The rules for casting `*mut X<dyn A>` -> `*mut Y<dyn B>` are as follows:
- If `B` has a principal
- `A` must have exactly the same principal (including generics)
- Auto traits of `B` must be a subset of autotraits in `A`
Note that `X<_>` and `Y<_>` can be identity, or arbitrary structs with last field being the dyn type.
The lifetime of the trait object itself (`dyn ... + 'a`) is not checked.
This prevents a few soundness issues with `#![feature(arbitrary_self_types)]` and trait upcasting.
Namely, these checks make sure that vtable is always valid for the pointee.
Stop using specialization in rustc_index and rustc_borrowck
For rustc_borrowck the version with specialization isn't much more readable anyway IMO. For rustc_index it probably doesn't affect perf in any noticeable way anyway.
Re-implement a type-size based limit
r? lcnr
This PR reintroduces the type length limit added in #37789, which was accidentally made practically useless by the caching changes to `Ty::walk` in #72412, which caused the `walk` function to no longer walk over identical elements.
Hitting this length limit is not fatal unless we are in codegen -- so it shouldn't affect passes like the mir inliner which creates potentially very large types (which we observed, for example, when the new trait solver compiles `itertools` in `--release` mode).
This also increases the type length limit from `1048576 == 2 ** 20` to `2 ** 24`, which covers all of the code that can be reached with craterbot-check. Individual crates can increase the length limit further if desired.
Perf regression is mild and I think we should accept it -- reinstating this limit is important for the new trait solver and to make sure we don't accidentally hit more type-size related regressions in the future.
Fixes#125460
Rewrite handling of universe-leaking placeholder regions into outlives constraints
This commit prepares for Polonius by moving handling of leak check/universe errors out of the inference step by rewriting any universe error into an outlives-static constraint.
This variant is a work in progress but seems to pass most tests.
Note that a few debug assertions no longer hold; a few extra eyes on those changes are appreciated!
This version is a squash-rebased version of a series
of exiermental commits, since large parts of them
were broken out into PR #125069.
It explicitly handles universe violations in higher-kinded
outlives constraints by adding extra outlives static constraints.
Automatically taint InferCtxt when errors are emitted
r? `@nnethercote`
Basically `InferCtxt::dcx` now returns a `DiagCtxt` that refers back to the `Cell<Option<ErrorGuaranteed>>` of the `InferCtxt` and thus when invoking `Diag::emit`, and the diagnostic is an error, we taint the `InferCtxt` directly.
That change on its own has no effect at all, because `InferCtxt` already tracks whether errors have been emitted by recording the global error count when it gets opened, and checking at the end whether the count changed. So I removed that error count check, which had a bit of fallout that I immediately fixed by invoking `InferCtxt::dcx` instead of `TyCtxt::dcx` in a bunch of places.
The remaining new errors are because an error was reported in another query, and never bubbled up. I think they are minor enough for this to be ok, and sometimes it actually improves diagnostics, by not silencing useful diagnostics anymore.
fixes#126485 (cc `@olafes)`
There are more improvements we can do (like tainting in hir ty lowering), but I would rather do that in follow up PRs, because it requires some refactorings.
Do not ICE when suggesting dereferencing closure arg
Account for `for` lifetimes when constructing closure to see if dereferencing the return value would be valid.
Fix#125634, fix#124563.
Remove confusing `use_polonius` flag and do less cloning
The `use_polonius` flag is both redundant and confusing since every function it's propagated to also checks if `all_facts` is `Some`, the true test of whether to generate Polonius facts for Polonius or for external consumers. This PR makes that path clearer by simply doing away with the argument and handling the logic in precisely two places: where facts are populated (check for `Some`), and where `all_facts` are initialised. It also delays some statements until after that check to avoid the miniscule performance penalty of executing them when Polonius is disabled.
This also addresses `@lqd's` concern in #125652 by reducing the size of what is cloned out of Polonius facts to just the facts being added, as opposed to the entire vector of potential inputs, and added descriptive comments.
*Reviewer note*: the comments in `add_extra_drop_facts` should be inspected by a reviewer, in particular the one on [L#259](https://github.com/rust-lang/rust/compare/master...amandasystems:you-dropped-this-again?expand=1#diff-aa727290e6670264df2face84f012897878e11a70e9c8b156543cfcd9619bac3R259) in this PR, which should be trivial for someone with the right background knowledge to address.
I also included some lints I found on the way there that I couldn't help myself from addressing.
Rename `InstanceDef` -> `InstanceKind`
Renames `InstanceDef` to `InstanceKind`. The `Def` here is confusing, and makes it hard to distinguish `Instance` and `InstanceDef`. `InstanceKind` makes this more obvious, since it's really just describing what *kind* of instance we have.
Not sure if this is large enough to warrant a types team MCP -- it's only 53 files. I don't personally think it does, but happy to write one if anyone disagrees. cc ``@rust-lang/types``
r? types
Convert a `span_bug` to a `span_delayed_bug`.
