[clang] [HLSL] Desugar ConstantArrayType when calculating cbuffer field layout (PR #134683)

[Eli Friedman via cfe-commits]

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@@ -195,7 +195,8 @@ bool HLSLBufferLayoutBuilder::layoutField(const FieldDecl *FD,
     // Unwrap array to find the element type and get combined array size.
     QualType Ty = FieldTy;
     while (Ty->isConstantArrayType()) {
-      const ConstantArrayType *ArrayTy = cast<ConstantArrayType>(Ty);
+      const ConstantArrayType *ArrayTy =
+          cast<ConstantArrayType>(Ty->getUnqualifiedDesugaredType());
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efriedma-quic wrote:

```suggestion
      auto *ArrayTy = CGM.getContext().getAsConstantArrayType(Ty);
```

https://github.com/llvm/llvm-project/pull/134683