Currently FirThisReceiverExpression of instance methods are translated
to references of the class' thisReceiver,
not the method's dispatch receiver,
which causes problems with IrFrameMap::typeOf,
as the class' thisReceiver is not in the typeMap.
This commit translates non-qualified "this" references of
instance methods to references of the methods' dispatch receiver.
Inner class constructors should use the argument instead of reading
outer `this` from a field because if such an access happens before a
delegating constructor call, e.g. when evaluating an argument, a JVM
bytecode validation error will be thrown. (The only operation on `this`
allowed before a delegating constructor call is SETFIELD, and only if
the field in question is declared in the same class.)
Juan Chen