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|
use clippy_utils::binop_traits;
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::implements_trait;
use clippy_utils::{eq_expr_value, trait_ref_of_method};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::intravisit::{walk_expr, Visitor};
use rustc_lint::LateContext;
use rustc_middle::mir::FakeReadCause;
use rustc_middle::ty::BorrowKind;
use rustc_trait_selection::infer::TyCtxtInferExt;
use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
use super::ASSIGN_OP_PATTERN;
pub(super) fn check<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx hir::Expr<'_>,
assignee: &'tcx hir::Expr<'_>,
e: &'tcx hir::Expr<'_>,
) {
if let hir::ExprKind::Binary(op, l, r) = &e.kind {
let lint = |assignee: &hir::Expr<'_>, rhs: &hir::Expr<'_>| {
let ty = cx.typeck_results().expr_ty(assignee);
let rty = cx.typeck_results().expr_ty(rhs);
if_chain! {
if let Some((_, lang_item)) = binop_traits(op.node);
if let Ok(trait_id) = cx.tcx.lang_items().require(lang_item);
let parent_fn = cx.tcx.hir().get_parent_item(e.hir_id);
if trait_ref_of_method(cx, parent_fn)
.map_or(true, |t| t.path.res.def_id() != trait_id);
if implements_trait(cx, ty, trait_id, &[rty.into()]);
then {
// Primitive types execute assign-ops right-to-left. Every other type is left-to-right.
if !(ty.is_primitive() && rty.is_primitive()) {
// TODO: This will have false negatives as it doesn't check if the borrows are
// actually live at the end of their respective expressions.
let mut_borrows = mut_borrows_in_expr(cx, assignee);
let imm_borrows = imm_borrows_in_expr(cx, rhs);
if mut_borrows.iter().any(|id| imm_borrows.contains(id)) {
return;
}
}
span_lint_and_then(
cx,
ASSIGN_OP_PATTERN,
expr.span,
"manual implementation of an assign operation",
|diag| {
if let (Some(snip_a), Some(snip_r)) =
(snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
{
diag.span_suggestion(
expr.span,
"replace it with",
format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
Applicability::MachineApplicable,
);
}
},
);
}
}
};
let mut visitor = ExprVisitor {
assignee,
counter: 0,
cx,
};
walk_expr(&mut visitor, e);
if visitor.counter == 1 {
// a = a op b
if eq_expr_value(cx, assignee, l) {
lint(assignee, r);
}
// a = b commutative_op a
// Limited to primitive type as these ops are know to be commutative
if eq_expr_value(cx, assignee, r) && cx.typeck_results().expr_ty(assignee).is_primitive_ty() {
match op.node {
hir::BinOpKind::Add
| hir::BinOpKind::Mul
| hir::BinOpKind::And
| hir::BinOpKind::Or
| hir::BinOpKind::BitXor
| hir::BinOpKind::BitAnd
| hir::BinOpKind::BitOr => {
lint(assignee, l);
},
_ => {},
}
}
}
}
}
struct ExprVisitor<'a, 'tcx> {
assignee: &'a hir::Expr<'a>,
counter: u8,
cx: &'a LateContext<'tcx>,
}
impl<'a, 'tcx> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
if eq_expr_value(self.cx, self.assignee, expr) {
self.counter += 1;
}
walk_expr(self, expr);
}
}
fn imm_borrows_in_expr(cx: &LateContext<'_>, e: &hir::Expr<'_>) -> hir::HirIdSet {
struct S(hir::HirIdSet);
impl Delegate<'_> for S {
fn borrow(&mut self, place: &PlaceWithHirId<'_>, _: hir::HirId, kind: BorrowKind) {
if matches!(kind, BorrowKind::ImmBorrow | BorrowKind::UniqueImmBorrow) {
self.0.insert(match place.place.base {
PlaceBase::Local(id) => id,
PlaceBase::Upvar(id) => id.var_path.hir_id,
_ => return,
});
}
}
fn consume(&mut self, _: &PlaceWithHirId<'_>, _: hir::HirId) {}
fn mutate(&mut self, _: &PlaceWithHirId<'_>, _: hir::HirId) {}
fn fake_read(&mut self, _: &PlaceWithHirId<'_>, _: FakeReadCause, _: hir::HirId) {}
fn copy(&mut self, _: &PlaceWithHirId<'_>, _: hir::HirId) {}
}
let mut s = S(hir::HirIdSet::default());
cx.tcx.infer_ctxt().enter(|infcx| {
let mut v = ExprUseVisitor::new(
&mut s,
&infcx,
cx.tcx.hir().body_owner_def_id(cx.enclosing_body.unwrap()),
cx.param_env,
cx.typeck_results(),
);
v.consume_expr(e);
});
s.0
}
fn mut_borrows_in_expr(cx: &LateContext<'_>, e: &hir::Expr<'_>) -> hir::HirIdSet {
struct S(hir::HirIdSet);
impl Delegate<'_> for S {
fn borrow(&mut self, place: &PlaceWithHirId<'_>, _: hir::HirId, kind: BorrowKind) {
if matches!(kind, BorrowKind::MutBorrow) {
self.0.insert(match place.place.base {
PlaceBase::Local(id) => id,
PlaceBase::Upvar(id) => id.var_path.hir_id,
_ => return,
});
}
}
fn consume(&mut self, _: &PlaceWithHirId<'_>, _: hir::HirId) {}
fn mutate(&mut self, _: &PlaceWithHirId<'_>, _: hir::HirId) {}
fn fake_read(&mut self, _: &PlaceWithHirId<'_>, _: FakeReadCause, _: hir::HirId) {}
fn copy(&mut self, _: &PlaceWithHirId<'_>, _: hir::HirId) {}
}
let mut s = S(hir::HirIdSet::default());
cx.tcx.infer_ctxt().enter(|infcx| {
let mut v = ExprUseVisitor::new(
&mut s,
&infcx,
cx.tcx.hir().body_owner_def_id(cx.enclosing_body.unwrap()),
cx.param_env,
cx.typeck_results(),
);
v.consume_expr(e);
});
s.0
}
|
