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False positive for box_default in #![no_std] crate #9653

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lukas-code opened this issue Oct 15, 2022 · 3 comments · Fixed by #9655
Closed

False positive for box_default in #![no_std] crate #9653

lukas-code opened this issue Oct 15, 2022 · 3 comments · Fixed by #9655
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C-bug Category: Clippy is not doing the correct thing I-false-positive Issue: The lint was triggered on code it shouldn't have

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@lukas-code
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lukas-code commented Oct 15, 2022

Summary

box_default fires in the Default impl of Box-like types in a #![no_std] crate

Lint Name

box_default

Reproducer

I tried this code: (Playground link)

#![no_std]

pub struct NotBox<T> {
    _value: T,
}

impl<T> NotBox<T> {
    pub fn new(value: T) -> Self {
        Self { 
            _value: value,
        }
    }
}

impl<T: Default> Default for NotBox<T> {
    fn default() -> Self {
        Self::new(T::default())
    }
}

I saw this happen:

    Checking playground v0.0.1 (/playground)
warning: `Box::new(_)` of default value
  --> src/lib.rs:17:9
   |
17 |         Self::new(T::default())
   |         ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: use `Box::default()` instead
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#box_default
   = note: `#[warn(clippy::box_default)]` on by default

warning: `playground` (lib) generated 1 warning
    Finished dev [unoptimized   debuginfo] target(s) in 0.97s

I expected to see this happen:
no output

Version

rustc 1.66.0-nightly (bf15a9e52 2022-10-14)
binary: rustc
commit-hash: bf15a9e5263fcea065a7ae9c179b2d24c2deb670
commit-date: 2022-10-14
host: x86_64-unknown-linux-gnu
release: 1.66.0-nightly
LLVM version: 15.0.2

Additional Labels

No response

@lukas-code lukas-code added C-bug Category: Clippy is not doing the correct thing I-false-positive Issue: The lint was triggered on code it shouldn't have labels Oct 15, 2022
@llogiq
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llogiq commented Oct 15, 2022

This should be very easy to fix by checking if the Box type exists.

@rustbot claim

@Alexendoo
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Ah, so that's why lang_items().owned_box() returns an Option

@llogiq
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llogiq commented Oct 15, 2022

Exactly.

@bors bors closed this as completed in ff33d6e Oct 16, 2022
linyihai pushed a commit to linyihai/rust-clippy that referenced this issue Oct 23, 2023
同步社区最新master分支代码

Created-by: lizheng 30020856
Author-id: 11958
MR-id: 457385
Commit-by: bors;Michael Krasnitski;Mara Bos;KaDiWa;Alex Macleod;Manish Goregaokar;Tyler Weaver;Niki4tap;koka;Sylvain Desodt;ksaleem;Philipp Krones;Collin Styles;xFrednet;Martin Fischer;Evan Typanski;Vincenzo Palazzo;Samuel Moelius;chansuke;Michael Woerister;Kyle Matsuda;Maria José Solano;Michael Goulet;Yuki Okushi;Jason Newcomb;Joshua Nelson;Oli Scherer;Robert Bastian;navh;asquared31415;Andre Bogus;Albert Larsan;dswij;Raiki Tamura;Caio;blyxyas;Robin Schroer;Kyle Huey;Eric Wu;Nilstrieb;Andy Russell;Max Baumann;Ardis Lu;Trevor Gross;Ray Redondo;Matthias Krüger;Esteban Küber;Lukas Lueg;alexey semenyuk;dboso;Samuel Tardieu;feniljain;Gary Guo;Nicholas Nethercote;Fridtjof Stoldt;naosense;alex-semenyuk;Taiki Endo;Hannah Town;Jakob Degen;Lukas Wirth;Vadim Petrochenkov;mdgaziur;Eric Huss;Yuri Astrakhan;kraktus;Ralf Jung;Santiago Pastorino;Camille GILLOT;hkalbasi;Arpad Borsos;Maybe Waffle;ozkanonur;Sosthène Guédon;Deadbeef;Kartavya Vashishtha;Aphek;Nadir Fejzic;Lukas Markeffsky;hrxi;clubby789;yukang;Ryan Scheidter;Grachev Mikhail;Elliot Bobrow;Dylan DPC;Steven Casper;bebecue;Trevor Arjeski;Onur Özkan;Cameron Steffen;Guillaume Gomez;Matthew Ingwersen;Alex ✨ Cosmic Princess ✨;dswijj;mejrs;Rageking8;Alex;est31;oxalica;JT;Doru-Florin Blanzeanu;Andreu Botella;royrustdev;flip1995;lcnr;Kevin Per;Josh Stone;TennyZhuang;Marijn Schouten;Steven Nguyen;Cody;Urgau;ouz-a;Nahua Kang;Felix Kohlgrüber
Merged-by: wangqilin 00349210
E2E-issues: 
Description:
add syntax-tree-patterns RFC,
Remove if_chain from equatable_if_let,
Lint suggests matches macro if PartialEq trait is not implemented,
Run cargo dev bless to update fixes & stderr,
Merge commit 'ac0e10aa68325235069a842f47499852b2dee79e' into clippyup,
Remove `mir::CastKind::Misc`,
Merge commit '8f1ebdd18bdecc621f16baaf779898cc08cc2766' into clippyup,
Introduce TypeErrCtxt

