On 3 March 2012 16:29, Lawson English <lenglish5 at cox.net> wrote:
> A discussion in IRC prompted me to try several things.
>
>
> In a nutshell, execute these two lines with two separate doits and you get
> an error.
> Select both lines and doit and you don't:
>
> a := [^true].
> a value.
>
> I assume there is a valid reason for the difference in behavior, but it DOES
> remind one that workspace behavior isn't always the same as method behavior,
> even for something as simple as the above.

Indeed. Given there's a non-local return in the block, the statement
"return from the method context that invoked me" means something
rather different in the two ways you run this.

In the second case, you'll have an UndefinedObject>>DoIt context (call
it C1) running "a := [^true]". The ^ captures the home context - C1 -
so that when the block returns, it will return from C1. Since "a
value" then executes within C1's context, there's no problem.

But in the first case, C1 executes "a := [^ true]", finishes, and then
pops off the call stack. When you select "a value", it too executes
within an UndefinedObject>>DoIt context (call it C2). The block then
executes and "^ true" tries to return... from C1. Only C1's now
garbage.

In fact, within the debugger, go to the MethodContext>>cannotReturn:
context, and explore  "self home". You'll see that receiver = nil,
indicating that it's not connected to a call stack. Compare that
context with thisContext, and you'll see that thisContext receiver ~=
nil.

frank