I feel like TypeScript would make this easy? You can define your functions as returning Error or some other type: function something(...):Error|<something

I feel like TypeScript would make this easy? You can define your functions as returning Error or some other type: function something(...):Error|<something else> { ... } Also, define `isError(...)`, like so: function isError(value: Error | any): pet is Error { return Object.hasPrototype( value, Error ) } You'd still have the if clauses, but maybe that's not so bad: function doStuff():Error|Result { let value = functionReturningValueOrError() if (value is Error) { return value } let value = otherFunctionReturningValueOrError() if (value is Error) { return value } ... }