TypeErrCtxt optionally has a TypeckResults so that InferCtxt doesn't
need to.,
Change InferCtxtBuilder from enter to build,
make const_err a hard error,
Auto merge of #102091 - RalfJung:const_err, r=oli-obk

make const_err a hard error

This lint has been deny-by-default with future incompat wording since [Rust 1.51](rust-lang/rust#80394) and the stable release of this week starts showing it in cargo's future compat reports. I can't wait to finally get rid of at least some of the mess in our const-err-reporting-code. ;)

r? `@oli-obk`
Fixes rust-lang/rust#71800
Fixes rust-lang/rust#100114,
Auto merge of rust-lang#2583 - RalfJung:rustup, r=oli-obk

initial josh subtree sync

This demonstrates what a josh-based rustup would look like with my patched josh. To create it I did
```
git fetch http://localhost:8000/rust-lang/rust.git:start=75dd959a3a40eb5b4574f8d2e23aa6efbeb33573[:prefix=src/tools/miri]:/src/tools/miri.git master
git merge FETCH_HEAD
./rustup-toolchain HEAD && ./miri fmt
git commit -am rustup
```
Unlike the [previous attempt](rust-lang/miri#2554), this does not add a new root commit to the repo.

Once we merge this, we committed to using josh for subtree syncing, and in particular a version of josh that includes josh-project/josh#961 (or something compatible).,
Stabilize half_open_range_patterns,
Rollup merge of #102675 - ouz-a:mir-technical-debt, r=oli-obk

Remove `mir::CastKind::Misc`

As discussed in #97649 `mir::CastKind::Misc` is not clear, this PR addresses that by creating a new enum variant for every valid cast.

r? ````@oli-obk````,
[`unnecessary_cast`] Do not lint negative hexadecimal literals when cast as float

Floats cannot be expressed as hexadecimal literals,
ImplItemKind::TyAlias => ImplItemKind::Type,
merge rustc history,
Fix clippy tests that trigger `for_loop_over_fallibles` lint,
fixup lint name,
deprecate `clippy::for_loops_over_fallibles`,
Rollup merge of #102829 - compiler-errors:rename-impl-item-kind, r=TaKO8Ki

rename `ImplItemKind::TyAlias` to `ImplItemKind::Type`

The naming of this variant seems inconsistent given that this is not really a "type alias", and the associated type variant for `TraitItemKind` is just called `Type`.,
Rollup merge of #102275 - Urgau:stabilize-half_open_range_patterns, r=cjgillot

Stabilize `half_open_range_patterns`

This PR stabilize `feature(half_open_range_patterns)`:
```
Allows using `..=X` as a pattern.
```

And adds a new `feature(half_open_range_patterns_in_slices)` for the slice part, rust-lang/rust#102275 (comment).

