[clang][NFC] Improve const-correctness in ParseLexedMethodDeclaration

Author: Endilll

clang/lib/Parse/ParseCXXInlineMethods.cpp

@@ -466,14 +466,14 @@ void Parser::ParseLexedMethodDeclaration(LateParsedMethodDeclaration &LM) {
         ConsumeAnyToken();
     } else if (HasUnparsed) {
       assert(Param->hasInheritedDefaultArg());
-      const FunctionDecl *Old;
+      FunctionDecl *Old;
       if (const auto *FunTmpl = dyn_cast<FunctionTemplateDecl>(LM.Method))
         Old =
             cast<FunctionDecl>(FunTmpl->getTemplatedDecl())->getPreviousDecl();
       else
         Old = cast<FunctionDecl>(LM.Method)->getPreviousDecl();
       if (Old) {
-        ParmVarDecl *OldParam = const_cast<ParmVarDecl*>(Old->getParamDecl(I));
+        ParmVarDecl *OldParam = Old->getParamDecl(I);
         assert(!OldParam->hasUnparsedDefaultArg());
         if (OldParam->hasUninstantiatedDefaultArg())
           Param->setUninstantiatedDefaultArg(