use crate::utils::meets_msrv; use clippy_utils::diagnostics::span_lint_and_then; use clippy_utils::source::snippet; use rustc_ast::ast::{Item, ItemKind, Ty, TyKind}; use rustc_errors::Applicability; use rustc_lint::{EarlyContext, EarlyLintPass}; use rustc_semver::RustcVersion; use rustc_session::{declare_tool_lint, impl_lint_pass}; const REDUNDANT_STATIC_LIFETIMES_MSRV: RustcVersion = RustcVersion::new(1, 17, 0); declare_clippy_lint! { /// **What it does:** Checks for constants and statics with an explicit `'static` lifetime. /// /// **Why is this bad?** Adding `'static` to every reference can create very /// complicated types. /// /// **Known problems:** None. /// /// **Example:** /// ```ignore /// const FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] = /// &[...] /// static FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] = /// &[...] /// ``` /// This code can be rewritten as /// ```ignore /// const FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...] /// static FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...] /// ``` pub REDUNDANT_STATIC_LIFETIMES, style, "Using explicit `'static` lifetime for constants or statics when elision rules would allow omitting them." } pub struct RedundantStaticLifetimes { msrv: Option, } impl RedundantStaticLifetimes { #[must_use] pub fn new(msrv: Option) -> Self { Self { msrv } } } impl_lint_pass!(RedundantStaticLifetimes => [REDUNDANT_STATIC_LIFETIMES]); impl RedundantStaticLifetimes { // Recursively visit types fn visit_type(&mut self, ty: &Ty, cx: &EarlyContext<'_>, reason: &str) { match ty.kind { // Be careful of nested structures (arrays and tuples) TyKind::Array(ref ty, _) => { self.visit_type(&*ty, cx, reason); }, TyKind::Tup(ref tup) => { for tup_ty in tup { self.visit_type(&*tup_ty, cx, reason); } }, // This is what we are looking for ! TyKind::Rptr(ref optional_lifetime, ref borrow_type) => { // Match the 'static lifetime if let Some(lifetime) = *optional_lifetime { match borrow_type.ty.kind { TyKind::Path(..) | TyKind::Slice(..) | TyKind::Array(..) | TyKind::Tup(..) => { if lifetime.ident.name == rustc_span::symbol::kw::StaticLifetime { let snip = snippet(cx, borrow_type.ty.span, ""); let sugg = format!("&{}", snip); span_lint_and_then( cx, REDUNDANT_STATIC_LIFETIMES, lifetime.ident.span, reason, |diag| { diag.span_suggestion( ty.span, "consider removing `'static`", sugg, Applicability::MachineApplicable, //snippet ); }, ); } }, _ => {}, } } self.visit_type(&*borrow_type.ty, cx, reason); }, TyKind::Slice(ref ty) => { self.visit_type(ty, cx, reason); }, _ => {}, } } } impl EarlyLintPass for RedundantStaticLifetimes { fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) { if !meets_msrv(self.msrv.as_ref(), &REDUNDANT_STATIC_LIFETIMES_MSRV) { return; } if !item.span.from_expansion() { if let ItemKind::Const(_, ref var_type, _) = item.kind { self.visit_type(var_type, cx, "constants have by default a `'static` lifetime"); // Don't check associated consts because `'static` cannot be elided on those (issue // #2438) } if let ItemKind::Static(ref var_type, _, _) = item.kind { self.visit_type(var_type, cx, "statics have by default a `'static` lifetime"); } } } extract_msrv_attr!(EarlyContext); }