Relax bounds on HashMap/HashSet #67642

Mark-Simulacrum · 2019-12-26T19:21:48Z

These APIs changed from the old bound listed to the new bound (possibly empty):

K: Hash + Eq -> K

new
with_capacity

K: Eq + Hash, S: BuildHasher -> K, S

with_hasher
with_capacity_and_hasher
hasher

K: Eq + Hash + Debug -> K: Debug
S: BuildHasher -> S
HashMap as Debug

K: Eq + Hash -> K
S: BuildHasher + Default -> S: Default
HashMap as Default

Resolves #44777.

No functional changes are made, and all APIs are moved to strictly less restrictive bounds. These APIs changed from the old bound listed to no trait bounds: K: Hash + Eq * new * with_capacity K: Eq + Hash, S: BuildHasher * with_hasher * with_capacity_and_hasher * hasher K: Eq + Hash + Debug -> K: Debug S: BuildHasher -> S <HashMap as Debug> K: Eq + Hash -> K S: BuildHasher + Default -> S: Default <HashMap as Default>

Amanieu · 2019-12-26T20:20:50Z

LGTM

@rfcbot fcp merge

rfcbot · 2019-12-26T20:20:51Z

Team member @Amanieu has proposed to merge this. The next step is review by the rest of the tagged team members:

No concerns currently listed.

Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up!

See this document for info about what commands tagged team members can give me.

Mark-Simulacrum · 2019-12-26T20:40:11Z

Test failure appears to be because it is now possible to create a HashSet from [u8; 33] whereas it wasn't before. I will rebless shortly.

sfackler · 2019-12-26T22:59:23Z

What's the rationale for allowing the creation of maps that can't be used?

Mark-Simulacrum · 2019-12-26T23:03:34Z

I think the primary rationale from my perspective (I am not the one who filed the original issue, nor do I have a use case myself) is to allow wrapping HashMap/HashSet in types that don't necessarily want to constrain themselves to using those always. I am not sure that I have a concrete use case -- most things I can come up with would know the type parameters (i.e., not actually be generic).

My loose idea is a type that wants to construct a HashSet/Map eagerly but may not use it except for some use cases (e.g., some graph data structure that caches nodes/edges if you call some methods, but can be used without those methods in some cases).

