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

[Erich Keane via cfe-commits]

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@@ -2253,6 +2260,53 @@ static void DiagnoseNonTriviallyCopyableReason(Sema &SemaRef,
   }
 }
 
+static void DiagnoseNonConstructibleReason(
+    Sema &SemaRef, SourceLocation Loc,
+    const llvm::SmallVector<clang::QualType, 1> &Ts) {
+  for (const auto &ArgTy : Ts) {
+    if (ArgTy->isVoidType())
+      SemaRef.Diag(Loc, diag::note_unsatisfied_trait_reason)
+          << diag::TraitNotSatisfiedReason::CVVoidType;
+  }
+
+  QualType T = Ts[0];
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erichkeane wrote:

Do we know that `Ts` is >=1? in size?  Maybe early-exit if `Ts.empty`?

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