rustc: Start moving toward "try_get is a bug" for incremental
This PR is an effort to burn down some of the work items on #42633. The basic change here was to leave the `try_get` function exposed but have it return a `DiagnosticBuilder` instead of a `CycleError`. This means that it should be a compiler bug to *not* handle the error as dropping a diagnostic should result in a complier panic.
After that change it was then necessary to update the compiler's callsites of `try_get` to handle the error coming out. These were handled as:
* The `sized_constraint` and `needs_drop_raw` checks take the diagnostic and defer it as a compiler bug. This was a new piece of functionality added to the error handling infrastructure, and the idea is that for both these checks a "real" compiler error should be emitted elsewhere, so it's only a bug if we don't actually emit the complier error elsewhere.
* MIR inlining was updated to just ignore the diagnostic. This is being tracked by https://github.com/rust-lang/rust/issues/43542 which sounded like it either already had some work underway or was planning to change regardless.
* The final case, `item_path`, is still sort of up for debate. At the time of this writing this PR simply removes the invocations of `try_get` there, assuming that the query will always succeed. This turns out to be true for the test suite anyway! It sounds like, though, that this logic was intended to assist in "weird" situations like `RUST_LOG` where debug implementations can trigger at any time. This PR would therefore, however, break those implementations.
I'm unfortunately sort of out of ideas on how to handle `item_path`, but other thoughts would be welcome!
Closes#42633
(This crept in during the shift from a transform to a query; I didn't
notice because my muscle memory was still always passing `-Z
mir-borrowck`, while my test cases *also* had the
`#[rustc_mir_borrowck]` attribute attached to them.)
Generate builtin impls for `Clone`
This fixes a long-standing ICE and limitation where some builtin types implement `Copy` but not `Clone` (whereas `Clone` is a super trait of `Copy`).
However, this PR has a few side-effects:
* `Clone` is now marked as a lang item.
* `[T; N]` is now `Clone` if `T: Clone` (currently, only if `T: Copy` and for `N <= 32`).
* `fn foo<'a>() where &'a mut (): Clone { }` won't compile anymore because of how bounds for builtin traits are handled (e.g. same thing currently if you replace `Clone` by `Copy` in this example). Of course this function is unusable anyway, an error would pop as soon as it is called.
Hence, I'm wondering wether this PR would need an RFC...
Also, cc-ing @nikomatsakis, @arielb1.
Related issues: #28229, #24000.
Mir borrowck as query
Turn the `mir-borrowck` pass (aka "transform") into a query.
(If I had realized how relatively easy this was going to be, I would have made it part of #43108. `let hindsight = 20/20;`)
rustc: Add `Local` to the HIR map of parents
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
One can either use `-Z borrowck-mir` or add the `#[rustc_mir_borrowck]` attribute
to opt into MIR based borrow checking.
Note that regardless of whether one opts in or not, AST-based borrow
check will still run as well. The errors emitted from AST-based
borrow check will include a "(Ast)" suffix in their error message,
while the errors emitted from MIR-based borrow check will include a
"(Mir)" suffix.
post-rebase: removed check for intra-statement mutual conflict;
replaced with assertion checking that at most one borrow is generated
per statement.
post-rebase: removed dead code: `IdxSet::pairs` and supporting stuff.
post-rebase: Do not put "(Ast)" suffix in error msg unless passed `-Z borrowck-mir`.
(But unconditionally include "(Mir)" suffix for mir-borrowck errors.)
emit StorageLive for box temporaries
We started emitting StorageDead, so we better emit the corrseponding
StorageLive to avoid problems.
cc #43772solson/miri#303
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?
