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

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