1 use clippy_utils::diagnostics::span_lint_and_help;
2 use rustc_ast::ast::{AssocItemKind, Extern, FnKind, FnSig, ImplKind, Item, ItemKind, TraitKind, Ty, TyKind};
3 use rustc_lint::{EarlyContext, EarlyLintPass};
4 use rustc_session::{declare_tool_lint, impl_lint_pass};
5 use rustc_span::{sym, Span};
7 use std::convert::TryInto;
11 /// Checks for excessive
12 /// use of bools in structs.
14 /// ### Why is this bad?
15 /// Excessive bools in a struct
16 /// is often a sign that it's used as a state machine,
17 /// which is much better implemented as an enum.
18 /// If it's not the case, excessive bools usually benefit
19 /// from refactoring into two-variant enums for better
20 /// readability and API.
27 /// is_processing: bool,
28 /// is_finished: bool,
40 pub STRUCT_EXCESSIVE_BOOLS,
42 "using too many bools in a struct"
45 declare_clippy_lint! {
47 /// Checks for excessive use of
48 /// bools in function definitions.
50 /// ### Why is this bad?
51 /// Calls to such functions
52 /// are confusing and error prone, because it's
53 /// hard to remember argument order and you have
54 /// no type system support to back you up. Using
55 /// two-variant enums instead of bools often makes
56 /// API easier to use.
61 /// fn f(is_round: bool, is_hot: bool) { ... }
71 /// enum Temperature {
76 /// fn f(shape: Shape, temperature: Temperature) { ... }
78 pub FN_PARAMS_EXCESSIVE_BOOLS,
80 "using too many bools in function parameters"
83 pub struct ExcessiveBools {
84 max_struct_bools: u64,
85 max_fn_params_bools: u64,
90 pub fn new(max_struct_bools: u64, max_fn_params_bools: u64) -> Self {
97 fn check_fn_sig(&self, cx: &EarlyContext<'_>, fn_sig: &FnSig, span: Span) {
98 match fn_sig.header.ext {
99 Extern::Implicit | Extern::Explicit(_) => return,
103 let fn_sig_bools = fn_sig
107 .filter(|param| is_bool_ty(¶m.ty))
111 if self.max_fn_params_bools < fn_sig_bools {
114 FN_PARAMS_EXCESSIVE_BOOLS,
116 &format!("more than {} bools in function parameters", self.max_fn_params_bools),
118 "consider refactoring bools into two-variant enums",
124 impl_lint_pass!(ExcessiveBools => [STRUCT_EXCESSIVE_BOOLS, FN_PARAMS_EXCESSIVE_BOOLS]);
126 fn is_bool_ty(ty: &Ty) -> bool {
127 if let TyKind::Path(None, path) = &ty.kind {
128 if let [name] = path.segments.as_slice() {
129 return name.ident.name == sym::bool;
135 impl EarlyLintPass for ExcessiveBools {
136 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
137 if item.span.from_expansion() {
141 ItemKind::Struct(variant_data, _) => {
142 if item.attrs.iter().any(|attr| attr.has_name(sym::repr)) {
146 let struct_bools = variant_data
149 .filter(|field| is_bool_ty(&field.ty))
153 if self.max_struct_bools < struct_bools {
156 STRUCT_EXCESSIVE_BOOLS,
158 &format!("more than {} bools in a struct", self.max_struct_bools),
160 "consider using a state machine or refactoring bools into two-variant enums",
164 ItemKind::Impl(box ImplKind {
165 of_trait: None, items, ..
167 | ItemKind::Trait(box TraitKind(.., items)) => {
169 if let AssocItemKind::Fn(box FnKind(_, fn_sig, _, _)) = &item.kind {
170 self.check_fn_sig(cx, fn_sig, item.span);
174 ItemKind::Fn(box FnKind(_, fn_sig, _, _)) => self.check_fn_sig(cx, fn_sig, item.span),