rust-highfive · 2019-12-27T00:05:09Z

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2019-12-26T22:50:33.8714030Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-12-26T22:50:33.8731087Z ##[command]git config gc.auto 0
2019-12-26T22:50:33.8733928Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-12-26T22:50:33.8736858Z ##[command]git config --get-all http.proxy
2019-12-26T22:50:33.8739306Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/67642/merge:refs/remotes/pull/67642/merge
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---
2019-12-27T00:05:02.4815984Z 10 error[E0277]: arrays only have std trait implementations for lengths 0..=32
2019-12-27T00:05:02.4816421Z -   --> $DIR/core-traits-no-impls-length-33.rs:10:16
2019-12-27T00:05:02.4817130Z +   --> $DIR/core-traits-no-impls-length-33.rs:9:16
2019-12-27T00:05:02.4817322Z 12    |
2019-12-27T00:05:02.4817714Z 13 LL |     set.insert([0_usize; 33]);
2019-12-27T00:05:02.4817924Z 14    |                ^^^^^^^^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[usize; 33]`
2019-12-27T00:05:02.4818062Z 
2019-12-27T00:05:02.4818270Z 16    = note: required because of the requirements on the impl of `std::cmp::Eq` for `[usize; 33]`
2019-12-27T00:05:02.4818580Z 18 error[E0369]: binary operation `==` cannot be applied to type `[usize; 33]`
2019-12-27T00:05:02.4819350Z -   --> $DIR/core-traits-no-impls-length-33.rs:15:19
2019-12-27T00:05:02.4820183Z +   --> $DIR/core-traits-no-impls-length-33.rs:14:19
2019-12-27T00:05:02.4820641Z 20    |
2019-12-27T00:05:02.4820641Z 20    |
2019-12-27T00:05:02.4820798Z 21 LL |     [0_usize; 33] == [1_usize; 33]
2019-12-27T00:05:02.4821210Z 22    |     ------------- ^^ ------------- [usize; 33]
2019-12-27T00:05:02.4821578Z 26    = note: an implementation of `std::cmp::PartialEq` might be missing for `[usize; 33]`
2019-12-27T00:05:02.4821723Z 27 
2019-12-27T00:05:02.4821723Z 27 
2019-12-27T00:05:02.4821896Z 28 error[E0369]: binary operation `<` cannot be applied to type `[usize; 33]`
2019-12-27T00:05:02.4822488Z -   --> $DIR/core-traits-no-impls-length-33.rs:20:19
2019-12-27T00:05:02.4826019Z +   --> $DIR/core-traits-no-impls-length-33.rs:19:19
2019-12-27T00:05:02.4826306Z 30    |
2019-12-27T00:05:02.4826455Z 31 LL |     [0_usize; 33] < [1_usize; 33]
2019-12-27T00:05:02.4827017Z 32    |     ------------- ^ ------------- [usize; 33]
2019-12-27T00:05:02.4827414Z 
2019-12-27T00:05:02.4827738Z 36    = note: an implementation of `std::cmp::PartialOrd` might be missing for `[usize; 33]`
2019-12-27T00:05:02.4827907Z 37 
2019-12-27T00:05:02.4828059Z 38 error[E0277]: the trait bound `&[usize; 33]: std::iter::IntoIterator` is not satisfied
2019-12-27T00:05:02.4829118Z -   --> $DIR/core-traits-no-impls-length-33.rs:25:14
2019-12-27T00:05:02.4829751Z +   --> $DIR/core-traits-no-impls-length-33.rs:24:14
2019-12-27T00:05:02.4829943Z 40    |
2019-12-27T00:05:02.4830088Z 41 LL |     for _ in &[0_usize; 33] {
2019-12-27T00:05:02.4830274Z 42    |              ^^^^^^^^^^^^^^ the trait `std::iter::IntoIterator` is not implemented for `&[usize; 33]`
2019-12-27T00:05:02.4830523Z 
2019-12-27T00:05:02.4830685Z The actual stderr differed from the expected stderr.
2019-12-27T00:05:02.4830685Z The actual stderr differed from the expected stderr.
2019-12-27T00:05:02.4831194Z Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/array-impls/core-traits-no-impls-length-33/core-traits-no-impls-length-33.stderr
2019-12-27T00:05:02.4831626Z To update references, rerun the tests and pass the `--bless` flag
2019-12-27T00:05:02.4832145Z To only update this specific test, also pass `--test-args const-generics/array-impls/core-traits-no-impls-length-33.rs`
2019-12-27T00:05:02.4832461Z error: 1 errors occurred comparing output.
2019-12-27T00:05:02.4832924Z status: exit code: 1
2019-12-27T00:05:02.4832924Z status: exit code: 1
2019-12-27T00:05:02.4834024Z command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/array-impls/core-traits-no-impls-length-33" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/const-generics/array-impls/core-traits-no-impls-length-33/auxiliary" "-A" "unused"
2019-12-27T00:05:02.4834847Z ------------------------------------------
2019-12-27T00:05:02.4835171Z 
2019-12-27T00:05:02.4835827Z ------------------------------------------
2019-12-27T00:05:02.4836217Z stderr:
2019-12-27T00:05:02.4836217Z stderr:
2019-12-27T00:05:02.4836933Z ------------------------------------------
2019-12-27T00:05:02.4837228Z error[E0277]: arrays only have std trait implementations for lengths 0..=32
2019-12-27T00:05:02.4837972Z   --> /checkout/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.rs:2:22
2019-12-27T00:05:02.4841909Z    |
2019-12-27T00:05:02.4845291Z LL |     println!("{:?}", [0_usize; 33]);
2019-12-27T00:05:02.4851033Z    |                      ^^^^^^^^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[usize; 33]`
