My ConstraintMorphs are parameterized using pluggable blocks. This is causing 
problems with dangling pointers:

	ConstraintMorph instvar targetBlock points to a BlockContext
	BlockContext home points to a MethodContext
	indexed fields of MethodContext hang on to their last arguments

That is, I'm doing something like this in 
ConstraintMorph>>connectToNearestPoint

	constraintMorph _ [ :c :m | m nearestPointTo: c center ].

And as soon as that block is evaluated with m set to another Morph, I can't 
get rid of the reference to m.

I'm using a WeakArray in ConstraintMorph, but it's not doing any good, since 
the indexed fields in the MethodContext aren't weak.

Is this a case of needing real closures?

Any suggestions? Should I stay away from pluggable blocks and use selectors 
instead (which is what seems to be done for the Pluggable*Morph family)?

One idea I had was, since the input to the constraint is typically a Morph, I 
could try to determine if the Morph had been deleted by looking at its owner. 
Is this likely to be reliable?

-- 
Ned Konz
currently: Stanwood, WA
email:     ned at bike-nomad.com
homepage:  http://bike-nomad.com