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|
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet;
use clippy_utils::ty::{implements_trait, is_copy};
use clippy_utils::{match_any_def_paths, path_def_id, paths};
use rustc_errors::Applicability;
use rustc_hir::{BinOpKind, Expr, ExprKind, UnOp};
use rustc_lint::LateContext;
use rustc_middle::ty::Ty;
use rustc_span::symbol::sym;
use super::CMP_OWNED;
pub(super) fn check(cx: &LateContext<'_>, op: BinOpKind, lhs: &Expr<'_>, rhs: &Expr<'_>) {
if op.is_comparison() {
check_op(cx, lhs, rhs, true);
check_op(cx, rhs, lhs, false);
}
}
#[derive(Default)]
struct EqImpl {
ty_eq_other: bool,
other_eq_ty: bool,
}
impl EqImpl {
fn is_implemented(&self) -> bool {
self.ty_eq_other || self.other_eq_ty
}
}
fn symmetric_partial_eq<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, other: Ty<'tcx>) -> Option<EqImpl> {
cx.tcx.lang_items().eq_trait().map(|def_id| EqImpl {
ty_eq_other: implements_trait(cx, ty, def_id, &[other.into()]),
other_eq_ty: implements_trait(cx, other, def_id, &[ty.into()]),
})
}
fn check_op(cx: &LateContext<'_>, expr: &Expr<'_>, other: &Expr<'_>, left: bool) {
let typeck = cx.typeck_results();
let (arg, arg_span) = match expr.kind {
ExprKind::MethodCall(_, arg, [], _)
if typeck
.type_dependent_def_id(expr.hir_id)
.and_then(|id| cx.tcx.trait_of_item(id))
.map_or(false, |id| {
matches!(cx.tcx.get_diagnostic_name(id), Some(sym::ToString | sym::ToOwned))
}) =>
{
(arg, arg.span)
},
ExprKind::Call(path, [arg])
if path_def_id(cx, path)
.and_then(|id| match_any_def_paths(cx, id, &[&paths::FROM_STR_METHOD, &paths::FROM_FROM]))
.map_or(false, |idx| match idx {
0 => true,
1 => !is_copy(cx, typeck.expr_ty(expr)),
_ => false,
}) =>
{
(arg, arg.span)
},
_ => return,
};
let arg_ty = typeck.expr_ty(arg);
let other_ty = typeck.expr_ty(other);
let without_deref = symmetric_partial_eq(cx, arg_ty, other_ty).unwrap_or_default();
let with_deref = arg_ty
.builtin_deref(true)
.and_then(|tam| symmetric_partial_eq(cx, tam.ty, other_ty))
.unwrap_or_default();
if !with_deref.is_implemented() && !without_deref.is_implemented() {
return;
}
let other_gets_derefed = matches!(other.kind, ExprKind::Unary(UnOp::Deref, _));
let lint_span = if other_gets_derefed {
expr.span.to(other.span)
} else {
expr.span
};
span_lint_and_then(
cx,
CMP_OWNED,
lint_span,
"this creates an owned instance just for comparison",
|diag| {
// This also catches `PartialEq` implementations that call `to_owned`.
if other_gets_derefed {
diag.span_label(lint_span, "try implementing the comparison without allocating");
return;
}
let arg_snip = snippet(cx, arg_span, "..");
let expr_snip;
let eq_impl;
if with_deref.is_implemented() {
expr_snip = format!("*{}", arg_snip);
eq_impl = with_deref;
} else {
expr_snip = arg_snip.to_string();
eq_impl = without_deref;
};
let span;
let hint;
if (eq_impl.ty_eq_other && left) || (eq_impl.other_eq_ty && !left) {
span = expr.span;
hint = expr_snip;
} else {
span = expr.span.to(other.span);
let cmp_span = if other.span < expr.span {
other.span.between(expr.span)
} else {
expr.span.between(other.span)
};
if eq_impl.ty_eq_other {
hint = format!(
"{}{}{}",
expr_snip,
snippet(cx, cmp_span, ".."),
snippet(cx, other.span, "..")
);
} else {
hint = format!(
"{}{}{}",
snippet(cx, other.span, ".."),
snippet(cx, cmp_span, ".."),
expr_snip
);
}
}
diag.span_suggestion(
span,
"try",
hint,
Applicability::MachineApplicable, // snippet
);
},
);
}
|
