Auto merge of #61105 - Centril:rollup-t9lemjf, r=Centril

Rollup of 6 pull requests

Successful merges:

 - #59545 (Use arenas to avoid Lrc in queries #2)
 - #61054 (Suggest dereferencing on assignment to mutable borrow)
 - #61056 (tweak discriminant on non-nullary enum diagnostic)
 - #61082 (fix dangling reference in Vec::append)
 - #61086 (Box::into_unique: do the reborrow-to-raw *after* destroying the Box)
 - #61098 (Fix overflowing literal lint in loops)

Failed merges:

r? @ghost

Cargo.lock

@@ -2877,6 +2877,7 @@ dependencies = [
  "rustc_errors 0.0.0",
  "rustc_target 0.0.0",
  "serialize 0.0.0",
+ "smallvec 0.6.7 (registry+https://github.com/rust-lang/crates.io-index)",
  "stable_deref_trait 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "syntax 0.0.0",
  "syntax_ext 0.0.0",

src/liballoc/boxed.rs

@@ -253,15 +253,16 @@ impl<T: ?Sized> Box<T> {
     #[unstable(feature = "ptr_internals", issue = "0", reason = "use into_raw_non_null instead")]
     #[inline]
     #[doc(hidden)]
-    pub fn into_unique(mut b: Box<T>) -> Unique<T> {
+    pub fn into_unique(b: Box<T>) -> Unique<T> {
+        let mut unique = b.0;
+        mem::forget(b);
         // Box is kind-of a library type, but recognized as a "unique pointer" by
         // Stacked Borrows.  This function here corresponds to "reborrowing to
         // a raw pointer", but there is no actual reborrow here -- so
         // without some care, the pointer we are returning here still carries
-        // the `Uniq` tag.  We round-trip through a mutable reference to avoid that.
-        let unique = unsafe { b.0.as_mut() as *mut T };
-        mem::forget(b);
-        unsafe { Unique::new_unchecked(unique) }
+        // the tag of `b`, with `Unique` permission.
+        // We round-trip through a mutable reference to avoid that.
+        unsafe { Unique::new_unchecked(unique.as_mut() as *mut T) }
     }
 
     /// Consumes and leaks the `Box`, returning a mutable reference,

src/liballoc/tests/vec.rs

@@ -1,5 +1,3 @@
-#![cfg(not(miri))]
-
 use std::borrow::Cow;
 use std::mem::size_of;
 use std::{usize, isize};
@@ -763,6 +761,7 @@ fn from_into_inner() {
     it.next().unwrap();
     let vec = it.collect::<Vec<_>>();
     assert_eq!(vec, [2, 3]);
+    #[cfg(not(miri))] // Miri does not support comparing dangling pointers
     assert!(ptr != vec.as_ptr());
 }
 
@@ -971,6 +970,7 @@ fn test_reserve_exact() {
 }
 
 #[test]
+#[cfg(not(miri))] // Miri does not support signalling OOM
 fn test_try_reserve() {
 
     // These are the interesting cases:
@@ -1073,6 +1073,7 @@ fn test_try_reserve() {
 }
 
 #[test]
+#[cfg(not(miri))] // Miri does not support signalling OOM
 fn test_try_reserve_exact() {
 
     // This is exactly the same as test_try_reserve with the method changed.

src/liballoc/vec.rs

@@ -1094,7 +1094,7 @@ impl<T> Vec<T> {
         let count = (*other).len();
         self.reserve(count);
         let len = self.len();
-        ptr::copy_nonoverlapping(other as *const T, self.get_unchecked_mut(len), count);
+        ptr::copy_nonoverlapping(other as *const T, self.as_mut_ptr().add(len), count);
         self.len += count;
     }
 

src/libarena/lib.rs

@@ -486,9 +486,31 @@ impl DroplessArena {
         }
     }
 
+    #[inline]
+    unsafe fn write_from_iter<T, I: Iterator<Item = T>>(
+        &self,
+        mut iter: I,
+        len: usize,
+        mem: *mut T,
+    ) -> &mut [T] {
+        let mut i = 0;
+        // Use a manual loop since LLVM manages to optimize it better for
+        // slice iterators
+        loop {
+            let value = iter.next();
+            if i >= len || value.is_none() {
+                // We only return as many items as the iterator gave us, even
+                // though it was supposed to give us `len`
+                return slice::from_raw_parts_mut(mem, i);
+            }
+            ptr::write(mem.offset(i as isize), value.unwrap());
+            i += 1;
+        }
+    }
+
     #[inline]
     pub fn alloc_from_iter<T, I: IntoIterator<Item = T>>(&self, iter: I) -> &mut [T] {
-        let mut iter = iter.into_iter();
+        let iter = iter.into_iter();
         assert!(mem::size_of::<T>() != 0);
         assert!(!mem::needs_drop::<T>());
 
