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Auto merge of #12122 - andrewbanchich:tostring-impl, r=llogiq
add to_string_trait_impl lint closes #12076 changelog: [`to_string_trait_impl`]: add lint for direct `ToString` implementations
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| use clippy_utils::diagnostics::span_lint_and_help; | ||
| use rustc_hir::{Impl, Item, ItemKind}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::declare_lint_pass; | ||
| use rustc_span::sym; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Checks for direct implementations of `ToString`. | ||
| /// ### Why is this bad? | ||
| /// This trait is automatically implemented for any type which implements the `Display` trait. | ||
| /// As such, `ToString` shouldn’t be implemented directly: `Display` should be implemented instead, | ||
| /// and you get the `ToString` implementation for free. | ||
| /// ### Example | ||
| /// ```no_run | ||
| /// struct Point { | ||
| /// x: usize, | ||
| /// y: usize, | ||
| /// } | ||
| /// | ||
| /// impl ToString for Point { | ||
| /// fn to_string(&self) -> String { | ||
| /// format!("({}, {})", self.x, self.y) | ||
| /// } | ||
| /// } | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```no_run | ||
| /// struct Point { | ||
| /// x: usize, | ||
| /// y: usize, | ||
| /// } | ||
| /// | ||
| /// impl std::fmt::Display for Point { | ||
| /// fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { | ||
| /// write!(f, "({}, {})", self.x, self.y) | ||
| /// } | ||
| /// } | ||
| /// ``` | ||
| #[clippy::version = "1.77.0"] | ||
| pub TO_STRING_TRAIT_IMPL, | ||
| style, | ||
| "check for direct implementations of `ToString`" | ||
| } | ||
|
|
||
| declare_lint_pass!(ToStringTraitImpl => [TO_STRING_TRAIT_IMPL]); | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for ToStringTraitImpl { | ||
| fn check_item(&mut self, cx: &LateContext<'tcx>, it: &'tcx Item<'tcx>) { | ||
| if let ItemKind::Impl(Impl { | ||
| of_trait: Some(trait_ref), | ||
| .. | ||
| }) = it.kind | ||
| && let Some(trait_did) = trait_ref.trait_def_id() | ||
| && cx.tcx.is_diagnostic_item(sym::ToString, trait_did) | ||
| { | ||
| span_lint_and_help( | ||
| cx, | ||
| TO_STRING_TRAIT_IMPL, | ||
| it.span, | ||
| "direct implementation of `ToString`", | ||
| None, | ||
| "prefer implementing `Display` instead", | ||
| ); | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,31 @@ | ||
| #![warn(clippy::to_string_trait_impl)] | ||
|
|
||
| use std::fmt::{self, Display}; | ||
|
|
||
| struct Point { | ||
| x: usize, | ||
| y: usize, | ||
| } | ||
|
|
||
| impl ToString for Point { | ||
| fn to_string(&self) -> String { | ||
| format!("({}, {})", self.x, self.y) | ||
| } | ||
| } | ||
|
|
||
| struct Foo; | ||
|
|
||
| impl Display for Foo { | ||
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { | ||
| write!(f, "Foo") | ||
| } | ||
| } | ||
|
|
||
| struct Bar; | ||
|
|
||
| impl Bar { | ||
| #[allow(clippy::inherent_to_string)] | ||
| fn to_string(&self) -> String { | ||
| String::from("Bar") | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,16 @@ | ||
| error: direct implementation of `ToString` | ||
| --> $DIR/to_string_trait_impl.rs:10:1 | ||
| | | ||
| LL | / impl ToString for Point { | ||
| LL | | fn to_string(&self) -> String { | ||
| LL | | format!("({}, {})", self.x, self.y) | ||
| LL | | } | ||
| LL | | } | ||
| | |_^ | ||
| | | ||
| = help: prefer implementing `Display` instead | ||
| = note: `-D clippy::to-string-trait-impl` implied by `-D warnings` | ||
| = help: to override `-D warnings` add `#[allow(clippy::to_string_trait_impl)]` | ||
|
|
||
| error: aborting due to 1 previous error | ||
|
|
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