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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::is_trait_method;
use clippy_utils::sugg::Sugg;
use clippy_utils::ty::implements_trait;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir::{Closure, Expr, ExprKind, Mutability, Param, Pat, PatKind, Path, PathSegment, QPath};
use rustc_lint::LateContext;
use rustc_middle::ty::{self, subst::GenericArgKind};
use rustc_span::sym;
use rustc_span::symbol::Ident;
use std::iter;
use super::UNNECESSARY_SORT_BY;
enum LintTrigger {
Sort(SortDetection),
SortByKey(SortByKeyDetection),
}
struct SortDetection {
vec_name: String,
}
struct SortByKeyDetection {
vec_name: String,
closure_arg: String,
closure_body: String,
reverse: bool,
}
/// Detect if the two expressions are mirrored (identical, except one
/// contains a and the other replaces it with b)
fn mirrored_exprs(a_expr: &Expr<'_>, a_ident: &Ident, b_expr: &Expr<'_>, b_ident: &Ident) -> bool {
match (&a_expr.kind, &b_expr.kind) {
// Two boxes with mirrored contents
(ExprKind::Box(left_expr), ExprKind::Box(right_expr)) => {
mirrored_exprs(left_expr, a_ident, right_expr, b_ident)
},
// Two arrays with mirrored contents
(ExprKind::Array(left_exprs), ExprKind::Array(right_exprs)) => {
iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
},
// The two exprs are function calls.
// Check to see that the function itself and its arguments are mirrored
(ExprKind::Call(left_expr, left_args), ExprKind::Call(right_expr, right_args)) => {
mirrored_exprs(left_expr, a_ident, right_expr, b_ident)
&& iter::zip(*left_args, *right_args).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
},
// The two exprs are method calls.
// Check to see that the function is the same and the arguments are mirrored
// This is enough because the receiver of the method is listed in the arguments
(
ExprKind::MethodCall(left_segment, left_receiver, left_args, _),
ExprKind::MethodCall(right_segment, right_receiver, right_args, _),
) => {
left_segment.ident == right_segment.ident
&& iter::zip(*left_args, *right_args).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
&& mirrored_exprs(left_receiver, a_ident, right_receiver, b_ident)
},
// Two tuples with mirrored contents
(ExprKind::Tup(left_exprs), ExprKind::Tup(right_exprs)) => {
iter::zip(*left_exprs, *right_exprs).all(|(left, right)| mirrored_exprs(left, a_ident, right, b_ident))
},
// Two binary ops, which are the same operation and which have mirrored arguments
(ExprKind::Binary(left_op, left_left, left_right), ExprKind::Binary(right_op, right_left, right_right)) => {
left_op.node == right_op.node
&& mirrored_exprs(left_left, a_ident, right_left, b_ident)
&& mirrored_exprs(left_right, a_ident, right_right, b_ident)
},
// Two unary ops, which are the same operation and which have the same argument
(ExprKind::Unary(left_op, left_expr), ExprKind::Unary(right_op, right_expr)) => {
left_op == right_op && mirrored_exprs(left_expr, a_ident, right_expr, b_ident)
},
// The two exprs are literals of some kind
(ExprKind::Lit(left_lit), ExprKind::Lit(right_lit)) => left_lit.node == right_lit.node,
(ExprKind::Cast(left, _), ExprKind::Cast(right, _)) => mirrored_exprs(left, a_ident, right, b_ident),
(ExprKind::DropTemps(left_block), ExprKind::DropTemps(right_block)) => {
mirrored_exprs(left_block, a_ident, right_block, b_ident)
},
(ExprKind::Field(left_expr, left_ident), ExprKind::Field(right_expr, right_ident)) => {
left_ident.name == right_ident.name && mirrored_exprs(left_expr, a_ident, right_expr, right_ident)
},
// Two paths: either one is a and the other is b, or they're identical to each other
(
ExprKind::Path(QPath::Resolved(
_,
Path {
segments: left_segments,
..
},
)),
ExprKind::Path(QPath::Resolved(
_,
Path {
segments: right_segments,
..
