Remove mistaken early exit from access checking

Warnings should not result in early exits because we might end up
missing an error!

Author: jrose-apple

lib/Sema/TypeCheckAttr.cpp

@@ -1645,15 +1645,13 @@ void AttributeChecker::visitAccessControlAttr(AccessControlAttr *attr) {
         // lead to diagnostic fights between this and "declaration must be at
         // least this accessible" checking for overrides and protocol
         // requirements.
-        return;
       } else if (attr->getAccess() == defaultAccess) {
         TC.diagnose(attr->getLocation(),
                     diag::access_control_ext_member_redundant,
                     attr->getAccess(),
                     D->getDescriptiveKind(),
                     extAttr->getAccess())
           .fixItRemove(attr->getRange());
-        return;
       }
     }
   }

test/attr/accessibility.swift

@@ -229,3 +229,9 @@ extension PublicProto2 where Self.T : OuterClass, Self.U == Self.T.InnerClass {
   public func cannotBePublic() {}
   // expected-error@-1 {{cannot declare a public instance method in an extension with internal requirements}}
 }
+
+public extension OuterClass {
+  open convenience init(x: ()) { self.init() }
+  // expected-warning@-1 {{'open' modifier conflicts with extension's default access of 'public'}}
+  // expected-error@-2 {{only classes and overridable class members can be declared 'open'; use 'public'}}
+}