[julia-users] expr and eval(expr) disagree about content of expr

[Constantin Berzan]

Hello,

I ran into some strange behavior with a piece of code that takes in Julia
expressions, transforms them, and then evaluates them.  Here is a minimal
example:

let
>     function make_expr(x)
>         body = x * 2
>         quote
>             function get()
>                 $body
>             end
>         end
>     end
>     ex1 = make_expr(1)
>     f1 = eval(ex1)
>     ex2 = make_expr(2)
>     f2 = eval(ex2)
>     println(ex1)
>     println(ex2)
>     println(code_lowered(f1, ()))
>     println(code_lowered(f2, ()))
>     println(f1())
>     println(f2())
> end


And here is the output I get when running this with Julia 0.3.2
(8227746b95):

begin
>     function get()
>         2
>     end
> end
> begin
>     function get()
>         4
>     end
> end
> {:($(Expr(:lambda, {}, {{},{},{}}, :(begin
>         return 4
>     end))))}
> {:($(Expr(:lambda, {}, {{},{},{}}, :(begin
>         return 4
>     end))))}
> 4
> 4


As you can see, inside the expressions we have the values 2 and 4, but
inside the compiled functions we have the values 4 and 4.

I've never seen expressions disagreeing with their eval-ed form before.  Is
this a bug?  Or am I misunderstanding something about scope?

I tried using a let statement for "body = x * 2", but that did not change
anything.

Thanks,
Constantin