79 lines
2.0 KiB
Rust
79 lines
2.0 KiB
Rust
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use rustc::lint::*;
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use rustc_front::hir;
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use rustc_front::intravisit::{FnKind, Visitor, walk_expr, walk_fn};
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use std::collections::HashMap;
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use syntax::ast;
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use syntax::codemap::Span;
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use syntax::parse::token::InternedString;
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use utils::{in_macro, span_lint};
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/// **What it does:** This lint 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 an error in the
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/// 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_lint! {
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pub UNUSED_LABEL,
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Warn,
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"unused label"
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}
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pub struct UnusedLabel;
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#[derive(Default)]
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struct UnusedLabelVisitor {
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labels: HashMap<InternedString, Span>,
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}
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impl UnusedLabelVisitor {
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pub fn new() -> UnusedLabelVisitor {
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::std::default::Default::default()
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}
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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 LateLintPass for UnusedLabel {
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fn check_fn(&mut self, cx: &LateContext, kind: FnKind, decl: &hir::FnDecl, body: &hir::Block, span: Span, _: ast::NodeId) {
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if in_macro(cx, span) {
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return;
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}
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let mut v = UnusedLabelVisitor::new();
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walk_fn(&mut v, kind, decl, body, span);
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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<'v> Visitor<'v> for UnusedLabelVisitor {
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fn visit_expr(&mut self, expr: &hir::Expr) {
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match expr.node {
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hir::ExprBreak(Some(label)) | hir::ExprAgain(Some(label)) => {
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self.labels.remove(&label.node.name.as_str());
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}
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hir::ExprLoop(_, Some(label)) | hir::ExprWhile(_, _, Some(label)) => {
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self.labels.insert(label.name.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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}
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