[clang] [Clang] Added explanation why a is constructible evaluated to false. (PR #143309)

[Erich Keane via cfe-commits]

================
@@ -1981,8 +1982,14 @@ static ExtractedTypeTraitInfo ExtractTypeTraitFromExpression(const Expr *E) {
     Trait = StdNameToTypeTrait(Name);
     if (!Trait)
       return std::nullopt;
-    for (const auto &Arg : VD->getTemplateArgs().asArray())
-      Args.push_back(Arg.getAsType());
+    for (const auto &Arg : VD->getTemplateArgs().asArray()) {
+      if (Arg.getKind() == TemplateArgument::ArgKind::Pack) {
+        for (const auto &InnerArg : Arg.pack_elements())
+          Args.push_back(InnerArg.getAsType());
+      }
+      if (Arg.getKind() == TemplateArgument::ArgKind::Type)
----------------
erichkeane wrote:

```suggestion
      else if (Arg.getKind() == TemplateArgument::ArgKind::Type)
```

https://github.com/llvm/llvm-project/pull/143309