PR #121208 converted this from a `span_delayed_bug` to a `span_bug` because nothing in the test suite caused execution to hit this path. But now fuzzing has found a test case that does hit it. So this commit converts it back to `span_delayed_bug` and adds the relevant test.
Fixes#126385.
r? `@lcnr`
Make suggestion to change `Fn` to `FnMut` work with methods as well
Fixes#125325
The issue occurred because the code that emitted the suggestion to change `Fn` to `FnMut` worked only for function calls and not method calls. This PR makes it work with methods as well.
PR #121208 converted this from a `span_delayed_bug` to a `span_bug`
because nothing in the test suite caused execution to hit this path. But
now fuzzing has found a test case that does hit it. So this commit
converts it back to `span_delayed_bug` and adds the relevant test.
Fixes#126385.
Make uninitialized_error_reported a set of locals
Another artifact of how places used to be able to be based on statics and not just locals. This set is exclusively filled with PlaceRefs that are just locals, so it should just contain locals directly.
smir: merge identical Constant and ConstOperand types
The first commit renames the const operand visitor functions on regular MIR to match the type name, that was forgotten in the original rename.
The second commit changes stable MIR, fixing https://github.com/rust-lang/project-stable-mir/issues/71. Previously there were two different smir types for the MIR type `ConstOperand`, one used in `Operand` and one in `VarDebugInfoContents`.
Maybe we should have done this with https://github.com/rust-lang/rust/pull/125967, so there's only a single breaking change... but I saw that PR too late.
Fixes https://github.com/rust-lang/project-stable-mir/issues/71
Use `Variance` glob imported variants everywhere
Fully commit to using the globbed variance. Could be convinced the other way, and change this PR to not use the globbed variants anywhere, but I'd rather we do one or the other.
r? lcnr
Extend SCC construction to enable extra functionality
Do YOU feel like your SCC construction doesn't do enough? Then I have a patch for you! SCCs can now do *everything*! Well, almost.
This patch has been extracted from #123720. It specifically enhances
`Sccs` to allow tracking arbitrary commutative properties (think min/max mappings on nodes vs arbitrary closures) of strongly connected components, including
- reachable values (max/min)
- SCC-internal values (max/min)
This helps with among other things universe computation. We can now identify
SCC universes as a reasonably straightforward "find max/min" operation during SCC construction. This is also included in this patch.
It's also more or less zero-cost; don't use the new features, don't pay for them.
This commit also vastly extends the documentation of the SCCs module, which I had a very hard time following. It may or may not have gotten easier to read for someone else.
I believe this logic can also be used in leak check, but haven't checked. Ha. ha. Ha.
This patch has been extracted from #123720. It specifically enhances
`Sccs` to allow tracking arbitrary commutative properties of SCCs, including
- reachable values (max/min)
- SCC-internal values (max/min)
This helps with among other things universe computation: we can now identify
SCC universes as a straightforward "find max/min" operation during SCC construction.
It's also more or less zero-cost; don't use the new features, don't pay for them.
This commit also vastly extends the documentation of the SCCs module, which I had a very hard time following.
Use `tidy` to sort crate attributes for all compiler crates.
We already do this for a number of crates, e.g. `rustc_middle`, `rustc_span`, `rustc_metadata`, `rustc_span`, `rustc_errors`.
For the ones we don't, in many cases the attributes are a mess.
- There is no consistency about order of attribute kinds (e.g. `allow`/`deny`/`feature`).
- Within attribute kind groups (e.g. the `feature` attributes), sometimes the order is alphabetical, and sometimes there is no particular order.
- Sometimes the attributes of a particular kind aren't even grouped all together, e.g. there might be a `feature`, then an `allow`, then another `feature`.
This commit extends the existing sorting to all compiler crates, increasing consistency. If any new attribute line is added there is now only one place it can go -- no need for arbitrary decisions.
Exceptions:
- `rustc_log`, `rustc_next_trait_solver` and `rustc_type_ir_macros`, because they have no crate attributes.
- `rustc_codegen_gcc`, because it's quasi-external to rustc (e.g. it's ignored in `rustfmt.toml`).
r? `@davidtwco`
We already do this for a number of crates, e.g. `rustc_middle`,
`rustc_span`, `rustc_metadata`, `rustc_span`, `rustc_errors`.
For the ones we don't, in many cases the attributes are a mess.
- There is no consistency about order of attribute kinds (e.g.
`allow`/`deny`/`feature`).
- Within attribute kind groups (e.g. the `feature` attributes),
sometimes the order is alphabetical, and sometimes there is no
particular order.
- Sometimes the attributes of a particular kind aren't even grouped
all together, e.g. there might be a `feature`, then an `allow`, then
another `feature`.
This commit extends the existing sorting to all compiler crates,
increasing consistency. If any new attribute line is added there is now
only one place it can go -- no need for arbitrary decisions.
Exceptions:
- `rustc_log`, `rustc_next_trait_solver` and `rustc_type_ir_macros`,
because they have no crate attributes.