},
)),
) => {
(iter::zip(*left_segments, *right_segments).all(|(left, right)| left.ident == right.ident)
&& left_segments
.iter()
.all(|seg| &seg.ident != a_ident && &seg.ident != b_ident))
|| (left_segments.len() == 1
&& &left_segments[0].ident == a_ident
&& right_segments.len() == 1
&& &right_segments[0].ident == b_ident)
},
// Matching expressions, but one or both is borrowed
(
ExprKind::AddrOf(left_kind, Mutability::Not, left_expr),
ExprKind::AddrOf(right_kind, Mutability::Not, right_expr),
) => left_kind == right_kind && mirrored_exprs(left_expr, a_ident, right_expr, b_ident),
(_, ExprKind::AddrOf(_, Mutability::Not, right_expr)) => mirrored_exprs(a_expr, a_ident, right_expr, b_ident),
(ExprKind::AddrOf(_, Mutability::Not, left_expr), _) => mirrored_exprs(left_expr, a_ident, b_expr, b_ident),
_ => false,
}
}
fn detect_lint(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, arg: &Expr<'_>) -> Option<LintTrigger> {
if_chain! {
if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
if cx.tcx.type_of(impl_id).subst_identity().is_slice();
if let ExprKind::Closure(&Closure { body, .. }) = arg.kind;
if let closure_body = cx.tcx.hir().body(body);
if let &[
Param { pat: Pat { kind: PatKind::Binding(_, _, left_ident, _), .. }, ..},
Param { pat: Pat { kind: PatKind::Binding(_, _, right_ident, _), .. }, .. }
] = &closure_body.params;
if let ExprKind::MethodCall(method_path, left_expr, [right_expr], _) = closure_body.value.kind;
if method_path.ident.name == sym::cmp;
if is_trait_method(cx, closure_body.value, sym::Ord);
then {
let (closure_body, closure_arg, reverse) = if mirrored_exprs(
left_expr,
left_ident,
right_expr,
right_ident
) {
(Sugg::hir(cx, left_expr, "..").to_string(), left_ident.name.to_string(), false)
} else if mirrored_exprs(left_expr, right_ident, right_expr, left_ident) {
(Sugg::hir(cx, left_expr, "..").to_string(), right_ident.name.to_string(), true)
} else {
return None;
};
let vec_name = Sugg::hir(cx, recv, "..").to_string();
if_chain! {
if let ExprKind::Path(QPath::Resolved(_, Path {
segments: [PathSegment { ident: left_name, .. }], ..
})) = &left_expr.kind;
if left_name == left_ident;
if cx.tcx.get_diagnostic_item(sym::Ord).map_or(false, |id| {
implements_trait(cx, cx.typeck_results().expr_ty(left_expr), id, &[])
});
then {
return Some(LintTrigger::Sort(SortDetection { vec_name }));
}
}
if !expr_borrows(cx, left_expr) {
return Some(LintTrigger::SortByKey(SortByKeyDetection {
vec_name,
closure_arg,
closure_body,
reverse,
}));
}
}
}
None
}
fn expr_borrows(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
let ty = cx.typeck_results().expr_ty(expr);
matches!(ty.kind(), ty::Ref(..)) || ty.walk().any(|arg| matches!(arg.unpack(), GenericArgKind::Lifetime(_)))
}
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
recv: &'tcx Expr<'_>,
arg: &'tcx Expr<'_>,
is_unstable: bool,
) {
match detect_lint(cx, expr, recv, arg) {
Some(LintTrigger::SortByKey(trigger)) => span_lint_and_sugg(
cx,
UNNECESSARY_SORT_BY,
expr.span,
"use Vec::sort_by_key here instead",
"try",
format!(
"{}.sort{}_by_key(|{}| {})",
trigger.vec_name,
if is_unstable { "_unstable" } else { "" },
trigger.closure_arg,
if trigger.reverse {
format!("std::cmp::Reverse({})", trigger.closure_body)
} else {
trigger.closure_body.to_string()
},
),
if trigger.reverse {
Applicability::MaybeIncorrect
} else {
Applicability::MachineApplicable
},
),
Some(LintTrigger::Sort(trigger)) => span_lint_and_sugg(
cx,
UNNECESSARY_SORT_BY,
expr.span,
"use Vec::sort here instead",
"try",
format!(
"{}.sort{}()",
trigger.vec_name,
if is_unstable { "_unstable" } else { "" },
),
Applicability::MachineApplicable,
),
None => {},
}
}
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