[Sema] Do not offer fixit for synthesized witness mismatch access

Author: LucianoPAlmeida

lib/Sema/TypeCheckProtocol.cpp

@@ -4348,9 +4348,9 @@ ConformanceChecker::resolveWitnessViaLookup(ValueDecl *requirement) {
                        protoAccessScope.accessLevelForDiagnostics(),
                        proto->getName());
 
-        if (auto *decl = dyn_cast<AbstractFunctionDecl>(witness))
-          if (decl->isMemberwiseInitializer())
-            return;
+        auto *decl = dyn_cast<AbstractFunctionDecl>(witness);
+        if (decl && decl->isSynthesized())
+          return;
 
         diagnoseWitnessFixAccessLevel(diags, witness, requiredAccess,
                                       isSetter);

test/attr/accessibility_proto.swift

@@ -104,3 +104,11 @@ public struct NonPublicMemberwiseInitStruct: PublicInitProto {
 // expected-error@-1 {{initializer 'init(value:)' must be declared public because it matches a requirement in public protocol 'PublicInitProto'}}
   public var value: Int
 }
+
+// SR-15273
+public protocol PublicEmptyInit {
+  init()
+}
+public struct Buggy: PublicEmptyInit { 
+  // expected-error@-1 {{initializer 'init()' must be declared public because it matches a requirement in public protocol 'PublicEmptyInit'}}
+}