Rollup of 5 pull requests

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -1773,6 +1773,22 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                 {
                     span_mirbug!(self, constant, "bad static type {:?} ({:?})", constant, terr);
                 }
+            } else if let Const::Ty(_, ct) = constant.const_
+                && let ty::ConstKind::Param(p) = ct.kind()
+            {
+                let body_def_id = self.universal_regions.defining_ty.def_id();
+                let const_param = tcx.generics_of(body_def_id).const_param(p, tcx);
+                self.ascribe_user_type(
+                    constant.const_.ty(),
+                    ty::UserType::new(ty::UserTypeKind::TypeOf(
+                        const_param.def_id,
+                        UserArgs {
+                            args: self.universal_regions.defining_ty.args(),
+                            user_self_ty: None,
+                        },
+                    )),
+                    locations.span(self.body),
+                );
             }
 
             if let ty::FnDef(def_id, args) = *constant.const_.ty().kind() {

compiler/rustc_borrowck/src/universal_regions.rs

@@ -184,6 +184,20 @@ impl<'tcx> DefiningTy<'tcx> {
             | DefiningTy::GlobalAsm(def_id) => def_id,
         }
     }
+
+    /// Returns the args of the `DefiningTy`. These are equivalent to the identity
+    /// substs of the body, but replaced with region vids.
+    pub(crate) fn args(&self) -> ty::GenericArgsRef<'tcx> {
+        match *self {
+            DefiningTy::Closure(_, args)
+            | DefiningTy::Coroutine(_, args)
+            | DefiningTy::CoroutineClosure(_, args)
+            | DefiningTy::FnDef(_, args)
+            | DefiningTy::Const(_, args)
+            | DefiningTy::InlineConst(_, args) => args,
+            DefiningTy::GlobalAsm(_) => ty::List::empty(),
+        }
+    }
 }
 
 #[derive(Debug)]

compiler/rustc_codegen_ssa/src/back/command.rs

@@ -137,12 +137,42 @@ impl Command {
     /// Returns a `true` if we're pretty sure that this'll blow OS spawn limits,
     /// or `false` if we should attempt to spawn and see what the OS says.
     pub(crate) fn very_likely_to_exceed_some_spawn_limit(&self) -> bool {
-        // We mostly only care about Windows in this method, on Unix the limits
-        // can be gargantuan anyway so we're pretty unlikely to hit them
-        if cfg!(unix) {
+        #[cfg(not(any(windows, unix)))]
+        {
             return false;
         }
 
+        // On Unix the limits can be gargantuan anyway so we're pretty
+        // unlikely to hit them, but might still exceed it.
+        // We consult ARG_MAX here to get an estimate.
+        #[cfg(unix)]
+        {
+            let ptr_size = mem::size_of::<usize>();
+            // arg + \0 + pointer
+            let args_size = self.args.iter().fold(0usize, |acc, a| {
+                let arg = a.as_encoded_bytes().len();
+                let nul = 1;
+                acc.saturating_add(arg).saturating_add(nul).saturating_add(ptr_size)
+            });
+            // key + `=` + value + \0 + pointer
+            let envs_size = self.env.iter().fold(0usize, |acc, (k, v)| {
+                let k = k.as_encoded_bytes().len();
+                let eq = 1;
+                let v = v.as_encoded_bytes().len();
+                let nul = 1;
+                acc.saturating_add(k)
+                    .saturating_add(eq)
+                    .saturating_add(v)
+                    .saturating_add(nul)
+                    .saturating_add(ptr_size)
+            });
+            let arg_max = match unsafe { libc::sysconf(libc::_SC_ARG_MAX) } {
+                -1 => return false, // Go to OS anyway.
+                max => max as usize,
+            };
+            return args_size.saturating_add(envs_size) > arg_max;
+        }
+
         // Ok so on Windows to spawn a process is 32,768 characters in its
         // command line [1]. Unfortunately we don't actually have access to that
         // as it's calculated just before spawning. Instead we perform a
@@ -165,9 +195,14 @@ impl Command {
         //
         // [1]: https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-createprocessa
         // [2]: https://devblogs.microsoft.com/oldnewthing/?p=41553
-
-        let estimated_command_line_len = self.args.iter().map(|a| a.len()).sum::<usize>();
-        estimated_command_line_len > 1024 * 6
+        #[cfg(windows)]
+        {
+            let estimated_command_line_len = self
+                .args
+                .iter()
+                .fold(0usize, |acc, a| acc.saturating_add(a.as_encoded_bytes().len()));
+            return estimated_command_line_len > 1024 * 6;
+        }
     }
 }
 

compiler/rustc_data_structures/src/unord.rs

@@ -259,6 +259,12 @@ impl<V: Eq + Hash> UnordSet<V> {
         self.inner.is_empty()
     }
 
