MIR-borrowck: moves of prefixes invalidate uses too
I overlooked the fact that when we check if a path is moved, we need to check for interference between the (shallow) prefixes and the use in question.
~~Long term, we may want to revise how this computation is done. For example, it might be better to represent the set of invalidated prefixes in the dataflow computation (the `maybe_uninitialized` dataflow), and thus avoid one of the loops in the code here.~~
* Update: I was wrong in my original recollection of the dataflow code, which actually does the right thing, in terms of precisely tracking substructure initialization and movement.
Fix#44833
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Update: The initial version of this PR's description (and the code as well) erroneously focused on supporting prefixes. ~~But the two main cases of interest are: 1. the *shallow* prefixes, and 2. the deref-free prefix built off a local (if the lvalue is indeed built off a local)~~
Update 2: The main cases of interest are in fact: 1. the nearest prefix with a MovePath, and 2. the suffixes.
Extend mir dump to dump each region
Building on #44878, implement the feature discussed in #44872.
Through discussions on the WG-nll-gitter, @nikomatsakis and I decided to implement this by extending `dump_mir` and all functions that it calls to take a callback of signature `FnMut(PassWhere, &mut Write) -> io::Result<()>` where `PassWhere` is an enum that represents possible locations that we may want to print out extra data in the process of dumping the MIR.
I'm not particularly wedded to the name `PassWhere`, but I felt that simply calling the enum `Where` wasn't the right thing to name it.
This work depends strongly on #44878, and should be rebased on the final version of that tree, whatever that may be.
MIR borrowck: print lvalues in error messages in the same way that the AST borrowck
Fix#44974
- Print fields with `.name` rather than `.<num>`
- Autoderef values if followed by a field or an index
- Output `[..]` when borrowing inside a slice
Fix#44833 (a very specific instance of a very broad bug).
In `check_if_path_is_moved(L)`, check nearest prefix of L with
MovePath, and suffixes of L with MovePaths.
Over the course of review, ariel pointed out a number of issues that
led to this version of the commit:
1. Looking solely at supporting prefixes does not suffice: it
overlooks checking if the path was ever actually initialized in the
first place. So you need to be willing to consider non-supporting
prefixes. Once you are looking at all prefixes, you *could* just
look at the local that forms the base of the projection, but to
handle partial initialization (which still needs to be formally
specified), this code instead looks at the nearest prefix of L that
has an associated MovePath (which, in the limit, will end up being
a local).
2. You also need to consider the suffixes of the given Lvalue, due to
how dataflow is representing partial moves of individual fields out
of struct values.
3. (There was originally a third search, but ariel pointed out that
the first and third could be folded into one.)
Also includes some drive-by refactorings to simplify some method
signatures and prefer `for _ in _` over `loop { }` (at least when it
comes semi-naturally).
MIR-borrowck: gather and signal any move errors
When building up the `MoveData` structure for a given MIR, also accumulate any erroneous actions, and then report all of those errors when the construction is complete.
This PR adds a host of move-related error constructor methods to `trait BorrowckErrors`. I think I got the notes right; but we should plan to audit all of the notes before turning MIR-borrowck on by default.
Fix#44830
Previously the constant index was reported as `[x of y]` or `[-x of y]` where
`x` was the offset and `y` the minimum length of the slice. The minus sign
wasn't in the right case since for `&[_, x, .., _, _]`, the error reported was
`[-1 of 4]`, and for `&[_, _, .., x, _]`, the error reported was `[2 of 4]`.
This commit fixes the sign so that the indexes 1 and -2 are reported, and
remove the ` of y` part of the message to make it more succinct.
`EndRegion` do not always correspond to borrow-data entries
Remove assertion that the argument to every `EndRegion` correspond to some dataflow-tracked borrow-data entry.
Fix#44828
(The comment thread on the aforementioned issue discusses why its best to just remove this assertion.)
Extend `dump_mir` and functions it calls in order to allow callers to
add custom information. We do this by adding an enum `PassWhere` and
an extra argument of type `FnMut(PassWhere, &mut Write) ->
io::Result<()>`. This callback is responsible for printing the extra
information when MIR is dumped at various stages.
For the "nll" pass, use the new mechanism to dump the `Region`
information after the header, but before the control flow graph for
every function.
In the interest of keeping the output somewhat concise, implement
a custom Debug impl for `Region`
Open Questions:
* What should we call what has been called `PassWhere` so far?
incr.comp.: Switch to red/green change tracking, remove legacy system.
This PR finally switches incremental compilation to [red/green tracking](https://github.com/rust-lang/rust/issues/42293) and completely removes the legacy dependency graph implementation -- which includes a few quite costly passes that are simply not needed with the new system anymore.
There's still some documentation to be done and there's certainly still lots of optimizing and tuning ahead -- but the foundation for red/green is in place with this PR. This has been in the making for a long time `:)`
r? @nikomatsakis
cc @alexcrichton, @rust-lang/compiler
Implicitly threaded `Location` through MoveData construction via a
`Gatherer` struct (so that we could look up the span corresponding to
the location when we need to signal an error).
Overlapping borrows can point to different lvalues.
Overlapping borrows can point to different lvalues.
There's always a basis for the overlap, so instead of removing the assert entirely, I instead pass in the prefix that we found and check that it actually is a prefix of both lvalues.
Fix#44829
MIR borrowck: move span_label to `borrowck_errors.rs`
The calls to `span_label` are moved and factorized for:
* E0503 (`cannot_use_when_mutably_borrowed()`)
* E0506 (`cannot_assign_to_borrowed()`)
Additionnally, the error E0594 (`cannot_assign_static()`) has been factorized between `check_loan.rs` and `borrowc_check.rs`.
Part of #44596
Move monomorphize::resolve() to librustc
this moves `monomorphize::resolve(..)` to librustc, and re-enables inlining for some trait methods, fixing #44389
@nikomatsakis I've kept the calls to the new `ty::Instance::resolve(....)` always `.unwrap()`-ing for the moment, how/do you want to add more debugging info via `.unwrap_or()` or something like this?
we still have some related `resolve_*` functions on monomorphize, but I wasn't sure moving them was into the scope for this PR too.
@eddyb mind to take a look too?
There's always a basis for the overlap, so instead of removing the
assert entirely, I instead pass in the prefix that we found and check
that it actually is a prefix of both lvalues.
Fix#44829
some dataflow-tracked borrow-data entry.
Fix#44828
(The comment thread on the aforementioned issue discusses why its best
to just remove this assertion.)
Mir pretty print: Add cleanup comment
I found it useful to add a comment indicating whether or not a
BasicBlock is a cleanup block or not. Hopefully you'll find it
useful too.
