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| 1 | +use crate::utils; |
| 2 | +use crate::utils::paths; |
| 3 | +use crate::utils::sugg::Sugg; |
| 4 | +use if_chain::if_chain; |
| 5 | +use rustc_errors::Applicability; |
| 6 | +use rustc_hir::{Expr, ExprKind, Mutability, Param, Pat, PatKind, Path, PathSegment, QPath}; |
| 7 | +use rustc_lint::{LateContext, LateLintPass}; |
| 8 | +use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| 9 | +use rustc_span::symbol::Ident; |
| 10 | + |
| 11 | +declare_clippy_lint! { |
| 12 | + /// **What it does:** |
| 13 | + /// Detects when people use `Vec::sort_by` and pass in a function |
| 14 | + /// which compares the two arguments, either directly or indirectly. |
| 15 | + /// |
| 16 | + /// **Why is this bad?** |
| 17 | + /// It is more clear to use `Vec::sort_by_key` (or `Vec::sort` if |
| 18 | + /// possible) than to use `Vec::sort_by` and and a more complicated |
| 19 | + /// closure. |
| 20 | + /// |
| 21 | + /// **Known problems:** |
| 22 | + /// If the suggested `Vec::sort_by_key` uses Reverse and it isn't |
| 23 | + /// imported by a use statement in the current frame, then a `use` |
| 24 | + /// statement that imports it will need to be added (which this lint |
| 25 | + /// can't do). |
| 26 | + /// |
| 27 | + /// **Example:** |
| 28 | + /// |
| 29 | + /// ```rust |
| 30 | + /// # struct A; |
| 31 | + /// # impl A { fn foo(&self) {} } |
| 32 | + /// # let mut vec: Vec<A> = Vec::new(); |
| 33 | + /// vec.sort_by(|a, b| a.foo().cmp(&b.foo())); |
| 34 | + /// ``` |
| 35 | + /// Use instead: |
| 36 | + /// ```rust |
| 37 | + /// # struct A; |
| 38 | + /// # impl A { fn foo(&self) {} } |
| 39 | + /// # let mut vec: Vec<A> = Vec::new(); |
| 40 | + /// vec.sort_by_key(|a| a.foo()); |
| 41 | + /// ``` |
| 42 | + pub UNNECESSARY_SORT_BY, |
| 43 | + complexity, |
| 44 | + "Use of `Vec::sort_by` when `Vec::sort_by_key` or `Vec::sort` would be clearer" |
| 45 | +} |
| 46 | + |
| 47 | +declare_lint_pass!(UnnecessarySortBy => [UNNECESSARY_SORT_BY]); |
| 48 | + |
| 49 | +enum LintTrigger { |
| 50 | + Sort(SortDetection), |
| 51 | + SortByKey(SortByKeyDetection), |
| 52 | +} |
| 53 | + |
| 54 | +struct SortDetection { |
| 55 | + vec_name: String, |
| 56 | + unstable: bool, |
| 57 | +} |
| 58 | + |
| 59 | +struct SortByKeyDetection { |
| 60 | + vec_name: String, |
| 61 | + closure_arg: String, |
| 62 | + closure_body: String, |
| 63 | + reverse: bool, |
| 64 | + unstable: bool, |
| 65 | +} |
| 66 | + |
| 67 | +/// Detect if the two expressions are mirrored (identical, except one |
| 68 | +/// contains a and the other replaces it with b) |
| 69 | +fn mirrored_exprs( |
| 70 | + cx: &LateContext<'_, '_>, |
| 71 | + a_expr: &Expr<'_>, |
| 72 | + a_ident: &Ident, |
| 73 | + b_expr: &Expr<'_>, |
| 74 | + b_ident: &Ident, |
| 75 | +) -> bool { |
| 76 | + match (&a_expr.kind, &b_expr.kind) { |
| 77 | + // Two boxes with mirrored contents |
| 78 | + (ExprKind::Box(left_expr), ExprKind::Box(right_expr)) => { |
| 79 | + mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident) |
| 80 | + }, |
| 81 | + // Two arrays with mirrored contents |
| 82 | + (ExprKind::Array(left_exprs), ExprKind::Array(right_exprs)) => left_exprs |
| 83 | + .iter() |
| 84 | + .zip(right_exprs.iter()) |
| 85 | + .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)), |
| 86 | + // The two exprs are function calls. |
| 87 | + // Check to see that the function itself and its arguments are mirrored |
| 88 | + (ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args)) => { |
| 89 | + mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident) |
| 90 | + && left_args |
| 91 | + .iter() |
| 92 | + .zip(right_args.iter()) |
| 93 | + .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)) |
| 94 | + }, |
