[clang] [clang][CUDA/HIP] Fix parsing of `operator<<<...>` (PR #218384)

[Mariya Podchishchaeva via cfe-commits]

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@@ -2485,6 +2485,30 @@ bool Parser::ParseUnqualifiedIdOperator(CXXScopeSpec &SS, bool EnteringContext,
       Actions.CodeCompletion().CodeCompleteOperatorName(getCurScope());
       return true;
     }
+    case tok::lesslessless: {
+      // For CUDA, the Lexer will greedily merge all three <<< in operator<<<
+      // which, in fact, can be a valid template specialization of operator<<,
+      // and will never be a valid kernel launch expression, so split.
+      bool CachingTokens = PP.IsPreviousCachedToken(Tok);
+      // If there was a cache, we should update it when doing token split.
+      // The code below never does.
+      assert(!CachingTokens && "No cache expected");
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Fznamznon wrote:

Added the test, thank you.

https://github.com/llvm/llvm-project/pull/218384