1 use clippy_utils::diagnostics::span_lint_and_sugg;
2 use clippy_utils::sugg::Sugg;
3 use clippy_utils::ty::is_type_diagnostic_item;
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_middle::ty::{self, subst::GenericArgKind};
9 use rustc_session::{declare_lint_pass, declare_tool_lint};
11 use rustc_span::symbol::Ident;
14 declare_clippy_lint! {
16 /// Detects uses of `Vec::sort_by` passing in a closure
17 /// which compares the two arguments, either directly or indirectly.
19 /// ### Why is this bad?
20 /// It is more clear to use `Vec::sort_by_key` (or `Vec::sort` if
21 /// possible) than to use `Vec::sort_by` and a more complicated
24 /// ### Known problems
25 /// If the suggested `Vec::sort_by_key` uses Reverse and it isn't already
26 /// imported by a use statement, then it will need to be added manually.
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()));
38 /// # impl A { fn foo(&self) {} }
39 /// # let mut vec: Vec<A> = Vec::new();
40 /// vec.sort_by_key(|a| a.foo());
42 pub UNNECESSARY_SORT_BY,
44 "Use of `Vec::sort_by` when `Vec::sort_by_key` or `Vec::sort` would be clearer"
47 declare_lint_pass!(UnnecessarySortBy => [UNNECESSARY_SORT_BY]);
51 SortByKey(SortByKeyDetection),
54 struct SortDetection {
59 struct SortByKeyDetection {
67 /// Detect if the two expressions are mirrored (identical, except one
68 /// contains a and the other replaces it with b)
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)
81 // Two arrays with mirrored contents
82 (ExprKind::Array(left_exprs), ExprKind::Array(right_exprs)) => {
83 iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
85 // The two exprs are function calls.
86 // Check to see that the function itself and its arguments are mirrored
87 (ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args)) => {
88 mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
89 && iter::zip(*left_args, *right_args)
90 .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
92 // The two exprs are method calls.
93 // Check to see that the function is the same and the arguments are mirrored
94 // This is enough because the receiver of the method is listed in the arguments
96 ExprKind::MethodCall(left_segment, _, left_args, _),
97 ExprKind::MethodCall(right_segment, _, right_args, _),
99 left_segment.ident == right_segment.ident
100 && iter::zip(*left_args, *right_args)
101 .all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
103 // Two tuples with mirrored contents
104 (ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs)) => {
105 iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(cx, left, a_ident, right, b_ident))
107 // Two binary ops, which are the same operation and which have mirrored arguments
108 (ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right)) => {
109 left_op.node == right_op.node
110 && mirrored_exprs(cx, left_left, a_ident, right_left, b_ident)
111 && mirrored_exprs(cx, left_right, a_ident, right_right, b_ident)
113 // Two unary ops, which are the same operation and which have the same argument
114 (ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr)) => {
115 left_op == right_op && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident)
117 // The two exprs are literals of some kind
118 (ExprKind::Lit(left_lit), ExprKind::Lit(right_lit)) => left_lit.node == right_lit.node,
119 (ExprKind::Cast(left, _), ExprKind::Cast(right, _)) => mirrored_exprs(cx, left, a_ident, right, b_ident),
120 (ExprKind::DropTemps(left_block), ExprKind::DropTemps(right_block)) => {
121 mirrored_exprs(cx, left_block, a_ident, right_block, b_ident)
123 (ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident)) => {
