make more efficient

Author: nikalra

mlir/include/mlir/Bindings/Python/Diagnostics.h

@@ -9,14 +9,14 @@
 #ifndef MLIR_BINDINGS_PYTHON_DIAGNOSTICS_H
 #define MLIR_BINDINGS_PYTHON_DIAGNOSTICS_H
 
+#include "mlir-c/Diagnostics.h"
+#include "mlir-c/IR.h"
+
 #include <cassert>
 #include <cstdint>
+#include <sstream>
 #include <string>
 
-#include "mlir-c/Diagnostics.h"
-#include "mlir-c/IR.h"
-#include "llvm/ADT/StringRef.h"
-
 namespace mlir {
 namespace python {
 
@@ -29,25 +29,28 @@ class CollectDiagnosticsToStringScope {
                                                    /*deleteUserData=*/nullptr);
   }
   ~CollectDiagnosticsToStringScope() {
-    assert(errorMessage.empty() && "unchecked error message");
     mlirContextDetachDiagnosticHandler(context, handlerID);
   }
 
-  [[nodiscard]] std::string takeMessage() { return std::move(errorMessage); }
+  [[nodiscard]] std::string takeMessage() {
+    std::ostringstream stream;
+    std::swap(stream, errorMessage);
+    return stream.str();
+  }
 
 private:
   static MlirLogicalResult handler(MlirDiagnostic diag, void *data) {
     auto printer = +[](MlirStringRef message, void *data) {
-      *static_cast<std::string *>(data) +=
-          llvm::StringRef(message.data, message.length);
+      *static_cast<std::ostringstream *>(data)
+          << std::string_view(message.data, message.length);
     };
     MlirLocation loc = mlirDiagnosticGetLocation(diag);
-    *static_cast<std::string *>(data) += "at ";
+    *static_cast<std::ostringstream *>(data) << "at ";
     mlirLocationPrint(loc, printer, data);
-    *static_cast<std::string *>(data) += ": ";
+    *static_cast<std::ostringstream *>(data) << ": ";
     mlirDiagnosticPrint(diag, printer, data);
     for (intptr_t i = 0; i < mlirDiagnosticGetNumNotes(diag); i++) {
-      *static_cast<std::string *>(data) += "\n";
+      *static_cast<std::ostringstream *>(data) << "\n";
       MlirDiagnostic note = mlirDiagnosticGetNote(diag, i);
       handler(note, data);
     }
@@ -56,7 +59,7 @@ class CollectDiagnosticsToStringScope {
 
   MlirContext context;
   MlirDiagnosticHandlerID handlerID;
-  std::string errorMessage = "";
+  std::ostringstream errorMessage;
 };
 
 } // namespace python