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f20569fa XL |
1 | //! lint on blocks unnecessarily using >= with a + 1 or - 1 |
2 | ||
cdc7bbd5 XL |
3 | use clippy_utils::diagnostics::span_lint_and_sugg; |
4 | use clippy_utils::source::snippet_opt; | |
f20569fa XL |
5 | use rustc_ast::ast::{BinOpKind, Expr, ExprKind, Lit, LitKind}; |
6 | use rustc_errors::Applicability; | |
7 | use rustc_lint::{EarlyContext, EarlyLintPass}; | |
8 | use rustc_session::{declare_lint_pass, declare_tool_lint}; | |
9 | ||
f20569fa | 10 | declare_clippy_lint! { |
94222f64 XL |
11 | /// ### What it does |
12 | /// Checks for usage of `x >= y + 1` or `x - 1 >= y` (and `<=`) in a block | |
f20569fa | 13 | /// |
94222f64 XL |
14 | /// ### Why is this bad? |
15 | /// Readability -- better to use `> y` instead of `>= y + 1`. | |
f20569fa | 16 | /// |
94222f64 | 17 | /// ### Example |
f20569fa XL |
18 | /// ```rust |
19 | /// # let x = 1; | |
20 | /// # let y = 1; | |
21 | /// if x >= y + 1 {} | |
22 | /// ``` | |
23 | /// | |
923072b8 | 24 | /// Use instead: |
f20569fa XL |
25 | /// ```rust |
26 | /// # let x = 1; | |
27 | /// # let y = 1; | |
28 | /// if x > y {} | |
29 | /// ``` | |
a2a8927a | 30 | #[clippy::version = "pre 1.29.0"] |
f20569fa XL |
31 | pub INT_PLUS_ONE, |
32 | complexity, | |
33 | "instead of using `x >= y + 1`, use `x > y`" | |
34 | } | |
35 | ||
36 | declare_lint_pass!(IntPlusOne => [INT_PLUS_ONE]); | |
37 | ||
38 | // cases: | |
39 | // BinOpKind::Ge | |
40 | // x >= y + 1 | |
41 | // x - 1 >= y | |
42 | // | |
43 | // BinOpKind::Le | |
44 | // x + 1 <= y | |
45 | // x <= y - 1 | |
46 | ||
47 | #[derive(Copy, Clone)] | |
48 | enum Side { | |
49 | Lhs, | |
50 | Rhs, | |
51 | } | |
52 | ||
53 | impl IntPlusOne { | |
923072b8 | 54 | #[expect(clippy::cast_sign_loss)] |
f20569fa XL |
55 | fn check_lit(lit: &Lit, target_value: i128) -> bool { |
56 | if let LitKind::Int(value, ..) = lit.kind { | |
57 | return value == (target_value as u128); | |
58 | } | |
59 | false | |
60 | } | |
61 | ||
62 | fn check_binop(cx: &EarlyContext<'_>, binop: BinOpKind, lhs: &Expr, rhs: &Expr) -> Option<String> { | |
63 | match (binop, &lhs.kind, &rhs.kind) { | |
64 | // case where `x - 1 >= ...` or `-1 + x >= ...` | |
65 | (BinOpKind::Ge, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _) => { | |
66 | match (lhskind.node, &lhslhs.kind, &lhsrhs.kind) { | |
67 | // `-1 + x` | |
68 | (BinOpKind::Add, &ExprKind::Lit(ref lit), _) if Self::check_lit(lit, -1) => { | |
69 | Self::generate_recommendation(cx, binop, lhsrhs, rhs, Side::Lhs) | |
70 | }, | |
71 | // `x - 1` | |
72 | (BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { | |
73 | Self::generate_recommendation(cx, binop, lhslhs, rhs, Side::Lhs) | |
74 | }, | |
75 | _ => None, | |
76 | } | |
77 | }, | |
78 | // case where `... >= y + 1` or `... >= 1 + y` | |
79 | (BinOpKind::Ge, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs)) | |
80 | if rhskind.node == BinOpKind::Add => | |
81 | { | |
82 | match (&rhslhs.kind, &rhsrhs.kind) { | |
83 | // `y + 1` and `1 + y` | |
84 | (&ExprKind::Lit(ref lit), _) if Self::check_lit(lit, 1) => { | |
