This patch makes error handling for region inference failures more
uniform by not reporting *any* region errors until the reigon inference
step. This requires threading through more information about what
caused a region constraint, so that we can still give informative
error messages.
I have only taken partial advantage of this information: when region
inference fails, we still report the same error we always did, despite
the fact that we now know precisely what caused the various constriants
and what the region variable represents, which we did not know before.
This change is required not only to improve error messages but
because the region hierarchy is not in fact fully known until regionck,
because it is not clear where closure bodies fit in (our current
treatment is unsound). Moreover, the relationships between free variables
cannot be fully determined until type inference is otherwise complete.
cc #3238.
borrow checker and generalize what moves are allowed. Fixes a nasty
bug or two in the pattern move checking code. Unifies dataflow code
used for initialization and other things. First step towards
once fns. Everybody wins.
Fixes#4384. Fixes#4715. cc once fns (#2202), optimizing local moves (#5016).
Changes:
- Refactor move mode computation
- Removes move mode arguments, unary move, capture clauses
(though they still parse for backwards compatibility)
- Simplify how moves are handled in trans
- Fix a number of illegal copies that cropped up
- Workaround for bug involving def-ids in params
(see details below)
Future work (I'll open bugs for these...):
- Improve error messages for moves that are due
to bindings
- Add support for moving owned content like a.b.c
to borrow check, test in trans (but I think it'll
"just work")
- Proper fix for def-ids in params
Def ids in params:
Move captures into a map instead of recomputing.
This is a workaround for a larger bug having to do with the def-ids associated
with ty_params, which are not always properly preserved when inlining. I am
not sure of my preferred fix for the larger bug yet. This current fix removes
the only code in trans that I know of which relies on ty_param def-ids, but
feels fragile.
