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| 1 | +use crate::utils::{snippet_opt, span_lint_and_then}; |
| 2 | +use if_chain::if_chain; |
| 3 | +use rustc_ast::ast::{Attribute, Ident, Item, ItemKind, StructField, TyKind, Variant, VariantData, VisibilityKind}; |
| 4 | +use rustc_attr as attr; |
| 5 | +use rustc_errors::Applicability; |
| 6 | +use rustc_lint::{EarlyContext, EarlyLintPass}; |
| 7 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 8 | + |
| 9 | +declare_clippy_lint! { |
| 10 | + /// **What it does:** Checks for manual implementations of the non-exhaustive pattern. |
| 11 | + /// |
| 12 | + /// **Why is this bad?** Using the #[non_exhaustive] attribute expresses better the intent |
| 13 | + /// and allows possible optimizations when applied to enums. |
| 14 | + /// |
| 15 | + /// **Known problems:** None. |
| 16 | + /// |
| 17 | + /// **Example:** |
| 18 | + /// |
| 19 | + /// ```rust |
| 20 | + /// struct S { |
| 21 | + /// pub a: i32, |
| 22 | + /// pub b: i32, |
| 23 | + /// _c: (), |
| 24 | + /// } |
| 25 | + /// |
| 26 | + /// enum E { |
| 27 | + /// A, |
| 28 | + /// B, |
| 29 | + /// #[doc(hidden)] |
| 30 | + /// _C, |
| 31 | + /// } |
| 32 | + /// |
| 33 | + /// struct T(pub i32, pub i32, ()); |
| 34 | + /// ``` |
| 35 | + /// Use instead: |
| 36 | + /// ```rust |
| 37 | + /// #[non_exhaustive] |
| 38 | + /// struct S { |
| 39 | + /// pub a: i32, |
| 40 | + /// pub b: i32, |
| 41 | + /// } |
| 42 | + /// |
| 43 | + /// #[non_exhaustive] |
| 44 | + /// enum E { |
| 45 | + /// A, |
| 46 | + /// B, |
| 47 | + /// } |
| 48 | + /// |
| 49 | + /// #[non_exhaustive] |
| 50 | + /// struct T(pub i32, pub i32); |
| 51 | + /// ``` |
| 52 | + pub MANUAL_NON_EXHAUSTIVE, |
| 53 | + style, |
| 54 | + "manual implementations of the non-exhaustive pattern can be simplified using #[non_exhaustive]" |
| 55 | +} |
| 56 | + |
| 57 | +declare_lint_pass!(ManualNonExhaustive => [MANUAL_NON_EXHAUSTIVE]); |
| 58 | + |
| 59 | +impl EarlyLintPass for ManualNonExhaustive { |
| 60 | + fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) { |
| 61 | + match &item.kind { |
| 62 | + ItemKind::Enum(def, _) => { |
| 63 | + check_manual_non_exhaustive_enum(cx, item, &def.variants); |
| 64 | + }, |
| 65 | + ItemKind::Struct(variant_data, _) => { |
| 66 | + if let VariantData::Unit(..) = variant_data { |
| 67 | + return; |
| 68 | + } |
| 69 | + |
| 70 | + check_manual_non_exhaustive_struct(cx, item, variant_data); |
| 71 | + }, |
| 72 | + _ => {}, |
| 73 | + } |
| 74 | + } |
| 75 | +} |
| 76 | + |
| 77 | +fn check_manual_non_exhaustive_enum(cx: &EarlyContext<'_>, item: &Item, variants: &[Variant]) { |
| 78 | + fn is_non_exhaustive_marker(variant: &Variant) -> bool { |
| 79 | + matches!(variant.data, VariantData::Unit(_)) |
| 80 | + && variant.ident.as_str().starts_with('_') |
| 81 | + && variant.attrs.iter().any(|a| is_doc_hidden(a)) |
| 82 | + } |
| 83 | + |
| 84 | + fn is_doc_hidden(attr: &Attribute) -> bool { |
| 85 | + attr.check_name(sym!(doc)) |
| 86 | + && match attr.meta_item_list() { |
| 87 | + Some(l) => attr::list_contains_name(&l, sym!(hidden)), |
| 88 | + None => false, |
| 89 | + } |
