[clang] [lldb] [Clang] Introduce OverflowBehaviorType for fine-grained overflow control (PR #148914)

[Justin Stitt via cfe-commits]

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@@ -2427,9 +2438,16 @@ static bool IsStandardConversion(Sema &S, Expr* From, QualType ToType,
     // Complex promotion (Clang extension)
     SCS.Second = ICK_Complex_Promotion;
     FromType = ToType.getUnqualifiedType();
+  } else if (S.IsOverflowBehaviorTypePromotion(FromType, ToType)) {
+    // OverflowBehaviorType promotions
+    SCS.Second = ICK_Integral_Promotion;
+    FromType = ToType.getUnqualifiedType();
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JustinStitt wrote:

As per the documentation and previously agreed upon semantics, these overflow behavior types have special promotion properties. We do this to preserve bitwidths when it matters.

https://github.com/llvm/llvm-project/pull/148914