- `rustc_codegen_gcc`, because it's quasi-external to rustc (e.g. it's
ignored in `rustfmt.toml`).
The `use_polonius` flag is both redundant and confusing since every
function it's propagated to also checks if `all_facts` is `Some`,
the true test of whether to generate Polonius facts for Polonius
or for external consumers. This PR makes that path clearer by
simply doing away with the argument and handling the logic in
precisely two places: where facts are populated (check for `Some`),
and where `all_facts` are initialised. It also delays some statements
until after that check to avoid the miniscule performance penalty
of executing them when Polonius is disabled.
This also addresses @lqd's concern in #125652 by reducing
the size of what is cloned out of Polonius facts to just the
facts being added, as opposed to the entire vector of potential
inputs, and added descriptive comments.
*Reviewer note*: the comments in [add_extra_drop_facts](85f90a4612/compiler/rustc_borrowck/src/type_check/liveness/trace.rs (L219)) should be inspected by a reviewer,
in particular the one on L#259 in this PR, which should be trivial
for someone with the right background knowledge.
I also included some minor lints I found on the way there that I
couldn't help myself from addressing.
Silence follow-up errors directly based on error types and regions
During type_of, we used to just return an error type if there were any errors encountered. This is problematic, because it means a struct declared as `struct Foo<'static>` will end up not finding any inherent or trait impls because those impl blocks' `Self` type will be `{type error}` instead of `Foo<'re_error>`. Now it's the latter, silencing nonsensical follow-up errors about `Foo` not having any methods.
Unfortunately that now allows for new follow-up errors, because borrowck treats `'re_error` as `'static`, causing nonsensical errors about non-error lifetimes not outliving `'static`. So what I also did was to just strip all outlives bounds that borrowck found, thus never letting it check them. There are probably more nuanced ways to do this, but I worried there would be other nonsensical errors if some outlives bounds were missing. Also from the test changes, it looked like an improvement everywhere.
Use parenthetical notation for `Fn` traits
Always use the `Fn(T) -> R` format when printing closure traits instead of `Fn<(T,), Output = R>`.
Address #67100:
```
error[E0277]: expected a `Fn()` closure, found `F`
--> file.rs:6:13
|
6 | call_fn(f)
| ------- ^ expected an `Fn()` closure, found `F`
| |
| required by a bound introduced by this call
|
= note: wrap the `F` in a closure with no arguments: `|| { /* code */ }`
note: required by a bound in `call_fn`
--> file.rs:1:15
|
1 | fn call_fn<F: Fn() -> ()>(f: &F) {
| ^^^^^^^^^^ required by this bound in `call_fn`
help: consider further restricting this bound
|
5 | fn call_any<F: std::any::Any + Fn()>(f: &F) {
| ++++++
```
Revert propagation of drop-live information from Polonius
#64749 introduced a flow of drop-use data from Polonius to `LivenessResults::add_extra_drop_facts()`, which makes `LivenessResults` agree with Polonius on liveness in the presence of free regions that may be dropped. Later changes accidentally removed this flow. This PR restores it.
Rename HIR `TypeBinding` to `AssocItemConstraint` and related cleanup
Rename `hir::TypeBinding` and `ast::AssocConstraint` to `AssocItemConstraint` and update all items and locals using the old terminology.
Motivation: The terminology *type binding* is extremely outdated. "Type bindings" not only include constraints on associated *types* but also on associated *constants* (feature `associated_const_equality`) and on RPITITs of associated *functions* (feature `return_type_notation`). Hence the word *item* in the new name. Furthermore, the word *binding* commonly refers to a mapping from a binder/identifier to a "value" for some definition of "value". Its use in "type binding" made sense when equality constraints (e.g., `AssocTy = Ty`) were the only kind of associated item constraint. Nowadays however, we also have *associated type bounds* (e.g., `AssocTy: Bound`) for which the term *binding* doesn't make sense.
---
Old terminology (HIR, rustdoc):
```
`TypeBinding`: (associated) type binding
├── `Constraint`: associated type bound
└── `Equality`: (associated) equality constraint (?)
├── `Ty`: (associated) type binding
└── `Const`: associated const equality (constraint)
```
Old terminology (AST, abbrev.):
```
`AssocConstraint`
├── `Bound`
└── `Equality`
├── `Ty`
└── `Const`
```
New terminology (AST, HIR, rustdoc):
```
`AssocItemConstraint`: associated item constraint
├── `Bound`: associated type bound
└── `Equality`: associated item equality constraint OR associated item binding (for short)
├── `Ty`: associated type equality constraint OR associated type binding (for short)
└── `Const`: associated const equality constraint OR associated const binding (for short)
```
r? compiler-errors
Always use the `Fn(T) -> R` format when printing closure traits instead of `Fn<(T,), Output = R>`.
