Address a comment.

Author: kazutakahirata

llvm/include/llvm/Support/CommandLine.h

@@ -1459,18 +1459,16 @@ class opt
     }
   }
 
-  template <class T> void setDefaultImpl() {
-    if constexpr (std::is_assignable_v<T &, T>) {
+  void setDefault() override {
+    if constexpr (std::is_assignable_v<DataType &, DataType>) {
       const OptionValue<DataType> &V = this->getDefault();
       if (V.hasValue())
         this->setValue(V.getValue());
       else
-        this->setValue(T());
+        this->setValue(DataType());
     }
   }
 
-  void setDefault() override { setDefaultImpl<DataType>(); }
-
   void done() {
     addArgument();
     Parser.initialize();