clippy_lints/src/methods/filter_next.rs

   1 use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg};
   2 use clippy_utils::is_trait_method;
   3 use clippy_utils::source::snippet;
   4 use rustc_errors::Applicability;
   5 use rustc_hir as hir;
   6 use rustc_lint::LateContext;
   7 use rustc_span::sym;
   8
   9 use super::FILTER_NEXT;
  10
  11 /// lint use of `filter().next()` for `Iterators`
  12 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, filter_args: &'tcx [hir::Expr<'_>]) {
  13     // lint if caller of `.filter().next()` is an Iterator
  14     if is_trait_method(cx, expr, sym::Iterator) {
  15         let msg = "called `filter(..).next()` on an `Iterator`. This is more succinctly expressed by calling \
  16                    `.find(..)` instead";
  17         let filter_snippet = snippet(cx, filter_args[1].span, "..");
  18         if filter_snippet.lines().count() <= 1 {
  19             let iter_snippet = snippet(cx, filter_args[0].span, "..");
  20             // add note if not multi-line
  21             span_lint_and_sugg(
  22                 cx,
  23                 FILTER_NEXT,
  24                 expr.span,
  25                 msg,
  26                 "try this",
  27                 format!("{}.find({})", iter_snippet, filter_snippet),
  28                 Applicability::MachineApplicable,
  29             );
  30         } else {
  31             span_lint(cx, FILTER_NEXT, expr.span, msg);
  32         }
  33     }
  34 }