Added error code for overlapping function signatures

docs/source/error_code_list.rst

@@ -1149,6 +1149,26 @@ types you expect.
 
 See :ref:`overloading <function-overloading>` for more explanation.
 
+
+.. _code-overloaded-function-matching:
+
+Check error code of overload function signature match
+--------------------------------------------------------------------------
+
+.. code-block:: python
+
+    from typing import overload, Union
+
+    @overload
+    def process(response1: float,response2: float) -> float:
+        ...
+    @overload
+    def process(response1: int,response2: int) -> int: # E: Overloaded function signature 2 will never be matched: signature 1's parameter type(s) are the same or broader  [overloaded-function-matching]
+        ...
+
+    def process(response1,response2)-> Union[float,int]:
+    return response1 + response2
+
 .. _code-annotation-unchecked:
 
 Notify about an annotation in an unchecked function [annotation-unchecked]

mypy/checker.py

@@ -768,6 +768,7 @@ def check_overlapping_overloads(self, defn: OverloadedFuncDef) -> None:
                     continue
 
                 if overload_can_never_match(sig1, sig2):
+
                     self.msg.overloaded_signature_will_never_match(i + 1, i + j + 2, item2.func)
                 elif not is_descriptor_get:
                     # Note: we force mypy to check overload signatures in strict-optional mode

mypy/errorcodes.py

@@ -262,6 +262,12 @@ def __hash__(self) -> int:
     default_enabled=False,
 )
 
+OVERLOADED_FUNCTION_MATCHING: Final[ErrorCode] = ErrorCode(
+    "overloaded-function-matching",
+    "Warn user about signature matching for overloaded functions.",
+    "General",
+)
+
 # Syntax errors are often blocking.
 SYNTAX: Final[ErrorCode] = ErrorCode("syntax", "Report syntax errors", "General")
 

mypy/message_registry.py

@@ -362,3 +362,8 @@ def with_additional_msg(self, info: str) -> ErrorMessage:
 TYPE_ALIAS_WITH_AWAIT_EXPRESSION: Final = ErrorMessage(
     "Await expression cannot be used within a type alias", codes.SYNTAX
 )
+
+# Overloads
+OVERLOADED_FUNCTION_SIGNATURE: Final = ErrorMessage(
+    "Overloaded function signature {} will never be matched", codes.OVERLOADED_FUNCTION_MATCHING
+)

mypy/messages.py

@@ -1653,6 +1653,7 @@ def overloaded_signature_will_never_match(
                 index1=index1, index2=index2
             ),
             context,
+            code=codes.OVERLOADED_FUNCTION_MATCHING,
         )
 
     def overloaded_signatures_typevar_specific(self, index: int, context: Context) -> None:

test-data/unit/check-errorcodes.test

@@ -1196,3 +1196,17 @@ def f(x: str) -> TypeIs[int]:  # E: Narrowed type "int" is not a subtype of inpu
     pass
 
 [builtins fixtures/tuple.pyi]
+
+
+[case testOverloadedFunctionSignature]
+from typing import overload, Union
+
+@overload
+def process(response1: float,response2: float) -> float:
+    ...
+@overload
+def process(response1: int,response2: int) -> int: # E: Overloaded function signature 2 will never be matched: signature 1's parameter type(s) are the same or broader  [overloaded-function-matching]
+    ...
+
+def process(response1,response2)-> Union[float,int]:
+   return response1 + response2