[clang] Fix build break in SemaHLSL.cpp on MSVC 2022: warning C4715: 'getResourceClass': not all control paths return a value (PR #112767)

[Daniel Paoliello via cfe-commits]

https://github.com/dpaoliello created https://github.com/llvm/llvm-project/pull/112767

Adds a default case to the switch to the existing `llvm_unreachable` statement.

Build break was introduced by #111203

It was not caught by the builders as they use Visual Studio 2019, whereas this warning only appears in 2022.

>From 20f602b8c28d966a7cc957a3ca4c6ed43e71258e Mon Sep 17 00:00:00 2001
From: "Daniel Paoliello (HE/HIM)" <danpao at microsoft.com>
Date: Thu, 17 Oct 2024 12:21:25 -0700
Subject: [PATCH] Fix build break in SemaHLSL.cpp on MSVC 2022: warning C4715:
 'getResourceClass': not all control paths return a value

---
 clang/lib/Sema/SemaHLSL.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index efb0fbaa432d76..50f0a553bc86e3 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -102,6 +102,7 @@ static ResourceClass getResourceClass(RegisterType RT) {
     return ResourceClass::Sampler;
   case RegisterType::C:
   case RegisterType::I:
+  default:
     llvm_unreachable("unexpected RegisterType value");
   }
 }