[beta] backports

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -10,7 +10,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::parse::feature_err;
 use rustc_span::{Span, Symbol, sym};
-use rustc_target::target_features;
+use rustc_target::target_features::{self, Stability};
 
 use crate::errors;
 
@@ -87,12 +87,17 @@ pub(crate) fn from_target_feature_attr(
                     // But ensure the ABI does not forbid enabling this.
                     // Here we do assume that LLVM doesn't add even more implied features
                     // we don't know about, at least no features that would have ABI effects!
-                    if abi_feature_constraints.incompatible.contains(&name.as_str()) {
-                        tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
-                            span: item.span(),
-                            feature: name.as_str(),
-                            reason: "this feature is incompatible with the target ABI",
-                        });
+                    // We skip this logic in rustdoc, where we want to allow all target features of
+                    // all targets, so we can't check their ABI compatibility and anyway we are not
+                    // generating code so "it's fine".
+                    if !tcx.sess.opts.actually_rustdoc {
+                        if abi_feature_constraints.incompatible.contains(&name.as_str()) {
+                            tcx.dcx().emit_err(errors::ForbiddenTargetFeatureAttr {
+                                span: item.span(),
+                                feature: name.as_str(),
+                                reason: "this feature is incompatible with the target ABI",
+                            });
+                        }
                     }
                     target_features.push(TargetFeature { name, implied: name != feature_sym })
                 }
@@ -142,11 +147,38 @@ pub(crate) fn provide(providers: &mut Providers) {
         rust_target_features: |tcx, cnum| {
             assert_eq!(cnum, LOCAL_CRATE);
             if tcx.sess.opts.actually_rustdoc {
-                // rustdoc needs to be able to document functions that use all the features, so
-                // whitelist them all
-                rustc_target::target_features::all_rust_features()
-                    .map(|(a, b)| (a.to_string(), b))
-                    .collect()
+                // HACK: rustdoc would like to pretend that we have all the target features, so we
+                // have to merge all the lists into one. To ensure an unstable target never prevents
+                // a stable one from working, we merge the stability info of all instances of the
+                // same target feature name, with the "most stable" taking precedence. And then we
+                // hope that this doesn't cause issues anywhere else in the compiler...
+                let mut result: UnordMap<String, Stability> = Default::default();
+                for (name, stability) in rustc_target::target_features::all_rust_features() {
+                    use std::collections::hash_map::Entry;
+                    match result.entry(name.to_owned()) {
+                        Entry::Vacant(vacant_entry) => {
+                            vacant_entry.insert(stability);
+                        }
+                        Entry::Occupied(mut occupied_entry) => {
+                            // Merge the two stabilities, "more stable" taking precedence.
+                            match (occupied_entry.get(), stability) {
+                                (Stability::Stable, _)
+                                | (
+                                    Stability::Unstable { .. },
+                                    Stability::Unstable { .. } | Stability::Forbidden { .. },
+                                )
+                                | (Stability::Forbidden { .. }, Stability::Forbidden { .. }) => {
+                                    // The stability in the entry is at least as good as the new one, just keep it.
+                                }
+                                _ => {
+                                    // Overwrite stabilite.
+                                    occupied_entry.insert(stability);
+                                }
+                            }
+                        }
+                    }
+                }
+                result
             } else {
                 tcx.sess
                     .target

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1110,7 +1110,6 @@ fn check_associated_item(
                 let ty = tcx.type_of(item.def_id).instantiate_identity();
                 let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                 wfcx.register_wf_obligation(span, loc, ty.into());
-                check_sized_if_body(wfcx, item.def_id.expect_local(), ty, Some(span));
                 Ok(())
             }
             ty::AssocKind::Fn => {
@@ -1235,7 +1234,7 @@ fn check_type_defn<'tcx>(
                     ),
                     wfcx.param_env,
                     ty,
-                    tcx.require_lang_item(LangItem::Sized, Some(hir_ty.span)),
+                    tcx.require_lang_item(LangItem::Sized, None),
                 );
             }
 
@@ -1360,7 +1359,7 @@ fn check_item_type(
                 ),
                 wfcx.param_env,
                 item_ty,
-                tcx.require_lang_item(LangItem::Sized, Some(ty_span)),
+                tcx.require_lang_item(LangItem::Sized, None),
             );
         }
 
