Auto merge of rust-lang#98359 - JohnTitor:rollup-v30vyzr, r=JohnTitor

Rollup of 6 pull requests

Successful merges:

 - rust-lang#97867 (lub: don't bail out due to empty binders)
 - rust-lang#98099 (interpret: convert_tag_add_extra: allow tagger to raise errors)
 - rust-lang#98199 (Move some tests to more reasonable directories)
 - rust-lang#98334 (Add a full regression test for rust-lang#73727)
 - rust-lang#98336 (Remove the unused-`#[doc(hidden)]` logic from the `unused_attributes` lint)
 - rust-lang#98344 (This comment is out dated and misleading, the arm is about TAITs)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

compiler/rustc_const_eval/src/interpret/machine.rs

@@ -334,12 +334,14 @@ pub trait Machine<'mir, 'tcx>: Sized {
     /// allocation (because a copy had to be done to add tags or metadata), machine memory will
     /// cache the result. (This relies on `AllocMap::get_or` being able to add the
     /// owned allocation to the map even when the map is shared.)
+    ///
+    /// This must only fail if `alloc` contains relocations.
     fn init_allocation_extra<'b>(
         ecx: &InterpCx<'mir, 'tcx, Self>,
         id: AllocId,
         alloc: Cow<'b, Allocation>,
         kind: Option<MemoryKind<Self::MemoryKind>>,
-    ) -> Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>;
+    ) -> InterpResult<'tcx, Cow<'b, Allocation<Self::PointerTag, Self::AllocExtra>>>;
 
     /// Hook for performing extra checks on a memory read access.
     ///
@@ -485,9 +487,9 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) {
         _id: AllocId,
         alloc: Cow<'b, Allocation>,
         _kind: Option<MemoryKind<Self::MemoryKind>>,
-    ) -> Cow<'b, Allocation<Self::PointerTag>> {
+    ) -> InterpResult<$tcx, Cow<'b, Allocation<Self::PointerTag>>> {
         // We do not use a tag so we can just cheaply forward the allocation
-        alloc
+        Ok(alloc)
     }
 
     fn extern_static_base_pointer(

compiler/rustc_const_eval/src/interpret/memory.rs

@@ -199,7 +199,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         kind: MemoryKind<M::MemoryKind>,
     ) -> InterpResult<'tcx, Pointer<M::PointerTag>> {
         let alloc = Allocation::uninit(size, align, M::PANIC_ON_ALLOC_FAIL)?;
-        Ok(self.allocate_raw_ptr(alloc, kind))
+        // We can `unwrap` since `alloc` contains no pointers.
+        Ok(self.allocate_raw_ptr(alloc, kind).unwrap())
     }
 
     pub fn allocate_bytes_ptr(
@@ -210,23 +211,25 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         mutability: Mutability,
     ) -> Pointer<M::PointerTag> {
         let alloc = Allocation::from_bytes(bytes, align, mutability);
-        self.allocate_raw_ptr(alloc, kind)
+        // We can `unwrap` since `alloc` contains no pointers.
+        self.allocate_raw_ptr(alloc, kind).unwrap()
     }
 
+    /// This can fail only of `alloc` contains relocations.
     pub fn allocate_raw_ptr(
         &mut self,
         alloc: Allocation,
         kind: MemoryKind<M::MemoryKind>,
-    ) -> Pointer<M::PointerTag> {
+    ) -> InterpResult<'tcx, Pointer<M::PointerTag>> {
         let id = self.tcx.reserve_alloc_id();
         debug_assert_ne!(
             Some(kind),
             M::GLOBAL_KIND.map(MemoryKind::Machine),
             "dynamically allocating global memory"
         );
-        let alloc = M::init_allocation_extra(self, id, Cow::Owned(alloc), Some(kind));
+        let alloc = M::init_allocation_extra(self, id, Cow::Owned(alloc), Some(kind))?;
         self.memory.alloc_map.insert(id, (kind, alloc.into_owned()));
-        M::tag_alloc_base_pointer(self, Pointer::from(id))
+        Ok(M::tag_alloc_base_pointer(self, Pointer::from(id)))
     }
 
     pub fn reallocate_ptr(
@@ -510,13 +513,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         };
         M::before_access_global(*self.tcx, &self.machine, id, alloc, def_id, is_write)?;
         // We got tcx memory. Let the machine initialize its "extra" stuff.
-        let alloc = M::init_allocation_extra(
+        M::init_allocation_extra(
             self,
             id, // always use the ID we got as input, not the "hidden" one.
             Cow::Borrowed(alloc.inner()),
             M::GLOBAL_KIND.map(MemoryKind::Machine),
-        );
-        Ok(alloc)
+        )
     }
 
