Given a singleton class 'S' with possibly uninitialized static instance
(enum entry, interface companion object).
Such singleton can be referenced by name, or as an explicit or implicit
'this'.
For a given singleton class 'S' we
either use 'this@S' from context (local or captured),
or 'S' as a static instance.
Local or captured 'this@S' should be used if:
- we are in the constructor for 'S',
and corresponding instance is initialized
by super or delegating constructor call;
- we are in any other member of 'S' or any of its inner classes.
Otherwise, a static instance should be used.
(cherry picked from commit 41b1594)
