Lint against manual impl Default that could have been derived
#134175
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
rustbot
added
S-waiting-on-review
This comment has been minimized.
This comment has been minimized.
|
This adds a new warn-by-default lint, so make sure it gets I-lang-nominated when it's ready |
This comment has been minimized.
This comment has been minimized.
jieyouxu
added
T-lang
estebank
force-pushed
the
manual-default-could-be-derive
branch
from
5d36626 to
ab57d60
Compare
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
estebank
added
the
I-lang-nominated
|
The new |
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
estebank
force-pushed
the
manual-default-could-be-derive
branch
from
5b4a086 to
0411790
Compare
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
estebank
force-pushed
the
manual-default-could-be-derive
branch
2 times, most recently
from
874b484 to
a861c8e
Compare
This comment has been minimized.
This comment has been minimized.
estebank
force-pushed
the
manual-default-could-be-derive
branch
from
a861c8e to
4d2f468
Compare
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
This comment has been minimized.
estebank
force-pushed
the
manual-default-could-be-derive
branch
from
ffdc153 to
55a1857
Compare
Store a mapping betweein the `DefId` for an `impl Default for Ty` and the `DefId` of either a Unit variant/struct or an fn with no arguments that is called within `<Ty as Default>::default()`. When linting `impl`s, if it is for `Default`, we evaluate the contents of their `fn default()`. If it is *only* an ADT literal for `Self` and every field is either a "known to be defaulted" value (`0` or `false`), an explicit `Default::default()` call or a call or path to the same "equivalent" `DefId` from that field's type's `Default::default()` implementation.
estebank
force-pushed
the
manual-default-could-be-derive
branch
from
21ac4fd to
6fa30b6
Compare
|
Let me know if this is ready for review / you want me to look at it, I'm going to mark it as waiting-on-author for the time being. |
rustbot
added
S-waiting-on-author
|
@bors try |
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Dec 16, 2024
…ive, r=<try>
Lint against manual `impl Default` that could have been `derive`d
```
error: `impl Default` that could be derived
--> $DIR/manual-default-impl-could-be-derived.rs:74:1
|
LL | / impl Default for G {
LL | | fn default() -> Self {
LL | | G {
LL | | f: F::Unit,
LL | | }
LL | | }
LL | | }
| |_^
|
help: you don't need to manually `impl Default`, you can derive it
|
LL ~ #[derive(Default)] struct G {
|
```
As part of rust-lang#132162/rust-lang/rfcs#3681 we want to lint when default fields values could preclude the need of a manual `impl Default`, but there are already cases where these manual impls could be derived. This PR introduces a new `default_could_be_derived` lint that makes a best effort check of the body of the `Default::default()` implementation to see if all the fields of a single expression in that body are either known to be `Default` already (like an explicit call to `Default::default()`, a `0` literal, or `Option::None` path) or are identified to be equivalent to the field's type's `Default` value (by opportunistically looking at the `Default::default()` body for that field's type).
|
The job Click to see the possible cause of the failure (guessed by this bot) |
|
💔 Test failed - checks-actions |
|
☔ The latest upstream changes (presumably #134243) made this pull request unmergeable. Please resolve the merge conflicts. |
matthiaskrgr
added a commit
to matthiaskrgr/rust
that referenced
this pull request
Dec 23, 2024
Use `#[derive(Default)]` instead of manual `impl` when possible While working on rust-lang#134175 I noticed a few manual `Default` `impl`s that could be `derive`d instead. These likely predate the existence of the `#[default]` attribute for `enum`s.
rust-timer
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Dec 23, 2024
Rollup merge of rust-lang#134363 - estebank:derive-default, r=SparrowLii Use `#[derive(Default)]` instead of manual `impl` when possible While working on rust-lang#134175 I noticed a few manual `Default` `impl`s that could be `derive`d instead. These likely predate the existence of the `#[default]` attribute for `enum`s.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
As part of #132162/rust-lang/rfcs#3681 we want to lint when default fields values could preclude the need of a manual
impl Default, but there are already cases where these manual impls could be derived. This PR introduces a newdefault_could_be_derivedlint that makes a best effort check of the body of theDefault::default()implementation to see if all the fields of a single expression in that body are either known to beDefaultalready (like an explicit call toDefault::default(), a0literal, orOption::Nonepath) or are identified to be equivalent to the field's type'sDefaultvalue (by opportunistically looking at theDefault::default()body for that field's type).