Neither require nor imply lifetime bounds on opaque type for well formedness
The actual hidden type can live arbitrarily longer than any individual lifetime and arbitrarily shorter than all but one of the lifetimes.
fixes#86218fixes#84305
This is a **breaking change** but it is a necessary soundness fix
Make cycle errors recoverable
In particular, this allows rustdoc to recover from cycle errors when normalizing associated types for documentation.
In the past, ```@jackh726``` has said we need to be careful about overflow errors: https://github.com/rust-lang/rust/pull/91430#issuecomment-983997013
> Off the top of my head, we definitely should be careful about treating overflow errors the same as
"not implemented for some reason" errors. Otherwise, you could end up with behavior that is
different depending on recursion depth. But, that might be context-dependent.
But cycle errors should be safe to unconditionally report; they don't depend on the recursion depth, they will always be an error whenever they're encountered.
Helps with https://github.com/rust-lang/rust/issues/81091.
r? ```@lcnr``` cc ```@matthewjasper```
In particular, this allows rustdoc to recover from cycle errors when normalizing associated types for documentation.
In the past, `@jackh726` has said we need to be careful about overflow errors:
> Off the top of my head, we definitely should be careful about treating overflow errors the same as
"not implemented for some reason" errors. Otherwise, you could end up with behavior that is
different depending on recursion depth. But, that might be context-dependent.
But cycle errors should be safe to unconditionally report; they don't depend on the recursion depth, they will always be an error whenever they're encountered.
don't succeed `evaluate_obligation` query if new opaque types were registered
fixes#98608fixes#98604
The root cause of all this is that in type flag computation we entirely ignore nongeneric things like struct fields and the signature of function items. So if a flag had to be set for a struct if it is set for a field, that will only happen if the field is generic, as only the generic parameters are checked.
I now believe we cannot use type flags to handle opaque types. They seem like the wrong tool for this.
Instead, this PR replaces the previous logic by adding a new variant of `EvaluatedToOk`: `EvaluatedToOkModuloOpaqueTypes`, which says that there were some opaque types that got hidden types bound, but that binding may not have been legal (because we don't know if the opaque type was in its defining scope or not).
This commit makes type folding more like the way chalk does it.
Currently, `TypeFoldable` has `fold_with` and `super_fold_with` methods.
- `fold_with` is the standard entry point, and defaults to calling
`super_fold_with`.
- `super_fold_with` does the actual work of traversing a type.
- For a few types of interest (`Ty`, `Region`, etc.) `fold_with` instead
calls into a `TypeFolder`, which can then call back into
`super_fold_with`.
With the new approach, `TypeFoldable` has `fold_with` and
`TypeSuperFoldable` has `super_fold_with`.
- `fold_with` is still the standard entry point, *and* it does the
actual work of traversing a type, for all types except types of
interest.
- `super_fold_with` is only implemented for the types of interest.
Benefits of the new model.
- I find it easier to understand. The distinction between types of
interest and other types is clearer, and `super_fold_with` doesn't
exist for most types.
- With the current model is easy to get confused and implement a
`super_fold_with` method that should be left defaulted. (Some of the
precursor commits fixed such cases.)
- With the current model it's easy to call `super_fold_with` within
`TypeFolder` impls where `fold_with` should be called. The new
approach makes this mistake impossible, and this commit fixes a number
of such cases.
- It's potentially faster, because it avoids the `fold_with` ->
`super_fold_with` call in all cases except types of interest. A lot of
the time the compile would inline those away, but not necessarily
always.
`MultiSpan` contains labels, which are more complicated with the
introduction of diagnostic translation and will use types from
`rustc_errors` - however, `rustc_errors` depends on `rustc_span` so
`rustc_span` cannot use types like `DiagnosticMessage` without
dependency cycles. Introduce a new `rustc_error_messages` crate that can
contain `DiagnosticMessage` and `MultiSpan`.