2019-12-27T00:05:02.4852368Z    = note: required because of the requirements on the impl of `std::fmt::Debug` for `[usize; 33]`
2019-12-27T00:05:02.4852583Z    = note: required by `std::fmt::Debug::fmt`
2019-12-27T00:05:02.4852713Z 
2019-12-27T00:05:02.4852974Z error[E0277]: arrays only have std trait implementations for lengths 0..=32
2019-12-27T00:05:02.4852974Z error[E0277]: arrays only have std trait implementations for lengths 0..=32
2019-12-27T00:05:02.4853587Z   --> /checkout/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.rs:9:16
2019-12-27T00:05:02.4853819Z    |
2019-12-27T00:05:02.4854068Z LL |     set.insert([0_usize; 33]);
2019-12-27T00:05:02.4854318Z    |                ^^^^^^^^^^^^^ the trait `std::array::LengthAtMost32` is not implemented for `[usize; 33]`
2019-12-27T00:05:02.4854588Z    |
2019-12-27T00:05:02.4854834Z    = note: required because of the requirements on the impl of `std::cmp::Eq` for `[usize; 33]`
2019-12-27T00:05:02.4855289Z error[E0369]: binary operation `==` cannot be applied to type `[usize; 33]`
2019-12-27T00:05:02.4855860Z   --> /checkout/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.rs:14:19
2019-12-27T00:05:02.4856773Z    |
2019-12-27T00:05:02.4856773Z    |
2019-12-27T00:05:02.4856844Z LL |     [0_usize; 33] == [1_usize; 33]
2019-12-27T00:05:02.4857161Z    |     ------------- ^^ ------------- [usize; 33]
2019-12-27T00:05:02.4857275Z    |     [usize; 33]
2019-12-27T00:05:02.4857316Z    |
2019-12-27T00:05:02.4857378Z    = note: an implementation of `std::cmp::PartialEq` might be missing for `[usize; 33]`
2019-12-27T00:05:02.4857411Z 
2019-12-27T00:05:02.4857411Z 
2019-12-27T00:05:02.4857485Z error[E0369]: binary operation `<` cannot be applied to type `[usize; 33]`
2019-12-27T00:05:02.4857766Z   --> /checkout/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.rs:19:19
2019-12-27T00:05:02.4857816Z    |
2019-12-27T00:05:02.4857879Z LL |     [0_usize; 33] < [1_usize; 33]
2019-12-27T00:05:02.4858103Z    |     ------------- ^ ------------- [usize; 33]
2019-12-27T00:05:02.4858213Z    |     [usize; 33]
2019-12-27T00:05:02.4858254Z    |
2019-12-27T00:05:02.4858254Z    |
2019-12-27T00:05:02.4858304Z    = note: an implementation of `std::cmp::PartialOrd` might be missing for `[usize; 33]`
2019-12-27T00:05:02.4858338Z 
2019-12-27T00:05:02.4858406Z error[E0277]: the trait bound `&[usize; 33]: std::iter::IntoIterator` is not satisfied
2019-12-27T00:05:02.4858681Z   --> /checkout/src/test/ui/const-generics/array-impls/core-traits-no-impls-length-33.rs:24:14
2019-12-27T00:05:02.4858739Z    |
2019-12-27T00:05:02.4858805Z LL |     for _ in &[0_usize; 33] {
2019-12-27T00:05:02.4858866Z    |              ^^^^^^^^^^^^^^ the trait `std::iter::IntoIterator` is not implemented for `&[usize; 33]`
2019-12-27T00:05:02.4859330Z    = help: the following implementations were found:
2019-12-27T00:05:02.4859330Z    = help: the following implementations were found:
2019-12-27T00:05:02.4859606Z              <&'a [T; _] as std::iter::IntoIterator>
2019-12-27T00:05:02.4859830Z              <&'a [T] as std::iter::IntoIterator>
2019-12-27T00:05:02.4860080Z              <&'a mut [T; _] as std::iter::IntoIterator>
2019-12-27T00:05:02.4860310Z              <&'a mut [T] as std::iter::IntoIterator>
2019-12-27T00:05:02.4860394Z 
2019-12-27T00:05:02.4860456Z error: aborting due to 5 previous errors
2019-12-27T00:05:02.4860485Z 
2019-12-27T00:05:02.4860529Z Some errors have detailed explanations: E0277, E0369.
---
2019-12-27T00:05:02.4862409Z thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:385:22
2019-12-27T00:05:02.4862486Z note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
2019-12-27T00:05:02.4862520Z 
2019-12-27T00:05:02.4862545Z 
2019-12-27T00:05:02.4864314Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-7/bin/FileCheck" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "7.0.0\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
2019-12-27T00:05:02.4864743Z 
2019-12-27T00:05:02.4864772Z 
2019-12-27T00:05:02.4867965Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
2019-12-27T00:05:02.4868038Z Build completed unsuccessfully in 1:07:42
2019-12-27T00:05:02.4868038Z Build completed unsuccessfully in 1:07:42
2019-12-27T00:05:02.4905930Z == clock drift check ==
2019-12-27T00:05:02.4922803Z   local time: Fri Dec 27 00:05:02 UTC 2019
2019-12-27T00:05:02.6557093Z   network time: Fri, 27 Dec 2019 00:05:02 GMT
2019-12-27T00:05:02.6564415Z == end clock drift check ==
2019-12-27T00:05:03.8093606Z 
2019-12-27T00:05:03.8241560Z ##[error]Bash exited with code '1'.
2019-12-27T00:05:03.8288174Z ##[section]Starting: Checkout
2019-12-27T00:05:03.8290895Z ==============================================================================
2019-12-27T00:05:03.8290970Z Task         : Get sources
2019-12-27T00:05:03.8291019Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

