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use clippy_utils::consts::{constant, Constant};
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::{is_from_proc_macro, is_trait_method};
use rustc_errors::Applicability;
use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_span::sym;
use super::ITER_SKIP_ZERO;
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, arg_expr: &Expr<'_>) {
if !expr.span.from_expansion()
&& is_trait_method(cx, expr, sym::Iterator)
&& let Some(arg) = constant(cx, cx.typeck_results(), arg_expr).and_then(|constant| {
if let Constant::Int(arg) = constant {
Some(arg)
} else {
None
}
})
&& arg == 0
&& !is_from_proc_macro(cx, expr)
{
span_lint_and_then(cx, ITER_SKIP_ZERO, arg_expr.span, "usage of `.skip(0)`", |diag| {
diag.span_suggestion(
arg_expr.span,
"if you meant to skip the first element, use",
"1",
Applicability::MaybeIncorrect,
)
.note("this call to `skip` does nothing and is useless; remove it");
});
}
}
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