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Rollup merge of #101698 - raldone01:feat/const_cmp_typeid, r=scottmcm

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Constify `TypeId` ordering impls

Tracking issue: #101871

Adding const ordering to `TypeId` allows rtti crates to optimize some casting scenarios (without transmuting to `u64`). This would also prevent these crates from breaking if the underlying type is changed from `u64` to something different.

Feature gate: `#![feature(const_cmp_type_id)]`
This commit is contained in:
Dylan DPC 2023-01-17 20:33:03 +05:30 committed by GitHub
commit 09faa266da
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5 changed files with 32 additions and 23 deletions
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3
library/core/src/any.rs
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@ -662,7 +662,8 @@ impl dyn Any + Send + Sync {
/// While `TypeId` implements `Hash`, `PartialOrd`, and `Ord`, it is worth
/// noting that the hashes and ordering will vary between Rust releases. Beware
/// of relying on them inside of your code!
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
#[derive(Clone, Copy, Debug, Hash, Eq)]
#[derive_const(PartialEq, PartialOrd, Ord)]
#[stable(feature = "rust1", since = "1.0.0")]
pub struct TypeId {
t: u64,

4
tests/ui/const-generics/issues/issue-90318.rs
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@ -12,14 +12,14 @@ impl True for If<true> {}
fn consume<T: 'static>(_val: T)
where
If<{ TypeId::of::<T>() != TypeId::of::<()>() }>: True,
//~^ ERROR: can't compare
//~^ overly complex generic constant
{
}
fn test<T: 'static>()
where
If<{ TypeId::of::<T>() != TypeId::of::<()>() }>: True,
//~^ ERROR: can't compare
//~^ overly complex generic constant
{
}

33
tests/ui/const-generics/issues/issue-90318.stderr
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@ -1,29 +1,24 @@
error[E0277]: can't compare `TypeId` with `_` in const contexts
--> $DIR/issue-90318.rs:14:28
error: overly complex generic constant
--> $DIR/issue-90318.rs:14:8
|
LL | If<{ TypeId::of::<T>() != TypeId::of::<()>() }>: True,
| ^^ no implementation for `TypeId == _`
| ^^-----------------^^^^^^^^^^^^^^^^^^^^^^^^
| |
| borrowing is not supported in generic constants
|
= help: the trait `~const PartialEq<_>` is not implemented for `TypeId`
note: the trait `PartialEq<_>` is implemented for `TypeId`, but that implementation is not `const`
--> $DIR/issue-90318.rs:14:28
|
LL | If<{ TypeId::of::<T>() != TypeId::of::<()>() }>: True,
| ^^
= help: consider moving this anonymous constant into a `const` function
= note: this operation may be supported in the future
error[E0277]: can't compare `TypeId` with `_` in const contexts
--> $DIR/issue-90318.rs:21:28
error: overly complex generic constant
--> $DIR/issue-90318.rs:21:8
|
LL | If<{ TypeId::of::<T>() != TypeId::of::<()>() }>: True,
| ^^ no implementation for `TypeId == _`
| ^^-----------------^^^^^^^^^^^^^^^^^^^^^^^^
| |
| borrowing is not supported in generic constants
|
= help: the trait `~const PartialEq<_>` is not implemented for `TypeId`
note: the trait `PartialEq<_>` is implemented for `TypeId`, but that implementation is not `const`
--> $DIR/issue-90318.rs:21:28
|
LL | If<{ TypeId::of::<T>() != TypeId::of::<()>() }>: True,
| ^^
= help: consider moving this anonymous constant into a `const` function
= note: this operation may be supported in the future
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0277`.

12
tests/ui/consts/const_cmp_type_id.rs Normal file
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@ -0,0 +1,12 @@
// run-pass
#![feature(const_type_id)]
#![feature(const_trait_impl)]
use std::any::TypeId;
const fn main() {
assert!(TypeId::of::<u8>() == TypeId::of::<u8>());
assert!(TypeId::of::<()>() != TypeId::of::<u8>());
const _A: bool = TypeId::of::<u8>() < TypeId::of::<u16>();
// can't assert `_A` because it is not deterministic
}

3
tests/ui/consts/issue-73976-monomorphic.rs
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@ -7,6 +7,7 @@
#![feature(const_type_id)]
#![feature(const_type_name)]
#![feature(const_trait_impl)]
use std::any::{self, TypeId};
@ -17,7 +18,7 @@ impl<T: 'static> GetTypeId<T> {
}
const fn check_type_id<T: 'static>() -> bool {
matches!(GetTypeId::<T>::VALUE, GetTypeId::<usize>::VALUE)
GetTypeId::<T>::VALUE == GetTypeId::<usize>::VALUE
}
pub struct GetTypeNameLen<T>(T);