Signed-off-by: David Wood <david.wood@huawei.com>
Specifically, rename the `Const` struct as `ConstS` and re-introduce `Const` as
this:
```
pub struct Const<'tcx>(&'tcx Interned<ConstS>);
```
This now matches `Ty` and `Predicate` more closely, including using
pointer-based `eq` and `hash`.
Notable changes:
- `mk_const` now takes a `ConstS`.
- `Const` was copy, despite being 48 bytes. Now `ConstS` is not, so need a
we need separate arena for it, because we can't use the `Dropless` one any
more.
- Many `&'tcx Const<'tcx>`/`&Const<'tcx>` to `Const<'tcx>` changes
- Many `ct.ty` to `ct.ty()` and `ct.val` to `ct.val()` changes.
- Lots of tedious sigil fiddling.
by using an opaque type obligation to bubble up comparisons between opaque types and other types
Also uses proper obligation causes so that the body id works, because out of some reason nll uses body ids for logic instead of just diagnostics.
Include Projections when elaborating TypeOutlives
Fixes#92280
In `Elaborator`, we elaborate that `Foo<<Bar as Baz>::Assoc>: 'a` -> `<Bar as Baz>::Assoc: 'a`. This is the same rule that would be applied to any other `Param`. If there are escaping vars, we continue to do nothing.
r? `@nikomatsakis`
Prefer projection candidates instead of param_env candidates for Sized predicates
Fixes#89352
Also includes some drive by logging and verbose printing changes that I found useful when debugging this, but I can remove this if needed.
This is a little hacky - but imo no more than the rest of `candidate_should_be_dropped_in_favor_of`. Importantly, in a Chalk-like world, both candidates should be completely compatible.
r? ```@nikomatsakis```
This makes `Obligation` two words bigger, but avoids allocating a lot of
the time.
I previously tried this in #73983 and it didn't help much, but local
timings look more promising now.
Remove `in_band_lifetimes` from `rustc_infer`
See #91867 for more information.
This crate actually had a typo `'ctx` in one of its functions:
```diff
-pub fn same_type_modulo_infer(a: Ty<'tcx>, b: Ty<'ctx>) -> bool {
+pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
```
Also, I wasn't entirely sure about the lifetimes in `suggest_new_region_bound`:
```diff
pub fn suggest_new_region_bound(
- tcx: TyCtxt<'tcx>,
+ tcx: TyCtxt<'_>,
err: &mut DiagnosticBuilder<'_>,
fn_returns: Vec<&rustc_hir::Ty<'_>>,
```
Should all of those lifetimes really be distinct?
Instead of clearing out the cache entirely, we store
the intermediate evaluation result into the cache entry.
This accomplishes several things:
* We avoid the performance hit associated with re-evaluating
the sub-obligations
* We avoid causing issues with incremental compilation, since
the final evaluation result is always the same
* We avoid affecting other uses of the same `InferCtxt` which
might care about 'side effects' from processing the sub-obligations
(e,g. region constraints). Only code that is specifically aware
of the new 'complete' code is affected
This crate actually had a typo `'ctx` in one of its functions:
```diff
-pub fn same_type_modulo_infer(a: Ty<'tcx>, b: Ty<'ctx>) -> bool {
+pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
```
Make `TypeFolder::fold_*` return `Result`
Implements rust-lang/compiler-team#432.
Initially this is just a rebase of `@LeSeulArtichaut's` work in #85469 (abandoned; see https://github.com/rust-lang/rust/pull/85485#issuecomment-908781112). At that time, it caused a regression in performance that required some further exploration... with this rebased PR bors can hopefully report some perf analysis from which we can investigate further (if the regression is indeed still present).
r? `@jackh726` cc `@nikomatsakis`
The spans for "trait bound not satisfied" errors in trivial trait bounds referenced the entire item (fn, impl, struct) before.
Now they only reference the obligation itself (`String: Copy`)
Address #90869
