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f20569fa XL |
1 | use if_chain::if_chain; |
2 | use rustc_hir::{ImplItem, ImplItemKind}; | |
3 | use rustc_lint::{LateContext, LateLintPass}; | |
4 | use rustc_session::{declare_lint_pass, declare_tool_lint}; | |
5 | use rustc_span::sym; | |
6 | ||
7 | use crate::utils::{ | |
8 | get_trait_def_id, implements_trait, is_type_diagnostic_item, paths, return_ty, span_lint_and_help, | |
9 | trait_ref_of_method, | |
10 | }; | |
11 | ||
12 | declare_clippy_lint! { | |
13 | /// **What it does:** Checks for the definition of inherent methods with a signature of `to_string(&self) -> String`. | |
14 | /// | |
15 | /// **Why is this bad?** This method is also implicitly defined if a type implements the `Display` trait. As the functionality of `Display` is much more versatile, it should be preferred. | |
16 | /// | |
17 | /// **Known problems:** None | |
18 | /// | |
19 | /// ** Example:** | |
20 | /// | |
21 | /// ```rust | |
22 | /// // Bad | |
23 | /// pub struct A; | |
24 | /// | |
25 | /// impl A { | |
26 | /// pub fn to_string(&self) -> String { | |
27 | /// "I am A".to_string() | |
28 | /// } | |
29 | /// } | |
30 | /// ``` | |
31 | /// | |
32 | /// ```rust | |
33 | /// // Good | |
34 | /// use std::fmt; | |
35 | /// | |
36 | /// pub struct A; | |
37 | /// | |
38 | /// impl fmt::Display for A { | |
39 | /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
40 | /// write!(f, "I am A") | |
41 | /// } | |
42 | /// } | |
43 | /// ``` | |
44 | pub INHERENT_TO_STRING, | |
45 | style, | |
46 | "type implements inherent method `to_string()`, but should instead implement the `Display` trait" | |
47 | } | |
48 | ||
49 | declare_clippy_lint! { | |
50 | /// **What it does:** Checks for the definition of inherent methods with a signature of `to_string(&self) -> String` and if the type implementing this method also implements the `Display` trait. | |
51 | /// | |
52 | /// **Why is this bad?** This method is also implicitly defined if a type implements the `Display` trait. The less versatile inherent method will then shadow the implementation introduced by `Display`. | |
53 | /// | |
54 | /// **Known problems:** None | |
55 | /// | |
56 | /// ** Example:** | |
57 | /// | |
58 | /// ```rust | |
59 | /// // Bad | |
60 | /// use std::fmt; | |
61 | /// | |
62 | /// pub struct A; | |
63 | /// | |
64 | /// impl A { | |
65 | /// pub fn to_string(&self) -> String { | |
66 | /// "I am A".to_string() | |
67 | /// } | |
68 | /// } | |
69 | /// | |
70 | /// impl fmt::Display for A { | |
71 | /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
72 | /// write!(f, "I am A, too") | |
73 | /// } | |
74 | /// } | |
75 | /// ``` | |
76 | /// | |
77 | /// ```rust | |
78 | /// // Good | |
79 | /// use std::fmt; | |
80 | /// | |
81 | /// pub struct A; | |
82 | /// | |
83 | /// impl fmt::Display for A { | |
84 | /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { | |
85 | /// write!(f, "I am A") | |
86 | /// } | |
87 | /// } | |
88 | /// ``` | |
89 | pub INHERENT_TO_STRING_SHADOW_DISPLAY, | |
90 | correctness, | |
91 | "type implements inherent method `to_string()`, which gets shadowed by the implementation of the `Display` trait" | |
92 | } | |
93 | ||
94 | declare_lint_pass!(InherentToString => [INHERENT_TO_STRING, INHERENT_TO_STRING_SHADOW_DISPLAY]); | |
95 | ||
96 | impl<'tcx> LateLintPass<'tcx> for InherentToString { | |
97 | fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) { | |
98 | if impl_item.span.from_expansion() { | |
99 | return; | |
100 | } | |
101 | ||
102 | if_chain! { | |
103 | // Check if item is a method, called to_string and has a parameter 'self' | |
104 | if let ImplItemKind::Fn(ref signature, _) = impl_item.kind; | |
105 | if impl_item.ident.name.as_str() == "to_string"; | |
106 | let decl = &signature.decl; | |
107 | if decl.implicit_self.has_implicit_self(); | |
108 | if decl.inputs.len() == 1; | |
109 | if impl_item.generics.params.is_empty(); | |
110 | ||
111 | // Check if return type is String | |
112 | if is_type_diagnostic_item(cx, return_ty(cx, impl_item.hir_id()), sym::string_type); | |
113 | ||
114 | // Filters instances of to_string which are required by a trait | |
115 | if trait_ref_of_method(cx, impl_item.hir_id()).is_none(); | |
116 | ||
117 | then { | |
118 | show_lint(cx, impl_item); | |
119 | } | |
120 | } | |
121 | } | |
122 | } | |
123 | ||
124 | fn show_lint(cx: &LateContext<'_>, item: &ImplItem<'_>) { | |
125 | let display_trait_id = get_trait_def_id(cx, &paths::DISPLAY_TRAIT).expect("Failed to get trait ID of `Display`!"); | |
126 | ||
127 | // Get the real type of 'self' | |
128 | let self_type = cx.tcx.fn_sig(item.def_id).input(0); | |
129 | let self_type = self_type.skip_binder().peel_refs(); | |
130 | ||
131 | // Emit either a warning or an error | |
132 | if implements_trait(cx, self_type, display_trait_id, &[]) { | |
133 | span_lint_and_help( | |
134 | cx, | |
135 | INHERENT_TO_STRING_SHADOW_DISPLAY, | |
136 | item.span, | |
137 | &format!( | |
138 | "type `{}` implements inherent method `to_string(&self) -> String` which shadows the implementation of `Display`", | |
139 | self_type.to_string() | |
140 | ), | |
141 | None, | |
142 | &format!("remove the inherent method from type `{}`", self_type.to_string()), | |
143 | ); | |
144 | } else { | |
145 | span_lint_and_help( | |
146 | cx, | |
147 | INHERENT_TO_STRING, | |
148 | item.span, | |
149 | &format!( | |
150 | "implementation of inherent method `to_string(&self) -> String` for type `{}`", | |
151 | self_type.to_string() | |
152 | ), | |
153 | None, | |
154 | &format!("implement trait `Display` for type `{}` instead", self_type.to_string()), | |
155 | ); | |
156 | } | |
157 | } |