Fix#67100:
```
error[E0277]: expected a `Fn()` closure, found `F`
--> file.rs:6:13
|
6 | call_fn(f)
| ------- ^ expected an `Fn()` closure, found `F`
| |
| required by a bound introduced by this call
|
= note: wrap the `F` in a closure with no arguments: `|| { /* code */ }`
note: required by a bound in `call_fn`
--> file.rs:1:15
|
1 | fn call_fn<F: Fn() -> ()>(f: &F) {
| ^^^^^^^^^^ required by this bound in `call_fn`
help: consider further restricting this bound
|
5 | fn call_any<F: std::any::Any + Fn()>(f: &F) {
| ++++++
```
This shunts all the complexity of siphoning off the drop-use facts
into `LivenessResults::add_extra_drop_facts()`, which may or may
not be a good approach.
Follow-up fixes to `report_return_mismatched_types`
Some renames, simplifications, fixes, etc. Follow-ups to #123804. I don't think it totally disentangles this code, but it does remove some of the worst offenders on the "I am so confused" scale (e.g. `get_node_fn_decl`).
Uplift `RegionVid`, `TermKind` to `rustc_type_ir`, and `EagerResolver` to `rustc_next_trait_solver`
- Uplift `RegionVid`. This was complicated due to the fact that we implement `polonius_engine::Atom` for `RegionVid` -- but I just separated that into `PoloniusRegionVid`, and added `From`/`Into` impls so it can be defined in `rustc_borrowck` separately. Coherence 😵
- Change `InferCtxtLike` to expose `opportunistically_resolve_{ty,ct,lt,int,float}_var` so that we can uplift `EagerResolver` for use in the canonicalization methods.
- Uplift `TermKind` much like `GenericArgKind`
All of this is miscellaneous dependencies for making more `EvalCtxt` methods generic.
Coroutines can be prefixed with the `static` keyword to make them
`!Unpin`.
However, given the following function:
```rust
fn check() -> impl Sized {
let x = 0;
#[coroutine]
static || {
yield;
x
}
}
```
We currently suggest prefixing `move` before `static`, which is
syntactically incorrect:
```
error[E0373]: coroutine may outlive the current function, but it borrows
...
--> src/main.rs:6:5
|
6 | static || {
| ^^^^^^^^^ may outlive borrowed value `x`
7 | yield;
8 | x
| - `x` is borrowed here
|
note: coroutine is returned here
--> src/main.rs:6:5
|
6 | / static || {
7 | | yield;
8 | | x
9 | | }
| |_____^
help: to force the coroutine to take ownership of `x` (and any other
referenced variables), use the `move` keyword
| // this is syntactically incorrect, it should be `static move ||`
6 | move static || {
| ++++
```
This PR suggests adding `move` after `static` for these coroutines.
chore: Remove repeated words (extension of #124924)
When I saw #124924 I thought "Hey, I'm sure that there are far more than just two typos of this nature in the codebase". So here's some more typo-fixing.
Some found with regex, some found with a spellchecker. Every single one manually reviewed by me (along with hundreds of false negatives by the tools)
Rename Unsafe to Safety
Alternative to #124455, which is to just have one Safety enum to use everywhere, this opens the posibility of adding `ast::Safety::Safe` that's useful for unsafe extern blocks.
This leaves us today with:
```rust
enum ast::Safety {
Unsafe(Span),
Default,
// Safe (going to be added for unsafe extern blocks)
}
enum hir::Safety {
Unsafe,
Safe,
}
```
We would convert from `ast::Safety::Default` into the right Safety level according the context.
Rename some `FulfillmentErrorCode`/`ObligationCauseCode` variants to be less redundant
1. Rename some `FulfillmentErrorCode` variants.
2. Always use `ObligationCauseCode::` to prefix a code, rather than using a glob import and naming them through `traits::`.
3. Rename some `ObligationCauseCode` variants -- I wasn't particularly thorough with thinking of a new names for these, so could workshop them if necessary.
4. Misc stuff from renaming.
r? lcnr
Eliminate some `FIXME(lcnr)` comments
In some cases this involved changing code. In some cases the comment was able to removed or replaced.
r? ``@lcnr``
Rename `Generics::params` to `Generics::own_params`
I hope this makes it slightly more obvious that `generics.own_params` is insufficient when considering nested items. I didn't actually audit any of the usages, for the record.
r? lcnr
`InferCtxt::next_{ty,const}_var*` all take an origin, but the
`param_def_id` is almost always `None`. This commit changes them to just
take a `Span` and build the origin within the method, and adds new
methods for the rare cases where `param_def_id` might not be `None`.
This avoids a lot of tedious origin building.
Specifically:
- next_ty_var{,_id_in_universe,_in_universe}: now take `Span` instead of
`TypeVariableOrigin`
- next_ty_var_with_origin: added
- next_const_var{,_in_universe}: takes Span instead of ConstVariableOrigin
- next_const_var_with_origin: added
- next_region_var, next_region_var_in_universe: these are unchanged,
still take RegionVariableOrigin
The API inconsistency (ty/const vs region) seems worth it for the
large conciseness improvements.