124 left_ident.name == right_ident.name && mirrored_exprs(cx, left_expr, a_ident, right_expr, right_ident)
126 // Two paths: either one is a and the other is b, or they're identical to each other
128 ExprKind::Path(QPath::Resolved(
131 segments: left_segments,
135 ExprKind::Path(QPath::Resolved(
138 segments: right_segments,
143 (iter::zip(*left_segments, *right_segments).all(|(left, right)| left.ident == right.ident)
146 .all(|seg| &seg.ident != a_ident && &seg.ident != b_ident))
147 || (left_segments.len() == 1
148 && &left_segments[0].ident == a_ident
149 && right_segments.len() == 1
150 && &right_segments[0].ident == b_ident)
152 // Matching expressions, but one or both is borrowed
154 ExprKind::AddrOf(left_kind, Mutability::Not, left_expr),
155 ExprKind::AddrOf(right_kind, Mutability::Not, right_expr),
156 ) => left_kind == right_kind && mirrored_exprs(cx, left_expr, a_ident, right_expr, b_ident),
157 (_, ExprKind::AddrOf(_, Mutability::Not, right_expr)) => {
158 mirrored_exprs(cx, a_expr, a_ident, right_expr, b_ident)
160 (ExprKind::AddrOf(_, Mutability::Not, left_expr), _) => mirrored_exprs(cx, left_expr, a_ident, b_expr, b_ident),
165 fn detect_lint(cx: &LateContext<'_>, expr: &Expr<'_>) -> Option<LintTrigger> {
167 if let ExprKind::MethodCall(name_ident, _, args, _) = &expr.kind;
168 if let name = name_ident.ident.name.to_ident_string();
169 if name == "sort_by" || name == "sort_unstable_by";
170 if let [vec, Expr { kind: ExprKind::Closure(_, _, closure_body_id, _, _), .. }] = args;
171 if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(vec), sym::vec_type);
172 if let closure_body = cx.tcx.hir().body(*closure_body_id);
174 Param { pat: Pat { kind: PatKind::Binding(_, _, left_ident, _), .. }, ..},
175 Param { pat: Pat { kind: PatKind::Binding(_, _, right_ident, _), .. }, .. }
176 ] = &closure_body.params;
177 if let ExprKind::MethodCall(method_path, _, [ref left_expr, ref right_expr], _) = &closure_body.value.kind;
178 if method_path.ident.name == sym::cmp;
180 let (closure_body, closure_arg, reverse) = if mirrored_exprs(
187 (Sugg::hir(cx, left_expr, "..").to_string(), left_ident.name.to_string(), false)
188 } else if mirrored_exprs(cx, left_expr, right_ident, right_expr, left_ident) {
189 (Sugg::hir(cx, left_expr, "..").to_string(), right_ident.name.to_string(), true)
193 let vec_name = Sugg::hir(cx, &args[0], "..").to_string();
194 let unstable = name == "sort_unstable_by";
196 if let ExprKind::Path(QPath::Resolved(_, Path {
197 segments: [PathSegment { ident: left_name, .. }], ..
198 })) = &left_expr.kind {
199 if left_name == left_ident {
200 return Some(LintTrigger::Sort(SortDetection { vec_name, unstable }));
204 if !expr_borrows(cx, left_expr) {
205 return Some(LintTrigger::SortByKey(SortByKeyDetection {
219 fn expr_borrows(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
220 let ty = cx.typeck_results().expr_ty(expr);
221 matches!(ty.kind(), ty::Ref(..))
224 .any(|arg| matches!(arg.unpack(), GenericArgKind::Lifetime(_)))
227 impl LateLintPass<'_> for UnnecessarySortBy {
228 fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
229 match detect_lint(cx, expr) {
230 Some(LintTrigger::SortByKey(trigger)) => span_lint_and_sugg(
234 "use Vec::sort_by_key here instead",
237 "{}.sort{}_by_key(|{}| {})",
239 if trigger.unstable { "_unstable" } else { "" },
242 format!("Reverse({})", trigger.closure_body)
244 trigger.closure_body.to_string()
248 Applicability::MaybeIncorrect
250 Applicability::MachineApplicable
253 Some(LintTrigger::Sort(trigger)) => span_lint_and_sugg(
257 "use Vec::sort here instead",
262 if trigger.unstable { "_unstable" } else { "" },
264 Applicability::MachineApplicable,