1 files changed, 64 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/methods/manual_ok_or.rs b/src/tools/clippy/clippy_lints/src/methods/manual_ok_or.rs
new file mode 100644
index 000000000..ffd2f4a38
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/methods/manual_ok_or.rs
@@ -0,0 +1,64 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::{indent_of, reindent_multiline, snippet_opt};
+use clippy_utils::ty::is_type_diagnostic_item;
+use clippy_utils::{is_lang_ctor, path_to_local_id};
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::LangItem::{ResultErr, ResultOk};
+use rustc_hir::{Closure, Expr, ExprKind, PatKind};
+use rustc_lint::LateContext;
+use rustc_span::symbol::sym;
+
+use super::MANUAL_OK_OR;
+
+pub(super) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    expr: &'tcx Expr<'tcx>,
+    recv: &'tcx Expr<'_>,
+    or_expr: &'tcx Expr<'_>,
+    map_expr: &'tcx Expr<'_>,
+) {
+    if_chain! {
+        if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
+        if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
+        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id), sym::Option);
+        if let ExprKind::Call(Expr { kind: ExprKind::Path(err_path), .. }, [err_arg]) = or_expr.kind;
+        if is_lang_ctor(cx, err_path, ResultErr);
+        if is_ok_wrapping(cx, map_expr);
+        if let Some(recv_snippet) = snippet_opt(cx, recv.span);
+        if let Some(err_arg_snippet) = snippet_opt(cx, err_arg.span);
+        if let Some(indent) = indent_of(cx, expr.span);
+        then {
+            let reindented_err_arg_snippet = reindent_multiline(err_arg_snippet.into(), true, Some(indent + 4));
+            span_lint_and_sugg(
+                cx,
+                MANUAL_OK_OR,
+                expr.span,
+                "this pattern reimplements `Option::ok_or`",
+                "replace with",
+                format!(
+                    "{}.ok_or({})",
+                    recv_snippet,
+                    reindented_err_arg_snippet
+                ),
+                Applicability::MachineApplicable,
+            );
+        }
+    }
+}
+
+fn is_ok_wrapping(cx: &LateContext<'_>, map_expr: &Expr<'_>) -> bool {
+    if let ExprKind::Path(ref qpath) = map_expr.kind {
+        if is_lang_ctor(cx, qpath, ResultOk) {
+            return true;
+        }
+    }
+    if_chain! {
+        if let ExprKind::Closure(&Closure { body, .. }) = map_expr.kind;
+        let body = cx.tcx.hir().body(body);
+        if let PatKind::Binding(_, param_id, ..) = body.params[0].pat.kind;
+        if let ExprKind::Call(Expr { kind: ExprKind::Path(ok_path), .. }, &[ref ok_arg]) = body.value.kind;
+        if is_lang_ctor(cx, ok_path, ResultOk);
+        then { path_to_local_id(ok_arg, param_id) } else { false }
+    }
+}