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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,113 @@ | ||
| use clippy_utils::diagnostics::span_lint_and_help; | ||
| use clippy_utils::{in_macro, is_automatically_derived, is_default_equivalent, remove_blocks}; | ||
| use rustc_hir::{ | ||
| def::Res, Body, Expr, ExprKind, GenericArg, Impl, ImplItemKind, Item, ItemKind, Node, QPath, Ty, TyKind, | ||
| }; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::{declare_lint_pass, declare_tool_lint}; | ||
| use rustc_span::sym; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Detects manual `std::default::Default` implementations that are identical to a derived implementation. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// It is less concise. | ||
| /// | ||
| /// ### Example | ||
| /// ```rust | ||
| /// struct Foo { | ||
| /// bar: bool | ||
| /// } | ||
| /// | ||
| /// impl std::default::Default for Foo { | ||
| /// fn default() -> Self { | ||
| /// Self { | ||
| /// bar: false | ||
| /// } | ||
| /// } | ||
| /// } | ||
| /// ``` | ||
| /// | ||
| /// Could be written as: | ||
| /// | ||
| /// ```rust | ||
| /// #[derive(Default)] | ||
| /// struct Foo { | ||
| /// bar: bool | ||
| /// } | ||
| /// ``` | ||
| pub DERIVABLE_IMPLS, | ||
| complexity, | ||
| "manual implementation of the `Default` trait which is equal to a derive" | ||
| } | ||
|
|
||
| declare_lint_pass!(DerivableImpls => [DERIVABLE_IMPLS]); | ||
|
|
||
| fn is_path_self(e: &Expr<'_>) -> bool { | ||
| if let ExprKind::Path(QPath::Resolved(_, p)) = e.kind { | ||
| matches!(p.res, Res::SelfCtor(..)) | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
|
|
||
| impl<'tcx> LateLintPass<'tcx> for DerivableImpls { | ||
| fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) { | ||
| if_chain! { | ||
| if let ItemKind::Impl(Impl { | ||
| of_trait: Some(ref trait_ref), | ||
| items: [child], | ||
| self_ty, | ||
| .. | ||
| }) = item.kind; | ||
| if let attrs = cx.tcx.hir().attrs(item.hir_id()); | ||
| if !is_automatically_derived(attrs); | ||
| if !in_macro(item.span); | ||
| if let Some(def_id) = trait_ref.trait_def_id(); | ||
| if cx.tcx.is_diagnostic_item(sym::Default, def_id); | ||
| if let impl_item_hir = child.id.hir_id(); | ||
| if let Some(Node::ImplItem(impl_item)) = cx.tcx.hir().find(impl_item_hir); | ||
| if let ImplItemKind::Fn(_, b) = &impl_item.kind; | ||
| if let Body { value: func_expr, .. } = cx.tcx.hir().body(*b); | ||
| if let Ty { | ||
| kind: TyKind::Path(QPath::Resolved(_, self_ty_path)), | ||
| .. | ||
| } = self_ty; | ||
| then { | ||
| if let Some(generic) = self_ty_path.segments.last().and_then(|s| s.args) { | ||
| for arg in generic.args { | ||
| if !matches!(arg, GenericArg::Lifetime(_)) { | ||
| return; | ||
| } | ||
| } | ||
| } | ||
| let should_emit = match remove_blocks(func_expr).kind { | ||
| ExprKind::Tup(fields) => fields.iter().all(|e| is_default_equivalent(cx, e)), | ||
| ExprKind::Call(callee, args) | ||
| if is_path_self(callee) => args.iter().all(|e| is_default_equivalent(cx, e)), | ||
| ExprKind::Struct(_, fields, _) => fields.iter().all(|ef| is_default_equivalent(cx, ef.expr)), | ||
| _ => false, | ||
| }; | ||
| if should_emit { | ||
| let path_string = self_ty_path | ||
| .segments | ||
| .iter() | ||
| .map(|segment| { | ||
| segment.ident.to_string() | ||
| }) | ||
| .collect::<Vec<_>>() | ||
| .join("::"); | ||
| span_lint_and_help( | ||
| cx, | ||
| DERIVABLE_IMPLS, | ||
| item.span, | ||
| "this `impl` can be derived", | ||
| None, | ||
| &format!("try annotating `{}` with `#[derive(Default)]`", path_string), | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } |
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