add diagnostic for non-zero int literal as flag

Author: inbelic

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1810,4 +1810,6 @@ def err_hlsl_packoffset_invalid_reg : Error<"invalid resource class specifier '%
 def err_hlsl_rootsig_unexpected_eos : Error<"unexpected end to token stream">;
 def err_hlsl_rootsig_unexpected_token_kind : Error<"expected the %select{following|one of the following}0 token kinds '%1'">;
 def err_hlsl_rootsig_repeat_param : Error<"specified the same parameter '%0' multiple times">;
+def err_hlsl_rootsig_non_zero_flag : Error<"specified a non-zero integer as a flag">;
+
 } // end of Parser diagnostics

clang/lib/Parse/ParseHLSLRootSignature.cpp

@@ -476,6 +476,7 @@ bool RootSignatureParser::ParseEnum(
   // Handle the edge case when '0' is used to specify None
   if (CurTok->Kind == TokenKind::int_literal) {
     if (CurTok->NumLiteral.getInt() != 0) {
+      Diags.Report(CurTok->TokLoc, diag::err_hlsl_rootsig_non_zero_flag);
       return true;
     }
     // Set enum to None equivalent

clang/unittests/Parse/ParseHLSLRootSignatureTest.cpp

@@ -511,4 +511,30 @@ TEST_F(ParseHLSLRootSignatureTest, InvalidParseRepeatedVisibilityTest) {
   ASSERT_TRUE(Consumer->IsSatisfied());
 }
 
+TEST_F(ParseHLSLRootSignatureTest, InvalidParseNonZeroFlagTest) {
+  const llvm::StringLiteral Source = R"cc(
+    DescriptorTable(
+      CBV(b0, flags = 3)
+    )
+  )cc";
+
+  TrivialModuleLoader ModLoader;
+  auto PP = CreatePP(Source, ModLoader);
+  auto TokLoc = SourceLocation();
+
+  // Test correct diagnostic produced
+  Consumer->SetExpected(diag::err_hlsl_rootsig_non_zero_flag);
+  hlsl::RootSignatureLexer Lexer(Source, TokLoc, *PP);
+
+  SmallVector<hlsl::RootSignatureToken> Tokens;
+  ASSERT_FALSE(Lexer.Lex(Tokens));
+
+  SmallVector<RootElement> Elements;
+  hlsl::RootSignatureParser Parser(Elements, Tokens, Diags);
+
+  ASSERT_TRUE(Parser.Parse());
+
+  ASSERT_TRUE(Consumer->IsSatisfied());
+}
+
 } // anonymous namespace