When encountering a move conflict, on an expression that is `!Copy` passed as an argument to an `fn` that is `impl AsRef`, suggest borrowing the expression.
```
error[E0382]: use of moved value: `bar`
--> f204.rs:14:15
|
12 | let bar = Bar;
| --- move occurs because `bar` has type `Bar`, which does not implement the `Copy` trait
13 | foo(bar);
| --- value moved here
14 | let baa = bar;
| ^^^ value used here after move
|
help: borrow the value to avoid moving it
|
13 | foo(&bar);
| +
```
Fix#41708
It provides a way to effectively embed a linked list within an
`IndexVec` and also iterate over that list. It's written in a very
generic way, involving two traits `Links` and `LinkElem`. But the
`Links` trait is only impl'd for `IndexVec` and `&IndexVec`, and the
whole thing is only used in one module within `rustc_borrowck`. So I
think it's over-engineered and hard to read. Plus it has no comments.
This commit removes it, and adds a (non-generic) local iterator for the
use within `rustc_borrowck`. Much simpler.
Remove many `#[macro_use] extern crate foo` items
This requires the addition of more `use` items, which often make the code more verbose. But they also make the code easier to read, because `#[macro_use]` obscures where macros are defined.
r? `@fee1-dead`
Remove optionality from MoveData::base_local
This is an artifact from when Places could be based on statics and not just locals. Now, all move paths either are locals or have parents, so this doesn't need to return Option anymore.
```
error[E0499]: cannot borrow `foo` as mutable more than once at a time
--> $DIR/suggest-split-at-mut.rs:13:18
|
LL | let a = &mut foo[..2];
| --- first mutable borrow occurs here
LL | let b = &mut foo[2..];
| ^^^ second mutable borrow occurs here
LL | a[0] = 5;
| ---- first borrow later used here
|
= help: use `.split_at_mut(position)` or similar method to obtain two mutable non-overlapping sub-slices
```
Address most of #58792.
For follow up work, we should emit a structured suggestion for cases where we can identify the exact `let (a, b) = foo.split_at_mut(2);` call that is needed.
```
error[E0507]: cannot move out of `bar`, a captured variable in an `FnMut` closure
--> $DIR/borrowck-move-by-capture.rs:9:29
|
LL | let bar: Box<_> = Box::new(3);
| --- captured outer variable
LL | let _g = to_fn_mut(|| {
| -- captured by this `FnMut` closure
LL | let _h = to_fn_once(move || -> isize { *bar });
| ^^^^^^^^^^^^^^^^ ----
| | |
| | variable moved due to use in closure
| | move occurs because `bar` has type `Box<isize>`, which does not implement the `Copy` trait
| `bar` is moved here
|
help: clone the value before moving it into the closure
|
LL ~ let value = bar.clone();
LL ~ let _h = to_fn_once(move || -> isize { value });
|
```
```
error[E0382]: use of moved value: `t`
--> $DIR/use_of_moved_value_copy_suggestions.rs:7:9
|
LL | fn duplicate_t<T>(t: T) -> (T, T) {
| - move occurs because `t` has type `T`, which does not implement the `Copy` trait
...
LL | (t, t)
| - ^ value used here after move
| |
| value moved here
|
help: if `T` implemented `Clone`, you could clone the value
--> $DIR/use_of_moved_value_copy_suggestions.rs:4:16
|
LL | fn duplicate_t<T>(t: T) -> (T, T) {
| ^ consider constraining this type parameter with `Clone`
...
LL | (t, t)
| - you could clone this value
help: consider restricting type parameter `T`
|
LL | fn duplicate_t<T: Copy>(t: T) -> (T, T) {
| ++++++
```
The `help` is new. On ADTs, we also extend the output with span labels:
```
error[E0507]: cannot move out of static item `FOO`
--> $DIR/issue-17718-static-move.rs:6:14
|
LL | let _a = FOO;
| ^^^ move occurs because `FOO` has type `Foo`, which does not implement the `Copy` trait
|
note: if `Foo` implemented `Clone`, you could clone the value
--> $DIR/issue-17718-static-move.rs:1:1
|
LL | struct Foo;
| ^^^^^^^^^^ consider implementing `Clone` for this type
...
LL | let _a = FOO;
| --- you could clone this value
help: consider borrowing here
|
LL | let _a = &FOO;
| +
```
Start pointing to where bindings were declared when they are captured in closures:
```
error[E0597]: `x` does not live long enough
--> $DIR/suggest-return-closure.rs:23:9
|
LL | let x = String::new();
| - binding `x` declared here
...
LL | |c| {
| --- value captured here
LL | x.push(c);
| ^ borrowed value does not live long enough
...