| 90 | + } |
| 91 | + |
| 92 | + if_chain! { |
| 93 | + if !attr::contains_name(&item.attrs, sym!(non_exhaustive)); |
| 94 | + let markers = variants.iter().filter(|v| is_non_exhaustive_marker(v)).count(); |
| 95 | + if markers == 1 && variants.len() > markers; |
| 96 | + if let Some(variant) = variants.last(); |
| 97 | + if is_non_exhaustive_marker(variant); |
| 98 | + then { |
| 99 | + span_lint_and_then( |
| 100 | + cx, |
| 101 | + MANUAL_NON_EXHAUSTIVE, |
| 102 | + item.span, |
| 103 | + "this seems like a manual implementation of the non-exhaustive pattern", |
| 104 | + |diag| { |
| 105 | + let header_span = cx.sess.source_map().span_until_char(item.span, '{'); |
| 106 | + |
| 107 | + if let Some(snippet) = snippet_opt(cx, header_span) { |
| 108 | + diag.span_suggestion( |
| 109 | + item.span, |
| 110 | + "add the attribute", |
| 111 | + format!("#[non_exhaustive] {}", snippet), |
| 112 | + Applicability::Unspecified, |
| 113 | + ); |
| 114 | + diag.span_help(variant.span, "and remove this variant"); |
| 115 | + } |
| 116 | + }); |
| 117 | + } |
| 118 | + } |
| 119 | +} |
| 120 | + |
| 121 | +fn check_manual_non_exhaustive_struct(cx: &EarlyContext<'_>, item: &Item, data: &VariantData) { |
| 122 | + fn is_private(field: &StructField) -> bool { |
| 123 | + matches!(field.vis.node, VisibilityKind::Inherited) |
| 124 | + } |
| 125 | + |
| 126 | + fn is_non_exhaustive_marker(name: &Option<Ident>) -> bool { |
| 127 | + name.map(|n| n.as_str().starts_with('_')).unwrap_or(true) |
| 128 | + } |
| 129 | + |
| 130 | + let fields = data.fields(); |
| 131 | + let private_fields = fields.iter().filter(|f| is_private(f)).count(); |
| 132 | + let public_fields = fields.iter().filter(|f| f.vis.node.is_pub()).count(); |
| 133 | + |
| 134 | + if_chain! { |
| 135 | + if !attr::contains_name(&item.attrs, sym!(non_exhaustive)); |
| 136 | + if private_fields == 1 && public_fields >= private_fields && public_fields == fields.len() - 1; |
| 137 | + if let Some(field) = fields.iter().find(|f| is_private(f)); |
| 138 | + if is_non_exhaustive_marker(&field.ident); |
| 139 | + if let TyKind::Tup(tup_fields) = &field.ty.kind; |
| 140 | + if tup_fields.is_empty(); |
| 141 | + then { |
| 142 | + span_lint_and_then( |
| 143 | + cx, |
| 144 | + MANUAL_NON_EXHAUSTIVE, |
| 145 | + item.span, |
| 146 | + "this seems like a manual implementation of the non-exhaustive pattern", |
| 147 | + |diag| { |
| 148 | + let delimiter = match data { |
| 149 | + VariantData::Struct(..) => '{', |
| 150 | + VariantData::Tuple(..) => '(', |
| 151 | + _ => unreachable!(), |
| 152 | + }; |
| 153 | + let header_span = cx.sess.source_map().span_until_char(item.span, delimiter); |
| 154 | + |
| 155 | + if let Some(snippet) = snippet_opt(cx, header_span) { |
| 156 | + diag.span_suggestion( |
| 157 | + item.span, |
| 158 | + "add the attribute", |
| 159 | + format!("#[non_exhaustive] {}", snippet), |
| 160 | + Applicability::Unspecified, |
| 161 | + ); |
| 162 | + diag.span_help(field.span, "and remove this field"); |
| 163 | + } |
| 164 | + }); |
| 165 | + } |
| 166 | + } |
| 167 | +} |
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