Improve the error message for Y060 (#453)

CHANGELOG.md

@@ -7,6 +7,7 @@ New error codes:
 
 Other changes:
 * Y061 is no longer emitted in situations where Y062 would also be emitted.
+* Improve error message for Y060.
 
 ## 23.11.0
 

pyi.py

@@ -1655,7 +1655,8 @@ def _check_class_bases(self, bases: list[ast.expr]) -> None:
             if len(subscript_bases) > 1 and all_equal(
                 ast.dump(subscript_base.slice) for subscript_base in subscript_bases
             ):
-                self.error(Generic_basenode, Y060)
+                msg = Y060.format(redundant_base=unparse(Generic_basenode))
+                self.error(Generic_basenode, msg)
 
     def visit_ClassDef(self, node: ast.ClassDef) -> None:
         if node.name.startswith("_") and not self.in_class.active:
@@ -2295,7 +2296,7 @@ def parse_options(options: argparse.Namespace) -> None:
 )
 Y059 = 'Y059 "Generic[]" should always be the last base class'
 Y060 = (
-    'Y060 Redundant inheritance from "Generic[]"; '
+    'Y060 Redundant inheritance from "{redundant_base}"; '
     "class would be inferred as generic anyway"
 )
 Y061 = 'Y061 None inside "Literal[]" expression. Replace with "{suggestion}"'

tests/classdefs.pyi

@@ -203,19 +203,19 @@ class GoodGeneric3(int, str, typing_extensions.Generic[_T]): ...
 class BadGeneric4(Generic[_T], Iterable[int], str): ...  # Y059 "Generic[]" should always be the last base class
 class GoodGeneric4(Iterable[int], str, Generic[_T]): ...
 
-class RedundantGeneric1(Iterable[_T], Generic[_T]): ...  # Y060 Redundant inheritance from "Generic[]"; class would be inferred as generic anyway
+class RedundantGeneric1(Iterable[_T], Generic[_T]): ...  # Y060 Redundant inheritance from "Generic[_T]"; class would be inferred as generic anyway
 class Corrected1(Iterable[_T]): ...
 
-class RedundantGeneric2(Generic[_S], GoodGeneric[_S]): ...  # Y059 "Generic[]" should always be the last base class  # Y060 Redundant inheritance from "Generic[]"; class would be inferred as generic anyway
+class RedundantGeneric2(Generic[_S], GoodGeneric[_S]): ...  # Y059 "Generic[]" should always be the last base class  # Y060 Redundant inheritance from "Generic[_S]"; class would be inferred as generic anyway
 class Corrected2(GoodGeneric[_S]): ...
 
-class RedundantGeneric3(int, Iterator[_T], str, float, memoryview, bytes, Generic[_T]): ...  # Y060 Redundant inheritance from "Generic[]"; class would be inferred as generic anyway
+class RedundantGeneric3(int, Iterator[_T], str, float, memoryview, bytes, Generic[_T]): ...  # Y060 Redundant inheritance from "Generic[_T]"; class would be inferred as generic anyway
 class Corrected3(int, Iterator[_T], str, float, memoryview, bytes): ...
 
-class RedundantGeneric4(Iterable[_T], Iterator[_T], Generic[_T]): ...  # Y060 Redundant inheritance from "Generic[]"; class would be inferred as generic anyway
+class RedundantGeneric4(Iterable[_T], Iterator[_T], Generic[_T]): ...  # Y060 Redundant inheritance from "Generic[_T]"; class would be inferred as generic anyway
 class Corrected4(Iterable[_T], Iterator[_T]): ...
 
-class BadAndRedundantGeneric(object, Generic[_T], Container[_T]): ...  # Y040 Do not inherit from "object" explicitly, as it is redundant in Python 3  # Y059 "Generic[]" should always be the last base class  # Y060 Redundant inheritance from "Generic[]"; class would be inferred as generic anyway
+class BadAndRedundantGeneric(object, Generic[_T], Container[_T]): ...  # Y040 Do not inherit from "object" explicitly, as it is redundant in Python 3  # Y059 "Generic[]" should always be the last base class  # Y060 Redundant inheritance from "Generic[_T]"; class would be inferred as generic anyway
 class Corrected5(Container[_T]): ...
 
 # Strictly speaking this inheritance from Generic is "redundant",