Call to `enable_result_type_inference` is not safe

[Danacus]

Calling enable_result_type_inference on OperationBuilder may trigger undefined behavior if types cannot be inferred, since mlirOperationCreate returns a nullptr in this case. OperationBuilder::build does not check for nullity, and as such an invalid Operation may be constructed, causing undefined behavior when it is accessed or dropped.

Code to reproduce:

{
    let _ = OperationBuilder::new("test", location)
        .enable_result_type_inference()
        .build();
}

Suggested fix: check for nullity before calling Operation::from_raw in OperationBuilder::build and return a Result<Operation, _> or simply panic.

[Danacus]

After looking into it a bit more, I now think that this only really happens if you use an unregistered/unloaded dialect, so in that sense it's related to #23. I was writing tests for #274 and was using custom test dialects that weren't registered to MLIR, hence issues ocurred when trying to use operation interfaces such as InferTypeOpInterface.

[raviqqe]

Thanks for the research!

I see. The unregistered dialects should be fixed asap...

[raviqqe]

Sorry, I closed by mistake!