroidChecker, ITokenChecker
 
 
 class ElseifUsedChecker(BaseTokenChecker):
@@ -38,37 +38,27 @@ def __init__(self, linter=None):
         self._init()
 
     def _init(self):
-        self._elifs = []
-        self._if_counter = 0
+        self._elifs = {}
 
     def process_tokens(self, tokens):
-        # Process tokens and look for 'if' or 'elif'
-        for _, token, _, _, _ in tokens:
-            if token == "elif":
-                self._elifs.append(True)
-            elif token == "if":
-                self._elifs.append(False)
+        """Process tokens and look for 'if' or 'elif'"""
+        self._elifs = {
+            begin: token for _, token, begin, _, _ in tokens if token in {"elif", "if"}
+        }
 
     def leave_module(self, _: nodes.Module) -> None:
         self._init()
 
-    def visit_ifexp(self, node: nodes.IfExp) -> None:
-        if isinstance(node.parent, nodes.FormattedValue):
-            return
-        self._if_counter += 1
-
-    def visit_comprehension(self, node: nodes.Comprehension) -> None:
-        self._if_counter += len(node.ifs)
-
     @check_messages("else-if-used")
     def visit_if(self, node: nodes.If) -> None:
-        if isinstance(node.parent, nodes.If):
-            orelse = node.parent.orelse
-            # current if node must directly follow an "else"
-            if orelse and orelse == [node]:
-                if not self._elifs[self._if_counter]:
-                    self.add_message("else-if-used", node=node)
-        self._if_counter += 1
+        """Current if node must directly follow an 'else'"""
+        if (
+            isinstance(node.parent, nodes.If)
+            and node.parent.orelse == [node]
+            and (node.lineno, node.col_offset) in self._elifs
+            and self._elifs[(node.lineno, node.col_offset)] == "if"
+        ):
+            self.add_message("else-if-used", node=node, confidence=HIGH)
 
 
 def register(linter):

tests/functional/ext/check_elif/check_elif.py

@@ -1,4 +1,7 @@
+# pylint: disable=no-else-raise,unsupported-membership-test,using-constant-test
+
 """Checks use of "else if" triggers a refactor message"""
+from typing import Union, Sequence, Any, Mapping
 
 
 def my_function():
@@ -7,7 +10,7 @@ def my_function():
     if myint > 5:
         pass
     else:
-        if myint <= 5:  #  [else-if-used]
+        if myint <= 5:  # [else-if-used]
             pass
         else:
             myint = 3
@@ -25,3 +28,21 @@ def my_function():
                 if myint:
                     pass
                 myint = 4
+
+
+def _if_in_fstring_comprehension_with_elif(
+    params: Union[Sequence[Any], Mapping[str, Any]]
+):
+    order = {}
+    if "z" not in "false":
+        raise TypeError(
+            f" {', '.join(sorted(i for i in order or () if i not in params))}"
+        )
+    elif "z" not in "true":
+        pass
+    else:
+        if "t" not in "false":  # [else-if-used]
+            raise TypeError("d")
+        else:
+            if "y" in "life":  # [else-if-used]
+                print("e")

tests/functional/ext/check_elif/check_elif.txt

@@ -1,2 +1,4 @@
-else-if-used:10:8:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
-else-if-used:22:20:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:13:8:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:25:20:my_function:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:44:8:_if_in_fstring_comprehension_with_elif:"Consider using ""elif"" instead of ""else if""":HIGH
+else-if-used:47:12:_if_in_fstring_comprehension_with_elif:"Consider using ""elif"" instead of ""else if""":HIGH