When walking parents for lints we want to be sure to hit `let` statements which
can have attributes, so hook up these statements in the HIR map.
Closes#43910
post-rebase: Do not put "(Ast)" suffix in error msg unless passed `-Z borrowck-mir`.
(But unconditionally include "(Mir)" suffix for mir-borrowck errors.)
Use hir::ItemLocalId as keys in TypeckTables.
This PR makes `TypeckTables` use `ItemLocalId` instead of `NodeId` as key. This is needed for incremental compilation -- for stable hashing and for being able to persist and reload these tables. The PR implements the most important part of https://github.com/rust-lang/rust/issues/40303.
Some notes on the implementation:
* The PR adds the `HirId` to HIR nodes where needed (`Expr`, `Local`, `Block`, `Pat`) which obviates the need to store a `NodeId -> HirId` mapping in crate metadata. Thanks @eddyb for the suggestion! In the future the `HirId` should completely replace the `NodeId` in HIR nodes.
* Before something is read or stored in one of the various `TypeckTables` subtables, the entry's key is validated via the new `TypeckTables::validate_hir_id()` method. This makes sure that we are not mixing information from different items in a single table.
That last part could be made a bit nicer by either (a) new-typing the table-key and making `validate_hir_id()` the only way to convert a `HirId` to the new-typed key, or (b) just encapsulate sub-table access a little better. This PR, however, contents itself with not making things significantly worse.
Also, there's quite a bit of switching around between `NodeId`, `HirId`, and `DefIndex`. These conversions are cheap except for `HirId -> NodeId`, so if the valued reviewer finds such an instance in a performance critical place, please let me know.
Ideally we convert more and more code from `NodeId` to `HirId` in the future so that there are no more `NodeId`s after HIR lowering anywhere. Then the amount of switching should be minimal again.
r? @eddyb, maybe?
The mutability system now checks where derefs go through borrows in the
loan chain, and can correctly detect mutable borrows inside structs and
tuples.
borrowck: skip CFG construction when there is nothing to propagate
CFG construction takes a large amount of time and memory, especially for
large constants. If such a constant contains no actions on lvalues, it
can't have borrowck problems and can be ignored by it.
This removes the 4.9GB borrowck peak from #36799. It seems that HIR had
grown by 300MB and MIR had grown by 500MB from the last massif
collection and that remains to be investigated, but this at least shaves
the borrowck peak.
r? @nikomatsakis
default binding modes: add pat_binding_modes
This PR kicks off the implementation of the [default binding modes RFC][1] by
introducing the `pat_binding_modes` typeck table mentioned in the [mentoring
instructions][2].
It is a WIP because I wasn't able to avoid all uses of the binding modes as
not all call sites are close enough to the typeck tables. I added marker
comments to any line matching `BindByRef|BindByValue` so that reviewers
are aware of all of them.
I will look into changing the HIR (as suggested in [2]) to not carry a
`BindingMode` unless one was explicitly specified, but this PR is good for
a first round of comments.
The actual changes are quite small and CI will fail due to overlong lines
caused by the marker comments.
See #42640.
cc @nikomatsakis
[1]: https://github.com/rust-lang/rfcs/pull/2005
[2]: https://github.com/rust-lang/rust/issues/42640#issuecomment-313535089
CFG construction takes a large amount of time and memory, especially for
large constants. If such a constant contains no actions on lvalues, it
can't have borrowck problems and can be ignored by it.
This removes the 4.9GB borrowck peak from #36799. It seems that HIR had
grown by 300MB and MIR had grown by 500MB from the last massif
collection and that remains to be investigated, but this at least shaves
the borrowck peak.
This PR kicks off the implementation of the [default binding modes RFC][1] by
introducing the `pat_binding_modes` typeck table mentioned in the [mentoring
instructions][2].
`pat_binding_modes` is populated in `librustc_typeck/check/_match.rs` and
used wherever the HIR would be scraped prior to this PR. Unfortunately, one
blemish, namely a two callers to `contains_explicit_ref_binding`, remains.
This will likely have to be removed when the second part of [1], the
`pat_adjustments` table, is tackled. Appropriate comments have been added.
See #42640.
[1]: https://github.com/rust-lang/rfcs/pull/2005
[2]: https://github.com/rust-lang/rust/issues/42640#issuecomment-313535089
Also, remove the explicit code detecting borrows over a yield. It
turns out not to be necessary -- any such borrow winds up with a
lifetime that is part of the generator type, and therefore which will
outlive the generator expression itself, which yields an
`err_out_of_scope`. So instead we intercept those errors and display
them in a nicer way.
Extended error message for mut borrow conflicts in loops
RFC issue: https://github.com/rust-lang/rfcs/issues/2080
The error message for multiple mutable borrows on the same value over loop iterations now makes it clear that the conflict comes from the borrow outlasting the loop. The wording of the error is based on the special case of the moved-value error for a value moved in a loop. Following the example of that error, the code remains the same for the special case.
This is mainly because I felt the current message is confusing in the loop case : https://github.com/rust-lang/rust/issues/43437. It's not clear that the two conflicting borrows are in different iterations of the loop, and instead it just looks like the compiler has an issue with a single line.
Error message now makes clear that mutable borrow conflicts on a single
value in a loop body is caused by the borrow outlasting a single pass of
the loop.
Loop conflicts are detected by seeing when two borrow locations are the
same - which indicates the same code being run more than once.
Turn `elaborate_drops` and `rustc_peek` implementations into MIR
passes that also live in `rustc_mir` crate.
Rewire things so `rustc_driver` uses the `ElaborateDrops` from
`rustc_mir` crate.
Replaced by adding extra imports, adding hidden code (`# ...`), modifying
examples to be runnable (sorry Homura), specifying non-Rust code, and
converting to should_panic, no_run, or compile_fail.
Remaining "```ignore"s received an explanation why they are being ignored.
MIR EndRegion Statements (was MIR dataflow for Borrows)
This PR adds an `EndRegion` statement to MIR (where the `EndRegion` statement is what terminates a borrow).
An earlier version of the PR implemented a dataflow analysis on borrow expressions, but I am now factoring that into a follow-up PR so that reviewing this one is easier. (And also because there are some revisions I want to make to that dataflow code, but I want this PR to get out of WIP status...)
This is a baby step towards MIR borrowck. I just want to get the review process going while I independently work on the remaining steps.