| 95 | + // The two exprs are method calls. |
| 96 | + // Check to see that the function is the same and the arguments are mirrored |
| 97 | + // This is enough because the receiver of the method is listed in the arguments |
| 98 | + (ExprKind::MethodCall(left_segment, _, left_args), ExprKind::MethodCall(right_segment, _, right_args)) => { |
| 99 | + left_segment.ident == right_segment.ident |
| 100 | + && left_args |
| 101 | + .iter() |
| 102 | + .zip(right_args.iter()) |
| 103 | + .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)) |
| 104 | + }, |
| 105 | + // Two tuples with mirrored contents |
| 106 | + (ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs)) => left_exprs |
| 107 | + .iter() |
| 108 | + .zip(right_exprs.iter()) |
| 109 | + .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)), |
| 110 | + // Two binary ops, which are the same operation and which have mirrored arguments |
| 111 | + (ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right)) => { |
| 112 | + left_op.node == right_op.node |
| 113 | + && mirrored_exprs(cx, left_left, a_ident, right_left, b_ident) |
| 114 | + && mirrored_exprs(cx, left_right, a_ident, right_right, b_ident) |
| 115 | + }, |
| 116 | + // Two unary ops, which are the same operation and which have the same argument |
| 117 | + (ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr)) => { |
| 118 | + left_op == right_op && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident) |
| 119 | + }, |
| 120 | + // The two exprs are literals of some kind |
| 121 | + (ExprKind::Lit(left_lit), ExprKind::Lit(right_lit)) => left_lit.node == right_lit.node, |
| 122 | + (ExprKind::Cast(left, _), ExprKind::Cast(right, _)) => mirrored_exprs(cx, left, a_ident, right, b_ident), |
| 123 | + (ExprKind::DropTemps(left_block), ExprKind::DropTemps(right_block)) => { |
| 124 | + mirrored_exprs(cx, left_block, a_ident, right_block, b_ident) |
| 125 | + }, |
| 126 | + (ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident)) => { |
| 127 | + left_ident.name == right_ident.name && mirrored_exprs(cx, left_expr, a_ident, right_expr, right_ident) |
| 128 | + }, |
| 129 | + // Two paths: either one is a and the other is b, or they're identical to each other |
| 130 | + ( |
| 131 | + ExprKind::Path(QPath::Resolved( |
| 132 | + _, |
| 133 | + Path { |
| 134 | + segments: left_segments, |
| 135 | + .. |
| 136 | + }, |
| 137 | + )), |
| 138 | + ExprKind::Path(QPath::Resolved( |
| 139 | + _, |
| 140 | + Path { |
| 141 | + segments: right_segments, |
| 142 | + .. |
| 143 | + }, |
| 144 | + )), |
| 145 | + ) => { |
| 146 | + (left_segments |
| 147 | + .iter() |
| 148 | + .zip(right_segments.iter()) |
| 149 | + .all(|(left, right)| left.ident == right.ident) |
| 150 | + && left_segments |
| 151 | + .iter() |
| 152 | + .all(|seg| &seg.ident != a_ident && &seg.ident != b_ident)) |
| 153 | + || (left_segments.len() == 1 |
| 154 | + && &left_segments[0].ident == a_ident |
| 155 | + && right_segments.len() == 1 |
| 156 | + && &right_segments[0].ident == b_ident) |
| 157 | + }, |
| 158 | + // Matching expressions, but one or both is borrowed |
| 159 | + ( |
| 160 | + ExprKind::AddrOf(left_kind, Mutability::Not, left_expr), |
| 161 | + ExprKind::AddrOf(right_kind, Mutability::Not, right_expr), |
| 162 | + ) => left_kind == right_kind && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident), |
| 163 | + (_, ExprKind::AddrOf(_, Mutability::Not, right_expr)) => { |
| 164 | + mirrored_exprs(cx, a_expr, a_ident, right_expr, b_ident) |
| 165 | + }, |
| 166 | + (ExprKind::AddrOf(_, Mutability::Not, left_expr), _) => mirrored_exprs(cx, left_expr, a_ident, b_expr, b_ident), |
| 167 | + _ => false, |
| 168 | + } |
| 169 | +} |
| 170 | + |
| 171 | +fn detect_lint(cx: &LateContext<'_, '_>, expr: &Expr<'_>) -> Option<LintTrigger> { |
