[AST] #SR-13906 (Improvement)

Updated Error message for types conforming to
AnyObject or its Composition

Author: Aniket Ray

include/swift/AST/DiagnosticsSema.def

@@ -2633,9 +2633,9 @@ WARNING(anyobject_class_inheritance_deprecated,none,
 ERROR(multiple_inheritance,none,
   "multiple inheritance from classes %0 and %1", (Type, Type))
 ERROR(inheritance_from_non_protocol_or_class,none,
-  "inheritance from non-protocol, non-class type %0", (Type))
+  "%0 type cannot inherit from non-protocol, non-class type %1", (DescriptiveDeclKind, Type))
 ERROR(inheritance_from_non_protocol,none,
-  "inheritance from non-protocol type %0", (Type))
+  "%0 type cannot inherit from non-protocol type %1", (DescriptiveDeclKind, Type))
 ERROR(superclass_not_first,none,
   "superclass %0 must appear first in the inheritance clause", (Type))
 ERROR(superclass_not_open,none,
@@ -2662,6 +2662,11 @@ ERROR(inheritance_from_cf_class,none,
 ERROR(inheritance_from_objc_runtime_visible_class,none,
       "cannot inherit from class %0 because it is only visible via the "
       "Objective-C runtime", (Identifier))
+ERROR(composition_of_protocol_and_anyobject,none,
+      "non-protocol type %0 cannot conform to composition type %1; "
+      "%0 must be a protocol type", 
+      (Identifier, Type))
+      
 
 // Enums
 ERROR(enum_case_access,none,

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -235,10 +235,19 @@ static void checkInheritanceClause(
       // AnyObject is not allowed except on protocols.
       if (layout.hasExplicitAnyObject &&
           !isa<ProtocolDecl>(decl)) {
-        decl->diagnose(canHaveSuperclass
-                       ? diag::inheritance_from_non_protocol_or_class
-                       : diag::inheritance_from_non_protocol,
-                       inheritedTy);
+        // Check if the inherited type is exclusively AnyObject
+        // If not, we can be sure of the composition of Protocol(s) with
+        // AnyObject
+        if (!layout.isAnyObject()) {
+          decl->diagnose(diag::composition_of_protocol_and_anyobject,
+                         typeDecl->getName(), inheritedTy);
+        } else {
+          decl->diagnose(canHaveSuperclass
+                             ? diag::inheritance_from_non_protocol_or_class
+                             : diag::inheritance_from_non_protocol,
+                         decl->getDescriptiveKind(), inheritedTy);
+        }
+
         continue;
       }
 
@@ -342,6 +351,7 @@ static void checkInheritanceClause(
     decl->diagnose(canHaveSuperclass
                    ? diag::inheritance_from_non_protocol_or_class
                    : diag::inheritance_from_non_protocol,
+                   decl->getDescriptiveKind(),
                    inheritedTy);
     // FIXME: Note pointing to the declaration 'inheritedTy' references?
   }