[llvm] [Support] Simplify setDefaultImpl (NFC) (PR #137528)

[Kazu Hirata via llvm-commits]

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@@ -1459,18 +1459,16 @@ class opt
     }
   }
 
-  template <class T, class = std::enable_if_t<std::is_assignable_v<T &, T>>>
-  void setDefaultImpl() {
-    const OptionValue<DataType> &V = this->getDefault();
-    if (V.hasValue())
-      this->setValue(V.getValue());
-    else
-      this->setValue(T());
+  template <class T> void setDefaultImpl() {
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kazutakahirata wrote:

Good idea!  Thanks!

https://github.com/llvm/llvm-project/pull/137528