AST: Address a FIXME in adjustSuperclassMemberDeclType()

This is NFC for now, but fixes tests after we remove eraseDynamicSelfType().

Author: slavapestov

lib/AST/Type.cpp

@@ -3587,9 +3587,14 @@ Type TypeBase::adjustSuperclassMemberDeclType(const ValueDecl *baseDecl,
     type = type->replaceSelfParameterType(this);
     if (afd->hasDynamicSelfResult())
       type = type->replaceCovariantResultType(this, /*uncurryLevel=*/2);
+  } else if (auto *sd = dyn_cast<SubscriptDecl>(baseDecl)) {
+    if (sd->getElementInterfaceType()->hasDynamicSelfType())
+      type = type->replaceCovariantResultType(this, /*uncurryLevel=*/1);
+  } else if (auto *vd = dyn_cast<VarDecl>(baseDecl)) {
+    if (vd->getValueInterfaceType()->hasDynamicSelfType())
+      type = type->replaceCovariantResultType(this, /*uncurryLevel=*/0);
   }
 
-  // FIXME: Properties and subscripts can also have dynamic self returns...
   return type;
 }