reduce false positives of tail-expr-drop-order from consumed values

Author: dingxiangfei2009

Cargo.lock

@@ -4090,6 +4090,7 @@ dependencies = [
  "rustc_hir",
  "rustc_index",
  "rustc_infer",
+ "rustc_lint",
  "rustc_macros",
  "rustc_middle",
  "rustc_mir_build",

compiler/rustc_borrowck/src/lib.rs

@@ -690,7 +690,7 @@ impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
             TerminatorKind::SwitchInt { discr, targets: _ } => {
                 self.consume_operand(loc, (discr, span), state);
             }
-            TerminatorKind::Drop { place, target: _, unwind: _, replace } => {
+            TerminatorKind::Drop { place, target: _, scope: _, unwind: _, replace } => {
                 debug!(
                     "visit_terminator_drop \
                      loc: {:?} term: {:?} place: {:?} span: {:?}",

compiler/rustc_borrowck/src/polonius/loan_invalidations.rs

@@ -103,7 +103,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LoanInvalidationsGenerator<'a, 'tcx> {
             TerminatorKind::SwitchInt { discr, targets: _ } => {
                 self.consume_operand(location, discr);
             }
-            TerminatorKind::Drop { place: drop_place, target: _, unwind: _, replace } => {
+            TerminatorKind::Drop { place: drop_place, target: _, scope: _, unwind: _, replace } => {
                 let write_kind =
                     if *replace { WriteKind::Replace } else { WriteKind::StorageDeadOrDrop };
                 self.access_place(

compiler/rustc_codegen_cranelift/src/base.rs

@@ -549,7 +549,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
             | TerminatorKind::CoroutineDrop => {
                 bug!("shouldn't exist at codegen {:?}", bb_data.terminator());
             }
-            TerminatorKind::Drop { place, target, unwind: _, replace: _ } => {
+            TerminatorKind::Drop { place, target, unwind: _, scope: _, replace: _ } => {
                 let drop_place = codegen_place(fx, *place);
                 crate::abi::codegen_drop(fx, source_info, drop_place, *target);
             }

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -1322,7 +1322,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 MergingSucc::False
             }
 
-            mir::TerminatorKind::Drop { place, target, unwind, replace: _ } => self
+            mir::TerminatorKind::Drop { place, target, unwind, scope: _, replace: _ } => self
                 .codegen_drop_terminator(
                     helper,
                     bx,

compiler/rustc_const_eval/src/interpret/step.rs

@@ -528,7 +528,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 }
             }
 
-            Drop { place, target, unwind, replace: _ } => {
+            Drop { place, target, unwind, scope: _, replace: _ } => {
                 let place = self.eval_place(place)?;
                 let instance = Instance::resolve_drop_in_place(*self.tcx, place.layout.ty);
                 if let ty::InstanceKind::DropGlue(_, None) = instance.def {

compiler/rustc_hir_typeck/src/expr_use_visitor.rs

@@ -150,6 +150,50 @@ pub trait TypeInformationCtxt<'tcx> {
     fn tcx(&self) -> TyCtxt<'tcx>;
 }
 
+impl<'tcx> TypeInformationCtxt<'tcx> for (TyCtxt<'tcx>, LocalDefId) {
+    type TypeckResults<'a> = &'tcx ty::TypeckResults<'tcx>
+    where
+        Self: 'a;
+
+    type Error = !;
+
+    fn typeck_results(&self) -> Self::TypeckResults<'_> {
+        self.0.typeck(self.1)
+    }
+
+    fn resolve_vars_if_possible<T: TypeFoldable<TyCtxt<'tcx>>>(&self, t: T) -> T {
+        t
+    }
+
+    fn try_structurally_resolve_type(&self, _span: Span, ty: Ty<'tcx>) -> Ty<'tcx> {
+        ty
+    }
+
+    fn report_error(&self, span: Span, msg: impl ToString) -> Self::Error {
+        span_bug!(span, "{}", msg.to_string())
+    }
+
+    fn error_reported_in_ty(&self, _ty: Ty<'tcx>) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn tainted_by_errors(&self) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn type_is_copy_modulo_regions(&self, ty: Ty<'tcx>) -> bool {
+        ty.is_copy_modulo_regions(self.0, self.0.param_env(self.1))
+    }
+
+    fn body_owner_def_id(&self) -> LocalDefId {
+        self.1
+    }
+
+    fn tcx(&self) -> TyCtxt<'tcx> {
+        self.0
+    }
+}
+
 impl<'tcx> TypeInformationCtxt<'tcx> for &FnCtxt<'_, 'tcx> {
     type TypeckResults<'a> = Ref<'a, ty::TypeckResults<'tcx>>
     where