| 172 | + if_chain! { |
| 173 | + if let ExprKind::MethodCall(name_ident, _, args) = &expr.kind; |
| 174 | + if let name = name_ident.ident.name.to_ident_string(); |
| 175 | + if name == "sort_by" || name == "sort_unstable_by"; |
| 176 | + if let [vec, Expr { kind: ExprKind::Closure(_, _, closure_body_id, _, _), .. }] = args; |
| 177 | + if utils::match_type(cx, &cx.tables.expr_ty(vec), &paths::VEC); |
| 178 | + if let closure_body = cx.tcx.hir().body(*closure_body_id); |
| 179 | + if let &[ |
| 180 | + Param { pat: Pat { kind: PatKind::Binding(_, _, left_ident, _), .. }, ..}, |
| 181 | + Param { pat: Pat { kind: PatKind::Binding(_, _, right_ident, _), .. }, .. } |
| 182 | + ] = &closure_body.params; |
| 183 | + if let ExprKind::MethodCall(method_path, _, [ref left_expr, ref right_expr]) = &closure_body.value.kind; |
| 184 | + if method_path.ident.name.to_ident_string() == "cmp"; |
| 185 | + then { |
| 186 | + let (closure_body, closure_arg, reverse) = if mirrored_exprs( |
| 187 | + &cx, |
| 188 | + &left_expr, |
| 189 | + &left_ident, |
| 190 | + &right_expr, |
| 191 | + &right_ident |
| 192 | + ) { |
| 193 | + (Sugg::hir(cx, &left_expr, "..").to_string(), left_ident.name.to_string(), false) |
| 194 | + } else if mirrored_exprs(&cx, &left_expr, &right_ident, &right_expr, &left_ident) { |
| 195 | + (Sugg::hir(cx, &left_expr, "..").to_string(), right_ident.name.to_string(), true) |
| 196 | + } else { |
| 197 | + return None; |
| 198 | + }; |
| 199 | + let vec_name = Sugg::hir(cx, &args[0], "..").to_string(); |
| 200 | + let unstable = name == "sort_unstable_by"; |
| 201 | + if_chain! { |
| 202 | + if let ExprKind::Path(QPath::Resolved(_, Path { |
| 203 | + segments: [PathSegment { ident: left_name, .. }], .. |
| 204 | + })) = &left_expr.kind; |
| 205 | + if left_name == left_ident; |
| 206 | + then { |
| 207 | + Some(LintTrigger::Sort(SortDetection { vec_name, unstable })) |
| 208 | + } |
| 209 | + else { |
| 210 | + Some(LintTrigger::SortByKey(SortByKeyDetection { |
| 211 | + vec_name, |
| 212 | + unstable, |
| 213 | + closure_arg, |
| 214 | + closure_body, |
| 215 | + reverse |
| 216 | + })) |
| 217 | + } |
| 218 | + } |
| 219 | + } else { |
| 220 | + None |
| 221 | + } |
| 222 | + } |
| 223 | +} |
| 224 | + |
| 225 | +impl LateLintPass<'_, '_> for UnnecessarySortBy { |
| 226 | + fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &Expr<'_>) { |
| 227 | + match detect_lint(cx, expr) { |
| 228 | + Some(LintTrigger::SortByKey(trigger)) => utils::span_lint_and_sugg( |
| 229 | + cx, |
| 230 | + UNNECESSARY_SORT_BY, |
| 231 | + expr.span, |
| 232 | + "use Vec::sort_by_key here instead", |
| 233 | + "try", |
| 234 | + format!( |
| 235 | + "{}.sort{}_by_key(|&{}| {})", |
| 236 | + trigger.vec_name, |
| 237 | + if trigger.unstable { "_unstable" } else { "" }, |
| 238 | + trigger.closure_arg, |
| 239 | + if trigger.reverse { |
| 240 | + format!("Reverse({})", trigger.closure_body) |
| 241 | + } else { |
| 242 | + trigger.closure_body.to_string() |
| 243 | + }, |
| 244 | + ), |
| 245 | + if trigger.reverse { |
| 246 | + Applicability::MaybeIncorrect |
| 247 | + } else { |
| 248 | + Applicability::MachineApplicable |
| 249 | + }, |
| 250 | + ), |
| 251 | + Some(LintTrigger::Sort(trigger)) => utils::span_lint_and_sugg( |
| 252 | + cx, |
| 253 | + UNNECESSARY_SORT_BY, |
| 254 | + expr.span, |
| 255 | + "use Vec::sort here instead", |
| 256 | + "try", |
| 257 | + format!( |
| 258 | + "{}.sort{}()", |
| 259 | + trigger.vec_name, |
| 260 | + if trigger.unstable { "_unstable" } else { "" }, |
| 261 | + ), |
| 262 | + Applicability::MachineApplicable, |
| 263 | + ), |
| 264 | + None => {}, |
| 265 | + } |
| 266 | + } |
| 267 | +} |
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