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Implementation of RFC 2289 (associated_type_bounds)
This PR implements the [`asociated_type_bounds` feature](https://github.com/rust-lang/rfcs/blob/master/text/2289-associated-type-bounds.md).
Associated type bounds are implemented in:
- function/method arguments and return types
- structs, enums, unions
- associated items in traits
- type aliases
- type parameter defaults
- trait objects
- let bindings
CC @nikomatsakis @centril
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`TypeVariableOriginKind`
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Avoid `hygiene_data` lookups
These commits mostly introduce compound operations that allow two close adjacent `hygiene_data` lookups to be combined.
r? @petrochenkov
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It reduces two `hygiene_data` accesses to one on some hot paths.
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We are going to uniform the terminology of all associated items.
Methods that may or may not have `self` are called "associated
functions". Because `AssociatedFn` is a bit long, we rename `Associated`
to `Assoc`.
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- Add detail on origin of current parser when reaching EOF and stop
saying "found <eof>" and point at the end of macro calls
- Handle empty `cfg_attr` attribute
- Reword empty `derive` attribute error
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Always try to project predicates when finding auto traits in rustdoc
Fixes #60726
Previous, AutoTraitFinder would only try to project predicates when the
predicate type contained an inference variable. When finding auto
traits, we only project to try to unify inference variables - we don't
otherwise learn any new information about the required bounds.
However, this lead to failing to properly generate a negative auto trait
impl (indicating that a type never implements a certain auto trait) in
the following unusual scenario:
In almost all cases, a type has an (implicit) negative impl of an auto
trait due some other type having an explicit *negative* impl of that
auto trait. For example:
struct MyType<T> {
field: *const T
}
has an implicit 'impl<T> !Send for MyType<T>', due to the explicit
negative impl (in libcore) 'impl<T: ?Sized> !Send for *const T'.
However, as exposed by the 'abi_stable' crate, this isn't always the
case. This minimzed example shows how a type can never implement
'Send', due to a projection error:
```
pub struct True;
pub struct False;
pub trait MyTrait {
type Project;
}
pub struct MyStruct<T> {
field: T
}
impl MyTrait for u8 {
type Project = False;
}
unsafe impl<T> Send for MyStruct<T>
where T: MyTrait<Project=True> {}
pub struct Wrapper {
inner: MyStruct<u8>
}
```
In this example, `<u8 as MyTrait>::Project == True'
must hold for 'MyStruct<u8>: Send' to hold.
However, '<u8 as MyTrait>::Project == False' holds instead
To properly account for this unusual case, we need to call
'poly_project_and_unify' on *all* predicates, not just those with
inference variables. This ensures that we catch the projection error
that occurs above, and don't incorrectly determine that 'Wrapper: Send'
holds.
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Ban multi-trait objects via trait aliases
Obviously, multi-trait objects are not normally supported, so they should not be supported via trait aliases.
This has been factored out from the previous PR https://github.com/rust-lang/rust/pull/55994 (see point 1).
r? @Centril
CC @nikomatsakis
------------------
### RELNOTES:
We now allow `dyn Send + fmt::Debug` with equivalent semantics to `dyn fmt::Debug + Send`.
That is, the order of the mentioned traits does not matter wrt. principal/not-principal traits.
This is a small change that might deserve a mention in the blog post because it is a language change but most likely not.
See https://github.com/rust-lang/rust/blob/ce2ee305f9165c037ecddddb5792588a15ff6c37/src/test/ui/traits/wf-trait-object-reverse-order.rs.
// @Centril
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`Symbol` received the same treatment in #60630.
Also, we can derive `PartialEq` for `InternedString`.
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`InternedString::intern(x)` is preferable to
`Symbol::intern(x).as_interned_str()`, because the former involves one
call to `with_interner` while the latter involves two.
The case within InternedString::decode() is particularly hot, and this
change reduces the number of `with_interner` calls by up to 13%.
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r=petrochenkov
Declare DefIndex with the newtype_index macro
See #60666
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Explain that ? converts the error type using From
Fix #60917.
