2 use crate::utils::sugg::Sugg;
3 use if_chain::if_chain;
4 use rustc_errors::Applicability;
5 use rustc_hir::{Expr, ExprKind, Mutability, Param, Pat, PatKind, Path, PathSegment, QPath};
6 use rustc_lint::{LateContext, LateLintPass};
7 use rustc_middle::ty::{self, subst::GenericArgKind};
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
9 use rustc_span::symbol::Ident;
11 declare_clippy_lint! {
13 /// Detects uses of `Vec::sort_by` passing in a closure
14 /// which compares the two arguments, either directly or indirectly.
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 a more complicated
21 /// **Known problems:**
22 /// If the suggested `Vec::sort_by_key` uses Reverse and it isn't already
23 /// imported by a use statement, then it will need to be added manually.
29 /// # impl A { fn foo(&self) {} }
30 /// # let mut vec: Vec<A> = Vec::new();
31 /// vec.sort_by(|a, b| a.foo().cmp(&b.foo()));
36 /// # impl A { fn foo(&self) {} }
37 /// # let mut vec: Vec<A> = Vec::new();
38 /// vec.sort_by_key(|a| a.foo());
40 pub UNNECESSARY_SORT_BY,
42 "Use of `Vec::sort_by` when `Vec::sort_by_key` or `Vec::sort` would be clearer"
45 declare_lint_pass!(UnnecessarySortBy => [UNNECESSARY_SORT_BY]);
49 SortByKey(SortByKeyDetection),
52 struct SortDetection {
57 struct SortByKeyDetection {
65 /// Detect if the two expressions are mirrored (identical, except one
66 /// contains a and the other replaces it with b)
74 match (&a_expr.kind, &b_expr.kind) {
75 // Two boxes with mirrored contents
76 (ExprKind::Box(left_expr), ExprKind::Box(right_expr)) => {
77 mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
79 // Two arrays with mirrored contents
80 (ExprKind::Array(left_exprs), ExprKind::Array(right_exprs)) => left_exprs
82 .zip(right_exprs.iter())
83 .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)),
84 // The two exprs are function calls.
85 // Check to see that the function itself and its arguments are mirrored
86 (ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args)) => {
87 mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
90 .zip(right_args.iter())
91 .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
93 // The two exprs are method calls.
94 // Check to see that the function is the same and the arguments are mirrored
95 // This is enough because the receiver of the method is listed in the arguments
97 ExprKind::MethodCall(left_segment, _, left_args, _),
98 ExprKind::MethodCall(right_segment, _, right_args, _),
100 left_segment.ident == right_segment.ident
103 .zip(right_args.iter())
104 .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
106 // Two tuples with mirrored contents
107 (ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs)) => left_exprs
109 .zip(right_exprs.iter())
110 .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident)),
111 // Two binary ops, which are the same operation and which have mirrored arguments
112 (ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right)) => {
113 left_op.node == right_op.node
114 && mirrored_exprs(cx, left_left, a_ident, right_left, b_ident)
115 && mirrored_exprs(cx, left_right, a_ident, right_right, b_ident)
117 // Two unary ops, which are the same operation and which have the same argument
118 (ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr)) => {
119 left_op == right_op && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
121 // The two exprs are literals of some kind
122 (ExprKind::Lit(left_lit), ExprKind::Lit(right_lit)) => left_lit.node == right_lit.node,
123 (ExprKind::Cast(left, _), ExprKind::Cast(right, _)) => mirrored_exprs(cx, left, a_ident, right, b_ident),
124 (ExprKind::DropTemps(left_block), ExprKind::DropTemps(right_block)) => {
125 mirrored_exprs(cx, left_block, a_ident, right_block, b_ident)
