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| 1 | +use clippy_utils::diagnostics::span_lint; |
| 2 | +use clippy_utils::ty::is_type_diagnostic_item; |
| 3 | +use clippy_utils::{higher, peel_hir_expr_while, SpanlessEq}; |
| 4 | +use rustc_hir::intravisit::Visitor; |
| 5 | +use rustc_hir::{Block, Expr, ExprKind, Stmt, StmtKind, UnOp}; |
| 6 | +use rustc_lint::{LateContext, LateLintPass}; |
| 7 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 8 | +use rustc_span::sym; |
| 9 | + |
| 10 | +declare_clippy_lint! { |
| 11 | + /// Checks for usage of `contains` to see if a value is not |
| 12 | + /// present on `HashSet` followed by a `insert`. |
| 13 | + /// |
| 14 | + /// ### Why is this bad? |
| 15 | + /// Using just `insert` and checking the returned `bool` is more efficient. |
| 16 | + /// |
| 17 | + /// ### Example |
| 18 | + /// ```rust |
| 19 | + /// use std::collections::HashSet; |
| 20 | + /// let mut set = HashSet::new(); |
| 21 | + /// let value = 5; |
| 22 | + /// if !set.contains(&value) { |
| 23 | + /// set.insert(value); |
| 24 | + /// println!("inserted {value:?}"); |
| 25 | + /// } |
| 26 | + /// ``` |
| 27 | + /// Use instead: |
| 28 | + /// ```rust |
| 29 | + /// use std::collections::HashSet; |
| 30 | + /// let mut set = HashSet::new(); |
| 31 | + /// if set.insert(&value) { |
| 32 | + /// println!("inserted {value:?}"); |
| 33 | + /// } |
| 34 | + /// ``` |
| 35 | + #[clippy::version = "1.73.0"] |
| 36 | + pub HASHSET_INSERT_AFTER_CONTAINS, |
| 37 | + perf, |
| 38 | + "use of `contains` to see if a value is not present on a `HashSet` followed by a `insert`" |
| 39 | +} |
| 40 | +declare_lint_pass!(HashsetInsertAfterContains => [HASHSET_INSERT_AFTER_CONTAINS]); |
| 41 | + |
| 42 | +impl<'tcx> LateLintPass<'tcx> for HashsetInsertAfterContains { |
| 43 | + fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| 44 | + if expr.span.from_expansion() { |
| 45 | + return; |
| 46 | + } |
| 47 | + |
| 48 | + let Some(higher::If { |
| 49 | + cond: cond_expr, |
| 50 | + then: then_expr, |
| 51 | + .. |
| 52 | + }) = higher::If::hir(expr) |
| 53 | + else { |
| 54 | + return; |
| 55 | + }; |
| 56 | + |
| 57 | + let Some(contains_expr) = try_parse_contains(cx, cond_expr) else { |
| 58 | + return; |
| 59 | + }; |
| 60 | + |
| 61 | + if !find_insert_calls(cx, &contains_expr, then_expr) { |
| 62 | + return; |
| 63 | + }; |
| 64 | + span_lint( |
| 65 | + cx, |
| 66 | + HASHSET_INSERT_AFTER_CONTAINS, |
| 67 | + expr.span, |
| 68 | + "usage of `HashSet::insert` after `HashSet::contains`. Remove the usage of `HashSet::contains` and just call `HashSet::contains` instead", |
| 69 | + ); |
| 70 | + } |
| 71 | +} |
| 72 | + |
| 73 | +struct ContainsExpr<'tcx> { |
| 74 | + receiver: &'tcx Expr<'tcx>, |
| 75 | + value: &'tcx Expr<'tcx>, |
| 76 | +} |
| 77 | +fn try_parse_contains<'tcx>(cx: &LateContext<'_>, expr: &'tcx Expr<'_>) -> Option<ContainsExpr<'tcx>> { |
| 78 | + let expr = peel_hir_expr_while(expr, |e| match e.kind { |
| 79 | + ExprKind::Unary(UnOp::Not, e) => Some(e), |
| 80 | + _ => None, |
| 81 | + }); |
| 82 | + match expr.kind { |
| 83 | + ExprKind::MethodCall( |
| 84 | + path, |
| 85 | + receiver, |
| 86 | + [ |
| 87 | + Expr { |
| 88 | + kind: ExprKind::AddrOf(_, _, value), |