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r=petrochenkov
Avoid some unnecessary interning
r? @petrochenkov
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r=nikomatsakis
lint: convert incoherent_fundamental_impls into hard error
*Summary for affected authors:* If your crate depends on one of the following crates, please upgrade to a newer version:
- gtk-rs: upgrade to at least 0.4
- rusqlite: upgrade to at least 0.14
- nalgebra: upgrade to at least 0.15, or the last patch version of 0.14
- spade: upgrade or refresh the Cargo.lock file to use version 1.7
- imageproc: upgrade to at least 0.16 (newer versions no longer use nalgebra)
implement #46205
r? @nikomatsakis
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r=pnkfelix
forego caching for all participants in cycles, apart from root node
This is a targeted fix for #60010, which uncovered a pretty bad failure of our caching strategy in the face of coinductive cycles. The problem is explained in the comment in the PR on the new field, `in_cycle`, but I'll reproduce it here:
> Starts out as false -- if, during evaluation, we encounter a
> cycle, then we will set this flag to true for all participants
> in the cycle (apart from the "head" node). These participants
> will then forego caching their results. This is not the most
> efficient solution, but it addresses #60010. The problem we
> are trying to prevent:
>
> - If you have `A: AutoTrait` requires `B: AutoTrait` and `C: NonAutoTrait`
> - `B: AutoTrait` requires `A: AutoTrait` (coinductive cycle, ok)
> - `C: NonAutoTrait` requires `A: AutoTrait` (non-coinductive cycle, not ok)
>
> you don't want to cache that `B: AutoTrait` or `A: AutoTrait`
> is `EvaluatedToOk`; this is because they were only considered
> ok on the premise that if `A: AutoTrait` held, but we indeed
> encountered a problem (later on) with `A: AutoTrait. So we
> currently set a flag on the stack node for `B: AutoTrait` (as
> well as the second instance of `A: AutoTrait`) to supress
> caching.
>
> This is a simple, targeted fix. The correct fix requires
> deeper changes, but would permit more caching: we could
> basically defer caching until we have fully evaluated the
> tree, and then cache the entire tree at once.
I'm not sure what the impact of this fix will be in terms of existing crates or performance: we were accepting incorrect code before, so there will perhaps be some regressions, and we are now caching less.
As the comment above notes, we could do a lot better than this fix, but that would involve more invasive rewrites. I thought it best to start with something simple.
r? @pnkfelix -- but let's do crater/perf run
cc @arielb1
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modify the comment on `in_cycle` to reflect changes requested by ariel and myself.
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Fixes #60726
Previous, AutoTraitFinder would only try to project predicates when the
predicate type contained an inference variable. When finding auto
traits, we only project to try to unify inference variables - we don't
otherwise learn any new information about the required bounds.
However, this lead to failing to properly generate a negative auto trait
impl (indicating that a type never implements a certain auto trait) in
the following unusual scenario:
In almost all cases, a type has an (implicit) negative impl of an auto
trait due some other type having an explicit *negative* impl of that
auto trait. For example:
struct MyType<T> {
field: *const T
}
has an implicit 'impl<T> !Send for MyType<T>', due to the explicit
negative impl (in libcore) 'impl<T: ?Sized> !Send for *const T'.
However, as exposed by the 'abi_stable' crate, this isn't always the
case. This minimzed example shows how a type can never implement
'Send', due to a projection error:
```
pub struct True;
pub struct False;
pub trait MyTrait {
type Project;
}
pub struct MyStruct<T> {
field: T
}
impl MyTrait for u8 {
type Project = False;
}
unsafe impl<T> Send for MyStruct<T>
where T: MyTrait<Project=True> {}
pub struct Wrapper {
inner: MyStruct<u8>
}
```
In this example, `<u8 as MyTrait>::Project == True'
must hold for 'MyStruct<u8>: Send' to hold.
However, '<u8 as MyTrait>::Project == False' holds instead
To properly account for this unusual case, we need to call
'poly_project_and_unify' on *all* predicates, not just those with
inference variables. This ensures that we catch the projection error
that occurs above, and don't incorrectly determine that 'Wrapper: Send'
holds.
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And also the equality between `Path` and strings, because `Path` is made
up of `Symbol`s.
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cleanup: Remove `DefIndexAddressSpace`
The scheme with two address spaces for `DefIndex` was needed in the past, but apparently not needed anymore (after removing `DefId`s from locals and `HirId`-ification).
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Co-Authored-By: Gabriel Smith <yodaldevoid@users.noreply.github.com>
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Signed-off-by: Gabriel Smith <ga29smith@gmail.com>
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Co-Authored-By: Gabriel Smith <yodaldevoid@users.noreply.github.com>
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rustdoc: remove def_ctor hack.
~~No longer necessary since we have `describe_def`.~~
Turns out `def_ctor` was used in conjunction with abusing `tcx.type_of(def_id)` working on both type definitions and `impl`s (specifically, of builtin types), but also reimplementing a lot of the logic that `Clean` already provides on `Ty` / `ty::TraitRef`.
The first commit now does the minimal refactor to keep it working, while the second commit contains the rest of the refactor I started (parts of which I'm not sure we need to keep).
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Split `CommonTypes` into `CommonTypes` and `CommonLifetimes`
The so-called "`CommonTypes`" contains more than just types.
r? @eddyb
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Don't try to render auto-trait bounds with any inference variables
Previously, we checked if the target of a projection type was itself an
inference variable. However, for Rustdoc rendering purposes, there's no
distinction between an inference variable ('_') and a type containing
one (e.g. (MyStruct<u8, _>)) - we don't want to render either of them.
Fixes #60269
Due to the complexity of the original bug, which spans three different
crates (hyper, tower-hyper, and tower), I have been unable to create a
minimized reproduction for the issue.
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