The FCP was completed in rust-lang/rust#67264.,
Rename AssocItemKind::TyAlias to AssocItemKind::Type,
Rollup merge of #99696 - WaffleLapkin:uplift, r=fee1-dead

Uplift `clippy::for_loops_over_fallibles` lint into rustc

This PR, as the title suggests, uplifts [`clippy::for_loops_over_fallibles`] lint into rustc. This lint warns for code like this:
```rust
for _ in Some(1) {}
for _ in Ok::<_, ()>(1) {}
```
i.e. directly iterating over `Option` and `Result` using `for` loop.

There are a number of suggestions that this PR adds (on top of what clippy suggested):
1. If the argument (? is there a better name for that expression) of a `for` loop is a `.next()` call, then we can suggest removing it (or rather replacing with `.by_ref()` to allow iterator being used later)
   ```rust
    for _ in iter.next() {}
    // turns into
    for _ in iter.by_ref() {}
    ```
2. (otherwise) We can suggest using `while let`, this is useful for non-iterator, iterator-like things like [async] channels
   ```rust
   for _ in rx.recv() {}
   // turns into
   while let Some(_) = rx.recv() {}
   ```
3. If the argument type is `Result<impl IntoIterator, _>` and the body has a `Result<_, _>` type, we can suggest using `?`
   ```rust
   for _ in f() {}
   // turns into
   for _ in f()? {}
   ```
4. To preserve the original behavior and clear intent, we can suggest using `if let`
   ```rust
   for _ in f() {}
   // turns into
   if let Some(_) = f() {}
   ```
(P.S. `Some` and `Ok` are interchangeable depending on the type)

I still feel that the lint wording/look is somewhat off, so I'll be happy to hear suggestions (on how to improve suggestions :D)!

Resolves #99272

[`clippy::for_loops_over_fallibles`]: https://rust-lang.github.io/rust-clippy/master/index.html#for_loops_over_fallibles,
Rollup merge of #102868 - compiler-errors:rename-assoc-tyalias-to-ty, r=TaKO8Ki

Rename `AssocItemKind::TyAlias` to `AssocItemKind::Type`

Thanks `@camsteffen` for catching this in ast too, cc rust-lang/rust#102829 (comment),
merge rustc history,
Fix unclosed HTML tag in clippy doc,
fix `box-default` ignoring trait objects' types,
Fix allow_attributes_without_reason applying to external crate macros

Previously the `clippy::allow_attributes_without_reason` lint would
apply to external crate macros. Many macros in the Rust ecosystem
include these `allow` attributes without adding a reason, making this
lint pretty much unusable in any sizable Rust project.

This commit fixes that by adding a check to the lint if the attribute is
from an external crate macro and returning early.,
Fix bug in `referent_used_exactly_once`,
merge rustc history,
`default_numeric_fallback` do not lint on constants,
refactor `default_numeric_fallback`

We only need to store if the literal binding has an explicit type bound or not,
Book: Small grammar   link a11y change,
Remove CastCheckResult since it's unused,
add missing comma,
Auto merge of rust-lang#9644 - hkBst:patch-1, r=flip1995

add missing comma

changelog: none,
Auto merge of rust-lang#9643 - icecream17:patch-1, r=flip1995

Book: Small grammar   link a11y change

*Please write a short comment explaining your change (or "none" for internal only changes)*

changelog: none

---

Very minor

For the link accessibility change, `here` and related don't provide context for screen readers who are reading a list of links.
(Random supporting google links)
https://www.w3.org/QA/Tips/noClickHere
https://usability.yale.edu/web-accessibility/articles/links,
Don't lint `ptr_arg` when used as an incompatible trait object,
Auto merge of rust-lang#9645 - Jarcho:ptr_arg_9542, r=llogiq

