1 use clippy_utils::diagnostics::span_lint_and_then;
2 use clippy_utils::source::snippet;
3 use clippy_utils::{meets_msrv, msrvs};
4 use rustc_ast::ast::{Item, ItemKind, Ty, TyKind};
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};
10 declare_clippy_lint! {
12 /// Checks for constants and statics with an explicit `'static` lifetime.
14 /// ### Why is this bad?
15 /// Adding `'static` to every reference can create very
16 /// complicated types.
20 /// const FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] =
22 /// static FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] =
25 /// This code can be rewritten as
27 /// const FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...]
28 /// static FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...]
30 #[clippy::version = "1.37.0"]
31 pub REDUNDANT_STATIC_LIFETIMES,
33 "Using explicit `'static` lifetime for constants or statics when elision rules would allow omitting them."
36 pub struct RedundantStaticLifetimes {
37 msrv: Option<RustcVersion>,
40 impl RedundantStaticLifetimes {
42 pub fn new(msrv: Option<RustcVersion>) -> Self {
47 impl_lint_pass!(RedundantStaticLifetimes => [REDUNDANT_STATIC_LIFETIMES]);
49 impl RedundantStaticLifetimes {
50 // Recursively visit types
51 fn visit_type(ty: &Ty, cx: &EarlyContext<'_>, reason: &str) {
53 // Be careful of nested structures (arrays and tuples)
54 TyKind::Array(ref ty, _) | TyKind::Slice(ref ty) => {
55 Self::visit_type(ty, cx, reason);
57 TyKind::Tup(ref tup) => {
59 Self::visit_type(tup_ty, cx, reason);
62 // This is what we are looking for !
63 TyKind::Rptr(ref optional_lifetime, ref borrow_type) => {
64 // Match the 'static lifetime
65 if let Some(lifetime) = *optional_lifetime {
66 match borrow_type.ty.kind {
67 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Array(..) | TyKind::Tup(..) => {
68 if lifetime.ident.name == rustc_span::symbol::kw::StaticLifetime {
69 let snip = snippet(cx, borrow_type.ty.span, "<type>");
70 let sugg = format!("&{}", snip);
73 REDUNDANT_STATIC_LIFETIMES,
79 "consider removing `'static`",
81 Applicability::MachineApplicable, //snippet
90 Self::visit_type(&borrow_type.ty, cx, reason);
97 impl EarlyLintPass for RedundantStaticLifetimes {
98 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
99 if !meets_msrv(self.msrv, msrvs::STATIC_IN_CONST) {
103 if !item.span.from_expansion() {
104 if let ItemKind::Const(_, ref var_type, _) = item.kind {
105 Self::visit_type(var_type, cx, "constants have by default a `'static` lifetime");
106 // Don't check associated consts because `'static` cannot be elided on those (issue
110 if let ItemKind::Static(ref var_type, _, _) = item.kind {
111 Self::visit_type(var_type, cx, "statics have by default a `'static` lifetime");
116 extract_msrv_attr!(EarlyContext);