127 (ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident)) => {
128 left_ident.name == right_ident.name && mirrored_exprs(cx, left_expr, a_ident, right_expr, right_ident)
130 // Two paths: either one is a and the other is b, or they're identical to each other
132 ExprKind::Path(QPath::Resolved(
135 segments: left_segments,
139 ExprKind::Path(QPath::Resolved(
142 segments: right_segments,
149 .zip(right_segments.iter())
150 .all(|(left, right)| left.ident == right.ident)
153 .all(|seg| &seg.ident != a_ident && &seg.ident != b_ident))
154 || (left_segments.len() == 1
155 && &left_segments[0].ident == a_ident
156 && right_segments.len() == 1
157 && &right_segments[0].ident == b_ident)
159 // Matching expressions, but one or both is borrowed
161 ExprKind::AddrOf(left_kind, Mutability::Not, left_expr),
162 ExprKind::AddrOf(right_kind, Mutability::Not, right_expr),
163 ) => left_kind == right_kind && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident),
164 (_, ExprKind::AddrOf(_, Mutability::Not, right_expr)) => {
165 mirrored_exprs(cx, a_expr, a_ident, right_expr, b_ident)
167 (ExprKind::AddrOf(_, Mutability::Not, left_expr), _) => mirrored_exprs(cx, left_expr, a_ident, b_expr, b_ident),
172 fn detect_lint(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<LintTrigger> {
174 if let ExprKind::MethodCall(name_ident, _, args, _) = &expr.kind;
175 if let name = name_ident.ident.name.to_ident_string();
176 if name == "sort_by" || name == "sort_unstable_by";
177 if let [vec, Expr { kind: ExprKind::Closure(_, _, closure_body_id, _, _), .. }] = args;
178 if utils::is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(vec), sym!(vec_type));
179 if let closure_body = cx.tcx.hir().body(*closure_body_id);
181 Param { pat: Pat { kind: PatKind::Binding(_, _, left_ident, _), .. }, ..},
182 Param { pat: Pat { kind: PatKind::Binding(_, _, right_ident, _), .. }, .. }
183 ] = &closure_body.params;
184 if let ExprKind::MethodCall(method_path, _, [ref left_expr, ref right_expr], _) = &closure_body.value.kind;
185 if method_path.ident.name.to_ident_string() == "cmp";
187 let (closure_body, closure_arg, reverse) = if mirrored_exprs(
194 (Sugg::hir(cx, &left_expr, "..").to_string(), left_ident.name.to_string(), false)
195 } else if mirrored_exprs(&cx, &left_expr, &right_ident, &right_expr, &left_ident) {
196 (Sugg::hir(cx, &left_expr, "..").to_string(), right_ident.name.to_string(), true)
200 let vec_name = Sugg::hir(cx, &args[0], "..").to_string();
201 let unstable = name == "sort_unstable_by";
203 if let ExprKind::Path(QPath::Resolved(_, Path {
204 segments: [PathSegment { ident: left_name, .. }], ..
205 })) = &left_expr.kind {
206 if left_name == left_ident {
207 return Some(LintTrigger::Sort(SortDetection { vec_name, unstable }));
211 if !expr_borrows(cx, left_expr) {
212 return Some(LintTrigger::SortByKey(SortByKeyDetection {
226 fn expr_borrows(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
227 let ty = cx.typeck_results().expr_ty(expr);
228 matches!(ty.kind(), ty::Ref(..)) || ty.walk().any(|arg| matches!(arg.unpack(), GenericArgKind::Lifetime(_)))
231 impl LateLintPass<'_> for UnnecessarySortBy {
232 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
233 match detect_lint(cx, expr) {
234 Some(LintTrigger::SortByKey(trigger)) => utils::span_lint_and_sugg(
238 "use Vec::sort_by_key here instead",
241 "{}.sort{}_by_key(|{}| {})",
243 if trigger.unstable { "_unstable" } else { "" },
246 format!("Reverse({})", trigger.closure_body)
248 trigger.closure_body.to_string()
252 Applicability::MaybeIncorrect
254 Applicability::MachineApplicable
257 Some(LintTrigger::Sort(trigger)) => utils::span_lint_and_sugg(
261 "use Vec::sort here instead",
266 if trigger.unstable { "_unstable" } else { "" },
268 Applicability::MachineApplicable,