Don't lint `ptr_arg` when used as an incompatible trait object

fixes rust-lang#9542
changelog: [`ptr_arg`](https://rust-lang.github.io/rust-clippy/master/#ptr_arg): Don't lint when used as an incompatible trait object,
Add a suggestion and a note about orphan rules for `from_over_into`,
Auto merge of rust-lang#9649 - Alexendoo:from-over-into-suggestion, r=llogiq

Add a suggestion and a note about orphan rules for `from_over_into`

Adds a machine applicable suggestion to convert the `Into` impl into a `From` one to `from_over_into`

Also adds a note explaining that `impl From<Local> for Foreign` is fine if the `Into` type is foreign

Closes rust-lang#7444
Addresses half of rust-lang#9638

changelog: [`from_over_into`] Add a suggestion and a note about orphan rules,
Separate internal lints by pass,
Move some things around,
Expand `unnecessary_def_path` lint,
Fix adjacent code,
Format affected files,
`explicit_ty_bound` code golf,
[`zero_prefixed_literal`] Do not advise to use octal form if not possible,
Enable test no_std_main_recursion,
fix `box-default` linting `no_std` non-boxes,
Auto merge of rust-lang#9655 - llogiq:unbox-default, r=dswij

fix `box-default` linting `no_std` non-boxes

This fixes rust-lang#9653 by doing the check against the `Box` type correctly even if `Box` isn't there, as in `no_std` code. Thanks to `@lukas-code` for opening the issue and supplying a reproducer!

---

changelog: none,
Auto merge of rust-lang#9636 - kraktus:numeric-fallback, r=dswij

[`default_numeric_fallback`] do not lint on constants

fix rust-lang#9632

changelog:[`default_numeric_fallback`] do not lint on constants,
Auto merge of rust-lang#9566 - smoelius:diagnostic-item-path, r=dswij

Expand internal lint `unnecessary_def_path`

This PR does essentially two things:
* Separates the internal lints into modules by pass. (`internal_lints.rs` was over 1400 lines, which is a little unruly IMHO.)
* ~Adds a new~ Expands the `unnecessary_def_path` internal lint to flag hardcoded paths to diagnostic and language items.

My understanding is that the latter is currently done by reviewers. Automating this process should make things easier for both reviewers and contributors.

I could make the first bullet a separate PR, or remove it entirely, if desired.

changelog: Add internal lint `diagnostic_item_path`,
Add new lint `partial_pub_fields`

Signed-off-by: TennyZhuang <[email protected]>,
fix dogfood

Signed-off-by: TennyZhuang <[email protected]>,
add many tests

Signed-off-by: TennyZhuang <[email protected]>,
fix a doctest

Signed-off-by: TennyZhuang <[email protected]>,
Auto merge of rust-lang#9658 - TennyZhuang:partial-pub-fields, r=llogiq

Add new lint `partial_pub_fields`

Signed-off-by: TennyZhuang <[email protected]>

*Please write a short comment explaining your change (or "none" for internal only changes)*

changelog: `partial_pub_fields`: new lint to disallow partial fields of a struct be pub

Resolve rust-lang#9604,
Auto merge of rust-lang#9652 - kraktus:octo_89, r=xFrednet

[`zero_prefixed_literal`] Do not advise to use octal form if not possible

fix rust-lang#9651

changelog: [`zero_prefixed_literal`] Do not advise to use octal form if not possible,
Auto merge of rust-lang#9609 - kraktus:hexa_f32, r=giraffate

[`unnecessary_cast`] Do not lint negative he

See merge request innersource/rust/toolset/rust-clippy!8
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C-bug Category: Clippy is not doing the correct thing I-false-positive Issue: The lint was triggered on code it shouldn't have
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