michael@0: 
michael@0: try {
michael@0:     x = evalcx('')
michael@0:     toSource = (function() {
michael@0:         x = (new WeakMap).get(function() {})
michael@0:     })
michael@0:     valueOf = (function() {
michael@0:         schedulegc(x)
michael@0:     })
michael@0:     this + ''
michael@0:     for (v of this) {}
michael@0: } catch (e) {}
michael@0: gc()
michael@0: this + 1