Add new error kind for inconsistent inheritance

Author: fangyi-zhou

conformance/third_party/conformance.exp

@@ -9988,7 +9988,7 @@
       "concise_description": "Inconsistent types for field `x` inherited from multiple base classes: `int` from `X2`, `str` from `Y2`",
       "description": "Inconsistent types for field `x` inherited from multiple base classes: `int` from `X2`, `str` from `Y2`",
       "line": 65,
-      "name": "inconsistent-overload",
+      "name": "inconsistent-inheritance",
       "stop_column": 11,
       "stop_line": 65
     }

crates/pyrefly_config/src/error_kind.rs

@@ -140,6 +140,8 @@ pub enum ErrorKind {
     /// An error related to the import machinery.
     /// e.g. failed to import a module.
     ImportError,
+    /// An inconsistency between inherited fields or methods form multiple base classes.
+    InconsistentInheritance,
     /// An inconsistency between the signature of a function overload and the implementation.
     InconsistentOverload,
     /// Attempting to access a container with an incorrect index.

pyrefly/lib/alt/class/class_field.rs

@@ -1992,7 +1992,7 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
                     self.error(
                         errors,
                         cls.range(),
-                        ErrorInfo::Kind(ErrorKind::InconsistentOverload),
+                        ErrorInfo::Kind(ErrorKind::InconsistentInheritance),
                         format!(
                             "Inconsistent types for field `{field_name}` inherited from multiple base classes: {class_and_types_str}",
                         ),

website/docs/error-kinds.mdx

@@ -381,6 +381,19 @@ An error related to the import mechanism, such as when a module cannot be found.
 The error message will include which paths were searched, such as the site package paths.
 You may be missing a dependency, or you may need to inform Pyrefly where the module lives. See [Configuration](configuration.mdx) for further information.
 
+## inconsistent-inheritance
+
+When a class inherits from multiple base classes, the inherited fields must be consistent.
+
+Example:
+```python
+class A:
+    f: str
+class B:
+    f: int
+class C(A, B): ...  # error, the field `f` is inconsistent
+```
+
 ## inconsistent-overload
 
 The signature of a function overload is inconsistent with the implementation.