1 use crate::utils::{meets_msrv, snippet_opt, span_lint_and_then};
2 use if_chain::if_chain;
3 use rustc_ast::ast::{Attribute, Item, ItemKind, StructField, Variant, VariantData, VisibilityKind};
4 use rustc_attr as attr;
5 use rustc_errors::Applicability;
6 use rustc_lint::{EarlyContext, EarlyLintPass};
7 use rustc_semver::RustcVersion;
8 use rustc_session::{declare_tool_lint, impl_lint_pass};
9 use rustc_span::{sym, Span};
11 const MANUAL_NON_EXHAUSTIVE_MSRV: RustcVersion = RustcVersion::new(1, 40, 0);
13 declare_clippy_lint! {
14 /// **What it does:** Checks for manual implementations of the non-exhaustive pattern.
16 /// **Why is this bad?** Using the #[non_exhaustive] attribute expresses better the intent
17 /// and allows possible optimizations when applied to enums.
19 /// **Known problems:** None.
37 /// struct T(pub i32, pub i32, ());
54 /// struct T(pub i32, pub i32);
56 pub MANUAL_NON_EXHAUSTIVE,
58 "manual implementations of the non-exhaustive pattern can be simplified using #[non_exhaustive]"
62 pub struct ManualNonExhaustive {
63 msrv: Option<RustcVersion>,
66 impl ManualNonExhaustive {
68 pub fn new(msrv: Option<RustcVersion>) -> Self {
73 impl_lint_pass!(ManualNonExhaustive => [MANUAL_NON_EXHAUSTIVE]);
75 impl EarlyLintPass for ManualNonExhaustive {
76 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
77 if !meets_msrv(self.msrv.as_ref(), &MANUAL_NON_EXHAUSTIVE_MSRV) {
82 ItemKind::Enum(def, _) => {
83 check_manual_non_exhaustive_enum(cx, item, &def.variants);
85 ItemKind::Struct(variant_data, _) => {
86 if let VariantData::Unit(..) = variant_data {
90 check_manual_non_exhaustive_struct(cx, item, variant_data);
96 extract_msrv_attr!(EarlyContext);
99 fn check_manual_non_exhaustive_enum(cx: &EarlyContext<'_>, item: &Item, variants: &[Variant]) {
100 fn is_non_exhaustive_marker(variant: &Variant) -> bool {
101 matches!(variant.data, VariantData::Unit(_))
102 && variant.ident.as_str().starts_with('_')
103 && variant.attrs.iter().any(|a| is_doc_hidden(a))
106 fn is_doc_hidden(attr: &Attribute) -> bool {
107 attr.has_name(sym::doc)
108 && match attr.meta_item_list() {
109 Some(l) => attr::list_contains_name(&l, sym::hidden),
115 let mut markers = variants.iter().filter(|v| is_non_exhaustive_marker(v));
116 if let Some(marker) = markers.next();
117 if markers.count() == 0 && variants.len() > 1;
121 MANUAL_NON_EXHAUSTIVE,
123 "this seems like a manual implementation of the non-exhaustive pattern",
126 if !item.attrs.iter().any(|attr| attr.has_name(sym::non_exhaustive));
127 let header_span = cx.sess.source_map().span_until_char(item.span, '{');
128 if let Some(snippet) = snippet_opt(cx, header_span);
130 diag.span_suggestion(
133 format!("#[non_exhaustive] {}", snippet),
134 Applicability::Unspecified,
138 diag.span_help(marker.span, "remove this variant");
144 fn check_manual_non_exhaustive_struct(cx: &EarlyContext<'_>, item: &Item, data: &VariantData) {
145 fn is_private(field: &StructField) -> bool {
146 matches!(field.vis.kind, VisibilityKind::Inherited)
149 fn is_non_exhaustive_marker(field: &StructField) -> bool {
150 is_private(field) && field.ty.kind.is_unit() && field.ident.map_or(true, |n| n.as_str().starts_with('_'))
153 fn find_header_span(cx: &EarlyContext<'_>, item: &Item, data: &VariantData) -> Span {
154 let delimiter = match data {
155 VariantData::Struct(..) => '{',
156 VariantData::Tuple(..) => '(',
157 VariantData::Unit(_) => unreachable!("`VariantData::Unit` is already handled above"),
160 cx.sess.source_map().span_until_char(item.span, delimiter)
163 let fields = data.fields();
164 let private_fields = fields.iter().filter(|f| is_private(f)).count();
165 let public_fields = fields.iter().filter(|f| f.vis.kind.is_pub()).count();
168 if private_fields == 1 && public_fields >= 1 && public_fields == fields.len() - 1;
169 if let Some(marker) = fields.iter().find(|f| is_non_exhaustive_marker(f));
173 MANUAL_NON_EXHAUSTIVE,
175 "this seems like a manual implementation of the non-exhaustive pattern",
178 if !item.attrs.iter().any(|attr| attr.has_name(sym::non_exhaustive));
179 let header_span = find_header_span(cx, item, data);
180 if let Some(snippet) = snippet_opt(cx, header_span);
182 diag.span_suggestion(
185 format!("#[non_exhaustive] {}", snippet),
186 Applicability::Unspecified,
190 diag.span_help(marker.span, "remove this field");