don't lint enums, update note in lint description
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y21
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@ -2,22 +2,22 @@
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use clippy_utils::{
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diagnostics::span_lint_and_then,
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paths,
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is_path_lang_item, paths,
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ty::match_type,
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visitors::{for_each_expr, Visitable},
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};
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use rustc_ast::LitKind;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_hir::Block;
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use rustc_hir::{
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def::{DefKind, Res},
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Expr, ImplItemKind, MatchSource, Node,
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Expr, ImplItemKind, LangItem, Node,
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};
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use rustc_hir::{Block, PatKind};
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use rustc_hir::{ExprKind, Impl, ItemKind, QPath, TyKind};
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use rustc_hir::{ImplItem, Item, VariantData};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::ty::Ty;
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use rustc_middle::ty::TypeckResults;
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use rustc_middle::ty::{EarlyBinder, Ty};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::{sym, Span, Symbol};
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@ -38,11 +38,12 @@
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/// Oftentimes there is more logic to a `Debug` impl if it uses `write!` macro, so it tries
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/// to be on the conservative side and not lint in those cases in an attempt to prevent false positives.
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///
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/// This lint also does not look through function calls, so calling `.field(self.as_slice())` for example
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/// does not consider fields used inside of `as_slice()` as used by the `Debug` impl.
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/// This lint also does not look through function calls, so calling a function does not consider fields
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/// used inside of that function as used by the `Debug` impl.
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///
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/// Lastly, it also ignores tuple structs as their `DebugTuple` formatter does not have a `finish_non_exhaustive`
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/// method.
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/// method, as well as enums because their exhaustiveness is already checked by the compiler when matching on the enum,
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/// making it much less likely to accidentally forget to update the `Debug` impl when adding a new variant.
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///
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/// ### Example
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/// ```rust
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@ -185,8 +186,7 @@ fn check_struct<'tcx>(
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.fields()
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.iter()
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.filter_map(|field| {
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let EarlyBinder(field_ty) = cx.tcx.type_of(field.def_id);
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if field_accesses.contains(&field.ident.name) || field_ty.is_phantom_data() {
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if field_accesses.contains(&field.ident.name) || is_path_lang_item(cx, field.ty, LangItem::PhantomData) {
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None
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} else {
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Some((field.span, "this field is unused"))
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@ -201,82 +201,6 @@ fn check_struct<'tcx>(
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}
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}
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/// Attempts to find unused fields in variants assuming that
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/// the item is an enum.
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///
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/// Currently, only simple cases are detected where the user
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/// matches on `self` and calls `debug_struct` inside of the arms
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fn check_enum<'tcx>(
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cx: &LateContext<'tcx>,
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typeck_results: &TypeckResults<'tcx>,
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block: &'tcx Block<'tcx>,
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self_ty: Ty<'tcx>,
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item: &'tcx Item<'tcx>,
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) {
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let Some(arms) = for_each_expr(block, |expr| {
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if let ExprKind::Match(val, arms, MatchSource::Normal) = expr.kind
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&& let match_ty = typeck_results.expr_ty_adjusted(val).peel_refs()
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&& match_ty == self_ty
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{
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ControlFlow::Break(arms)
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} else {
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ControlFlow::Continue(())
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}
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}) else {
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return;
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};
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let mut span_notes = Vec::new();
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for arm in arms {
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if !should_lint(cx, typeck_results, arm.body) {
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continue;
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}
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arm.pat.walk_always(|pat| match pat.kind {
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PatKind::Wild => span_notes.push((pat.span, "unused field here due to wildcard `_`")),
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PatKind::Tuple(_, rest) | PatKind::TupleStruct(.., rest) if rest.as_opt_usize().is_some() => {
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span_notes.push((pat.span, "more unused fields here due to rest pattern `..`"));
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},
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PatKind::Struct(.., true) => {
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span_notes.push((pat.span, "more unused fields here due to rest pattern `..`"));
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},
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_ => {},
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});
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let mut field_accesses = FxHashSet::default();
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let mut check_field_access = |sym, expr| {
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if !typeck_results.expr_ty(expr).is_phantom_data() {
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arm.pat.each_binding(|_, _, _, pat_ident| {
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if sym == pat_ident.name {
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field_accesses.insert(pat_ident);
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}
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});
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}
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};
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for_each_expr(arm.body, |expr| {
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if let ExprKind::Path(QPath::Resolved(_, path)) = expr.kind && let Some(segment) = path.segments.first()
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{
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check_field_access(segment.ident.name, expr);
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} else if let Some(sym) = as_field_call(cx, typeck_results, expr) {
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check_field_access(sym, expr);
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}
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ControlFlow::<!, _>::Continue(())
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});
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arm.pat.each_binding(|_, _, span, pat_ident| {
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if !field_accesses.contains(&pat_ident) {
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span_notes.push((span, "the field referenced by this binding is unused"));
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}
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});
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}
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if !span_notes.is_empty() {
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report_lints(cx, item.span, span_notes);
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}
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}
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impl<'tcx> LateLintPass<'tcx> for MissingFieldsInDebug {
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fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx rustc_hir::Item<'tcx>) {
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// is this an `impl Debug for X` block?
