Auto merge of rust-lang#125923 - matthewjasper:no-return-leak, r=<try>

Fix leaks from panics in destructors

Resurrects rust-lang#78373.

This avoids the problem with rust-lang#80949 by not unscheduling drops of function arguments until after the call (so they still get a drop terminator on the function unwind path).

Closes rust-lang#47949

r? `@lcnr`

Author: bors

compiler/rustc_mir_build/src/build/block.rs

@@ -1,4 +1,5 @@
 use crate::build::matches::{DeclareLetBindings, EmitStorageLive, ScheduleDrops};
+use crate::build::scope::DropKind;
 use crate::build::ForGuard::OutsideGuard;
 use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
 use rustc_middle::middle::region::Scope;
@@ -12,6 +13,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     pub(crate) fn ast_block(
         &mut self,
         destination: Place<'tcx>,
+        scope: Option<Scope>,
         block: BasicBlock,
         ast_block: BlockId,
         source_info: SourceInfo,
@@ -20,18 +22,27 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             self.thir[ast_block];
         self.in_scope((region_scope, source_info), LintLevel::Inherited, move |this| {
             if targeted_by_break {
-                this.in_breakable_scope(None, destination, span, |this| {
-                    Some(this.ast_block_stmts(destination, block, span, stmts, expr, region_scope))
+                this.in_breakable_scope(None, destination, scope, span, |this| {
+                    Some(this.ast_block_stmts(
+                        destination,
+                        scope,
+                        block,
+                        span,
+                        stmts,
+                        expr,
+                        region_scope,
+                    ))
                 })
             } else {
-                this.ast_block_stmts(destination, block, span, stmts, expr, region_scope)
+                this.ast_block_stmts(destination, scope, block, span, stmts, expr, region_scope)
             }
         })
     }
 
     fn ast_block_stmts(
         &mut self,
         destination: Place<'tcx>,
+        scope: Option<Scope>,
         mut block: BasicBlock,
         span: Span,
         stmts: &[StmtId],
@@ -169,6 +180,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     unpack!(
                         failure_block = this.ast_block(
                             dummy_place,
+                            None,
                             failure_entry,
                             *else_block,
                             this.source_info(else_block_span),
@@ -333,7 +345,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             this.block_context
                 .push(BlockFrame::TailExpr { tail_result_is_ignored, span: expr.span });
 
-            unpack!(block = this.expr_into_dest(destination, block, expr_id));
+            unpack!(block = this.expr_into_dest(destination, scope, block, expr_id));
             let popped = this.block_context.pop();
 
             assert!(popped.is_some_and(|bf| bf.is_tail_expr()));
@@ -350,6 +362,10 @@ 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()
+                && let Some(scope) = scope
+            {
+                this.schedule_drop(span, scope, destination_local, DropKind::Value);
             }
         }
         // Finally, we pop all the let scopes before exiting out from the scope of block

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

@@ -20,6 +20,8 @@ use rustc_middle::ty::{self, Ty, UpvarArgs};
 use rustc_span::{Span, DUMMY_SP};
 use tracing::debug;
 
+use std::slice;
+
 impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// Returns an rvalue suitable for use until the end of the current
     /// scope expression.
@@ -184,15 +186,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let box_ = Rvalue::ShallowInitBox(Operand::Move(storage), value_ty);
                 this.cfg.push_assign(block, source_info, Place::from(result), box_);
 
-                // initialize the box contents:
+                // Initialize the box contents. No scope is needed since the
+                // `Box` is already scheduled to be dropped.
                 unpack!(
                     block = this.expr_into_dest(
                         this.tcx.mk_place_deref(Place::from(result)),
+                        None,
                         block,
                         value,
                     )
                 );
-                block.and(Rvalue::Use(Operand::Move(Place::from(result))))
+                let result_operand = Operand::Move(Place::from(result));
+                this.record_operands_moved(slice::from_ref(&result_operand));
+                block.and(Rvalue::Use(result_operand))
             }
             ExprKind::Cast { source } => {
                 let source_expr = &this.thir[source];
@@ -360,6 +366,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     })
                     .collect();
 
+                this.record_operands_moved(&fields.raw);
                 block.and(Rvalue::Aggregate(Box::new(AggregateKind::Array(el_ty)), fields))
             }
             ExprKind::Tuple { ref fields } => {
@@ -381,6 +388,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     })
                     .collect();
 
+                this.record_operands_moved(&fields.raw);
                 block.and(Rvalue::Aggregate(Box::new(AggregateKind::Tuple), fields))
             }
             ExprKind::Closure(box ClosureExpr {
@@ -483,6 +491,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         Box::new(AggregateKind::CoroutineClosure(closure_id.to_def_id(), args))
                     }
                 };
+                this.record_operands_moved(&operands.raw);
                 block.and(Rvalue::Aggregate(result, operands))
             }
             ExprKind::Assign { .. } | ExprKind::AssignOp { .. } => {
@@ -738,7 +747,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 this.diverge_from(block);
                 block = success;
             }
-            this.record_operands_moved(&[Spanned { node: value_operand, span: DUMMY_SP }]);
+            this.record_operands_moved(&[value_operand]);
         }
         block.and(Rvalue::Aggregate(Box::new(AggregateKind::Array(elem_ty)), IndexVec::new()))
     }

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

@@ -112,11 +112,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
         }
 
-        unpack!(block = this.expr_into_dest(temp_place, block, expr_id));
-
-        if let Some(temp_lifetime) = temp_lifetime {
-            this.schedule_drop(expr_span, temp_lifetime, temp, DropKind::Value);
-        }
+        unpack!(block = this.expr_into_dest(temp_place, temp_lifetime, block, expr_id));
 
         block.and(temp)
     }