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use clippy_utils::diagnostics::span_lint_and_note;
use if_chain::if_chain;
use rustc_ast::LitKind;
use rustc_hir::{Expr, ExprKind};
use rustc_lint::LateContext;
use rustc_span::source_map::Spanned;
use super::SUSPICIOUS_SPLITN;
pub(super) fn check(cx: &LateContext<'_>, method_name: &str, expr: &Expr<'_>, self_arg: &Expr<'_>, count: u128) {
if_chain! {
if count <= 1;
if let Some(call_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
if let Some(impl_id) = cx.tcx.impl_of_method(call_id);
if cx.tcx.impl_trait_ref(impl_id).is_none();
let self_ty = cx.tcx.type_of(impl_id);
if self_ty.is_slice() || self_ty.is_str();
then {
// Ignore empty slice and string literals when used with a literal count.
if matches!(self_arg.kind, ExprKind::Array([]))
|| matches!(self_arg.kind, ExprKind::Lit(Spanned { node: LitKind::Str(s, _), .. }) if s.is_empty())
{
return;
}
let (msg, note_msg) = if count == 0 {
(format!("`{method_name}` called with `0` splits"),
"the resulting iterator will always return `None`")
} else {
(format!("`{method_name}` called with `1` split"),
if self_ty.is_slice() {
"the resulting iterator will always return the entire slice followed by `None`"
} else {
"the resulting iterator will always return the entire string followed by `None`"
})
};
span_lint_and_note(
cx,
SUSPICIOUS_SPLITN,
expr.span,
&msg,
None,
note_msg,
);
}
}
}
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