sus™

Author: lcnr

compiler/rustc_mir_build/src/build/block.rs

@@ -362,7 +362,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 // We only want to assign an implicit `()` as the return value of the block if the
                 // block does not diverge. (Otherwise, we may try to assign a unit to a `!`-type.)
                 this.cfg.push_assign_unit(block, source_info, destination, this.tcx);
-            } else if let Some(destination_local) = destination.as_local()
+            }
+
+            if let Some(destination_local) = destination.as_local()
                 && let Some(scope) = scope
             {
                 this.schedule_drop(span, scope, destination_local, DropKind::Value);

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -136,6 +136,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     // Generate the implicit `else {}` by assigning unit.
                     let correct_si = this.source_info(expr_span.shrink_to_hi());
                     this.cfg.push_assign_unit(else_blk, correct_si, destination, this.tcx);
+                    schedule_drop(this);
                 }
 
                 // The `then` and `else` arms have been lowered into their respective
@@ -339,6 +340,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 };
                 let borrow = Rvalue::Ref(this.tcx.lifetimes.re_erased, borrow_kind, arg_place);
                 this.cfg.push_assign(block, source_info, destination, borrow);
+                schedule_drop(this);
                 block.unit()
             }
             ExprKind::AddressOf { mutability, arg } => {
@@ -653,6 +655,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
         };
 
+        if let Some(drop_scope) = scope {
+            let local = destination.as_local().expect("cannot unschedule drop of non-Local place");
+            this.may_unschedule_drop(drop_scope, local, expr);
+        }
+
         if !expr_is_block_or_scope {
             let popped = this.block_context.pop();
             assert!(popped.is_some());

compiler/rustc_mir_build/src/build/scope.rs

@@ -90,7 +90,6 @@ use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::middle::region;
 use rustc_middle::mir::*;
 use rustc_middle::thir::{ExprId, LintLevel};
-use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::{bug, span_bug};
 use rustc_session::lint::Level;
 use rustc_span::{Span, DUMMY_SP};
@@ -1143,8 +1142,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     {
                         return;
                     }
-                    // Opaque type may not have been scheduled if its underlying
-                    // type does not need drop.
                     _ => bug!(
                         "found wrong drop, expected value drop of {:?} in scope {:?}, found {:?}, all scopes {:?}",
                         local,
@@ -1159,6 +1156,43 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         bug!("region scope {:?} not in scope to unschedule drop of {:?}", region_scope, local);
     }
 
+    pub(crate) fn may_unschedule_drop(
+        &mut self,
+        region_scope: region::Scope,
+        local: Local,
+        x: &dyn std::fmt::Debug,
+    ) {
+        if !self.local_decls[local].ty.needs_drop(self.tcx, self.param_env) {
+            return;
+        }
+        for scope in self.scopes.scopes.iter().rev() {
+            if scope.region_scope == region_scope {
+                let drop = scope.drops.last();
+
+                match drop {
+                    Some(&DropData { local: removed_local, kind: DropKind::Value, .. })
+                        if removed_local == local =>
+                    {
+                        return;
+                    }
+                    _ => tracing::warn!(
+                        "expected drop to unschedule {x:?}, expected value drop of {:?} in scope {:?}, found {:?}, all scopes {:?}",
+                        local,
+                        region_scope,
+                        drop,
+                        self.scopes.scopes,
+                    ),
+                }
+            }
+        }
+
+        tracing::warn!(
+            "region scope {:?} to unschedule {x:?} not in scope to unschedule drop of {:?}",
+            region_scope,
+            local
+        );
+    }
+
     /// Indicates that the "local operands" stored in `local` are
     /// *moved* at some point during execution (see `local_scope` for
     /// more information about what a "local operand" is -- in short,