LL | }
| -- borrow later used here
| |
| `x` dropped here while still borrowed
```
Suggest cloning in more cases involving closures:
```
error[E0507]: cannot move out of `foo` in pattern guard
--> $DIR/issue-27282-move-ref-mut-into-guard.rs:11:19
|
LL | if { (|| { let mut bar = foo; bar.take() })(); false } => {},
| ^^ --- move occurs because `foo` has type `&mut Option<&i32>`, which does not implement the `Copy` trait
| |
| `foo` is moved here
|
= note: variables bound in patterns cannot be moved from until after the end of the pattern guard
help: consider cloning the value if the performance cost is acceptable
|
LL | if { (|| { let mut bar = foo.clone(); bar.take() })(); false } => {},
| ++++++++
```
deref patterns: lower deref patterns to MIR
This lowers deref patterns to MIR. This is a bit tricky because this is the first kind of pattern that requires storing a value in a temporary. Thanks to https://github.com/rust-lang/rust/pull/123324 false edges are no longer a problem.
The thing I'm not confident about is the handling of fake borrows. This PR ignores any fake borrows inside a deref pattern. We are guaranteed to at least fake borrow the place of the first pointer value, which could be enough, but I'm not certain.
Make `suggest_deref_closure_return` more idiomatic/easier to understand
The only functional change here really is just making it not use a fresh type variable for upvars. I'll point that out in the code.
The rest of the changes are just stylistic, because reading this code was really confusing me (variable names were vague, ways of accessing types were unidiomatic, order of operations was kind of strange, etc).
This is stacked on #123989.
r? oli-obk since you approved #122213
Better graphviz output for SCCs and NLL constraints
This PR modifies the output for `-Z dump-mir-graphviz=yes`. Specifically, it changes the output of the files `.-------.nll.0.regioncx.all.dot` and `nll.0.regioncx.scc.dot` to be easier to read and contain some information that helped me during debugging. In particular:
- SCC indices are contracted to `SCC(n)` instead of `ConstraintSccIndex(n)` to compress the nodes
- SCC regions are in `{}` rather than `[]` (controversial since they are technically ordered by index, but I figured they're more sets than arrays conceptually since they're equivalence classes).
- For regions in other universes than the root, also show the region universe (as ?8/U1)
- For regions with external names, show the external name in parenthesis
- For the region graph where edges are locations, render the All variant of the enum without the file since it's extremely long and often destroys the rendering
- For region graph edge annotations for single locations, remove the wrapping around the Location variant and just add its contents since this can be unambiguously done
Example output (from the function `foo()` of `tests/ui/error-codes/E0582.rs`) for an SCC graph:
...and for the constraints:
This PR also gives `UniverseIndex`es the `is_root()` method since this is now an operation that happens three times in the borrowck crate.
Remove `TypeVariableOriginKind` and `ConstVariableOriginKind`
It's annoying to have to import `TypeVariableOriginKind` just to fill it with `MiscVariable` for almost every use. Every other usage other than `TypeParameterDefinition` wasn't even used -- I can see how it may have been useful once for debugging, but I do quite a lot of typeck debugging and I've never really needed it.
So let's just remove it, and keep around the only useful thing which is the `DefId` of the param for `var_for_def`.
This is based on #123006, which removed the special use of `TypeVariableOriginKind::OpaqueInference`, which I'm pretty sure I was the one that added.
r? lcnr or re-roll to types
Fix various bugs in `ty_kind_suggestion`
Consolidates two implementations of `ty_kind_suggestion`
Fixes some misuse of the empty param-env
Fixes a problem where we suggested `(42)` instead of `(42,)` for tuple suggestions
Suggest a value when `return;`, making it consistent with `break;`
Fixes#123906
Does not necessarily change much, but we never overwrite it, so I see no reason
for it to be in the `Successors` trait. (+we already have a similar `is_cyclic`)
Detect borrow checker errors where `.clone()` would be an appropriate user action
When a value is moved twice, suggest cloning the earlier move:
```
error[E0509]: cannot move out of type `U2`, which implements the `Drop` trait
--> $DIR/union-move.rs:49:18
|
LL | move_out(x.f1_nocopy);
| ^^^^^^^^^^^
| |
| cannot move out of here
| move occurs because `x.f1_nocopy` has type `ManuallyDrop<RefCell<i32>>`, which does not implement the `Copy` trait
|
help: consider cloning the value if the performance cost is acceptable
|
LL | move_out(x.f1_nocopy.clone());
| ++++++++
```
When a value is borrowed by an `fn` call, consider if cloning the result of the call would be reasonable, and suggest cloning that, instead of the argument:
```
error[E0505]: cannot move out of `a` because it is borrowed
--> $DIR/variance-issue-20533.rs:53:14
|
LL | let a = AffineU32(1);
| - binding `a` declared here
LL | let x = bat(&a);
| -- borrow of `a` occurs here
LL | drop(a);
| ^ move out of `a` occurs here
LL | drop(x);
| - borrow later used here
|
help: consider cloning the value if the performance cost is acceptable
|
LL | let x = bat(&a).clone();
| ++++++++
```
otherwise, suggest cloning the argument:
```
error[E0505]: cannot move out of `a` because it is borrowed
--> $DIR/variance-issue-20533.rs:59:14
|
LL | let a = ClonableAffineU32(1);
| - binding `a` declared here
LL | let x = foo(&a);
| -- borrow of `a` occurs here
LL | drop(a);
| ^ move out of `a` occurs here
LL | drop(x);
| - borrow later used here
|
help: consider cloning the value if the performance cost is acceptable
|
LL - let x = foo(&a);
LL + let x = foo(a.clone());
|
```
This suggestion doesn't attempt to square out the types between what's cloned and what the `fn` expects, to allow the user to make a determination on whether to change the `fn` call or `fn` definition themselves.
