[llvm] [clang] DiagnosticHandler: refactor error checking (PR #75889)

[Fangrui Song via cfe-commits]

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@@ -256,10 +256,13 @@ void LLVMContext::diagnose(const DiagnosticInfo &DI) {
       RS->emit(*OptDiagBase);
 
   // If there is a report handler, use it.
-  if (pImpl->DiagHandler &&
-      (!pImpl->RespectDiagnosticFilters || isDiagnosticEnabled(DI)) &&
-      pImpl->DiagHandler->handleDiagnostics(DI))
-    return;
+  if (pImpl->DiagHandler) {
+    if (DI.getSeverity() == DS_Error)
+      pImpl->DiagHandler->HasErrors = true;
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MaskRay wrote:

> Also, should this be set when handleDiagnostics is not called?

The `RespectDiagnosticFilters` condition is here to suppress remarks for legacy LTOCodeGenerator (test: `llvm/test/LTO/X86/diagnostic-handler-remarks.ll`). It's not used for errors. I think conveying the `HasErrors` bit seems more useful, although the client does not use this information.

https://github.com/llvm/llvm-project/pull/75889