[clang] [clang] Implement `__builtin_is_implicit_lifetime()` (PR #101807)

[via cfe-commits]

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@@ -5637,6 +5638,38 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
     return false;
   case UTT_IsTriviallyEqualityComparable:
     return isTriviallyEqualityComparableType(Self, T, KeyLoc);
+  case UTT_IsImplicitLifetime: {
+    DiagnoseVLAInCXXTypeTrait(Self, TInfo,
+                              tok::kw___builtin_is_implicit_lifetime);
+
+    // [basic.types.general] p9
+    // Scalar types, implicit-lifetime class types ([class.prop]),
+    // array types, and cv-qualified versions of these types
+    // are collectively called implicit-lifetime types.
+    QualType UnqualT = T->getCanonicalTypeUnqualified();
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cor3ntin wrote:

I don't think we want to old this PR on _Atomic, but I don't know what the answer ought to be.
Rejecting that code all together might be the most conservative solution.

@zygoloid 


https://github.com/llvm/llvm-project/pull/101807