Special case move errors caused by `FnOnce`:
```
error[E0382]: use of moved value: `blk`
--> $DIR/once-cant-call-twice-on-heap.rs:8:5
|
LL | fn foo<F:FnOnce()>(blk: F) {
| --- move occurs because `blk` has type `F`, which does not implement the `Copy` trait
LL | blk();
| ----- `blk` moved due to this call
LL | blk();
| ^^^ value used here after move
|
note: `FnOnce` closures can only be called once
--> $DIR/once-cant-call-twice-on-heap.rs:6:10
|
LL | fn foo<F:FnOnce()>(blk: F) {
| ^^^^^^^^ `F` is made to be an `FnOnce` closure here
LL | blk();
| ----- this value implements `FnOnce`, which causes it to be moved when called
```
Account for redundant `.clone()` calls in resulting suggestions:
```
error[E0507]: cannot move out of dereference of `S`
--> $DIR/needs-clone-through-deref.rs:15:18
|
LL | for _ in self.clone().into_iter() {}
| ^^^^^^^^^^^^ ----------- value moved due to this method call
| |
| move occurs because value has type `Vec<usize>`, which does not implement the `Copy` trait
|
note: `into_iter` takes ownership of the receiver `self`, which moves value
--> $SRC_DIR/core/src/iter/traits/collect.rs:LL:COL
help: you can `clone` the value and consume it, but this might not be your desired behavior
|
LL | for _ in <Vec<usize> as Clone>::clone(&self).into_iter() {}
| ++++++++++++++++++++++++++++++ ~
```
We use the presence of `&mut` values in a move error as a proxy for the user caring about side effects, so we don't emit a clone suggestion in that case:
```
error[E0505]: cannot move out of `s` because it is borrowed
--> $DIR/borrowck-overloaded-index-move-index.rs:53:7
|
LL | let mut s = "hello".to_string();
| ----- binding `s` declared here
LL | let rs = &mut s;
| ------ borrow of `s` occurs here
...
LL | f[s] = 10;
| ^ move out of `s` occurs here
...
LL | use_mut(rs);
| -- borrow later used here
```
We properly account for `foo += foo;` errors where we *don't* suggest `foo.clone() += foo;`, instead suggesting `foo += foo.clone();`.
---
Each commit can be reviewed in isolation. There are some "cleanup" commits, but kept them separate in order to show *why* specific changes were being made, and their effect on tests' output.
Fix#49693, CC #64167.
Account for trait/impl difference when suggesting changing argument from ref to mut ref
Do not ICE when encountering a lifetime error involving an argument with an immutable reference of a method that differs from the trait definition.
Fix#123414.
We attempt to suggest an appropriate clone for move errors on expressions
like `S { ..s }` where a field isn't `Copy`. If we can't suggest, we still don't
emit the incorrect suggestion of `S { ..s }.clone()`.
```
error[E0509]: cannot move out of type `S<K>`, which implements the `Drop` trait
--> $DIR/borrowck-struct-update-with-dtor.rs:28:19
|
LL | let _s2 = S { a: 2, ..s0 };
| ^^^^^^^^^^^^^^^^
| |
| cannot move out of here
| move occurs because `s0.c` has type `K`, which does not implement the `Copy` trait
|
help: clone the value from the field instead of using the spread operator syntax
|
LL | let _s2 = S { a: 2, c: s0.c.clone(), ..s0 };
| +++++++++++++++++
```
```
error[E0509]: cannot move out of type `S<()>`, which implements the `Drop` trait
--> $DIR/borrowck-struct-update-with-dtor.rs:20:19
|
LL | let _s2 = S { a: 2, ..s0 };
| ^^^^^^^^^^^^^^^^
| |
| cannot move out of here
| move occurs because `s0.b` has type `B`, which does not implement the `Copy` trait
|
note: `B` doesn't implement `Copy` or `Clone`
--> $DIR/borrowck-struct-update-with-dtor.rs:4:1
|
LL | struct B;
| ^^^^^^^^
help: if `B` implemented `Clone`, you could clone the value from the field instead of using the spread operator syntax
|
LL | let _s2 = S { a: 2, b: s0.b.clone(), ..s0 };
| +++++++++++++++++
```
```
error[E0382]: use of moved value: `blk`
--> $DIR/once-cant-call-twice-on-heap.rs:8:5
|
LL | fn foo<F:FnOnce()>(blk: F) {
| --- move occurs because `blk` has type `F`, which does not implement the `Copy` trait
LL | blk();
| ----- `blk` moved due to this call
LL | blk();
| ^^^ value used here after move
|
note: `FnOnce` closures can only be called once
--> $DIR/once-cant-call-twice-on-heap.rs:6:10
|
LL | fn foo<F:FnOnce()>(blk: F) {
| ^^^^^^^^ `F` is made to be an `FnOnce` closure here