No functional changes are made, and all APIs are moved to strictly less restrictive bounds. These APIs changed from the old bound listed to the new bound: T: Hash + Eq -> T * new * with_capacity T: Eq + Hash, S: BuildHasher -> T * with_hasher * with_capacity_and_hasher * hasher T: Eq + Hash + Debug -> T: Debug S: BuildHasher -> S <HashSet as Debug> T: Eq + Hash -> T S: BuildHasher + Default -> S: Default <HashSet as Default>

Amanieu · 2019-12-28T11:35:10Z

@bors r+

bors · 2019-12-28T11:35:11Z

📌 Commit 48859db has been approved by Amanieu

Amanieu · 2019-12-28T11:35:32Z

@bors r-

Oops, wrong window.

alexcrichton · 2020-01-06T15:44:16Z

IIRC this is a general guideline that we've used for libstd historically, only requiring bounds when absolutely necessary. While there's not much use in creating defunkt objects relaxing the bounds can often make generic programming much easier since you don't have to thread through so many bounds in so many places.

For example Arc::new doesn't require Send+Sync values, and while Arc<T> is more useful than HashMap<K, V, NotAHasher> I think roughly the same principle applies.

Now that being said there's also the point to be made of being conservative. I suspect these bounds were actually used at some point and refactorings have since enabled us to not need them. By removing them we're never going to be able to design a hash map where they're required for these methods. That being said the current hash table is quite good, so I suspect we won't have to worry about this too too much.

Mark-Simulacrum · 2020-01-06T15:50:40Z

That being said the current hash table is quite good, so I suspect we won't have to worry about this too too much.

We already provide iter() without requiring anything (i.e., K, V, and S are boundless), so Debug is implementable atop that.

The construction methods are the only ones which are a bit up in the air -- I could see us wanting to use some property of the hasher to decide how much to allocate in the future (e.g., how many "spare bits" we need or so), but I don't think it's a huge concern as I'm not aware of cases where HashMaps specialize for the hasher being used in such a way.

withoutboats · 2020-02-12T16:38:17Z

Since no one has brought anything up, I've checked my box, don't block on my vague concern.

Mark-Simulacrum · 2020-02-12T18:40:50Z

Okay, then I believe we are ready to go ahead with this. I'm not sure if @Amanieu meant the original "LGTM" comment as a review as well, so let's do r? @Amanieu for final review

Amanieu · 2020-02-12T21:06:06Z

@bors r+

bors · 2020-02-12T21:06:07Z

📌 Commit 48859db has been approved by Amanieu

…nieu Relax bounds on HashMap/HashSet These APIs changed from the old bound listed to the new bound (possibly empty): K: Hash + Eq -> K * new * with_capacity K: Eq + Hash, S: BuildHasher -> K, S * with_hasher * with_capacity_and_hasher * hasher K: Eq + Hash + Debug -> K: Debug S: BuildHasher -> S HashMap as Debug K: Eq + Hash -> K S: BuildHasher + Default -> S: Default HashMap as Default Resolves rust-lang#44777.

@ghost

Rollup of 9 pull requests Successful merges: - #67642 (Relax bounds on HashMap/HashSet) - #68848 (Hasten macro parsing) - #69008 (Properly use parent generics for opaque types) - #69048 (Suggestion when encountering assoc types from hrtb) - #69049 (Optimize image sizes) - #69050 (Micro-optimize the heck out of LEB128 reading and writing.) - #69068 (Make the SGX arg cleanup implementation a NOP) - #69082 (When expecting `BoxFuture` and using `async {}`, suggest `Box::pin`) - #69104 (bootstrap: Configure cmake when building sanitizer runtimes) Failed merges: r? @ghost

bors · 2020-02-13T08:12:06Z

⌛ Testing commit 48859db with merge 2e6eace...

matklad · 2020-04-09T09:39:49Z

For posterity, one specific case where we don't want the K: Hash + Eq bound on new is the hashbrown-style raw API, like insert_with_hashing. It can be used to build this cute interner (full impl):

struct Span { lo: u32, hi: u32 }

struct Interner {
  interned: HashSet<Span>,  // equality & hash is determined by `&self.storage[span]`
  storage: String,
}

Kixunil · 2020-04-23T19:03:14Z

Damn, this ship has sailed, but I'm going to bring the argument about why this wasn't that great idea and hope to avoid such thing in the future.