| 89 | + span: value_span, |
| 90 | + .. |
| 91 | + }, |
| 92 | + ], |
| 93 | + _, |
| 94 | + ) => { |
| 95 | + let receiver_ty = cx.typeck_results().expr_ty(receiver); |
| 96 | + if value_span.ctxt() == expr.span.ctxt() |
| 97 | + && is_type_diagnostic_item(cx, receiver_ty, sym::HashSet) |
| 98 | + && path.ident.name == sym!(contains) |
| 99 | + { |
| 100 | + Some(ContainsExpr { receiver, value }) |
| 101 | + } else { |
| 102 | + None |
| 103 | + } |
| 104 | + }, |
| 105 | + _ => None, |
| 106 | + } |
| 107 | +} |
| 108 | + |
| 109 | +struct InsertExpr<'tcx> { |
| 110 | + receiver: &'tcx Expr<'tcx>, |
| 111 | + value: &'tcx Expr<'tcx>, |
| 112 | +} |
| 113 | +fn try_parse_insert<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<InsertExpr<'tcx>> { |
| 114 | + if let ExprKind::MethodCall(path, receiver, [value], _) = expr.kind { |
| 115 | + let receiver_ty = cx.typeck_results().expr_ty(receiver); |
| 116 | + if is_type_diagnostic_item(cx, receiver_ty, sym::HashSet) && path.ident.name == sym!(insert) { |
| 117 | + Some(InsertExpr { receiver, value }) |
| 118 | + } else { |
| 119 | + None |
| 120 | + } |
| 121 | + } else { |
| 122 | + None |
| 123 | + } |
| 124 | +} |
| 125 | + |
| 126 | +fn find_insert_calls<'tcx>(cx: &LateContext<'tcx>, contains_expr: &ContainsExpr<'tcx>, expr: &'tcx Expr<'_>) -> bool { |
| 127 | + let mut s = InsertSearcher { |
| 128 | + cx, |
| 129 | + receiver: contains_expr.receiver, |
| 130 | + value: contains_expr.value, |
| 131 | + should_lint: false, |
| 132 | + }; |
| 133 | + s.visit_expr(expr); |
| 134 | + s.should_lint |
| 135 | +} |
| 136 | + |
| 137 | +struct InsertSearcher<'cx, 'tcx> { |
| 138 | + cx: &'cx LateContext<'tcx>, |
| 139 | + /// The receiver expression used in the contains call. |
| 140 | + receiver: &'tcx Expr<'tcx>, |
| 141 | + /// The value expression used in the contains call. |
| 142 | + value: &'tcx Expr<'tcx>, |
| 143 | + /// Whether or a lint shoud be emitted. |
| 144 | + should_lint: bool, |
| 145 | +} |
| 146 | + |
| 147 | +impl<'tcx> Visitor<'tcx> for InsertSearcher<'_, 'tcx> { |
| 148 | + fn visit_block(&mut self, block: &'tcx Block<'_>) { |
| 149 | + for stmt in block.stmts { |
| 150 | + self.visit_stmt(stmt); |
| 151 | + } |
| 152 | + if let Some(expr) = block.expr { |
| 153 | + self.visit_expr(expr); |
| 154 | + } |
| 155 | + } |
| 156 | + |
| 157 | + fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { |
| 158 | + match try_parse_insert(self.cx, expr) { |
| 159 | + Some(insert_expr) => { |
| 160 | + if SpanlessEq::new(self.cx).eq_expr(self.receiver, insert_expr.receiver) |
| 161 | + && SpanlessEq::new(self.cx).eq_expr(self.value, insert_expr.value) |
| 162 | + { |
| 163 | + self.should_lint = true; |
| 164 | + } |
| 165 | + }, |
| 166 | + _ => { |
| 167 | + if let ExprKind::Block(block, _) = expr.kind { |
| 168 | + self.visit_block(block); |
| 169 | + } |
| 170 | + }, |
| 171 | + } |
| 172 | + } |
| 173 | + |
| 174 | + fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) { |
| 175 | + match stmt.kind { |
| 176 | + StmtKind::Semi(e) => { |
| 177 | + self.visit_expr(e); |
| 178 | + }, |
| 179 | + StmtKind::Expr(e) => self.visit_expr(e), |
| 180 | + _ => (), |
| 181 | + } |
| 182 | + } |
| 183 | +} |
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