Update upstream source from tag 'upstream/1.52.1+dfsg1'

[rustc.git] / src / tools / clippy / clippy_lints / src / loops / mut_range_bound.rs

diff --git a/src/tools/clippy/clippy_lints/src/loops/mut_range_bound.rs b/src/tools/clippy/clippy_lints/src/loops/mut_range_bound.rs
new file mode 100644 (file)
index 0000000..cb56512
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/loops/mut_range_bound.rs
@@ -0,0 +1,118 @@
+use super::MUT_RANGE_BOUND;
+use crate::utils::{higher, path_to_local, span_lint};
+use if_chain::if_chain;
+use rustc_hir::{BindingAnnotation, Expr, HirId, Node, PatKind};
+use rustc_infer::infer::TyCtxtInferExt;
+use rustc_lint::LateContext;
+use rustc_middle::mir::FakeReadCause;
+use rustc_middle::ty;
+use rustc_span::source_map::Span;
+use rustc_typeck::expr_use_visitor::{ConsumeMode, Delegate, ExprUseVisitor, PlaceBase, PlaceWithHirId};
+
+pub(super) fn check(cx: &LateContext<'_>, arg: &Expr<'_>, body: &Expr<'_>) {
+    if let Some(higher::Range {
+        start: Some(start),
+        end: Some(end),
+        ..
+    }) = higher::range(arg)
+    {
+        let mut_ids = vec![check_for_mutability(cx, start), check_for_mutability(cx, end)];
+        if mut_ids[0].is_some() || mut_ids[1].is_some() {
+            let (span_low, span_high) = check_for_mutation(cx, body, &mut_ids);
+            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(
+            cx,
+            MUT_RANGE_BOUND,
+            sp,
+            "attempt to mutate range bound within loop; note that 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::Binding(pat) = cx.tcx.hir().get(hir_id);
+        if let PatKind::Binding(BindingAnnotation::Mutable, ..) = pat.kind;
+        then {
+            return Some(hir_id);
+        }
+    }
+    None
+}
+
+fn check_for_mutation<'tcx>(
+    cx: &LateContext<'tcx>,
+    body: &Expr<'_>,
+    bound_ids: &[Option<HirId>],
+) -> (Option<Span>, Option<Span>) {
+    let mut delegate = MutatePairDelegate {
+        cx,
+        hir_id_low: bound_ids[0],
+        hir_id_high: bound_ids[1],
+        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, _: ConsumeMode) {}
+
+    fn borrow(&mut self, cmt: &PlaceWithHirId<'tcx>, diag_expr_id: HirId, bk: ty::BorrowKind) {
+        if let ty::BorrowKind::MutBorrow = bk {
+            if let PlaceBase::Local(id) = cmt.place.base {
+                if Some(id) == self.hir_id_low {
+                    self.span_low = Some(self.cx.tcx.hir().span(diag_expr_id))
+                }
+                if Some(id) == self.hir_id_high {
+                    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 {
+                self.span_low = Some(self.cx.tcx.hir().span(diag_expr_id))
+            }
+            if Some(id) == self.hir_id_high {
+                self.span_high = Some(self.cx.tcx.hir().span(diag_expr_id))
+            }
+        }
+    }
+
+    fn fake_read(&mut self, _: rustc_typeck::expr_use_visitor::Place<'tcx>, _: FakeReadCause, _:HirId) { }
+}
+
+impl MutatePairDelegate<'_, '_> {
+    fn mutation_span(&self) -> (Option<Span>, Option<Span>) {
+        (self.span_low, self.span_high)
+    }
+}