A TypeExpr and other kinds of non-lvalue bases that the borrowed-base
visitor doesn't care about can be handled by calling back into the
original SILGenLValue instance.
resolves rdar://117082469
I ran into this while fixing the parent commit when attempting to add the
interpreter test in this commit into the aforementioned parent commit.
rdar://107974302
This is used to teach the checker that the thing being checked is supposed to be
uninitialized at the mark_must_check point so that we don't put a destroy_addr
there.
The way this is implemented is that we always initially add
assignable_but_not_consumable but in DI once we discover that the assign we are
guarding is an init, we convert the assignable to its initable variant.
rdar://106525988
I also added an interpreter test that validates that ref_element_addr works as
expected (I fixed that in an earlier commit, but did not add an interpreter
test).
rdar://106724277
the main things still left behind the experimental flag(s) are
- move-only classes (guarded by MoveOnlyClasses feature)
- noimplicitcopy
- the _borrow operator
