Auto merge of #105436 - nnethercote:inline-place_contents_drop_state_cannot_differ, r=spastorino

Inline and remove `place_contents_drop_state_cannot_differ`.

It has a single call site and is hot enough to be worth inlining. And make sure `is_terminal_path` is inlined, too.

r? `@ghost`

Author: bors

compiler/rustc_mir_dataflow/src/drop_flag_effects.rs

@@ -29,56 +29,6 @@ where
     None
 }
 
-/// When enumerating the child fragments of a path, don't recurse into
-/// paths (1.) past arrays, slices, and pointers, nor (2.) into a type
-/// that implements `Drop`.
-///
-/// Places behind references or arrays are not tracked by elaboration
-/// and are always assumed to be initialized when accessible. As
-/// references and indexes can be reseated, trying to track them can
-/// only lead to trouble.
-///
-/// Places behind ADT's with a Drop impl are not tracked by
-/// elaboration since they can never have a drop-flag state that
-/// differs from that of the parent with the Drop impl.
-///
-/// In both cases, the contents can only be accessed if and only if
-/// their parents are initialized. This implies for example that there
-/// is no need to maintain separate drop flags to track such state.
-//
-// FIXME: we have to do something for moving slice patterns.
-fn place_contents_drop_state_cannot_differ<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    body: &Body<'tcx>,
-    place: mir::Place<'tcx>,
-) -> bool {
-    let ty = place.ty(body, tcx).ty;
-    match ty.kind() {
-        ty::Array(..) => {
-            debug!(
-                "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} => false",
-                place, ty
-            );
-            false
-        }
-        ty::Slice(..) | ty::Ref(..) | ty::RawPtr(..) => {
-            debug!(
-                "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} refd => true",
-                place, ty
-            );
-            true
-        }
-        ty::Adt(def, _) if (def.has_dtor(tcx) && !def.is_box()) || def.is_union() => {
-            debug!(
-                "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} Drop => true",
-                place, ty
-            );
-            true
-        }
-        _ => false,
-    }
-}
-
 pub fn on_lookup_result_bits<'tcx, F>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
@@ -105,13 +55,58 @@ pub fn on_all_children_bits<'tcx, F>(
 ) where
     F: FnMut(MovePathIndex),
 {
+    #[inline]
     fn is_terminal_path<'tcx>(
         tcx: TyCtxt<'tcx>,
         body: &Body<'tcx>,
         move_data: &MoveData<'tcx>,
         path: MovePathIndex,
     ) -> bool {
-        place_contents_drop_state_cannot_differ(tcx, body, move_data.move_paths[path].place)
+        let place = move_data.move_paths[path].place;
+
+        // When enumerating the child fragments of a path, don't recurse into
+        // paths (1.) past arrays, slices, and pointers, nor (2.) into a type
+        // that implements `Drop`.
+        //
+        // Places behind references or arrays are not tracked by elaboration
+        // and are always assumed to be initialized when accessible. As
+        // references and indexes can be reseated, trying to track them can
+        // only lead to trouble.
+        //
+        // Places behind ADT's with a Drop impl are not tracked by
+        // elaboration since they can never have a drop-flag state that
+        // differs from that of the parent with the Drop impl.
+        //
+        // In both cases, the contents can only be accessed if and only if
+        // their parents are initialized. This implies for example that there
+        // is no need to maintain separate drop flags to track such state.
+        //
+        // FIXME: we have to do something for moving slice patterns.
+        let ty = place.ty(body, tcx).ty;
+        match ty.kind() {
+            ty::Adt(def, _) if (def.has_dtor(tcx) && !def.is_box()) || def.is_union() => {
+                debug!(
+                    "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} Drop => true",
+                    place, ty
+                );
+                true
+            }
+            ty::Array(..) => {
+                debug!(
+                    "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} => false",
+                    place, ty
+                );
+                false
+            }
+            ty::Slice(..) | ty::Ref(..) | ty::RawPtr(..) => {
+                debug!(
+                    "place_contents_drop_state_cannot_differ place: {:?} ty: {:?} refd => true",
+                    place, ty
+                );
+                true
+            }
+            _ => false,
+        }
     }
 
     fn on_all_children_bits<'tcx, F>(