Consider error messages for this program in different versions: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=38b035ac5545bc6fe2d7caa805571067

old: the trait bound Foo: std::cmp::Eq is not satisfied
new: no method named extendfound for structstd::collections::HashMap<Foo, std::string::String> in the current scope

I think the old message was much clearer than the new one. :(

dtolnay · 2020-04-23T19:09:12Z

That would be a diagnostics bug. The program calls extend on a HashMap<K, V>. HashMap has an extend method but it requires K: Eq. Diagnostic should say so. Please file an issue to follow up.

Kixunil · 2020-04-24T10:27:05Z

OK, I filed the bug. Just note that these kinds of things become worse when combinators are used, as the resulting type gets complicated and the code that passed a wrong type is far away from the place at which rustc found the issue. This is also the reason why error messages from futures are so difficult to understand. That's why I opened rust-lang/api-guidelines#217

I don't think that there's a general solution to such error messages. If there was, it might be a good reason to stop requiring types in (non-public) function signatures too.

Pkgsrc changes: * Bump rust bootstrap version to 1.42.0, except for Darwin/i686 where the bootstrap is not (yet?) available. Upstream changes: Version 1.43.0 (2020-04-23) ========================== Language -------- - [Fixed using binary operations with `&{number}` (e.g. `&1.0`) not having the type inferred correctly.][68129] - [Attributes such as `#[cfg()]` can now be used on `if` expressions.][69201] **Syntax only changes** - [Allow `type Foo: Ord` syntactically.][69361] - [Fuse associated and extern items up to defaultness.][69194] - [Syntactically allow `self` in all `fn` contexts.][68764] - [Merge `fn` syntax + cleanup item parsing.][68728] - [`item` macro fragments can be interpolated into `trait`s, `impl`s, and `extern` blocks.][69366] For example, you may now write: ```rust macro_rules! mac_trait { ($i:item) => { trait T { $i } } } mac_trait! { fn foo() {} } ``` These are still rejected *semantically*, so you will likely receive an error but these changes can be seen and parsed by macros and conditional compilation. Compiler -------- - [You can now pass multiple lint flags to rustc to override the previous flags.][67885] For example; `rustc -D unused -A unused-variables` denies everything in the `unused` lint group except `unused-variables` which is explicitly allowed. However, passing `rustc -A unused-variables -D unused` denies everything in the `unused` lint group **including** `unused-variables` since the allow flag is specified before the deny flag (and therefore overridden). - [rustc will now prefer your system MinGW libraries over its bundled libraries if they are available on `windows-gnu`.][67429] - [rustc now buffers errors/warnings printed in JSON.][69227] Libraries --------- - [`Arc<[T; N]>`, `Box<[T; N]>`, and `Rc<[T; N]>`, now implement `TryFrom<Arc<[T]>>`,`TryFrom<Box<[T]>>`, and `TryFrom<Rc<[T]>>` respectively.][69538] **Note** These conversions are only available when `N` is `0..=32`. - [You can now use associated constants on floats and integers directly, rather than having to import the module.][68952] e.g. You can now write `u32::MAX` or `f32::NAN` with no imports. - [`u8::is_ascii` is now `const`.][68984] - [`String` now implements `AsMut<str>`.][68742] - [Added the `primitive` module to `std` and `core`.][67637] This module reexports Rust's primitive types. This is mainly useful in macros where you want avoid these types being shadowed. - [Relaxed some of the trait bounds on `HashMap` and `HashSet`.][67642] - [`string::FromUtf8Error` now implements `Clone + Eq`.][68738] Stabilized APIs --------------- - [`Once::is_completed`] - [`f32::LOG10_2`] - [`f32::LOG2_10`] - [`f64::LOG10_2`] - [`f64::LOG2_10`] - [`iter::once_with`] Cargo ----- - [You can now set config `[profile]`s in your `.cargo/config`, or through your environment.][cargo/7823] - [Cargo will now set `CARGO_BIN_EXE_<name>` pointing to a binary's executable path when running integration tests or benchmarks.][cargo/7697] `<name>` is the name of your binary as-is e.g. If you wanted the executable path for a binary named `my-program`you would use `env!("CARGO_BIN_EXE_my-program")`. Misc ---- - [Certain checks in the `const_err` lint were deemed unrelated to const evaluation][69185], and have been moved to the `unconditional_panic` and `arithmetic_overflow` lints. Compatibility Notes ------------------- - [Having trailing syntax in the `assert!` macro is now a hard error.][69548] This has been a warning since 1.36.0. - [Fixed `Self` not having the correctly inferred type.][69340] This incorrectly led to some instances being accepted, and now correctly emits a hard error. [69340]: rust-lang/rust#69340 Internal Only ------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of `rustc` and related tools. - [All components are now built with `opt-level=3` instead of `2`.][67878] - [Improved how rustc generates drop code.][67332] - [Improved performance from `#[inline]`-ing certain hot functions.][69256] - [traits: preallocate 2 Vecs of known initial size][69022] - [Avoid exponential behaviour when relating types][68772] - [Skip `Drop` terminators for enum variants without drop glue][68943] - [Improve performance of coherence checks][68966] - [Deduplicate types in the generator witness][68672] - [Invert control in struct_lint_level.][68725] [67332]: rust-lang/rust#67332 [67429]: rust-lang/rust#67429 [67637]: rust-lang/rust#67637 [67642]: rust-lang/rust#67642 [67878]: rust-lang/rust#67878 [67885]: rust-lang/rust#67885 [68129]: rust-lang/rust#68129 [68672]: rust-lang/rust#68672 [68725]: rust-lang/rust#68725 [68728]: rust-lang/rust#68728 [68738]: rust-lang/rust#68738 [68742]: rust-lang/rust#68742 [68764]: rust-lang/rust#68764 [68772]: rust-lang/rust#68772 [68943]: rust-lang/rust#68943 [68952]: rust-lang/rust#68952 [68966]: rust-lang/rust#68966 [68984]: rust-lang/rust#68984 [69022]: rust-lang/rust#69022 [69185]: rust-lang/rust#69185 [69194]: rust-lang/rust#69194 [69201]: rust-lang/rust#69201 [69227]: rust-lang/rust#69227 [69548]: rust-lang/rust#69548 [69256]: rust-lang/rust#69256 [69361]: rust-lang/rust#69361 [69366]: rust-lang/rust#69366 [69538]: rust-lang/rust#69538 [cargo/7823]: rust-lang/cargo#7823 [cargo/7697]: rust-lang/cargo#7697 [`Once::is_completed`]: https://doc.rust-lang.org/std/sync/struct.Once.html#method.is_completed [`f32::LOG10_2`]: https://doc.rust-lang.org/std/f32/consts/constant.LOG10_2.html [`f32::LOG2_10`]: https://doc.rust-lang.org/std/f32/consts/constant.LOG2_10.html [`f64::LOG10_2`]: https://doc.rust-lang.org/std/f64/consts/constant.LOG10_2.html [`f64::LOG2_10`]: https://doc.rust-lang.org/std/f64/consts/constant.LOG2_10.html [`iter::once_with`]: https://doc.rust-lang.org/std/iter/fn.once_with.html