@@ -1690,36 +1689,6 @@ fn check_fn_or_method<'tcx>(
             );
         }
     }
-
-    // If the function has a body, additionally require that the return type is sized.
-    check_sized_if_body(
-        wfcx,
-        def_id,
-        sig.output(),
-        match hir_decl.output {
-            hir::FnRetTy::Return(ty) => Some(ty.span),
-            hir::FnRetTy::DefaultReturn(_) => None,
-        },
-    );
-}
-
-fn check_sized_if_body<'tcx>(
-    wfcx: &WfCheckingCtxt<'_, 'tcx>,
-    def_id: LocalDefId,
-    ty: Ty<'tcx>,
-    maybe_span: Option<Span>,
-) {
-    let tcx = wfcx.tcx();
-    if let Some(body) = tcx.hir().maybe_body_owned_by(def_id) {
-        let span = maybe_span.unwrap_or(body.value.span);
-
-        wfcx.register_bound(
-            ObligationCause::new(span, def_id, traits::ObligationCauseCode::SizedReturnType),
-            wfcx.param_env,
-            ty,
-            tcx.require_lang_item(LangItem::Sized, Some(span)),
-        );
-    }
 }
 
 /// The `arbitrary_self_types_pointers` feature implies `arbitrary_self_types`.

compiler/rustc_hir_typeck/src/check.rs

@@ -117,17 +117,22 @@ pub(super) fn check_fn<'a, 'tcx>(
 
     fcx.typeck_results.borrow_mut().liberated_fn_sigs_mut().insert(fn_id, fn_sig);
 
-    // We checked the root's ret ty during wfcheck, but not the child.
-    if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
-        let return_or_body_span = match decl.output {
-            hir::FnRetTy::DefaultReturn(_) => body.value.span,
-            hir::FnRetTy::Return(ty) => ty.span,
-        };
+    let return_or_body_span = match decl.output {
+        hir::FnRetTy::DefaultReturn(_) => body.value.span,
+        hir::FnRetTy::Return(ty) => ty.span,
+    };
 
+    fcx.require_type_is_sized(
+        declared_ret_ty,
+        return_or_body_span,
+        ObligationCauseCode::SizedReturnType,
+    );
+    // We checked the root's signature during wfcheck, but not the child.
+    if fcx.tcx.is_typeck_child(fn_def_id.to_def_id()) {
         fcx.require_type_is_sized(
             declared_ret_ty,
             return_or_body_span,
-            ObligationCauseCode::SizedReturnType,
+            ObligationCauseCode::WellFormed(None),
         );
     }
 

compiler/rustc_hir_typeck/src/lib.rs

@@ -186,6 +186,8 @@ fn typeck_with_inspect<'tcx>(
         let wf_code = ObligationCauseCode::WellFormed(Some(WellFormedLoc::Ty(def_id)));
         fcx.register_wf_obligation(expected_type.into(), body.value.span, wf_code);
 
+        fcx.require_type_is_sized(expected_type, body.value.span, ObligationCauseCode::ConstSized);
+
         // Gather locals in statics (because of block expressions).
         GatherLocalsVisitor::new(&fcx).visit_body(body);
 

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -707,6 +707,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         };
 
         self.note_obligation_cause(&mut err, &obligation);
+        self.point_at_returns_when_relevant(&mut err, &obligation);
         err.emit()
     }
 }
@@ -809,6 +810,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     "Async",
                 );
                 self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
                 return Some(err.emit());
             }
         }
@@ -854,6 +856,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     "",
                 );
                 self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
                 return Some(err.emit());
             }
 
