1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::last_path_segment;
3 use clippy_utils::source::snippet;
4 use if_chain::if_chain;
5 use rustc_errors::Applicability;
6 use rustc_hir::{GenericArg, Mutability, Ty, TyKind};
7 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
9 use rustc_span::symbol::sym;
11 declare_clippy_lint! {
13 /// Checks for usage of `&Option<&T>`.
15 /// ### Why is this bad?
16 /// Since `&` is Copy, it's useless to have a
17 /// reference on `Option<&T>`.
19 /// ### Known problems
20 /// It may be irrelevant to use this lint on
21 /// public API code as it will make a breaking change to apply it.
25 /// let x: &Option<&u32> = &Some(&0u32);
29 /// let x: Option<&u32> = Some(&0u32);
31 #[clippy::version = "1.49.0"]
34 "use `Option<&T>` instead of `&Option<&T>`"
37 declare_lint_pass!(RefOptionRef => [REF_OPTION_REF]);
39 impl<'tcx> LateLintPass<'tcx> for RefOptionRef {
40 fn check_ty(&mut self, cx: &LateContext<'tcx>, ty: &'tcx Ty<'tcx>) {
42 if let TyKind::Rptr(_, ref mut_ty) = ty.kind;
43 if mut_ty.mutbl == Mutability::Not;
44 if let TyKind::Path(ref qpath) = &mut_ty.ty.kind;
45 let last = last_path_segment(qpath);
46 if let Some(res) = last.res;
47 if let Some(def_id) = res.opt_def_id();
49 if cx.tcx.is_diagnostic_item(sym::Option, def_id);
50 if let Some(params) = last_path_segment(qpath).args ;
51 if !params.parenthesized;
52 if let Some(inner_ty) = params.args.iter().find_map(|arg| match arg {
53 GenericArg::Type(inner_ty) => Some(inner_ty),
56 if let TyKind::Rptr(_, _) = inner_ty.kind;
63 "since `&` implements the `Copy` trait, `&Option<&T>` can be simplified to `Option<&T>`",
65 format!("Option<{}>", &snippet(cx, inner_ty.span, "..")),
66 Applicability::MaybeIncorrect,