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use super::MUT_RANGE_BOUND;
use clippy_utils::diagnostics::span_lint_and_note;
use clippy_utils::{get_enclosing_block, higher, path_to_local};
use if_chain::if_chain;
use rustc_hir::intravisit::{self, Visitor};
use rustc_hir::{BindingAnnotation, Expr, ExprKind, HirId, Node, PatKind};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::LateContext;
use rustc_middle::{mir::FakeReadCause, ty};
use rustc_span::source_map::Span;
use rustc_typeck::expr_use_visitor::{Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
pub(super) fn check(cx: &LateContext<'_>, arg: &Expr<'_>, body: &Expr<'_>) {
if_chain! {
if let Some(higher::Range {
start: Some(start),
end: Some(end),
..
}) = higher::Range::hir(arg);
let (mut_id_start, mut_id_end) = (check_for_mutability(cx, start), check_for_mutability(cx, end));
if mut_id_start.is_some() || mut_id_end.is_some();
then {
let (span_low, span_high) = check_for_mutation(cx, body, mut_id_start, mut_id_end);
mut_warn_with_span(cx, span_low);
mut_warn_with_span(cx, span_high);
}
}
}
fn mut_warn_with_span(cx: &LateContext<'_>, span: Option<Span>) {
if let Some(sp) = span {
span_lint_and_note(
cx,
MUT_RANGE_BOUND,
sp,
"attempt to mutate range bound within loop",
None,
"the range of the loop is unchanged",
);
}
}
fn check_for_mutability(cx: &LateContext<'_>, bound: &Expr<'_>) -> Option<HirId> {
if_chain! {
if let Some(hir_id) = path_to_local(bound);
if let Node::Pat(pat) = cx.tcx.hir().get(hir_id);
if let PatKind::Binding(BindingAnnotation::MUT, ..) = pat.kind;
then {
return Some(hir_id);
}
}
None
}
fn check_for_mutation<'tcx>(
cx: &LateContext<'tcx>,
body: &Expr<'_>,
bound_id_start: Option<HirId>,
bound_id_end: Option<HirId>,
) -> (Option<Span>, Option<Span>) {
let mut delegate = MutatePairDelegate {
cx,
hir_id_low: bound_id_start,
hir_id_high: bound_id_end,
span_low: None,
span_high: None,
};
cx.tcx.infer_ctxt().enter(|infcx| {
ExprUseVisitor::new(
&mut delegate,
&infcx,
body.hir_id.owner,
cx.param_env,
cx.typeck_results(),
)
.walk_expr(body);
});
delegate.mutation_span()
}
struct MutatePairDelegate<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
hir_id_low: Option<HirId>,
hir_id_high: Option<HirId>,
span_low: Option<Span>,
span_high: Option<Span>,
}
impl<'tcx> Delegate<'tcx> for MutatePairDelegate<'_, 'tcx> {
fn consume(&mut self, _: &PlaceWithHirId<'tcx>, _: HirId) {}
fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, diag_expr_id: HirId, bk: ty::BorrowKind) {
if bk == ty::BorrowKind::MutBorrow {
if let PlaceBase::Local(id) = cmt.place.base {
if Some(id) == self.hir_id_low && !BreakAfterExprVisitor::is_found(self.cx, diag_expr_id) {
self.span_low = Some(self.cx.tcx.hir().span(diag_expr_id));
}
if Some(id) == self.hir_id_high && !BreakAfterExprVisitor::is_found(self.cx, diag_expr_id) {
self.span_high = Some(self.cx.tcx.hir().span(diag_expr_id));
}
}
}
}
fn mutate(&mut self, cmt: &PlaceWithHirId<'tcx>, diag_expr_id: HirId) {
if let PlaceBase::Local(id) = cmt.place.base {
if Some(id) == self.hir_id_low && !BreakAfterExprVisitor::is_found(self.cx, diag_expr_id) {
self.span_low = Some(self.cx.tcx.hir().span(diag_expr_id));
}
if Some(id) == self.hir_id_high && !BreakAfterExprVisitor::is_found(self.cx, diag_expr_id) {
self.span_high = Some(self.cx.tcx.hir().span(diag_expr_id));
}
}
}
fn fake_read(&mut self, _: &rustc_typeck::expr_use_visitor::PlaceWithHirId<'tcx>, _: FakeReadCause, _: HirId) {}
}
impl MutatePairDelegate<'_, '_> {
fn mutation_span(&self) -> (Option<Span>, Option<Span>) {
(self.span_low, self.span_high)
}
}
struct BreakAfterExprVisitor {
hir_id: HirId,
past_expr: bool,
past_candidate: bool,
break_after_expr: bool,
}
impl BreakAfterExprVisitor {
pub fn is_found(cx: &LateContext<'_>, hir_id: HirId) -> bool {
let mut visitor = BreakAfterExprVisitor {
hir_id,
past_expr: false,
past_candidate: false,
break_after_expr: false,
};
get_enclosing_block(cx, hir_id).map_or(false, |block| {
visitor.visit_block(block);
visitor.break_after_expr
})
}
}
impl<'tcx> intravisit::Visitor<'tcx> for BreakAfterExprVisitor {
fn visit_expr(&mut self, expr: &'tcx Expr<'tcx>) {
if self.past_candidate {
return;
}
if expr.hir_id == self.hir_id {
self.past_expr = true;
} else if self.past_expr {
if matches!(&expr.kind, ExprKind::Break(..)) {
self.break_after_expr = true;
}
self.past_candidate = true;
} else {
intravisit::walk_expr(self, expr);
}
}
}
|
