Good error messages

[jar1]

The only example makes me think the idea should be to give the proof of the error condition.

@jules

We could print all the elements if there are at max let’s say five or so, but not after that as there could be way too many.

For only, we need to prove it has 2 elements, no more.

@jules

You could write the type instead of Collection but that might be a huge thing.

It would be nice to have a Base function abbreviated_type to use in error messages.

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In another post I tried Elm style errors, and Mason came up with a macro to use like

function f(x::Real)
    if x>= 0.0
        x + 1
    else
        @noinline_block x throw(DomainError("f requires inputs greater than 0, you gave $x which is less than 0"))
    end
end