[clang] [HLSL] Vector standard conversions (PR #71098)

[Justin Bogner via cfe-commits]

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@@ -4772,6 +4788,76 @@ Sema::PerformImplicitConversion(Expr *From, QualType ToType,
     llvm_unreachable("Improper second standard conversion");
   }
 
+  if (SCS.Element != ICK_Identity) {
+    // If SCS.Element is not ICK_Identity the To and From types must be HLSL
+    // vectors or matrices. HLSL matrices aren't yet supported so this code only
+    // handles vectors for now.
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bogner wrote:

The comment about matrices should probably be a `TODO:`, and it might even be worth a separate assert that says "not implemented yet" for clarity

https://github.com/llvm/llvm-project/pull/71098