@@ -505,10 +527,7 @@ impl DroplessArena {
                 let size = len.checked_mul(mem::size_of::<T>()).unwrap();
                 let mem = self.alloc_raw(size, mem::align_of::<T>()) as *mut _ as *mut T;
                 unsafe {
-                    for i in 0..len {
-                        ptr::write(mem.offset(i as isize), iter.next().unwrap())
-                    }
-                    slice::from_raw_parts_mut(mem, len)
+                    self.write_from_iter(iter, len, mem)
                 }
             }
             (_, _) => {

src/librustc/arena.rs

@@ -6,6 +6,15 @@ use std::cell::RefCell;
 use std::marker::PhantomData;
 use smallvec::SmallVec;
 
+/// This declares a list of types which can be allocated by `Arena`.
+///
+/// The `few` modifier will cause allocation to use the shared arena and recording the destructor.
+/// This is faster and more memory efficient if there's only a few allocations of the type.
+/// Leaving `few` out will cause the type to get its own dedicated `TypedArena` which is
+/// faster and more memory efficient if there is lots of allocations.
+///
+/// Specifying the `decode` modifier will add decode impls for &T and &[T] where T is the type
+/// listed. These impls will appear in the implement_ty_decoder! macro.
 #[macro_export]
 macro_rules! arena_types {
     ($macro:path, $args:tt, $tcx:lifetime) => (
@@ -14,7 +23,7 @@ macro_rules! arena_types {
                 rustc::hir::def_id::DefId,
                 rustc::ty::subst::SubstsRef<$tcx>
             )>,
-            [few] mir_keys: rustc::util::nodemap::DefIdSet,
+            [few, decode] mir_keys: rustc::util::nodemap::DefIdSet,
             [decode] specialization_graph: rustc::traits::specialization_graph::Graph,
             [] region_scope_tree: rustc::middle::region::ScopeTree,
             [] item_local_set: rustc::util::nodemap::ItemLocalSet,
@@ -58,6 +67,40 @@ macro_rules! arena_types {
                 rustc::infer::canonical::Canonical<'tcx,
                     rustc::infer::canonical::QueryResponse<'tcx, rustc::ty::Ty<'tcx>>
                 >,
+            [few] crate_inherent_impls: rustc::ty::CrateInherentImpls,
+            [decode] borrowck: rustc::middle::borrowck::BorrowCheckResult,
+            [few] upstream_monomorphizations:
+                rustc::util::nodemap::DefIdMap<
+                    rustc_data_structures::fx::FxHashMap<
+                        rustc::ty::subst::SubstsRef<'tcx>,
+                        rustc::hir::def_id::CrateNum
+                    >
+                >,
+            [few] resolve_lifetimes: rustc::middle::resolve_lifetime::ResolveLifetimes,
+            [decode] generic_predicates: rustc::ty::GenericPredicates<'tcx>,
+            [few] lint_levels: rustc::lint::LintLevelMap,
+            [few] stability_index: rustc::middle::stability::Index<'tcx>,
+            [few] features: syntax::feature_gate::Features,
+            [few] all_traits: Vec<rustc::hir::def_id::DefId>,
+            [few] privacy_access_levels: rustc::middle::privacy::AccessLevels,
+            [few] target_features_whitelist: rustc_data_structures::fx::FxHashMap<
+                String,
+                Option<syntax::symbol::Symbol>
+            >,
+            [few] wasm_import_module_map: rustc_data_structures::fx::FxHashMap<
+                rustc::hir::def_id::DefId,
+                String
+            >,
+            [few] get_lib_features: rustc::middle::lib_features::LibFeatures,
+            [few] defined_lib_features: rustc::middle::lang_items::LanguageItems,
+            [few] visible_parent_map: rustc::util::nodemap::DefIdMap<rustc::hir::def_id::DefId>,
+            [few] foreign_module: rustc::middle::cstore::ForeignModule,
+            [few] foreign_modules: Vec<rustc::middle::cstore::ForeignModule>,
+            [few] reachable_non_generics: rustc::util::nodemap::DefIdMap<
+                rustc::middle::exported_symbols::SymbolExportLevel
+            >,
+            [few] crate_variances: rustc::ty::CrateVariancesMap<'tcx>,
+            [few] inferred_outlives_crate: rustc::ty::CratePredicatesMap<'tcx>,
         ], $tcx);
     )
 }
@@ -119,7 +162,7 @@ pub trait ArenaAllocatable {}
 
