fix(CAPI): remove Cpp code from CAPI

this required to have a CAPI that when asked for types, returns a
structure that can report if an error was faced during type creation.
This is required since a failure at that stage in the compiler would
lead to a segfault in the python bindings for example, and we want to be
able to handle this scenario gracefully.

compiler/include/concretelang-c/Dialect/FHE.h

@@ -8,19 +8,23 @@
 
 #include "mlir-c/IR.h"
 #include "mlir-c/Registration.h"
-#include "mlir/IR/Diagnostics.h"
-#include "mlir/Support/LLVM.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
+/// \brief structure to return an MlirType or report that there was an error
+/// during type creation.
+typedef struct {
+  MlirType type;
+  bool isError;
+} MlirTypeOrError;
+
 MLIR_DECLARE_CAPI_DIALECT_REGISTRATION(FHE, fhe);
 
 /// Creates an encrypted integer type of `width` bits
-MLIR_CAPI_EXPORTED MlirType fheEncryptedIntegerTypeGetChecked(
-    MlirContext context, unsigned width,
-    mlir::function_ref<mlir::InFlightDiagnostic()> emitError);
+MLIR_CAPI_EXPORTED MlirTypeOrError
+fheEncryptedIntegerTypeGetChecked(MlirContext context, unsigned width);
 
 /// If the type is an EncryptedInteger
 MLIR_CAPI_EXPORTED bool fheTypeIsAnEncryptedIntegerType(MlirType);

compiler/lib/Bindings/Python/FHEModule.cpp

@@ -28,12 +28,11 @@ void mlir::concretelang::python::populateDialectFHESubmodule(
   mlir_type_subclass(m, "EncryptedIntegerType", fheTypeIsAnEncryptedIntegerType)
       .def_classmethod("get", [](pybind11::object cls, MlirContext ctx,
                                  unsigned width) {
-        // We want the user to receive a python exception for not being able to
-        // create the eint
-        auto emitException = []() -> mlir::InFlightDiagnostic {
+        MlirTypeOrError typeOrError =
+            fheEncryptedIntegerTypeGetChecked(ctx, width);
+        if (typeOrError.isError) {
           throw std::invalid_argument("can't create eint with the given width");
-        };
-        return cls(
-            fheEncryptedIntegerTypeGetChecked(ctx, width, emitException));
+        }
+        return cls(typeOrError.type);
       });
 }

compiler/lib/CAPI/Dialect/FHE/FHE.cpp

@@ -10,6 +10,7 @@
 #include "mlir/CAPI/IR.h"
 #include "mlir/CAPI/Registration.h"
 #include "mlir/CAPI/Support.h"
+#include "mlir/IR/StorageUniquerSupport.h"
 
 using namespace mlir::concretelang::FHE;
 
@@ -27,8 +28,23 @@ bool fheTypeIsAnEncryptedIntegerType(MlirType type) {
   return unwrap(type).isa<EncryptedIntegerType>();
 }
 
-MlirType fheEncryptedIntegerTypeGetChecked(
-    MlirContext ctx, unsigned width,
-    mlir::function_ref<mlir::InFlightDiagnostic()> emitError) {
-  return wrap(EncryptedIntegerType::getChecked(emitError, unwrap(ctx), width));
+MlirTypeOrError fheEncryptedIntegerTypeGetChecked(MlirContext ctx,
+                                                  unsigned width) {
+  MlirTypeOrError type = {{NULL}, false};
+  auto catchError = [&]() -> mlir::InFlightDiagnostic {
+    type.isError = true;
+    mlir::DiagnosticEngine &engine = unwrap(ctx)->getDiagEngine();
+    // The goal here is to make getChecked working, but we don't want the CAPI
+    // to stop execution due to an error, and leave the error handling logic to
+    // the user of the CAPI
+    return engine.emit(mlir::UnknownLoc::get(unwrap(ctx)),
+                       mlir::DiagnosticSeverity::Warning);
+  };
+  EncryptedIntegerType eint =
+      EncryptedIntegerType::getChecked(catchError, unwrap(ctx), width);
+  if (type.isError) {
+    return type;
+  }
+  type.type = wrap(eint);
+  return type;
 }