clippy_lints/src/methods/unnecessary_sort_by.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::is_trait_method;
   3 use clippy_utils::sugg::Sugg;
   4 use clippy_utils::ty::implements_trait;
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::{Closure, Expr, ExprKind, Mutability, Param, Pat, PatKind, Path, PathSegment, QPath};
   8 use rustc_lint::LateContext;
   9 use rustc_middle::ty::{self, subst::GenericArgKind};
  10 use rustc_span::sym;
  11 use rustc_span::symbol::Ident;
  12 use std::iter;
  13
  14 use super::UNNECESSARY_SORT_BY;
  15
  16 enum LintTrigger {
  17     Sort(SortDetection),
  18     SortByKey(SortByKeyDetection),
  19 }
  20
  21 struct SortDetection {
  22     vec_name: String,
  23 }
  24
  25 struct SortByKeyDetection {
  26     vec_name: String,
  27     closure_arg: String,
  28     closure_body: String,
  29     reverse: bool,
  30 }
  31
  32 /// Detect if the two expressions are mirrored (identical, except one
  33 /// contains a and the other replaces it with b)
  34 fn mirrored_exprs(a_expr: &Expr<'_>, a_ident: &Ident, b_expr: &Expr<'_>, b_ident: &Ident) -> bool {
  35     match (&a_expr.kind, &b_expr.kind) {
  36         // Two boxes with mirrored contents
  37         (ExprKind::Box(left_expr), ExprKind::Box(right_expr)) => {
  38             mirrored_exprs(left_expr, a_ident, right_expr, b_ident)
  39         },
  40         // Two arrays with mirrored contents
  41         (ExprKind::Array(left_exprs), ExprKind::Array(right_exprs)) => {
  42             iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
  43         },
  44         // The two exprs are function calls.
  45         // Check to see that the function itself and its arguments are mirrored
  46         (ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args)) => {
  47             mirrored_exprs(left_expr, a_ident, right_expr, b_ident)
  48                 && iter::zip(*left_args, *right_args).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
  49         },
  50         // The two exprs are method calls.
  51         // Check to see that the function is the same and the arguments are mirrored
  52         // This is enough because the receiver of the method is listed in the arguments
  53         (ExprKind::MethodCall(left_segment, left_args, _), ExprKind::MethodCall(right_segment, right_args, _)) => {
  54             left_segment.ident == right_segment.ident
  55                 && iter::zip(*left_args, *right_args).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
  56         },
  57         // Two tuples with mirrored contents
  58         (ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs)) => {
  59             iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
  60         },
  61         // Two binary ops, which are the same operation and which have mirrored arguments
  62         (ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right)) => {
  63             left_op.node == right_op.node
  64                 && mirrored_exprs(left_left, a_ident, right_left, b_ident)
  65                 && mirrored_exprs(left_right, a_ident, right_right, b_ident)
  66         },
  67         // Two unary ops, which are the same operation and which have the same argument
  68         (ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr)) => {
  69             left_op == right_op && mirrored_exprs(left_expr, a_ident, right_expr, b_ident)
  70         },
  71         // The two exprs are literals of some kind
  72         (ExprKind::Lit(left_lit), ExprKind::Lit(right_lit)) => left_lit.node == right_lit.node,
  73         (ExprKind::Cast(left, _), ExprKind::Cast(right, _)) => mirrored_exprs(left, a_ident, right, b_ident),
  74         (ExprKind::DropTemps(left_block), ExprKind::DropTemps(right_block)) => {
  75             mirrored_exprs(left_block, a_ident, right_block, b_ident)
  76         },
  77         (ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident)) => {
  78             left_ident.name == right_ident.name && mirrored_exprs(left_expr, a_ident, right_expr, right_ident)
  79         },
  80         // Two paths: either one is a and the other is b, or they're identical to each other
  81         (
  82             ExprKind::Path(QPath::Resolved(
  83                 _,
  84                 Path {
  85                     segments: left_segments,
  86                     ..
  87                 },
  88             )),
  89             ExprKind::Path(QPath::Resolved(
  90                 _,
  91                 Path {
  92                     segments: right_segments,
  93                     ..
