src/tools/clippy/clippy_lints/src/methods/iter_nth.rs

   1 use super::utils::derefs_to_slice;
   2 use crate::methods::iter_nth_zero;
   3 use clippy_utils::diagnostics::span_lint_and_help;
   4 use clippy_utils::ty::is_type_diagnostic_item;
   5 use rustc_hir as hir;
   6 use rustc_lint::LateContext;
   7 use rustc_span::symbol::sym;
   8
   9 use super::ITER_NTH;
  10
  11 pub(super) fn check<'tcx>(
  12     cx: &LateContext<'tcx>,
  13     expr: &hir::Expr<'_>,
  14     iter_recv: &'tcx hir::Expr<'tcx>,
  15     nth_recv: &hir::Expr<'_>,
  16     nth_arg: &hir::Expr<'_>,
  17     is_mut: bool,
  18 ) {
  19     let mut_str = if is_mut { "_mut" } else { "" };
  20     let caller_type = if derefs_to_slice(cx, iter_recv, cx.typeck_results().expr_ty(iter_recv)).is_some() {
  21         "slice"
  22     } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(iter_recv), sym::Vec) {
  23         "Vec"
  24     } else if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(iter_recv), sym::VecDeque) {
  25         "VecDeque"
  26     } else {
  27         iter_nth_zero::check(cx, expr, nth_recv, nth_arg);
  28         return; // caller is not a type that we want to lint
  29     };
  30
  31     span_lint_and_help(
  32         cx,
  33         ITER_NTH,
  34         expr.span,
  35         &format!("called `.iter{mut_str}().nth()` on a {caller_type}"),
  36         None,
  37         &format!("calling `.get{mut_str}()` is both faster and more readable"),
  38     );
  39 }