src/tools/clippy/clippy_lints/src/matches/match_on_vec_items.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::source::snippet;
   3 use clippy_utils::ty::{is_type_diagnostic_item, is_type_lang_item};
   4 use if_chain::if_chain;
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{Expr, ExprKind, LangItem};
   7 use rustc_lint::LateContext;
   8 use rustc_span::sym;
   9
  10 use super::MATCH_ON_VEC_ITEMS;
  11
  12 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, scrutinee: &'tcx Expr<'_>) {
  13     if_chain! {
  14         if let Some(idx_expr) = is_vec_indexing(cx, scrutinee);
  15         if let ExprKind::Index(vec, idx) = idx_expr.kind;
  16
  17         then {
  18             // FIXME: could be improved to suggest surrounding every pattern with Some(_),
  19             // but only when `or_patterns` are stabilized.
  20             span_lint_and_sugg(
  21                 cx,
  22                 MATCH_ON_VEC_ITEMS,
  23                 scrutinee.span,
  24                 "indexing into a vector may panic",
  25                 "try this",
  26                 format!(
  27                     "{}.get({})",
  28                     snippet(cx, vec.span, ".."),
  29                     snippet(cx, idx.span, "..")
  30                 ),
  31                 Applicability::MaybeIncorrect
  32             );
  33         }
  34     }
  35 }
  36
  37 fn is_vec_indexing<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Option<&'tcx Expr<'tcx>> {
  38     if_chain! {
  39         if let ExprKind::Index(array, index) = expr.kind;
  40         if is_vector(cx, array);
  41         if !is_full_range(cx, index);
  42
  43         then {
  44             return Some(expr);
  45         }
  46     }
  47
  48     None
  49 }
  50
  51 fn is_vector(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
  52     let ty = cx.typeck_results().expr_ty(expr);
  53     let ty = ty.peel_refs();
  54     is_type_diagnostic_item(cx, ty, sym::Vec)
  55 }
  56
  57 fn is_full_range(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
  58     let ty = cx.typeck_results().expr_ty(expr);
  59     let ty = ty.peel_refs();
  60     is_type_lang_item(cx, ty, LangItem::RangeFull)
  61 }