     /// Gives raw access to the `Allocation`, without bounds or alignment checks.

compiler/rustc_infer/src/infer/glb.rs

@@ -95,12 +95,20 @@ impl<'tcx> TypeRelation<'tcx> for Glb<'_, '_, 'tcx> {
         T: Relate<'tcx>,
     {
         debug!("binders(a={:?}, b={:?})", a, b);
-
-        // When higher-ranked types are involved, computing the LUB is
-        // very challenging, switch to invariance. This is obviously
-        // overly conservative but works ok in practice.
-        self.relate_with_variance(ty::Variance::Invariant, ty::VarianceDiagInfo::default(), a, b)?;
-        Ok(a)
+        if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
+            // When higher-ranked types are involved, computing the GLB is
+            // very challenging, switch to invariance. This is obviously
+            // overly conservative but works ok in practice.
+            self.relate_with_variance(
+                ty::Variance::Invariant,
+                ty::VarianceDiagInfo::default(),
+                a,
+                b,
+            )?;
+            Ok(a)
+        } else {
+            Ok(ty::Binder::dummy(self.relate(a.skip_binder(), b.skip_binder())?))
+        }
     }
 }
 

compiler/rustc_infer/src/infer/lub.rs

@@ -95,12 +95,20 @@ impl<'tcx> TypeRelation<'tcx> for Lub<'_, '_, 'tcx> {
         T: Relate<'tcx>,
     {
         debug!("binders(a={:?}, b={:?})", a, b);
-
-        // When higher-ranked types are involved, computing the LUB is
-        // very challenging, switch to invariance. This is obviously
-        // overly conservative but works ok in practice.
-        self.relate_with_variance(ty::Variance::Invariant, ty::VarianceDiagInfo::default(), a, b)?;
-        Ok(a)
+        if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
+            // When higher-ranked types are involved, computing the LUB is
+            // very challenging, switch to invariance. This is obviously
+            // overly conservative but works ok in practice.
+            self.relate_with_variance(
+                ty::Variance::Invariant,
+                ty::VarianceDiagInfo::default(),
+                a,
+                b,
+            )?;
+            Ok(a)
+        } else {
+            Ok(ty::Binder::dummy(self.relate(a.skip_binder(), b.skip_binder())?))
+        }
     }
 }
 

compiler/rustc_middle/src/mir/interpret/allocation.rs

@@ -244,12 +244,12 @@ impl<Tag> Allocation<Tag> {
 
 impl Allocation {
     /// Convert Tag and add Extra fields
-    pub fn convert_tag_add_extra<Tag, Extra>(
+    pub fn convert_tag_add_extra<Tag, Extra, Err>(
         self,
         cx: &impl HasDataLayout,
         extra: Extra,
-        mut tagger: impl FnMut(Pointer<AllocId>) -> Pointer<Tag>,
-    ) -> Allocation<Tag, Extra> {
+        mut tagger: impl FnMut(Pointer<AllocId>) -> Result<Pointer<Tag>, Err>,
+    ) -> Result<Allocation<Tag, Extra>, Err> {
         // Compute new pointer tags, which also adjusts the bytes.
         let mut bytes = self.bytes;
         let mut new_relocations = Vec::with_capacity(self.relocations.0.len());
@@ -260,19 +260,19 @@ impl Allocation {
             let ptr_bytes = &mut bytes[idx..idx + ptr_size];
             let bits = read_target_uint(endian, ptr_bytes).unwrap();
             let (ptr_tag, ptr_offset) =
-                tagger(Pointer::new(alloc_id, Size::from_bytes(bits))).into_parts();
+                tagger(Pointer::new(alloc_id, Size::from_bytes(bits)))?.into_parts();
             write_target_uint(endian, ptr_bytes, ptr_offset.bytes().into()).unwrap();
             new_relocations.push((offset, ptr_tag));
         }
         // Create allocation.
-        Allocation {
+        Ok(Allocation {
             bytes,
             relocations: Relocations::from_presorted(new_relocations),
             init_mask: self.init_mask,
             align: self.align,
             mutability: self.mutability,
             extra,
-        }
+        })
     }
 }
 

compiler/rustc_passes/src/check_attr.rs

@@ -4,8 +4,7 @@
 //! conflicts between multiple such attributes attached to the same
 //! item.
 
