filter out ecosystem types earlier

Author: dingxiangfei2009

compiler/rustc_mir_transform/messages.ftl

@@ -40,7 +40,10 @@ mir_transform_tail_expr_drop_order = relative drop order changing in Rust 2024
         *[false] `{$name}` will be dropped later since Edition 2024
     }
 
-mir_transform_tail_expr_dtor = `{$name}` invokes this custom destructor
+mir_transform_tail_expr_dtor = {$dtor_kind ->
+    [dyn] `{$name}` may invoke a custom destructor because contains a trait object
+    *[concrete] `{$name}` invokes this custom destructor
+    }
 
 mir_transform_tail_expr_local = {$is_generated_name ->
         [true] this value will be stored in a temporary; let us call it `{$name}`

compiler/rustc_mir_transform/src/lint_tail_expr_drop_order.rs

@@ -3,7 +3,7 @@ use std::collections::hash_map;
 use std::rc::Rc;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::unord::UnordSet;
+use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::Subdiagnostic;
 use rustc_hir::CRATE_HIR_ID;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -20,7 +20,7 @@ use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
 use rustc_mir_dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
 use rustc_mir_dataflow::{Analysis, MaybeReachable, ResultsCursor};
 use rustc_session::lint;
-use rustc_span::{Span, Symbol};
+use rustc_span::{DUMMY_SP, Span, Symbol};
 use rustc_type_ir::data_structures::IndexMap;
 use smallvec::{SmallVec, smallvec};
 use tracing::{debug, instrument};
@@ -170,7 +170,9 @@ fn true_significant_drop_ty<'tcx>(
         debug!(?name_str);
         match name_str[..] {
             // These are the types from Rust core ecosystem
-            ["sym" | "proc_macro2", ..] | ["core" | "std", "task", "RawWaker"] => Some(smallvec![]),
+            ["sym" | "proc_macro2", ..]
+            | ["core" | "std", "task", "LocalWaker" | "Waker"]
+            | ["core" | "std", "task", "wake", "LocalWaker" | "Waker"] => Some(smallvec![]),
             // These are important types from Rust ecosystem
             ["tracing", "instrument", "Instrumented"] | ["bytes", "Bytes"] => Some(smallvec![]),
             ["hashbrown", "raw", "RawTable" | "RawIntoIter"] => {
@@ -328,9 +330,19 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
     // because they tend to be scheduled in the same drop ladder block.
     let mut bid_per_block = IndexMap::default();
     let mut bid_places = UnordSet::new();
+    let param_env = tcx.param_env(def_id).with_reveal_all_normalized(tcx);
+    let mut ty_dropped_components = UnordMap::default();
     for (block, data) in body.basic_blocks.iter_enumerated() {
         for (statement_index, stmt) in data.statements.iter().enumerate() {
             if let StatementKind::BackwardIncompatibleDropHint { place, reason: _ } = &stmt.kind {
+                let ty = place.ty(body, tcx).ty;
+                if ty_dropped_components
+                    .entry(ty)
+                    .or_insert_with(|| extract_component_with_significant_dtor(tcx, param_env, ty))
+                    .is_empty()
+                {
+                    continue;
+                }
                 bid_per_block
                     .entry(block)
                     .or_insert(vec![])
@@ -345,7 +357,6 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
 
     dump_mir(tcx, false, "lint_tail_expr_drop_order", &0 as _, body, |_, _| Ok(()));
     let locals_with_user_names = collect_user_names(body);
-    let param_env = tcx.param_env(def_id).with_reveal_all_normalized(tcx);
     let is_closure_like = tcx.is_closure_like(def_id.to_def_id());
     let move_data = MoveData::gather_moves(body, tcx, |_| true);
     let maybe_init = MaybeInitializedPlaces::new(tcx, body, &move_data);
@@ -401,7 +412,13 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
                 }
                 let observer_ty = move_path.place.ty(body, tcx).ty;
                 // d) The collect local has no custom destructor.
-                if !observer_ty.has_significant_drop(tcx, param_env) {
+                if ty_dropped_components
+                    .entry(observer_ty)
+                    .or_insert_with(|| {
+                        extract_component_with_significant_dtor(tcx, param_env, observer_ty)
+                    })
+                    .is_empty()
+                {
                     debug!(?dropped_local, "skip non-droppy types");
                     to_exclude.insert(path_idx);
                     continue;
@@ -449,12 +466,26 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
             }
 
             // Collect spans of the custom destructors.
-            let destructors =
-                extract_component_with_significant_dtor(tcx, param_env, linted_local_decl.ty)
-                    .into_iter()
-                    .filter_map(|ty| ty_dtor_span(tcx, ty))
-                    .map(|span| DestructorLabel { span, name })
-                    .collect();
+            let mut seen_dyn = false;
+            let destructors = ty_dropped_components
+                .get(&linted_local_decl.ty)
+                .unwrap()
+                .iter()
+                .filter_map(|&ty| {
+                    if let Some(span) = ty_dtor_span(tcx, ty) {
+                        Some(DestructorLabel { span, name, dtor_kind: "concrete" })
+                    } else if matches!(ty.kind(), ty::Dynamic(..)) {
+                        if seen_dyn {
+                            None
+                        } else {
+                            seen_dyn = true;
+                            Some(DestructorLabel { span: DUMMY_SP, name, dtor_kind: "dyn" })
+                        }
+                    } else {
+                        None
+                    }
+                })
+                .collect();
             local_labels.push(LocalLabel {
                 span: linted_local_decl.source_info.span,
                 destructors,
@@ -476,10 +507,23 @@ pub(crate) fn run_lint<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId, body: &Body<
             };
             let name = name.as_str();
 
+            let mut seen_dyn = false;
             let destructors = extract_component_with_significant_dtor(tcx, param_env, observer_ty)
                 .into_iter()
-                .filter_map(|ty| ty_dtor_span(tcx, ty))
-                .map(|span| DestructorLabel { span, name })
+                .filter_map(|ty| {
+                    if let Some(span) = ty_dtor_span(tcx, ty) {
+                        Some(DestructorLabel { span, name, dtor_kind: "concrete" })
+                    } else if matches!(ty.kind(), ty::Dynamic(..)) {
+                        if seen_dyn {
+                            None
+                        } else {
+                            seen_dyn = true;
+                            Some(DestructorLabel { span: DUMMY_SP, name, dtor_kind: "dyn" })
+                        }
+                    } else {
+                        None
+                    }
+                })
                 .collect();
             local_labels.push(LocalLabel {
                 span: observer_local_decl.source_info.span,
@@ -582,5 +626,6 @@ impl Subdiagnostic for LocalLabel<'_> {
 struct DestructorLabel<'a> {
     #[primary_span]
     span: Span,
+    dtor_kind: &'static str,
     name: &'a str,
 }