Eliot Miranda uploaded a new version of Compiler to project The Trunk:
http://source.squeak.org/trunk/Compiler-eem.251.mcz

==================== Summary ====================

Name: Compiler-eem.251
Author: eem
Time: 11 February 2013, 1:11:53.981 pm
UUID: caeb538b-aaa9-46a5-b43c-51dec9220273
Ancestors: Compiler-eem.250

Yet another fix for decompilation of to:do: loops compiled
with Compiler-nice.224 or later.  If the stack is non-empty
when convertDoDoLoop is invoked, the stack must be left
non-empty.  This fixes decompilation of e.g.
^nil to: 3 do: [:i| i class]

=============== Diff against Compiler-eem.250 ===============

Item was changed:
  ----- Method: Decompiler>>convertToDoLoop (in category 'private') -----
  convertToDoLoop
  	"If statements contains the pattern
  		var := startExpr.
  		[var <= limit] whileTrue: [...statements... var := var + incConst]
  	then replace this by
  		startExpr to: limit by: incConst do: [:var | ...statements...]"
+ 	| leaveOnStack initStmt toDoStmt limitStmt |
+ 	leaveOnStack := false.
- 	| initStmt toDoStmt limitStmt |
  	(stack notEmpty
  	 and: [stack last isAssignmentNode])
  		ifTrue:
  			[initStmt := stack last.
  			 (toDoStmt := statements last toDoFromWhileWithInit: initStmt) ifNil:
  				[^self].
  			 stack removeLast.
+ 			 statements removeLast; addLast: toDoStmt.
+ 			 leaveOnStack := true]
- 			 statements removeLast; addLast: toDoStmt]
  		ifFalse:
  			[statements size < 2 ifTrue:
  				[^self].
  			initStmt := statements at: statements size-1.
  			(toDoStmt := statements last toDoFromWhileWithInit: initStmt) ifNil:
  				[^self].
  			statements removeLast; removeLast; addLast: toDoStmt].
  	initStmt variable scope: -1.  "Flag arg as block temp"
  
  	"Attempt further conversion of the pattern
  		limitVar := limitExpr.
  		startExpr to: limitVar by: incConst do: [:var | ...statements...]
  	to
  		startExpr to: limitExpr by: incConst do: [:var | ...statements...].
  	The complication here is that limitVar := limitExpr's value may be used, in which case it'll
  	be statements last, or may not be used, in which case it'll be statements nextToLast."
+ 	statements size < 2 ifTrue:
+ 		[^self].
- 	statements size < 2 ifTrue: [^ self].
  	limitStmt := statements last.
  	((limitStmt isMemberOf: AssignmentNode)
  		and: [limitStmt variable isTemp
  		and: [limitStmt variable == toDoStmt arguments first]]) ifFalse:
  			[limitStmt := statements at: statements size-1.
  			((limitStmt isMemberOf: AssignmentNode)
  				and: [limitStmt variable isTemp
  				and: [limitStmt variable == toDoStmt arguments first]]) ifFalse:
+ 					[leaveOnStack ifTrue:
+ 						[stack addLast: statements removeLast].
+ 					^self]].
- 					[^self]].
  
  	(self blockScopeRefersOnlyOnceToTemp: limitStmt variable fieldOffset) ifFalse:
  		[^self].
  	toDoStmt arguments at: 1 put: limitStmt value.
  	limitStmt variable scope: -2.  "Flag limit var so it won't print"
  	statements last == limitStmt
  		ifTrue: [statements removeLast]
  		ifFalse: [statements removeLast; removeLast; addLast: toDoStmt]!