90 lines
2.5 KiB
Rust
90 lines
2.5 KiB
Rust
use crate::utils::{in_macro, span_lint};
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use rustc::hir;
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use rustc::hir::intravisit::{walk_expr, walk_fn, FnKind, NestedVisitorMap, Visitor};
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_tool_lint, lint_array};
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use rustc_data_structures::fx::FxHashMap;
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use syntax::ast;
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use syntax::source_map::Span;
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use syntax::symbol::LocalInternedString;
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/// **What it does:** Checks for unused labels.
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///
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/// **Why is this bad?** Maybe the label should be used in which case there is
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/// an error in the code or it should be removed.
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///
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/// **Known problems:** Hopefully none.
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///
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/// **Example:**
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/// ```rust,ignore
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/// fn unused_label() {
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/// 'label: for i in 1..2 {
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/// if i > 4 { continue }
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/// }
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/// ```
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declare_clippy_lint! {
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pub UNUSED_LABEL,
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complexity,
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"unused labels"
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}
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pub struct UnusedLabel;
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struct UnusedLabelVisitor<'a, 'tcx: 'a> {
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labels: FxHashMap<LocalInternedString, Span>,
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cx: &'a LateContext<'a, 'tcx>,
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}
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impl LintPass for UnusedLabel {
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fn get_lints(&self) -> LintArray {
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lint_array!(UNUSED_LABEL)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedLabel {
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fn check_fn(
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&mut self,
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cx: &LateContext<'a, 'tcx>,
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kind: FnKind<'tcx>,
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decl: &'tcx hir::FnDecl,
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body: &'tcx hir::Body,
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span: Span,
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fn_id: ast::NodeId,
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) {
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if in_macro(span) {
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return;
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}
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let mut v = UnusedLabelVisitor {
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cx,
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labels: FxHashMap::default(),
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};
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walk_fn(&mut v, kind, decl, body.id(), span, fn_id);
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for (label, span) in v.labels {
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span_lint(cx, UNUSED_LABEL, span, &format!("unused label `{}`", label));
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}
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}
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}
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impl<'a, 'tcx: 'a> Visitor<'tcx> for UnusedLabelVisitor<'a, 'tcx> {
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fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
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match expr.node {
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hir::ExprKind::Break(destination, _) | hir::ExprKind::Continue(destination) => {
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if let Some(label) = destination.label {
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self.labels.remove(&label.ident.as_str());
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}
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},
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hir::ExprKind::Loop(_, Some(label), _) | hir::ExprKind::While(_, _, Some(label)) => {
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self.labels.insert(label.ident.as_str(), expr.span);
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},
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_ => (),
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}
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walk_expr(self, expr);
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}
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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NestedVisitorMap::All(&self.cx.tcx.hir())
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}
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}
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