Augment GenericTypeParamDecl with bits indicating they came from opaque types

lib/Sema/CodeSynthesis.cpp

@@ -468,9 +468,10 @@ computeDesignatedInitOverrideSignature(ASTContext &ctx,
         depth = genericSig.getGenericParams().back()->getDepth() + 1;
 
       for (auto *param : genericParams->getParams()) {
-        auto *newParam = new (ctx) GenericTypeParamDecl(
+        auto *newParam = GenericTypeParamDecl::create(
             classDecl, param->getName(), SourceLoc(), param->isTypeSequence(),
-            depth, param->getIndex());
+            depth, param->getIndex(), param->isOpaqueType(),
+            /*opaqueTypeRepr=*/nullptr);
         newParams.push_back(newParam);
       }