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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_trait_method;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_span::{source_map::Span, sym};
use super::FLAT_MAP_OPTION;
use clippy_utils::ty::is_type_diagnostic_item;
pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, arg: &'tcx hir::Expr<'_>, span: Span) {
if !is_trait_method(cx, expr, sym::Iterator) {
return;
}
let arg_ty = cx.typeck_results().expr_ty_adjusted(arg);
let sig = match arg_ty.kind() {
ty::Closure(_, substs) => substs.as_closure().sig(),
_ if arg_ty.is_fn() => arg_ty.fn_sig(cx.tcx),
_ => return,
};
if !is_type_diagnostic_item(cx, sig.output().skip_binder(), sym::Option) {
return;
}
span_lint_and_sugg(
cx,
FLAT_MAP_OPTION,
span,
"used `flat_map` where `filter_map` could be used instead",
"try",
"filter_map".into(),
Applicability::MachineApplicable,
);
}
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