Relax bounds on HashSet constructors Relax bounds on `HashSet::with_hasher` and `with_capacity_and_hasher` to match the bounds on `HashMap` and on `std::collections::HashSet`. This will allow `std::collections::HashSet` to be based on `hashbrown::HashSet`. See also rust-lang/rust#67642

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Mark-Simulacrum force-pushed the relax-bounds branch from 515f642 to 48859db Compare December 27, 2019 00:24

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Dylan-DPC-zz mentioned this pull request Feb 13, 2020

Rollup of 9 pull requests #69118

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bors merged commit 48859db into rust-lang:master Feb 13, 2020

Kerollmops mentioned this pull request Feb 25, 2020

lots of polishing, regular maintenance, preparing for 0.4 (or 1.0?) release BurntSushi/fst#96

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jonhoo mentioned this pull request Feb 26, 2020

Relax bounds on many methods to be minimal jonhoo/flurry#64

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Mark-Simulacrum deleted the relax-bounds branch April 23, 2020 20:25

Kixunil mentioned this pull request Apr 24, 2020

Rustc says method doesn't exist instead of hinting at unsatisfied trait bounds #71505

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cuviper mentioned this pull request Jul 24, 2020

Relax some bounds to match std indexmap-rs/indexmap#141

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mbrubeck mentioned this pull request Aug 10, 2020

Relax bounds on HashSet constructors rust-lang/hashbrown#185

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rail-rain mentioned this pull request Dec 11, 2020

new_without_default_derive triggers on types which cannot #[derive(Default)] rust-lang/rust-clippy#1890

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Relax bounds on HashMap/HashSet #67642

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Relax bounds on HashMap/HashSet #67642

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