In 30456, I'm in the process of porting the Tiling Window Manager. I'm experiencing this confusing error... TWMDockingBarMorph DNU @ In DockingBarMorph>>updatePosition there is the following code: self isAdheringToLeft ifTrue: [| usedHeight usedWidth | usedHeight := self usedHeightByPredominantDockingBarsOfChastes: #(#top ). usedWidth := self usedWidthByPredominantDockingBarsOfChastes: #(#left ). (usedHeight isNumber not or: [usedWidth isNumber]) ifFalse: [ Halt once ]. usedHeight := 1000. usedWidth := 100. self topLeft: self owner topLeft - margin + (usedWidth @ usedHeight)]. Pharo is saying that usedWidth = aTWMDockingBarMorph, even though it's set to a number (for debugging) in the preceding statement. Any ideas? Thanks. ----- Cheers, Sean -- View this message in context: http://forum.world.st/How-is-this-possible-tp4713857.html Sent from the Pharo Smalltalk Developers mailing list archive at Nabble.com.