 impl<T: Copy> ArenaAllocatable for T {}
 
-pub unsafe trait ArenaField<'tcx>: Sized {
+unsafe trait ArenaField<'tcx>: Sized {
     /// Returns a specific arena to allocate from.
     /// If None is returned, the DropArena will be used.
     fn arena<'a>(arena: &'a Arena<'tcx>) -> Option<&'a TypedArena<Self>>;

src/librustc/lint/mod.rs

@@ -21,7 +21,7 @@
 pub use self::Level::*;
 pub use self::LintSource::*;
 
-use rustc_data_structures::sync::{self, Lrc};
+use rustc_data_structures::sync;
 
 use crate::hir::def_id::{CrateNum, LOCAL_CRATE};
 use crate::hir::intravisit;
@@ -35,7 +35,7 @@ use crate::util::nodemap::NodeMap;
 use errors::{DiagnosticBuilder, DiagnosticId};
 use std::{hash, ptr};
 use syntax::ast;
-use syntax::source_map::{MultiSpan, ExpnFormat};
+use syntax::source_map::{MultiSpan, ExpnFormat, CompilerDesugaringKind};
 use syntax::early_buffered_lints::BufferedEarlyLintId;
 use syntax::edition::Edition;
 use syntax::symbol::{Symbol, sym};
@@ -767,7 +767,7 @@ pub fn maybe_lint_level_root(tcx: TyCtxt<'_, '_, '_>, id: hir::HirId) -> bool {
 }
 
 fn lint_levels<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, cnum: CrateNum)
-    -> Lrc<LintLevelMap>
+    -> &'tcx LintLevelMap
 {
     assert_eq!(cnum, LOCAL_CRATE);
     let mut builder = LintLevelMapBuilder {
@@ -784,7 +784,7 @@ fn lint_levels<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, cnum: CrateNum)
     intravisit::walk_crate(&mut builder, krate);
     builder.levels.pop(push);
 
-    Lrc::new(builder.levels.build_map())
+    tcx.arena.alloc(builder.levels.build_map())
 }
 
 struct LintLevelMapBuilder<'a, 'tcx: 'a> {
@@ -887,21 +887,22 @@ pub fn in_external_macro(sess: &Session, span: Span) -> bool {
     };
 
     match info.format {
-        ExpnFormat::MacroAttribute(..) => return true, // definitely a plugin
-        ExpnFormat::CompilerDesugaring(_) => return true, // well, it's "external"
-        ExpnFormat::MacroBang(..) => {} // check below
-    }
-
-    let def_site = match info.def_site {
-        Some(span) => span,
-        // no span for the def_site means it's an external macro
-        None => return true,
-    };
+        ExpnFormat::MacroAttribute(..) => true, // definitely a plugin
+        ExpnFormat::CompilerDesugaring(CompilerDesugaringKind::ForLoop) => false,
+        ExpnFormat::CompilerDesugaring(_) => true, // well, it's "external"
+        ExpnFormat::MacroBang(..) => {
+            let def_site = match info.def_site {
+                Some(span) => span,
+                // no span for the def_site means it's an external macro
+                None => return true,
+            };
 
-    match sess.source_map().span_to_snippet(def_site) {
-        Ok(code) => !code.starts_with("macro_rules"),
-        // no snippet = external macro or compiler-builtin expansion
-        Err(_) => true,
+            match sess.source_map().span_to_snippet(def_site) {
+                Ok(code) => !code.starts_with("macro_rules"),
+                // no snippet = external macro or compiler-builtin expansion
+                Err(_) => true,
+            }
+        }
     }
 }
 

src/librustc/middle/cstore.rs

@@ -256,8 +256,8 @@ pub fn used_crates(tcx: TyCtxt<'_, '_, '_>, prefer: LinkagePreference)
             Some((cnum, path))
         })
         .collect::<Vec<_>>();
-    let mut ordering = tcx.postorder_cnums(LOCAL_CRATE);
-    Lrc::make_mut(&mut ordering).reverse();
+    let mut ordering = tcx.postorder_cnums(LOCAL_CRATE).to_owned();
+    ordering.reverse();
     libs.sort_by_cached_key(|&(a, _)| {
         ordering.iter().position(|x| *x == a)
     });

