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

   1 use clippy_utils::consts::{constant, Constant};
   2 use clippy_utils::diagnostics::span_lint_and_sugg;
   3 use clippy_utils::is_trait_method;
   4 use clippy_utils::source::snippet_with_applicability;
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir as hir;
   8 use rustc_lint::LateContext;
   9 use rustc_span::sym;
  10
  11 use super::ITER_NTH_ZERO;
  12
  13 pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
  14     if_chain! {
  15         if is_trait_method(cx, expr, sym::Iterator);
  16         if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), arg);
  17         then {
  18             let mut applicability = Applicability::MachineApplicable;
  19             span_lint_and_sugg(
  20                 cx,
  21                 ITER_NTH_ZERO,
  22                 expr.span,
  23                 "called `.nth(0)` on a `std::iter::Iterator`, when `.next()` is equivalent",
  24                 "try calling `.next()` instead of `.nth(0)`",
  25                 format!("{}.next()", snippet_with_applicability(cx, recv.span, "..", &mut applicability)),
  26                 applicability,
  27             );
  28         }
  29     }
  30 }