1 use crate::utils::{in_macro, snippet, span_lint_and_then};
2 use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
3 use rustc::{declare_tool_lint, lint_array};
4 use rustc_errors::Applicability;
8 /// **What it does:** Checks for constants with an explicit `'static` lifetime.
10 /// **Why is this bad?** Adding `'static` to every reference can create very
11 /// complicated types.
13 /// **Known problems:** None.
17 /// const FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] =
20 /// This code can be rewritten as
22 /// const FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...]
24 pub CONST_STATIC_LIFETIME,
26 "Using explicit `'static` lifetime for constants when elision rules would allow omitting them."
29 pub struct StaticConst;
31 impl LintPass for StaticConst {
32 fn get_lints(&self) -> LintArray {
33 lint_array!(CONST_STATIC_LIFETIME)
36 fn name(&self) -> &'static str {
42 // Recursively visit types
43 fn visit_type(&mut self, ty: &Ty, cx: &EarlyContext<'_>) {
45 // Be careful of nested structures (arrays and tuples)
46 TyKind::Array(ref ty, _) => {
47 self.visit_type(&*ty, cx);
49 TyKind::Tup(ref tup) => {
51 self.visit_type(&*tup_ty, cx);
54 // This is what we are looking for !
55 TyKind::Rptr(ref optional_lifetime, ref borrow_type) => {
56 // Match the 'static lifetime
57 if let Some(lifetime) = *optional_lifetime {
58 match borrow_type.ty.node {
59 TyKind::Path(..) | TyKind::Slice(..) | TyKind::Array(..) | TyKind::Tup(..) => {
60 if lifetime.ident.name == "'static" {
61 let snip = snippet(cx, borrow_type.ty.span, "<type>");
62 let sugg = format!("&{}", snip);
65 CONST_STATIC_LIFETIME,
67 "Constants have by default a `'static` lifetime",
71 "consider removing `'static`",
73 Applicability::MachineApplicable, //snippet
82 self.visit_type(&*borrow_type.ty, cx);
84 TyKind::Slice(ref ty) => {
85 self.visit_type(ty, cx);
92 impl EarlyLintPass for StaticConst {
93 fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
94 if !in_macro(item.span) {
95 // Match only constants...
96 if let ItemKind::Const(ref var_type, _) = item.node {
97 self.visit_type(var_type, cx);
102 // Don't check associated consts because `'static` cannot be elided on those (issue #2438)