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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::is_trait_method;
   3 use rustc_errors::Applicability;
   4 use rustc_hir as hir;
   5 use rustc_lint::LateContext;
   6 use rustc_middle::ty;
   7 use rustc_span::{source_map::Span, sym};
   8
   9 use super::FLAT_MAP_OPTION;
  10 use clippy_utils::ty::is_type_diagnostic_item;
  11
  12 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, arg: &'tcx hir::Expr<'_>, span: Span) {
  13     if !is_trait_method(cx, expr, sym::Iterator) {
  14         return;
  15     }
  16     let arg_ty = cx.typeck_results().expr_ty_adjusted(arg);
  17     let sig = match arg_ty.kind() {
  18         ty::Closure(_, substs) => substs.as_closure().sig(),
  19         _ if arg_ty.is_fn() => arg_ty.fn_sig(cx.tcx),
  20         _ => return,
  21     };
  22     if !is_type_diagnostic_item(cx, sig.output().skip_binder(), sym::Option) {
  23         return;
  24     }
  25     span_lint_and_sugg(
  26         cx,
  27         FLAT_MAP_OPTION,
  28         span,
  29         "used `flat_map` where `filter_map` could be used instead",
  30         "try",
  31         "filter_map".into(),
  32         Applicability::MachineApplicable,
  33     );
  34 }