Simon Peyton Jones authored Dec 30, 2020 and Marge Bot committed Jan 02, 2021

This patch fixes #19133 by using LitRubbish for strict constructor
fields, even if they are of lifted types.  Previously LitRubbish
worked only for unlifted (but boxed) types.

The change is very easy, although I needed a boolean field in
LitRubbish to say whether or not it is lifted.  (That seemed easier
than giving it another type argument.

This is preparing for Andreas's work on establishing the invariant
that strict constructor fields are always tagged and evaluated
(see #16970).

Meanwhile, nothing was actually wrong before, so there are no tests.