92 lines
3.1 KiB
Rust
92 lines
3.1 KiB
Rust
use syntax::ast::*;
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use rustc::lint::{EarlyContext, EarlyLintPass, LintArray, LintPass};
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use utils::{in_macro, snippet, span_lint_and_then};
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/// **What it does:** Checks for constants 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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/// ```rust
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/// const 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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/// ```rust
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/// const FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...]
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/// ```
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declare_lint! {
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pub CONST_STATIC_LIFETIME,
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Warn,
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"Using explicit `'static` lifetime for constants when elision rules would allow omitting them."
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}
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pub struct StaticConst;
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impl LintPass for StaticConst {
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fn get_lints(&self) -> LintArray {
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lint_array!(CONST_STATIC_LIFETIME)
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}
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}
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impl StaticConst {
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// Recursively visit types
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fn visit_type(&mut self, ty: &Ty, cx: &EarlyContext) {
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match ty.node {
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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);
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},
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TyKind::Tup(ref tup) => for tup_ty in tup {
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self.visit_type(&*tup_ty, cx);
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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.node {
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TyKind::Path(..) | TyKind::Slice(..) | TyKind::Array(..) |
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TyKind::Tup(..) => {
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if lifetime.ident.name == "'static" {
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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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CONST_STATIC_LIFETIME,
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lifetime.span,
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"Constants have by default a `'static` lifetime",
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|db| {
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db.span_suggestion(ty.span, "consider removing `'static`", sugg);
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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);
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},
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TyKind::Slice(ref ty) => {
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self.visit_type(ty, cx);
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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 StaticConst {
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fn check_item(&mut self, cx: &EarlyContext, item: &Item) {
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if !in_macro(item.span) {
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// Match only constants...
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if let ItemKind::Const(ref var_type, _) = item.node {
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self.visit_type(var_type, cx);
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}
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}
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}
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// Don't check associated consts because `'static` cannot be elided on those (issue #2438)
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}
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