Lint against manual impl Default that could have been derived
#134175
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This adds a new warn-by-default lint, so make sure it gets I-lang-nominated when it's ready |
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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. |
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@bors try |
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…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 | | }
| |_^
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help: you don't need to manually `impl Default`, you can derive it
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LL ~ #[derive(Default)] struct G {
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```
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).
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The job Click to see the possible cause of the failure (guessed by this bot) |
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💔 Test failed - checks-actions |
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☔ The latest upstream changes (presumably #134243) made this pull request unmergeable. Please resolve the merge conflicts. |
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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.
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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.
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Analyzing the body of a user-written function in search for known patterns feels very much like clippy territory to me. In fact clippy's |
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@Nadrieril yeah, I've filed a PR with some of the more advanced analysis to clippy, but not all of it. |
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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.
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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).