digraph A {
graph[]
node [color=grey, style=filled, fillcolor=white, fontcolor=black];
edge [color=grey, fontcolor=grey];
CanError [label="can the function error out?", shape=box];
HasValue1 [label="does it return a value?", shape=box];
HasValue2 [label="does it return a value?", shape=box];
HasValue3 [label="does it return a value?", shape=box];
NeedDifferentiating [label="does the caller\nneed to distinguish between\ndifferent kinds of error?", shape=box]
void;
T;
Outcome;
DifferentiatedFail;
NeedMessage [label="does the caller\nneed different error messages?", shape=box]
OptionT [label="Option<T>"];
ResultTDiffFail [label="Result<T, DifferentiatedFail>"];
ResultTContextual [label="Result<T, ContextualFail>"];

CanError -> HasValue1 [label="no"];
HasValue1 -> T [label="yes"];
HasValue1 -> void [label="no"];

CanError -> NeedDifferentiating [label="yes"];
NeedDifferentiating -> HasValue2 [label="no"];
NeedDifferentiating -> HasValue3 [label="yes"];

HasValue2 -> Outcome [label="no"];
HasValue2 -> OptionT [label="yes"];

HasValue3 -> DifferentiatedFail [label="no"];
HasValue3 -> NeedMessage [label="yes"];

NeedMessage -> ResultTDiffFail [label="no"];
NeedMessage -> ResultTContextual [label="yes"];
}