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Commit | Line | Data |
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f20569fa XL |
1 | use crate::utils::{last_path_segment, snippet, span_lint_and_sugg}; |
2 | use rustc_hir::{GenericArg, Mutability, Ty, TyKind}; | |
3 | use rustc_lint::{LateContext, LateLintPass}; | |
4 | use rustc_session::{declare_lint_pass, declare_tool_lint}; | |
5 | use rustc_span::symbol::sym; | |
6 | ||
7 | use if_chain::if_chain; | |
8 | use rustc_errors::Applicability; | |
9 | ||
10 | declare_clippy_lint! { | |
11 | /// **What it does:** Checks for usage of `&Option<&T>`. | |
12 | /// | |
13 | /// **Why is this bad?** Since `&` is Copy, it's useless to have a | |
14 | /// reference on `Option<&T>`. | |
15 | /// | |
16 | /// **Known problems:** It may be irrelevant to use this lint on | |
17 | /// public API code as it will make a breaking change to apply it. | |
18 | /// | |
19 | /// **Example:** | |
20 | /// | |
21 | /// ```rust,ignore | |
22 | /// let x: &Option<&u32> = &Some(&0u32); | |
23 | /// ``` | |
24 | /// Use instead: | |
25 | /// ```rust,ignore | |
26 | /// let x: Option<&u32> = Some(&0u32); | |
27 | /// ``` | |
28 | pub REF_OPTION_REF, | |
29 | pedantic, | |
30 | "use `Option<&T>` instead of `&Option<&T>`" | |
31 | } | |
32 | ||
33 | declare_lint_pass!(RefOptionRef => [REF_OPTION_REF]); | |
34 | ||
35 | impl<'tcx> LateLintPass<'tcx> for RefOptionRef { | |
36 | fn check_ty(&mut self, cx: &LateContext<'tcx>, ty: &'tcx Ty<'tcx>) { | |
37 | if_chain! { | |
38 | if let TyKind::Rptr(_, ref mut_ty) = ty.kind; | |
39 | if mut_ty.mutbl == Mutability::Not; | |
40 | if let TyKind::Path(ref qpath) = &mut_ty.ty.kind; | |
41 | let last = last_path_segment(qpath); | |
42 | if let Some(res) = last.res; | |
43 | if let Some(def_id) = res.opt_def_id(); | |
44 | ||
45 | if cx.tcx.is_diagnostic_item(sym::option_type, def_id); | |
46 | if let Some(ref params) = last_path_segment(qpath).args ; | |
47 | if !params.parenthesized; | |
48 | if let Some(inner_ty) = params.args.iter().find_map(|arg| match arg { | |
49 | GenericArg::Type(inner_ty) => Some(inner_ty), | |
50 | _ => None, | |
51 | }); | |
52 | if let TyKind::Rptr(_, _) = inner_ty.kind; | |
53 | ||
54 | then { | |
55 | span_lint_and_sugg( | |
56 | cx, | |
57 | REF_OPTION_REF, | |
58 | ty.span, | |
59 | "since `&` implements the `Copy` trait, `&Option<&T>` can be simplified to `Option<&T>`", | |
60 | "try", | |
61 | format!("Option<{}>", &snippet(cx, inner_ty.span, "..")), | |
62 | Applicability::MaybeIncorrect, | |
63 | ); | |
64 | } | |
65 | } | |
66 | } | |
67 | } |