[clang] [Clang] raise extension warning for unknown namespaced attributes (PR #120925)

[Aaron Ballman via cfe-commits]

================
@@ -166,7 +166,8 @@ getScopeFromNormalizedScopeName(StringRef ScopeName) {
       .Case("hlsl", AttributeCommonInfo::Scope::HLSL)
       .Case("msvc", AttributeCommonInfo::Scope::MSVC)
       .Case("omp", AttributeCommonInfo::Scope::OMP)
-      .Case("riscv", AttributeCommonInfo::Scope::RISCV);
+      .Case("riscv", AttributeCommonInfo::Scope::RISCV)
+      .Default(AttributeCommonInfo::Scope::NONE);
----------------
AaronBallman wrote:

Won't it be surprising that `""` and `"wobble"` will both come back as `NONE`? I would have expected the latter to return something like "Unknown" so it's distinguished from no scope name.

https://github.com/llvm/llvm-project/pull/120925