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|
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
use clippy_utils::{meets_msrv, msrvs};
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};
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.
///
/// ### 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)] = &[...]
/// ```
#[clippy::version = "1.37.0"]
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<RustcVersion>,
}
impl RedundantStaticLifetimes {
#[must_use]
pub fn new(msrv: Option<RustcVersion>) -> Self {
Self { msrv }
}
}
impl_lint_pass!(RedundantStaticLifetimes => [REDUNDANT_STATIC_LIFETIMES]);
impl RedundantStaticLifetimes {
// Recursively visit types
fn visit_type(ty: &Ty, cx: &EarlyContext<'_>, reason: &str) {
match ty.kind {
// Be careful of nested structures (arrays and tuples)
TyKind::Array(ref ty, _) | TyKind::Slice(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, "<type>");
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);
},
_ => {},
}
}
}
impl EarlyLintPass for RedundantStaticLifetimes {
fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
if !meets_msrv(self.msrv, msrvs::STATIC_IN_CONST) {
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);
}
|
