[clang] [HLSL][RootSignature] Implement diagnostic for missed comma (PR #147350)

[Justin Bogner via cfe-commits]

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@@ -34,3 +34,7 @@ void bad_root_signature_5() {}
 // expected-error at +1 {{expected ')' to denote end of parameters, or, another valid parameter of RootConstants}}
 [RootSignature(MultiLineRootSignature)]
 void bad_root_signature_6() {}
+
+// expected-error at +1 {{expected end of stream to denote end of parameters, or, another valid parameter of RootSignature}}
+[RootSignature("RootFlags() RootConstants(b0, num32BitConstants = 1))")]
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bogner wrote:

Does this also have an extra `)`? We should make sure we only have the error we're trying to detect here.

https://github.com/llvm/llvm-project/pull/147350