Merge commit '98e2b9f25b6db4b2680a3d388456d9f95cb28344' into clippyup

1 files changed, 34 insertions, 0 deletions

diff --git a/clippy_lints/src/methods/flat_map_option.rs b/clippy_lints/src/methods/flat_map_option.rs
new file mode 100644
index 00000000000..12d560653ed
--- /dev/null
+++ b/clippy_lints/src/methods/flat_map_option.rs
@@ -0,0 +1,34 @@
+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_type) {
+        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,
+    )
+}