Fixed regression in lub calculation.

Changing NullaryMethodType to be a SimpleTypeProxy because nearly all
its operations forward to its result type was it seems not such a good
idea, because it also meant that calling .underlying returned the result
type rather than the method type. The way this materialized was in
subtype checks of refinement types. A lub is calculated for two nullary
method types in the course of calculating a refinement, and then the
input types are checked against the calculated lub.

However in the lub refinement, the nullary method type has become a bare
typeref, and so the subtype check failed. Closes SI-5317.

This does give me confidence that all the malformed lubs one sees
logged under -Ydebug (and there are still many, especially with type
constructors) are alerting us to real bugs elsewhere in Types.

0 files changed, 0 insertions, 0 deletions