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