There is a certain risk, that the mustBeBooleanMagicIn method rewrite can crash the
vm

Issue 13805

The receiver of the rewritten method is the "nonboolean" value receiving the
ifTrue:ifFalse: message. But the rewritten method can include
instvar accessor and self sends of the original method.

We can include more rewrite rules in mustBeBooleanMagicIn like

�� "rewrite instvar accessing"

�� context receiver class instVarNamesAndOffsetsDo: [ :n :o |
�� RBParseTreeRewriter new
�� replace: n with: ('ThisContext receiver instVarAt: ', o asString);
�� executeTree: methodNode.
�� ].

"rewrite self sends"

�� RBParseTreeRewriter new
�� replace: 'self' with: 'ThisContext receiver';
�� executeTree: methodNode.

But I don't know if this works for all possible situations. Or if there are
better ways to do the rewriting.