-use rustc_ast::tokenstream::DelimSpan;
-use rustc_ast::{ast, AttrStyle, Attribute, Lit, LitKind, MacArgs, MetaItemKind, NestedMetaItem};
+use rustc_ast::{ast, AttrStyle, Attribute, Lit, LitKind, MetaItemKind, NestedMetaItem};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{pluralize, struct_span_err, Applicability, MultiSpan};
 use rustc_expand::base::resolve_path;
@@ -899,68 +898,6 @@ impl CheckAttrVisitor<'_> {
         }
     }
 
-    /// Checks `#[doc(hidden)]` attributes. Returns `true` if valid.
-    fn check_doc_hidden(
-        &self,
-        attr: &Attribute,
-        meta_index: usize,
-        meta: &NestedMetaItem,
-        hir_id: HirId,
-        target: Target,
-    ) -> bool {
-        if let Target::AssocConst
-        | Target::AssocTy
-        | Target::Method(MethodKind::Trait { body: true }) = target
-        {
-            let parent_hir_id = self.tcx.hir().get_parent_item(hir_id);
-            let containing_item = self.tcx.hir().expect_item(parent_hir_id);
-
-            if let hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }) = containing_item.kind {
-                let meta_items = attr.meta_item_list().unwrap();
-
-                let (span, replacement_span) = if meta_items.len() == 1 {
-                    (attr.span, attr.span)
-                } else {
-                    let meta_span = meta.span();
-                    (
-                        meta_span,
-                        meta_span.until(match meta_items.get(meta_index + 1) {
-                            Some(next_item) => next_item.span(),
-                            None => match attr.get_normal_item().args {
-                                MacArgs::Delimited(DelimSpan { close, .. }, ..) => close,
-                                _ => unreachable!(),
-                            },
-                        }),
-                    )
-                };
-
-                // FIXME: #[doc(hidden)] was previously erroneously allowed on trait impl items,
-                // so for backward compatibility only emit a warning and do not mark it as invalid.
-                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, span, |lint| {
-                    lint.build("`#[doc(hidden)]` is ignored on trait impl items")
-                        .warn(
-                            "this was previously accepted by the compiler but is \
-                             being phased out; it will become a hard error in \
-                             a future release!",
-                        )
-                        .note(
-                            "whether the impl item is `doc(hidden)` or not \
-                             entirely depends on the corresponding trait item",
-                        )
-                        .span_suggestion(
-                            replacement_span,
-                            "remove this attribute",
-                            "",
-                            Applicability::MachineApplicable,
-                        )
-                        .emit();
-                });
-            }
-        }
-
-        true
-    }
-
     /// Checks that an attribute is *not* used at the crate level. Returns `true` if valid.
     fn check_attr_not_crate_level(
         &self,
@@ -1079,7 +1016,7 @@ impl CheckAttrVisitor<'_> {
         let mut is_valid = true;
 
         if let Some(mi) = attr.meta() && let Some(list) = mi.meta_item_list() {
-            for (meta_index, meta) in list.into_iter().enumerate() {
+            for meta in list {
                 if let Some(i_meta) = meta.meta_item() {
                     match i_meta.name_or_empty() {
                         sym::alias
@@ -1127,15 +1064,6 @@ impl CheckAttrVisitor<'_> {
                             is_valid = false;
                         }
 
-                        sym::hidden if !self.check_doc_hidden(attr,
-                            meta_index,
-                            meta,
-                            hir_id,
-                            target,
-                            ) => {
-                            is_valid = false;
-                        }
-
                         // no_default_passes: deprecated
                         // passes: deprecated
                         // plugins: removed, but rustdoc warns about it itself

compiler/rustc_resolve/src/late/lifetimes.rs

@@ -846,8 +846,6 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 //                                      the opaque_ty generics
                 let opaque_ty = self.tcx.hir().item(item_id);
                 let (generics, bounds) = match opaque_ty.kind {
-                    // Named opaque `impl Trait` types are reached via `TyKind::Path`.
-                    // This arm is for `impl Trait` in the types of statics, constants and locals.
                     hir::ItemKind::OpaqueTy(hir::OpaqueTy {
                         origin: hir::OpaqueTyOrigin::TyAlias,
                         ..
@@ -866,7 +864,6 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
 
                         return;
                     }
-                    // RPIT (return position impl trait)
                     hir::ItemKind::OpaqueTy(hir::OpaqueTy {
                         origin: hir::OpaqueTyOrigin::FnReturn(..) | hir::OpaqueTyOrigin::AsyncFn(..),
                         ref generics,