Currently analyze_move_out_from checks all restrictions on all base
paths of the move path, but it only needs to check restrictions from
loans of the base paths, and can disregard restrictions from loans of
extensions of those base paths.
Instead of calling a borrow() function that takes a pointer type, just
create a local pointer and dereference it. The dereference is there to
outsmart any future liveness analysis in borrowck.
The move_after_borrow / fu_move_after_borrow tests in
run-pass/borrowck-field-sensitivity.rs are not testing the right thing,
since the scope of the borrow is limited to the call to borrow(). When
fixed, these tests fail and thus should be moved to the corresponding
compile-fail test file.
A number of borrowck field-sensitivity tests perform more moves and
copies than their naming scheme would indicate. This is only necessary
for borrowed pointers (to ensure that the borrowws stay alive in the
near future when borrow liveness is tracked), but all other test
functions should be changed to match their name more closely.
Some of the borrowck field-sensitivity test functions have 'use' in
their name, but they don't refer to the specific kind of use (whether a
copy or a deref). It would be better if the name more precisely
reflected what the function is testing.