src/librustc/middle/resolve_lifetime.rs

@@ -15,7 +15,6 @@ use crate::rustc::lint;
 use crate::session::Session;
 use crate::util::nodemap::{DefIdMap, FxHashMap, FxHashSet, HirIdMap, HirIdSet};
 use errors::{Applicability, DiagnosticBuilder};
-use rustc_data_structures::sync::Lrc;
 use rustc_macros::HashStable;
 use std::borrow::Cow;
 use std::cell::Cell;
@@ -211,10 +210,10 @@ struct NamedRegionMap {
 /// See [`NamedRegionMap`].
 #[derive(Default)]
 pub struct ResolveLifetimes {
-    defs: FxHashMap<LocalDefId, Lrc<FxHashMap<ItemLocalId, Region>>>,
-    late_bound: FxHashMap<LocalDefId, Lrc<FxHashSet<ItemLocalId>>>,
+    defs: FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Region>>,
+    late_bound: FxHashMap<LocalDefId, FxHashSet<ItemLocalId>>,
     object_lifetime_defaults:
-        FxHashMap<LocalDefId, Lrc<FxHashMap<ItemLocalId, Lrc<Vec<ObjectLifetimeDefault>>>>>,
+        FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Vec<ObjectLifetimeDefault>>>,
 }
 
 impl_stable_hash_for!(struct crate::middle::resolve_lifetime::ResolveLifetimes {
@@ -347,23 +346,21 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
 
         named_region_map: |tcx, id| {
             let id = LocalDefId::from_def_id(DefId::local(id)); // (*)
-            tcx.resolve_lifetimes(LOCAL_CRATE).defs.get(&id).cloned()
+            tcx.resolve_lifetimes(LOCAL_CRATE).defs.get(&id)
         },
 
         is_late_bound_map: |tcx, id| {
             let id = LocalDefId::from_def_id(DefId::local(id)); // (*)
             tcx.resolve_lifetimes(LOCAL_CRATE)
                 .late_bound
                 .get(&id)
-                .cloned()
         },
 
         object_lifetime_defaults_map: |tcx, id| {
             let id = LocalDefId::from_def_id(DefId::local(id)); // (*)
             tcx.resolve_lifetimes(LOCAL_CRATE)
                 .object_lifetime_defaults
                 .get(&id)
-                .cloned()
         },
 
         ..*providers
@@ -379,7 +376,7 @@ pub fn provide(providers: &mut ty::query::Providers<'_>) {
 fn resolve_lifetimes<'tcx>(
     tcx: TyCtxt<'_, 'tcx, 'tcx>,
     for_krate: CrateNum,
-) -> Lrc<ResolveLifetimes> {
+) -> &'tcx ResolveLifetimes {
     assert_eq!(for_krate, LOCAL_CRATE);
 
     let named_region_map = krate(tcx);
@@ -388,24 +385,22 @@ fn resolve_lifetimes<'tcx>(
 
     for (hir_id, v) in named_region_map.defs {
         let map = rl.defs.entry(hir_id.owner_local_def_id()).or_default();
-        Lrc::get_mut(map).unwrap().insert(hir_id.local_id, v);
+        map.insert(hir_id.local_id, v);
     }
     for hir_id in named_region_map.late_bound {
         let map = rl.late_bound
             .entry(hir_id.owner_local_def_id())
             .or_default();
-        Lrc::get_mut(map).unwrap().insert(hir_id.local_id);
+        map.insert(hir_id.local_id);
     }
     for (hir_id, v) in named_region_map.object_lifetime_defaults {
         let map = rl.object_lifetime_defaults
             .entry(hir_id.owner_local_def_id())
             .or_default();
-        Lrc::get_mut(map)
-            .unwrap()
-            .insert(hir_id.local_id, Lrc::new(v));
+        map.insert(hir_id.local_id, v);
     }
 
-    Lrc::new(rl)
+    tcx.arena.alloc(rl)
 }
 
 fn krate<'tcx>(tcx: TyCtxt<'_, 'tcx, 'tcx>) -> NamedRegionMap {

src/librustc/middle/stability.rs

@@ -883,7 +883,7 @@ pub fn check_unused_or_stable_features<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
     remaining_lib_features.remove(&Symbol::intern("test"));
 
     let check_features =
-        |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &Vec<_>| {
+        |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| {
             for &(feature, since) in defined_features {
                 if let Some(since) = since {
                     if let Some(span) = remaining_lib_features.get(&feature) {
@@ -908,7 +908,7 @@ pub fn check_unused_or_stable_features<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>) {
             if remaining_lib_features.is_empty() {
                 break;
             }
-            check_features(&mut remaining_lib_features, &tcx.defined_lib_features(cnum));
+            check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum));
         }
     }