  94                 },
  95             )),
  96         ) => {
  97             (iter::zip(*left_segments, *right_segments).all(|(left, right)| left.ident == right.ident)
  98                 && left_segments
  99                     .iter()
 100                     .all(|seg| &seg.ident != a_ident && &seg.ident != b_ident))
 101                 || (left_segments.len() == 1
 102                     && &left_segments[0].ident == a_ident
 103                     && right_segments.len() == 1
 104                     && &right_segments[0].ident == b_ident)
 105         },
 106         // Matching expressions, but one or both is borrowed
 107         (
 108             ExprKind::AddrOf(left_kind, Mutability::Not, left_expr),
 109             ExprKind::AddrOf(right_kind, Mutability::Not, right_expr),
 110         ) => left_kind == right_kind && mirrored_exprs(left_expr, a_ident, right_expr, b_ident),
 111         (_, ExprKind::AddrOf(_, Mutability::Not, right_expr)) => mirrored_exprs(a_expr, a_ident, right_expr, b_ident),
 112         (ExprKind::AddrOf(_, Mutability::Not, left_expr), _) => mirrored_exprs(left_expr, a_ident, b_expr, b_ident),
 113         _ => false,
 114     }
 115 }
 116
 117 fn detect_lint(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, arg: &Expr<'_>) -> Option<LintTrigger> {
 118     if_chain! {
 119         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
 120         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
 121         if cx.tcx.type_of(impl_id).is_slice();
 122         if let ExprKind::Closure(&Closure { body, .. }) = arg.kind;
 123         if let closure_body = cx.tcx.hir().body(body);
 124         if let &[
 125             Param { pat: Pat { kind: PatKind::Binding(_, _, left_ident, _), .. }, ..},
 126             Param { pat: Pat { kind: PatKind::Binding(_, _, right_ident, _), .. }, .. }
 127         ] = &closure_body.params;
 128         if let ExprKind::MethodCall(method_path, [left_expr, right_expr], _) = closure_body.value.kind;
 129         if method_path.ident.name == sym::cmp;
 130         if is_trait_method(cx, &closure_body.value, sym::Ord);
 131         then {
 132             let (closure_body, closure_arg, reverse) = if mirrored_exprs(
 133                 left_expr,
 134                 left_ident,
 135                 right_expr,
 136                 right_ident
 137             ) {
 138                 (Sugg::hir(cx, left_expr, "..").to_string(), left_ident.name.to_string(), false)
 139             } else if mirrored_exprs(left_expr, right_ident, right_expr, left_ident) {
 140                 (Sugg::hir(cx, left_expr, "..").to_string(), right_ident.name.to_string(), true)
 141             } else {
 142                 return None;
 143             };
 144             let vec_name = Sugg::hir(cx, recv, "..").to_string();
 145
 146             if_chain! {
 147                 if let ExprKind::Path(QPath::Resolved(_, Path {
 148                     segments: [PathSegment { ident: left_name, .. }], ..
 149                 })) = &left_expr.kind;
 150                 if left_name == left_ident;
 151                 if cx.tcx.get_diagnostic_item(sym::Ord).map_or(false, |id| {
 152                     implements_trait(cx, cx.typeck_results().expr_ty(left_expr), id, &[])
 153                 });
 154                 then {
 155                     return Some(LintTrigger::Sort(SortDetection { vec_name }));
 156                 }
 157             }
 158
 159             if !expr_borrows(cx, left_expr) {
 160                 return Some(LintTrigger::SortByKey(SortByKeyDetection {
 161                     vec_name,
 162                     closure_arg,
 163                     closure_body,
 164                     reverse,
 165                 }));
 166             }
 167         }
 168     }
 169
 170     None
 171 }
 172
 173 fn expr_borrows(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
 174     let ty = cx.typeck_results().expr_ty(expr);
 175     matches!(ty.kind(), ty::Ref(..)) || ty.walk().any(|arg| matches!(arg.unpack(), GenericArgKind::Lifetime(_)))
 176 }
 177
 178 pub(super) fn check<'tcx>(
 179     cx: &LateContext<'tcx>,
 180     expr: &'tcx Expr<'_>,
 181     recv: &'tcx Expr<'_>,
 182     arg: &'tcx Expr<'_>,
 183     is_unstable: bool,
 184 ) {
 185     match detect_lint(cx, expr, recv, arg) {
 186         Some(LintTrigger::SortByKey(trigger)) => span_lint_and_sugg(
 187             cx,
 188             UNNECESSARY_SORT_BY,
 189             expr.span,
 190             "use Vec::sort_by_key here instead",
 191             "try",
 192             format!(
 193                 "{}.sort{}_by_key(|{}| {})",
 194                 trigger.vec_name,
 195                 if is_unstable { "_unstable" } else { "" },
 196                 trigger.closure_arg,
 197                 if trigger.reverse {
 198                     format!("std::cmp::Reverse({})", trigger.closure_body)
 199                 } else {
 200                     trigger.closure_body.to_string()
 201                 },
 202             ),
 203             if trigger.reverse {
 204                 Applicability::MaybeIncorrect
 205             } else {
 206                 Applicability::MachineApplicable
 207             },
 208         ),
 209         Some(LintTrigger::Sort(trigger)) => span_lint_and_sugg(
 210             cx,
 211             UNNECESSARY_SORT_BY,
 212             expr.span,
 213             "use Vec::sort here instead",
 214             "try",
 215             format!(
 216                 "{}.sort{}()",
 217                 trigger.vec_name,
 218                 if is_unstable { "_unstable" } else { "" },
 219             ),
 220             Applicability::MachineApplicable,
 221         ),
 222         None => {},
 223     }
 224 }