1 use clippy_utils::diagnostics::span_lint_and_help;
2 use rustc_ast::ast::{AssocItemKind, Extern, Fn, FnSig, Impl, Item, ItemKind, Trait, 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 #[clippy::version = "1.43.0"]
41 pub STRUCT_EXCESSIVE_BOOLS,
43 "using too many bools in a struct"
46 declare_clippy_lint! {
48 /// Checks for excessive use of
49 /// bools in function definitions.
51 /// ### Why is this bad?
52 /// Calls to such functions
53 /// are confusing and error prone, because it's
54 /// hard to remember argument order and you have
55 /// no type system support to back you up. Using
56 /// two-variant enums instead of bools often makes
57 /// API easier to use.
62 /// fn f(is_round: bool, is_hot: bool) { ... }
72 /// enum Temperature {
77 /// fn f(shape: Shape, temperature: Temperature) { ... }
79 #[clippy::version = "1.43.0"]
80 pub FN_PARAMS_EXCESSIVE_BOOLS,
82 "using too many bools in function parameters"
85 pub struct ExcessiveBools {
86 max_struct_bools: u64,
87 max_fn_params_bools: u64,
92 pub fn new(max_struct_bools: u64, max_fn_params_bools: u64) -> Self {
99 fn check_fn_sig(&self, cx: &EarlyContext<'_>, fn_sig: &FnSig, span: Span) {
100 match fn_sig.header.ext {
101 Extern::Implicit | Extern::Explicit(_) => return,
105 let fn_sig_bools = fn_sig
109 .filter(|param| is_bool_ty(¶m.ty))
113 if self.max_fn_params_bools < fn_sig_bools {
116 FN_PARAMS_EXCESSIVE_BOOLS,
118 &format!("more than {} bools in function parameters", self.max_fn_params_bools),
120 "consider refactoring bools into two-variant enums",
126 impl_lint_pass!(ExcessiveBools => [STRUCT_EXCESSIVE_BOOLS, FN_PARAMS_EXCESSIVE_BOOLS]);
128 fn is_bool_ty(ty: &Ty) -> bool {
129 if let TyKind::Path(None, path) = &ty.kind {
130 if let [name] = path.segments.as_slice() {
131 return name.ident.name == sym::bool;
137 impl EarlyLintPass for ExcessiveBools {
138 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
139 if item.span.from_expansion() {
143 ItemKind::Struct(variant_data, _) => {
144 if item.attrs.iter().any(|attr| attr.has_name(sym::repr)) {
148 let struct_bools = variant_data
151 .filter(|field| is_bool_ty(&field.ty))
155 if self.max_struct_bools < struct_bools {
158 STRUCT_EXCESSIVE_BOOLS,
160 &format!("more than {} bools in a struct", self.max_struct_bools),
162 "consider using a state machine or refactoring bools into two-variant enums",
166 ItemKind::Impl(box Impl {
167 of_trait: None, items, ..
169 | ItemKind::Trait(box Trait { items, .. }) => {
171 if let AssocItemKind::Fn(box Fn { sig, .. }) = &item.kind {
172 self.check_fn_sig(cx, sig, item.span);
176 ItemKind::Fn(box Fn { sig, .. }) => self.check_fn_sig(cx, sig, item.span),