Re: tested index patch (was: Undefined variables returning nil)

[Sven Olsen <sven2718@...>]

“or” isn’t quite what is wanted here, is it?  it would (undesirably) catchobject.name == false (as opposed to just nil).

Ok, now it's starting to look like I've got myself a fairly clean, simple patch.  

   table!.field   

is syntax sugar for

   

   _CHECKED(table.field,"table","field")

where _CHECKED is defined as:

function _CHECKED(v,tname,kname)

if v~=nil then

return v

end

error(string.format("%s is missing required field: %q",tname or "<_expression_>", kname),2)

end

In the case that there's no clear name string associated with the table, then we can make the syntax sugar pass nil as the second argument to checked.  So, for example,

local a = (b or c)!.e

expands as:

local a =_CHECKED( (b or c).d, nil, "d" )

That's a limited semantic which seems to work fine in practice.  You can't use "table!.value" as an lvalue, but that's probably not a big deal, as most of the use cases I can think of are reads.

-Sven