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use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_trait_method;
use clippy_utils::source::snippet_with_applicability;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_span::sym;
use super::ITER_NTH_ZERO;
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>, arg: &hir::Expr<'_>) {
if_chain! {
if is_trait_method(cx, expr, sym::Iterator);
if let Some((Constant::Int(0), _)) = constant(cx, cx.typeck_results(), arg);
then {
let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
ITER_NTH_ZERO,
expr.span,
"called `.nth(0)` on a `std::iter::Iterator`, when `.next()` is equivalent",
"try calling `.next()` instead of `.nth(0)`",
format!("{}.next()", snippet_with_applicability(cx, recv.span, "..", &mut applicability)),
applicability,
);
}
}
}
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