LL | blk();
| ----- this value implements `FnOnce`, which causes it to be moved when called
```
```
error[E0505]: cannot move out of `a` because it is borrowed
--> $DIR/variance-issue-20533.rs:28:14
|
LL | let a = AffineU32(1);
| - binding `a` declared here
LL | let x = foo(&a);
| -- borrow of `a` occurs here
LL | drop(a);
| ^ move out of `a` occurs here
LL | drop(x);
| - borrow later used here
|
help: consider cloning the value if the performance cost is acceptable
|
LL | let x = foo(&a).clone();
| ++++++++
```
```
error[E0507]: cannot move out of `val`, a captured variable in an `FnMut` closure
--> $DIR/issue-87456-point-to-closure.rs:10:28
|
LL | let val = String::new();
| --- captured outer variable
LL |
LL | take_mut(|| {
| -- captured by this `FnMut` closure
LL |
LL | let _foo: String = val;
| ^^^ move occurs because `val` has type `String`, which does not implement the `Copy` trait
|
help: consider borrowing here
|
LL | let _foo: String = &val;
| +
help: consider cloning the value if the performance cost is acceptable
|
LL | let _foo: String = val.clone();
| ++++++++
```
```
error[E0507]: cannot move out of `*x` which is behind a shared reference
--> $DIR/borrowck-fn-in-const-a.rs:6:16
|
LL | return *x
| ^^ move occurs because `*x` has type `String`, which does not implement the `Copy` trait
|
help: consider cloning the value if the performance cost is acceptable
|
LL - return *x
LL + return x.clone()
|
```
Tweak value suggestions in `borrowck` and `hir_analysis`
Unify the output of `suggest_assign_value` and `ty_kind_suggestion`.
Ideally we'd make these a single function, but doing so would likely require modify the crate dependency tree.
Provide suggestion to dereference closure tail if appropriate
When encoutnering a case like
```rust
use std::collections::HashMap;
fn main() {
let vs = vec![0, 0, 1, 1, 3, 4, 5, 6, 3, 3, 3];
let mut counts = HashMap::new();
for num in vs {
let count = counts.entry(num).or_insert(0);
*count += 1;
}
let _ = counts.iter().max_by_key(|(_, v)| v);
```
produce the following suggestion
```
error: lifetime may not live long enough
--> $DIR/return-value-lifetime-error.rs:13:47
|
LL | let _ = counts.iter().max_by_key(|(_, v)| v);
| ------- ^ returning this value requires that `'1` must outlive `'2`
| | |
| | return type of closure is &'2 &i32
| has type `&'1 (&i32, &i32)`
|
help: dereference the return value
|
LL | let _ = counts.iter().max_by_key(|(_, v)| **v);
| ++
```
Fix#50195.
Unify the output of `suggest_assign_value` and `ty_kind_suggestion`.
Ideally we'd make these a single function, but doing so would likely require modify the crate dependency tree.
Pass list of defineable opaque types into canonical queries
This eliminates `DefiningAnchor::Bubble` for good and brings the old solver closer to the new one wrt cycles and nested obligations. At that point the difference between `DefiningAnchor::Bind([])` and `DefiningAnchor::Error` was academic. We only used the difference for some sanity checks, which actually had to be worked around in places, so I just removed `DefiningAnchor` entirely and just stored the list of opaques that may be defined.
fixes#108498
fixes https://github.com/rust-lang/rust/issues/116877
* [x] run crater
- https://github.com/rust-lang/rust/pull/122077#issuecomment-2013293931
Do not ICE when encountering a lifetime error involving an argument with
an immutable reference of a method that differs from the trait definition.
Fix#123414.
When encoutnering a case like
```rust
//@ run-rustfix
use std::collections::HashMap;
fn main() {
let vs = vec![0, 0, 1, 1, 3, 4, 5, 6, 3, 3, 3];
let mut counts = HashMap::new();
for num in vs {
let count = counts.entry(num).or_insert(0);
*count += 1;
}
let _ = counts.iter().max_by_key(|(_, v)| v);
```
produce the following suggestion
```
error: lifetime may not live long enough
--> $DIR/return-value-lifetime-error.rs:13:47
|
LL | let _ = counts.iter().max_by_key(|(_, v)| v);
| ------- ^ returning this value requires that `'1` must outlive `'2`
| | |
| | return type of closure is &'2 &i32
| has type `&'1 (&i32, &i32)`
|
help: dereference the return value
|
LL | let _ = counts.iter().max_by_key(|(_, v)| **v);
| ++
```
Fix#50195.