@@ -869,6 +872,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     kind: expected_kind.as_str(),
                 });
                 self.note_obligation_cause(&mut err, &obligation);
+                self.point_at_returns_when_relevant(&mut err, &obligation);
                 return Some(err.emit());
             }
         }
@@ -2829,6 +2833,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         err.span_note(self.tcx.def_span(def_id), "opaque type is declared here");
 
         self.note_obligation_cause(&mut err, &obligation);
+        self.point_at_returns_when_relevant(&mut err, &obligation);
         self.dcx().try_steal_replace_and_emit_err(self.tcx.def_span(def_id), StashKey::Cycle, err)
     }
 

compiler/rustc_trait_selection/src/error_reporting/traits/overflow.rs

@@ -185,6 +185,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
             suggest_increasing_limit,
         );
         self.note_obligation_cause(&mut err, &obligation);
+        self.point_at_returns_when_relevant(&mut err, &obligation);
         err.emit()
     }
 }

compiler/rustc_trait_selection/src/error_reporting/traits/suggestions.rs

@@ -1765,7 +1765,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         };
 
         err.code(E0746);
-        err.primary_message("return type cannot be a trait object without pointer indirection");
+        err.primary_message("return type cannot have an unboxed trait object");
         err.children.clear();
 
         let span = obligation.cause.span;
@@ -1781,13 +1781,25 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         } else {
             ("dyn ", span.shrink_to_lo())
         };
-
-        err.span_suggestion_verbose(
-            impl_span,
-            "consider returning an `impl Trait` instead of a `dyn Trait`",
-            "impl ",
-            Applicability::MaybeIncorrect,
-        );
+        let alternatively = if visitor
+            .returns
+            .iter()
+            .map(|expr| self.typeck_results.as_ref().unwrap().expr_ty_adjusted_opt(expr))
+            .collect::<FxHashSet<_>>()
+            .len()
+            <= 1
+        {
+            err.span_suggestion_verbose(
+                impl_span,
+                "consider returning an `impl Trait` instead of a `dyn Trait`",
+                "impl ",
+                Applicability::MaybeIncorrect,
+            );
+            "alternatively, "
+        } else {
+            err.help("if there were a single returned type, you could use `impl Trait` instead");
+            ""
+        };
 
         let mut sugg = vec![
             (span.shrink_to_lo(), format!("Box<{pre}")),
@@ -1819,7 +1831,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
         err.multipart_suggestion(
             format!(
-                "alternatively, box the return type, and wrap all of the returned values in \
+                "{alternatively}box the return type, and wrap all of the returned values in \
                  `Box::new`",
             ),
             sugg,
@@ -1829,6 +1841,41 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
         true
     }
 
+    pub(super) fn point_at_returns_when_relevant(
+        &self,
+        err: &mut Diag<'_>,
+        obligation: &PredicateObligation<'tcx>,
+    ) {
+        match obligation.cause.code().peel_derives() {
+            ObligationCauseCode::SizedReturnType => {}
+            _ => return,
+        }
+
+        let hir = self.tcx.hir();
+        let node = self.tcx.hir_node_by_def_id(obligation.cause.body_id);
+        if let hir::Node::Item(hir::Item {
+            kind: hir::ItemKind::Fn { body: body_id, .. }, ..
+        }) = node
+        {
+            let body = hir.body(*body_id);
+            // Point at all the `return`s in the function as they have failed trait bounds.
+            let mut visitor = ReturnsVisitor::default();
+            visitor.visit_body(body);
+            let typeck_results = self.typeck_results.as_ref().unwrap();
+            for expr in &visitor.returns {
+                if let Some(returned_ty) = typeck_results.node_type_opt(expr.hir_id) {
+                    let ty = self.resolve_vars_if_possible(returned_ty);
+                    if ty.references_error() {
+                        // don't print out the [type error] here
+                        err.downgrade_to_delayed_bug();
+                    } else {
+                        err.span_label(expr.span, format!("this returned value is of type `{ty}`"));
+                    }
+                }
+            }
+        }
+    }
+
     pub(super) fn report_closure_arg_mismatch(
         &self,
         span: Span,

library/std/src/fs.rs

@@ -2425,7 +2425,7 @@ pub fn symlink_metadata<P: AsRef<Path>>(path: P) -> io::Result<Metadata> {
 /// # Platform-specific behavior
 ///
 /// This function currently corresponds to the `rename` function on Unix
-/// and the `SetFileInformationByHandle` function on Windows.
+/// and the `MoveFileExW` or `SetFileInformationByHandle` function on Windows.
 ///
 /// Because of this, the behavior when both `from` and `to` exist differs. On
 /// Unix, if `from` is a directory, `to` must also be an (empty) directory. If