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

   1 use crate::consts::{constant, Constant};
   2 use crate::utils::{match_trait_method, paths, snippet_with_applicability, span_lint_and_sugg};
   3 use if_chain::if_chain;
   4 use rustc_errors::Applicability;
   5 use rustc_hir as hir;
   6 use rustc_lint::LateContext;
   7
   8 use super::ITER_NTH_ZERO;
   9
  10 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, nth_args: &'tcx [hir::Expr<'_>]) {
  11     if_chain! {
  12         if match_trait_method(cx, expr, &paths::ITERATOR);
  13         if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), &nth_args[1]);
  14         then {
  15             let mut applicability = Applicability::MachineApplicable;
  16             span_lint_and_sugg(
  17                 cx,
  18                 ITER_NTH_ZERO,
  19                 expr.span,
  20                 "called `.nth(0)` on a `std::iter::Iterator`, when `.next()` is equivalent",
  21                 "try calling `.next()` instead of `.nth(0)`",
  22                 format!("{}.next()", snippet_with_applicability(cx, nth_args[0].span, "..", &mut applicability)),
  23                 applicability,
  24             );
  25         }
  26     }
  27 }