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Commit | Line | Data |
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1 | use crate::consts::constant_simple; | |
2 | use crate::utils; | |
3 | use crate::utils::{path_to_local_id, sugg}; | |
4 | use if_chain::if_chain; | |
5 | use rustc_errors::Applicability; | |
6 | use rustc_hir::{Arm, Expr, ExprKind, Pat, PatKind}; | |
7 | use rustc_lint::LintContext; | |
8 | use rustc_lint::{LateContext, LateLintPass}; | |
9 | use rustc_middle::lint::in_external_macro; | |
10 | use rustc_session::{declare_lint_pass, declare_tool_lint}; | |
11 | use rustc_span::sym; | |
12 | ||
13 | declare_clippy_lint! { | |
14 | /// **What it does:** | |
15 | /// Finds patterns that reimplement `Option::unwrap_or` or `Result::unwrap_or`. | |
16 | /// | |
17 | /// **Why is this bad?** | |
18 | /// Concise code helps focusing on behavior instead of boilerplate. | |
19 | /// | |
20 | /// **Known problems:** None. | |
21 | /// | |
22 | /// **Example:** | |
23 | /// ```rust | |
24 | /// let foo: Option<i32> = None; | |
25 | /// match foo { | |
26 | /// Some(v) => v, | |
27 | /// None => 1, | |
28 | /// }; | |
29 | /// ``` | |
30 | /// | |
31 | /// Use instead: | |
32 | /// ```rust | |
33 | /// let foo: Option<i32> = None; | |
34 | /// foo.unwrap_or(1); | |
35 | /// ``` | |
36 | pub MANUAL_UNWRAP_OR, | |
37 | complexity, | |
38 | "finds patterns that can be encoded more concisely with `Option::unwrap_or` or `Result::unwrap_or`" | |
39 | } | |
40 | ||
41 | declare_lint_pass!(ManualUnwrapOr => [MANUAL_UNWRAP_OR]); | |
42 | ||
43 | impl LateLintPass<'_> for ManualUnwrapOr { | |
44 | fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { | |
45 | if in_external_macro(cx.sess(), expr.span) { | |
46 | return; | |
47 | } | |
48 | lint_manual_unwrap_or(cx, expr); | |
49 | } | |
50 | } | |
51 | ||
52 | #[derive(Copy, Clone)] | |
53 | enum Case { | |
54 | Option, | |
55 | Result, | |
56 | } | |
57 | ||
58 | impl Case { | |
59 | fn unwrap_fn_path(&self) -> &str { | |
60 | match self { | |
61 | Case::Option => "Option::unwrap_or", | |
62 | Case::Result => "Result::unwrap_or", | |
63 | } | |
64 | } | |
65 | } | |
66 | ||
67 | fn lint_manual_unwrap_or<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { | |
68 | fn applicable_or_arm<'a>(arms: &'a [Arm<'a>]) -> Option<&'a Arm<'a>> { | |
69 | if_chain! { | |
70 | if arms.len() == 2; | |
71 | if arms.iter().all(|arm| arm.guard.is_none()); | |
72 | if let Some((idx, or_arm)) = arms.iter().enumerate().find(|(_, arm)| | |
73 | match arm.pat.kind { | |
74 | PatKind::Path(ref some_qpath) => | |
75 | utils::match_qpath(some_qpath, &utils::paths::OPTION_NONE), | |
76 | PatKind::TupleStruct(ref err_qpath, &[Pat { kind: PatKind::Wild, .. }], _) => | |
77 | utils::match_qpath(err_qpath, &utils::paths::RESULT_ERR), | |
78 | _ => false, | |
79 | } | |
80 | ); | |
81 | let unwrap_arm = &arms[1 - idx]; | |
82 | if let PatKind::TupleStruct(ref unwrap_qpath, &[unwrap_pat], _) = unwrap_arm.pat.kind; | |
83 | if utils::match_qpath(unwrap_qpath, &utils::paths::OPTION_SOME) | |
84 | || utils::match_qpath(unwrap_qpath, &utils::paths::RESULT_OK); | |
85 | if let PatKind::Binding(_, binding_hir_id, ..) = unwrap_pat.kind; | |
86 | if path_to_local_id(unwrap_arm.body, binding_hir_id); | |
87 | if !utils::usage::contains_return_break_continue_macro(or_arm.body); | |
88 | then { | |
89 | Some(or_arm) | |
90 | } else { | |
91 | None | |
92 | } | |
93 | } | |
94 | } | |
95 | ||
96 | if_chain! { | |
97 | if let ExprKind::Match(scrutinee, match_arms, _) = expr.kind; | |
98 | let ty = cx.typeck_results().expr_ty(scrutinee); | |
99 | if let Some(case) = if utils::is_type_diagnostic_item(cx, ty, sym::option_type) { | |
100 | Some(Case::Option) | |
101 | } else if utils::is_type_diagnostic_item(cx, ty, sym::result_type) { | |
102 | Some(Case::Result) | |
103 | } else { | |
104 | None | |
105 | }; | |
106 | if let Some(or_arm) = applicable_or_arm(match_arms); | |
107 | if let Some(or_body_snippet) = utils::snippet_opt(cx, or_arm.body.span); | |
108 | if let Some(indent) = utils::indent_of(cx, expr.span); | |
109 | if constant_simple(cx, cx.typeck_results(), or_arm.body).is_some(); | |
110 | then { | |
111 | let reindented_or_body = | |
112 | utils::reindent_multiline(or_body_snippet.into(), true, Some(indent)); | |
113 | utils::span_lint_and_sugg( | |
114 | cx, | |
115 | MANUAL_UNWRAP_OR, expr.span, | |
116 | &format!("this pattern reimplements `{}`", case.unwrap_fn_path()), | |
117 | "replace with", | |
118 | format!( | |
119 | "{}.unwrap_or({})", | |
120 | sugg::Sugg::hir(cx, scrutinee, "..").maybe_par(), | |
121 | reindented_or_body, | |
122 | ), | |
123 | Applicability::MachineApplicable, | |
124 | ); | |
125 | } | |
126 | } | |
127 | } |