Re: Upvalues and static typing

[Andrew Starks <andrew.starks@...>]

On Friday, April 10, 2015, Dibyendu Majumdar <mobile@majumdar.org.uk> wrote:
> Hi,
>
> While working on the core API the realization dawned that up-values
> can subvert static typing of local variables :-(
>
> > function x() local i: integer; return function(j) i = j; end; end
> > f=x()
> > f(5)
> > f('hello')
>
> Haven't thought yet how to fix this:
> a) Probably easiest to disallow referencing typed values in up-values
> b) Alternatively up-values need to be typed ... not sure if that is
> possible to enforce at compile time
>
> Regards
> Dibyendu

I don't understand. Is it a design problem or implementation issue? As a design question, it seems straightforward. The last line should error and that seems unambiguous to me. 

local i: integer --declaration. 

return function(j) --argument j is declared as a non-typed value.

  i = j --at runtime, you'll need to check if j is an integer or not because i is a reference to a static type. 

...

Anything other than that would be confusing to me, r am I missing something?

-Andrew