Sort names for consistent diagnostics order

Author: sterliakov

mypy/checker.py

@@ -2734,7 +2734,8 @@ def check_multiple_inheritance(self, typ: TypeInfo) -> None:
         # Verify that inherited attributes are compatible.
         mro = typ.mro[1:]
         all_names = {name for base in mro for name in base.names}
-        for name in all_names - typ.names.keys():
+        for name in sorted(all_names - typ.names.keys()):
+            # Sort for reproducible message order.
             # Attributes defined in both the type and base are skipped.
             # Normal checks for attribute compatibility should catch any problems elsewhere.
             if is_private(name):

test-data/unit/check-generic-subtyping.test

@@ -1085,19 +1085,18 @@ class B(Generic[T]):
     def fn(self, t: T) -> None: ...
 
 class C1(A2[str], B[str]): pass
-class C2(A2[str], B[int]): pass  # E: Definition of "x" in base class "A" is incompatible with definition in base class "B" \
-                                 # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B"
+class C2(A2[str], B[int]): pass  # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B" \
+                                 # E: Definition of "x" in base class "A" is incompatible with definition in base class "B"
 class C3(A2[T], B[T]): pass
 class C4(A2[U], B[U]): pass
-class C5(A2[U], B[T]): pass  # E: Definition of "x" in base class "A" is incompatible with definition in base class "B" \
-                             # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B"
+class C5(A2[U], B[T]): pass  # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B" \
+                             # E: Definition of "x" in base class "A" is incompatible with definition in base class "B"
 
 class D1(A[str], B[str]): pass
-class D2(A[str], B[int]): pass  # E: Definition of "x" in base class "A" is incompatible with definition in base class "B" \
-                                 # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B"
+class D2(A[str], B[int]): pass  # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B" \
+                                # E: Definition of "x" in base class "A" is incompatible with definition in base class "B"
 class D3(A[T], B[T]): pass
 class D4(A[U], B[U]): pass
-class D5(A[U], B[T]): pass  # E: Definition of "x" in base class "A" is incompatible with definition in base class "B" \
-                             # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B"
-
+class D5(A[U], B[T]): pass  # E: Definition of "fn" in base class "A" is incompatible with definition in base class "B" \
+                            # E: Definition of "x" in base class "A" is incompatible with definition in base class "B"
 [builtins fixtures/tuple.pyi]