Add requested changes

Author: 1c3t3a

compiler/rustc_mir_transform/src/check_alignment.rs

@@ -20,6 +20,10 @@ impl<'tcx> crate::MirPass<'tcx> for CheckAlignment {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         // Skip trivially aligned place types.
         let excluded_pointees = [tcx.types.bool, tcx.types.i8, tcx.types.u8];
+
+        // We have to exclude borrows here: in `&x.field`, the exact
+        // requirement is that the final reference must be aligned, but
+        // `check_pointers` would check that `x` is aligned, which would be wrong.
         check_pointers(
             tcx,
             body,

compiler/rustc_mir_transform/src/check_pointers.rs

@@ -151,29 +151,34 @@ impl<'a, 'tcx> PointerFinder<'a, 'tcx> {
     fn into_found_pointers(self) -> Vec<(Place<'tcx>, Ty<'tcx>)> {
         self.pointers
     }
-}
 
-impl<'a, 'tcx> Visitor<'tcx> for PointerFinder<'a, 'tcx> {
-    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
+    /// Whether or not we should visit a [Place] with [PlaceContext].
+    ///
+    /// We generally only visit Reads/Writes to a place and only Borrows if
+    /// requested.
+    fn should_visit_place(&self, context: PlaceContext) -> bool {
         match context {
             PlaceContext::MutatingUse(
                 MutatingUseContext::Store
                 | MutatingUseContext::Call
                 | MutatingUseContext::Yield
                 | MutatingUseContext::Drop,
-            ) => {}
+            ) => true,
             PlaceContext::NonMutatingUse(
                 NonMutatingUseContext::Copy | NonMutatingUseContext::Move,
-            ) => {}
+            ) => true,
             PlaceContext::MutatingUse(MutatingUseContext::Borrow)
-            | PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow)
-                if matches!(self.borrow_check_mode, BorrowCheckMode::IncludeBorrows) => {}
-            _ => {
-                return;
+            | PlaceContext::NonMutatingUse(NonMutatingUseContext::SharedBorrow) => {
+                matches!(self.borrow_check_mode, BorrowCheckMode::IncludeBorrows)
             }
+            _ => false,
         }
+    }
+}
 
-        if !place.is_indirect() {
+impl<'a, 'tcx> Visitor<'tcx> for PointerFinder<'a, 'tcx> {
+    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
+        if !self.should_visit_place(context) && !place.is_indirect() {
             return;
         }