[clang] [HLSL] Disallow writing to readonly resources (PR #147806)

[Ashley Coleman via cfe-commits]

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@@ -697,7 +699,9 @@ BuiltinTypeDeclBuilder &BuiltinTypeDeclBuilder::addArraySubscriptOperators() {
       AST.DeclarationNames.getCXXOperatorName(OO_Subscript);
 
   addHandleAccessFunction(Subscript, /*IsConst=*/true, /*IsRef=*/true);
-  addHandleAccessFunction(Subscript, /*IsConst=*/false, /*IsRef=*/true);
+  if (ResClass == llvm::dxil::ResourceClass::UAV)
+    addHandleAccessFunction(Subscript, /*IsConst=*/false, /*IsRef=*/true);
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V-FEXrt wrote:

had to drop the `const` since `getResourceHandleField` isn't `const` but otherwise done!

https://github.com/llvm/llvm-project/pull/147806