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@ -301,10 +225,9 @@ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx rustc_hir::Item<'tc
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&& let typeck_results = cx.tcx.typeck_body(*body_id)
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&& should_lint(cx, typeck_results, block)
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{
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match &self_item.kind {
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ItemKind::Struct(data, _) => check_struct(cx, typeck_results, block, self_ty, item, data),
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ItemKind::Enum(..) => check_enum(cx, typeck_results, block, self_ty, item),
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_ => {}
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// we intentionally only lint structs, see lint description
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if let ItemKind::Struct(data, _) = &self_item.kind {
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check_struct(cx, typeck_results, block, self_ty, item, data);
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}
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}
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}
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@ -97,140 +97,12 @@ fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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}
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}
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enum SingleVariantEnumUnnamed {
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A(u8),
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}
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// ok
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impl fmt::Debug for SingleVariantEnumUnnamed {
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::A(n) => formatter.debug_tuple("A").field(&n).finish(),
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}
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}
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}
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enum MultiVariantEnum {
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A(u8),
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B { a: u8, b: String },
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C,
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}
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impl fmt::Debug for MultiVariantEnum {
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// match arm Self::B ignores `b`
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::A(n) => formatter.debug_tuple("A").field(&n).finish(),
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Self::B { a, b } => formatter.debug_struct("B").field("a", &a).finish(),
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Self::C => formatter.debug_struct("C").finish(),
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}
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}
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}
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enum MultiVariantEnumOk {
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A(u8),
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B { a: u8, b: String },
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C,
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}
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// ok
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impl fmt::Debug for MultiVariantEnumOk {
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::A(n) => formatter.debug_tuple("A").field(&n).finish(),
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Self::B { a, b } => formatter.debug_struct("B").field("a", &a).field("b", &b).finish(),
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Self::C => formatter.debug_struct("C").finish(),
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}
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}
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}
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enum MultiVariantEnumNonExhaustive {
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A(u8),
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B { a: u8, b: String },
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C,
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}
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// ok
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impl fmt::Debug for MultiVariantEnumNonExhaustive {
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::A(n) => formatter.debug_tuple("A").field(&n).finish(),
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Self::B { a, b } => formatter.debug_struct("B").field("b", &b).finish_non_exhaustive(),
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Self::C => formatter.debug_struct("C").finish(),
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}
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}
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}
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enum MultiVariantRest {
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A(u8),
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B { a: u8, b: String },
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C,
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}
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impl fmt::Debug for MultiVariantRest {
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// `a` field ignored due to rest pattern
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::A(n) => formatter.debug_tuple("A").field(&n).finish(),
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Self::B { b, .. } => formatter.debug_struct("B").field("b", &b).finish(),
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Self::C => formatter.debug_struct("C").finish(),
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}
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}
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}
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enum MultiVariantRestNonExhaustive {
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A(u8),
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B { a: u8, b: String },
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C,
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}
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// ok
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impl fmt::Debug for MultiVariantRestNonExhaustive {
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::A(n) => formatter.debug_tuple("A").field(&n).finish(),
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Self::B { b, .. } => formatter.debug_struct("B").field("b", &b).finish_non_exhaustive(),
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Self::C => formatter.debug_struct("C").finish(),
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}
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}
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}
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enum Wildcard {
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A(u8),
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B(String),
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}
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// ok
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impl fmt::Debug for Wildcard {
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match self {
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Self::A(n) => formatter.debug_tuple("A").field(&n).finish(),
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_ => todo!(),
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}
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}
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}
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enum Empty {}
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// ok
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impl fmt::Debug for Empty {
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fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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match *self {}
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}
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}
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#[derive(Debug)]
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struct DerivedStruct {
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a: u8,
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b: i32,
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}
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#[derive(Debug)]
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enum DerivedEnum {
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A(i32),
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B { a: String },
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}
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// https://github.com/rust-lang/rust-clippy/pull/10616#discussion_r1166846953
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struct Inner {
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@ -69,45 +69,5 @@ LL | b: String,
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= help: consider including all fields in this `Debug` impl
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= help: consider calling `.finish_non_exhaustive()` if you intend to ignore fields
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error: manual `Debug` impl does not include all fields
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--> $DIR/missing_fields_in_debug.rs:119:1
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LL | / impl fmt::Debug for MultiVariantEnum {
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LL | | // match arm Self::B ignores `b`
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LL | | fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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LL | | match self {
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... |
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LL | | }
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LL | | }
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| |_^
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note: the field referenced by this binding is unused
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--> $DIR/missing_fields_in_debug.rs:124:26
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LL | Self::B { a, b } => formatter.debug_struct("B").field("a", &a).finish(),
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| ^
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= help: consider including all fields in this `Debug` impl
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= help: consider calling `.finish_non_exhaustive()` if you intend to ignore fields
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error: manual `Debug` impl does not include all fields
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--> $DIR/missing_fields_in_debug.rs:170:1
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LL | / impl fmt::Debug for MultiVariantRest {
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LL | | // `a` field ignored due to rest pattern
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LL | | fn fmt(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result {
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LL | | match self {
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... |
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LL | | }
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LL | | }
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| |_^
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note: more unused fields here due to rest pattern `..`
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--> $DIR/missing_fields_in_debug.rs:175:13
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LL | Self::B { b, .. } => formatter.debug_struct("B").field("b", &b).finish(),
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| ^^^^^^^^^^^^^^^^^
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= help: consider including all fields in this `Debug` impl
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= help: consider calling `.finish_non_exhaustive()` if you intend to ignore fields
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error: aborting due to 5 previous errors
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error: aborting due to 3 previous errors
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