Perhaps. But a) apparently branch prediction is good enough to make all this constant checking for exceptional returns to slow down the execution by only a cou

Perhaps. But a) apparently branch prediction is good enough to make all this constant checking for exceptional returns to slow down the execution by only a couple of percents; b) apparently exception propagation and re-throwing is way, way faster than in the standard implementation; c) the exclusion of the unwind tables makes the code 3 times smaller on ARM, and 5 times smaller on x86-64. That's pretty huge. So all in all, I'd say that if those figures actually hold, then this approach is pretty solid. It's just surprising, given how much complaining there is about how Go's idiom of "if err != nil { return nil, err }", or Rust's "let v = some_fun()?" kills performance because of branch mis-prediction and hot path code bloat, so maybe those figures don't actually hold?