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| 1 | +use crate::utils::{is_type_diagnostic_item, snippet, span_lint_and_sugg, walk_ptrs_ty}; |
| 2 | +use if_chain::if_chain; |
| 3 | +use rustc_errors::Applicability; |
| 4 | +use rustc_hir::{Expr, ExprKind, MatchSource}; |
| 5 | +use rustc_lint::{LateContext, LateLintPass, LintContext}; |
| 6 | +use rustc_middle::lint::in_external_macro; |
| 7 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 8 | + |
| 9 | +declare_clippy_lint! { |
| 10 | + /// **What it does:** Checks for `match vec[idx]` or `match vec[n..m]`. |
| 11 | + /// |
| 12 | + /// **Why is this bad?** This can panic at runtime. |
| 13 | + /// |
| 14 | + /// **Known problems:** None. |
| 15 | + /// |
| 16 | + /// **Example:** |
| 17 | + /// ```rust, no_run |
| 18 | + /// let arr = vec![0, 1, 2, 3]; |
| 19 | + /// let idx = 1; |
| 20 | + /// |
| 21 | + /// // Bad |
| 22 | + /// match arr[idx] { |
| 23 | + /// 0 => println!("{}", 0), |
| 24 | + /// 1 => println!("{}", 3), |
| 25 | + /// _ => {}, |
| 26 | + /// } |
| 27 | + /// ``` |
| 28 | + /// Use instead: |
| 29 | + /// ```rust, no_run |
| 30 | + /// let arr = vec![0, 1, 2, 3]; |
| 31 | + /// let idx = 1; |
| 32 | + /// |
| 33 | + /// // Good |
| 34 | + /// match arr.get(idx) { |
| 35 | + /// Some(0) => println!("{}", 0), |
| 36 | + /// Some(1) => println!("{}", 3), |
| 37 | + /// _ => {}, |
| 38 | + /// } |
| 39 | + /// ``` |
| 40 | + pub MATCH_ON_VEC_ITEMS, |
| 41 | + correctness, |
| 42 | + "matching on vector elements can panic" |
| 43 | +} |
| 44 | + |
| 45 | +declare_lint_pass!(MatchOnVecItems => [MATCH_ON_VEC_ITEMS]); |
| 46 | + |
| 47 | +impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MatchOnVecItems { |
| 48 | + fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) { |
| 49 | + if_chain! { |
| 50 | + if !in_external_macro(cx.sess(), expr.span); |
| 51 | + if let ExprKind::Match(ref match_expr, _, MatchSource::Normal) = expr.kind; |
| 52 | + if let Some(idx_expr) = is_vec_indexing(cx, match_expr); |
| 53 | + if let ExprKind::Index(vec, idx) = idx_expr.kind; |
| 54 | + |
| 55 | + then { |
| 56 | + // FIXME: could be improved to suggest surrounding every pattern with Some(_), |
| 57 | + // but only when `or_patterns` are stabilized. |
| 58 | + span_lint_and_sugg( |
| 59 | + cx, |
| 60 | + MATCH_ON_VEC_ITEMS, |
| 61 | + match_expr.span, |
| 62 | + "indexing into a vector may panic", |
| 63 | + "try this", |
| 64 | + format!( |
| 65 | + "{}.get({})", |
| 66 | + snippet(cx, vec.span, ".."), |
| 67 | + snippet(cx, idx.span, "..") |
| 68 | + ), |
| 69 | + Applicability::MaybeIncorrect |
| 70 | + ); |
| 71 | + } |
| 72 | + } |
| 73 | + } |
| 74 | +} |
| 75 | + |
| 76 | +fn is_vec_indexing<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> { |
| 77 | + if_chain! { |
| 78 | + if let ExprKind::Index(ref array, _) = expr.kind; |
| 79 | + let ty = cx.tables.expr_ty(array); |
| 80 | + let ty = walk_ptrs_ty(ty); |
| 81 | + if is_type_diagnostic_item(cx, ty, sym!(vec_type)); |
| 82 | + |
| 83 | + then { |
| 84 | + return Some(expr); |
| 85 | + } |
| 86 | + } |
| 87 | + |
| 88 | + None |
| 89 | +} |
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