compiler/rustc_hir_typeck/src/lib.rs

@@ -30,6 +30,7 @@ mod fallback;
 mod fn_ctxt;
 mod gather_locals;
 mod intrinsicck;
+mod lint;
 mod method;
 mod op;
 mod pat;
@@ -506,5 +507,6 @@ fn fatally_break_rust(tcx: TyCtxt<'_>, span: Span) -> ! {
 
 pub fn provide(providers: &mut Providers) {
     method::provide(providers);
+    lint::provide(providers);
     *providers = Providers { typeck, diagnostic_only_typeck, used_trait_imports, ..*providers };
 }

compiler/rustc_hir_typeck/src/lint.rs

@@ -0,0 +1,67 @@
+use rustc_hir::def_id::DefId;
+use rustc_hir::{HirId, HirIdSet};
+use rustc_middle::hir::place::{PlaceBase, PlaceWithHirId};
+use rustc_middle::mir::FakeReadCause;
+use rustc_middle::query::Providers;
+use rustc_middle::ty::{self, TyCtxt};
+use tracing::instrument;
+
+use crate::expr_use_visitor::{Delegate, ExprUseVisitor};
+
+#[derive(Default)]
+struct ExtractConsumingNodeDelegate {
+    nodes: HirIdSet,
+}
+
+impl<'tcx> Delegate<'tcx> for ExtractConsumingNodeDelegate {
+    #[instrument(level = "debug", skip(self))]
+    fn consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, _: HirId) {
+        match place_with_id.place.base {
+            PlaceBase::Rvalue => {
+                self.nodes.insert(place_with_id.hir_id);
+            }
+            PlaceBase::Local(id) => {
+                self.nodes.insert(id);
+            }
+            PlaceBase::Upvar(upvar) => {
+                self.nodes.insert(upvar.var_path.hir_id);
+            }
+            PlaceBase::StaticItem => {}
+        }
+    }
+
+    fn borrow(
+        &mut self,
+        _place_with_id: &PlaceWithHirId<'tcx>,
+        _diag_expr_id: HirId,
+        _bk: ty::BorrowKind,
+    ) {
+        // do nothing
+    }
+
+    fn mutate(&mut self, _assignee_place: &PlaceWithHirId<'tcx>, _diag_expr_id: HirId) {
+        // do nothing
+    }
+
+    fn fake_read(
+        &mut self,
+        _place_with_id: &PlaceWithHirId<'tcx>,
+        _cause: FakeReadCause,
+        _diag_expr_id: HirId,
+    ) {
+        // do nothing
+    }
+}
+
+fn extract_tail_expr_consuming_nodes<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx HirIdSet {
+    let hir = tcx.hir();
+    let body = hir.body_owned_by(def_id.expect_local());
+    let mut delegate = ExtractConsumingNodeDelegate::default();
+    let euv = ExprUseVisitor::new((tcx, def_id.expect_local()), &mut delegate);
+    let _ = euv.walk_expr(body.value);
+    tcx.arena.alloc(delegate.nodes)
+}
+
+pub(crate) fn provide(providers: &mut Providers) {
+    providers.extract_tail_expr_consuming_nodes = extract_tail_expr_consuming_nodes;
+}

compiler/rustc_lint/messages.ftl

@@ -789,9 +789,6 @@ lint_suspicious_double_ref_clone =
 lint_suspicious_double_ref_deref =
     using `.deref()` on a double reference, which returns `{$ty}` instead of dereferencing the inner type
 
-lint_tail_expr_drop_order = these values and local bindings have significant drop implementation that will have a different drop order from that of Edition 2021
-    .label = these values have significant drop implementation and will observe changes in drop order under Edition 2024
-
 lint_trailing_semi_macro = trailing semicolon in macro used in expression position
     .note1 = macro invocations at the end of a block are treated as expressions
     .note2 = to ignore the value produced by the macro, add a semicolon after the invocation of `{$name}`

compiler/rustc_lint/src/lib.rs

@@ -82,7 +82,6 @@ mod redundant_semicolon;
 mod reference_casting;
 mod shadowed_into_iter;
 mod static_mut_refs;
-mod tail_expr_drop_order;
 mod traits;
 mod types;
 mod unit_bindings;
@@ -122,7 +121,6 @@ use rustc_middle::ty::TyCtxt;
 use shadowed_into_iter::ShadowedIntoIter;
 pub use shadowed_into_iter::{ARRAY_INTO_ITER, BOXED_SLICE_INTO_ITER};
 use static_mut_refs::*;
-use tail_expr_drop_order::TailExprDropOrder;
 use traits::*;
 use types::*;
 use unit_bindings::*;
@@ -246,7 +244,6 @@ late_lint_methods!(
             AsyncFnInTrait: AsyncFnInTrait,
             NonLocalDefinitions: NonLocalDefinitions::default(),
             ImplTraitOvercaptures: ImplTraitOvercaptures,
-            TailExprDropOrder: TailExprDropOrder,
             IfLetRescope: IfLetRescope::default(),
             StaticMutRefs: StaticMutRefs,
         ]