85 | Self::generate_recommendation(cx, binop, rhsrhs, lhs, Side::Rhs) | |
86 | }, | |
87 | (_, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { | |
88 | Self::generate_recommendation(cx, binop, rhslhs, lhs, Side::Rhs) | |
89 | }, | |
90 | _ => None, | |
91 | } | |
c295e0f8 | 92 | }, |
f20569fa XL |
93 | // case where `x + 1 <= ...` or `1 + x <= ...` |
94 | (BinOpKind::Le, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _) | |
95 | if lhskind.node == BinOpKind::Add => | |
96 | { | |
97 | match (&lhslhs.kind, &lhsrhs.kind) { | |
98 | // `1 + x` and `x + 1` | |
99 | (&ExprKind::Lit(ref lit), _) if Self::check_lit(lit, 1) => { | |
100 | Self::generate_recommendation(cx, binop, lhsrhs, rhs, Side::Lhs) | |
101 | }, | |
102 | (_, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { | |
103 | Self::generate_recommendation(cx, binop, lhslhs, rhs, Side::Lhs) | |
104 | }, | |
105 | _ => None, | |
106 | } | |
c295e0f8 | 107 | }, |
f20569fa XL |
108 | // case where `... >= y - 1` or `... >= -1 + y` |
109 | (BinOpKind::Le, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs)) => { | |
110 | match (rhskind.node, &rhslhs.kind, &rhsrhs.kind) { | |
111 | // `-1 + y` | |
112 | (BinOpKind::Add, &ExprKind::Lit(ref lit), _) if Self::check_lit(lit, -1) => { | |
113 | Self::generate_recommendation(cx, binop, rhsrhs, lhs, Side::Rhs) | |
114 | }, | |
115 | // `y - 1` | |
116 | (BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { | |
117 | Self::generate_recommendation(cx, binop, rhslhs, lhs, Side::Rhs) | |
118 | }, | |
119 | _ => None, | |
120 | } | |
121 | }, | |
122 | _ => None, | |
123 | } | |
124 | } | |
125 | ||
126 | fn generate_recommendation( | |
127 | cx: &EarlyContext<'_>, | |
128 | binop: BinOpKind, | |
129 | node: &Expr, | |
130 | other_side: &Expr, | |
131 | side: Side, | |
132 | ) -> Option<String> { | |
133 | let binop_string = match binop { | |
134 | BinOpKind::Ge => ">", | |
135 | BinOpKind::Le => "<", | |
136 | _ => return None, | |
137 | }; | |
138 | if let Some(snippet) = snippet_opt(cx, node.span) { | |
139 | if let Some(other_side_snippet) = snippet_opt(cx, other_side.span) { | |
140 | let rec = match side { | |
141 | Side::Lhs => Some(format!("{} {} {}", snippet, binop_string, other_side_snippet)), | |
142 | Side::Rhs => Some(format!("{} {} {}", other_side_snippet, binop_string, snippet)), | |
143 | }; | |
144 | return rec; | |
145 | } | |
146 | } | |
147 | None | |
148 | } | |
149 | ||
150 | fn emit_warning(cx: &EarlyContext<'_>, block: &Expr, recommendation: String) { | |
151 | span_lint_and_sugg( | |
152 | cx, | |
153 | INT_PLUS_ONE, | |
154 | block.span, | |
155 | "unnecessary `>= y + 1` or `x - 1 >=`", | |
156 | "change it to", | |
157 | recommendation, | |
158 | Applicability::MachineApplicable, // snippet | |
159 | ); | |
160 | } | |
161 | } | |
162 | ||
163 | impl EarlyLintPass for IntPlusOne { | |
164 | fn check_expr(&mut self, cx: &EarlyContext<'_>, item: &Expr) { | |
165 | if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = item.kind { | |
166 | if let Some(rec) = Self::check_binop(cx, kind.node, lhs, rhs) { | |
167 | Self::emit_warning(cx, item, rec); | |
168 | } | |
169 | } | |
170 | } | |
171 | } |