clippy_lints/src/methods/iter_count.rs

   1 use super::utils::derefs_to_slice;
   2 use clippy_utils::diagnostics::span_lint_and_sugg;
   3 use clippy_utils::paths;
   4 use clippy_utils::source::snippet_with_applicability;
   5 use clippy_utils::ty::{is_type_diagnostic_item, match_type};
   6 use rustc_errors::Applicability;
   7 use rustc_hir::Expr;
   8 use rustc_lint::LateContext;
   9 use rustc_span::sym;
  10
  11 use super::ITER_COUNT;
  12
  13 pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, recv: &'tcx Expr<'tcx>, iter_method: &str) {
  14     let ty = cx.typeck_results().expr_ty(recv);
  15     let caller_type = if derefs_to_slice(cx, recv, ty).is_some() {
  16         "slice"
  17     } else if is_type_diagnostic_item(cx, ty, sym::vec_type) {
  18         "Vec"
  19     } else if is_type_diagnostic_item(cx, ty, sym::vecdeque_type) {
  20         "VecDeque"
  21     } else if is_type_diagnostic_item(cx, ty, sym::hashset_type) {
  22         "HashSet"
  23     } else if is_type_diagnostic_item(cx, ty, sym::hashmap_type) {
  24         "HashMap"
  25     } else if match_type(cx, ty, &paths::BTREEMAP) {
  26         "BTreeMap"
  27     } else if match_type(cx, ty, &paths::BTREESET) {
  28         "BTreeSet"
  29     } else if match_type(cx, ty, &paths::LINKED_LIST) {
  30         "LinkedList"
  31     } else if match_type(cx, ty, &paths::BINARY_HEAP) {
  32         "BinaryHeap"
  33     } else {
  34         return;
  35     };
  36     let mut applicability = Applicability::MachineApplicable;
  37     span_lint_and_sugg(
  38         cx,
  39         ITER_COUNT,
  40         expr.span,
  41         &format!("called `.{}().count()` on a `{}`", iter_method, caller_type),
  42         "try",
  43         format!(
  44             "{}.len()",
  45             snippet_with_applicability(cx, recv.span, "..", &mut applicability),
  46         ),
  47         applicability,
  48     );
  49 }