Throw.onOverflow

typeof(~ Lhs()) onOverflow(string x, Lhs)(Lhs lhs)

Called automatically upon an overflow during a unary or binary operation.

`x`	The operator, e.g. `-`
`lhs`	The left-hand side (or sole) argument
`rhs`	The right-hand side type involved in the operator

Nominally the result is the desired value of the operator, which

will be forwarded as result. For Throw, the function never returns because it throws an exception.

CheckFailure on overflow

typeof(Lhs() + Rhs()) onOverflow(string x, Lhs, Rhs)(Lhs lhs, Rhs rhs)

ditto