+    /// If the set has only one element, returns it, otherwise returns `None`.
+    #[inline]
+    pub fn get_only(&self) -> Option<&V> {
+        if self.inner.len() == 1 { self.inner.iter().next() } else { None }
+    }
+
     #[inline]
     pub fn insert(&mut self, v: V) -> bool {
         self.inner.insert(v)

compiler/rustc_middle/src/ty/mod.rs

@@ -33,6 +33,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
+use rustc_data_structures::unord::UnordMap;
 use rustc_errors::{Diag, ErrorGuaranteed};
 use rustc_hir::LangItem;
 use rustc_hir::def::{CtorKind, CtorOf, DefKind, DocLinkResMap, LifetimeRes, Res};
@@ -168,7 +169,7 @@ pub struct ResolverGlobalCtxt {
     /// Item with a given `LocalDefId` was defined during macro expansion with ID `ExpnId`.
     pub expn_that_defined: FxHashMap<LocalDefId, ExpnId>,
     pub effective_visibilities: EffectiveVisibilities,
-    pub extern_crate_map: FxHashMap<LocalDefId, CrateNum>,
+    pub extern_crate_map: UnordMap<LocalDefId, CrateNum>,
     pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
     pub module_children: LocalDefIdMap<Vec<ModChild>>,
     pub glob_map: FxHashMap<LocalDefId, FxHashSet<Symbol>>,

compiler/rustc_mir_transform/src/coroutine/by_move_body.rs

@@ -178,17 +178,18 @@ pub(crate) fn coroutine_by_move_body_def_id<'tcx>(
                 ),
             };
 
-            (
+            Some((
                 FieldIdx::from_usize(child_field_idx + num_args),
                 (
                     FieldIdx::from_usize(parent_field_idx + num_args),
                     parent_capture_ty,
                     peel_deref,
                     child_precise_captures,
                 ),
-            )
+            ))
         },
     )
+    .flatten()
     .collect();
 
     if coroutine_kind == ty::ClosureKind::FnOnce {
@@ -312,10 +313,46 @@ impl<'tcx> MutVisitor<'tcx> for MakeByMoveBody<'tcx> {
         self.super_place(place, context, location);
     }
 
+    fn visit_statement(&mut self, statement: &mut mir::Statement<'tcx>, location: mir::Location) {
+        // Remove fake borrows of closure captures if that capture has been
+        // replaced with a by-move version of that capture.
+        //
+        // For example, imagine we capture `Foo` in the parent and `&Foo`
+        // in the child. We will emit two fake borrows like:
+        //
+        // ```
+        //    _2 = &fake shallow (*(_1.0: &Foo));
+        //    _3 = &fake shallow (_1.0: &Foo);
+        // ```
+        //
+        // However, since this transform is responsible for replacing
+        // `_1.0: &Foo` with `_1.0: Foo`, that makes the second fake borrow
+        // obsolete, and we should replace it with a nop.
+        //
+        // As a side-note, we don't actually even care about fake borrows
+        // here at all since they're fully a MIR borrowck artifact, and we
+        // don't need to borrowck by-move MIR bodies. But it's best to preserve
+        // as much as we can between these two bodies :)
+        if let mir::StatementKind::Assign(box (_, rvalue)) = &statement.kind
+            && let mir::Rvalue::Ref(_, mir::BorrowKind::Fake(mir::FakeBorrowKind::Shallow), place) =
+                rvalue
+            && let mir::PlaceRef {
+                local: ty::CAPTURE_STRUCT_LOCAL,
+                projection: [mir::ProjectionElem::Field(idx, _)],
+            } = place.as_ref()
+            && let Some(&(_, _, true, _)) = self.field_remapping.get(&idx)
+        {
+            statement.kind = mir::StatementKind::Nop;
+        }
+
+        self.super_statement(statement, location);
+    }
+
     fn visit_local_decl(&mut self, local: mir::Local, local_decl: &mut mir::LocalDecl<'tcx>) {
         // Replace the type of the self arg.
         if local == ty::CAPTURE_STRUCT_LOCAL {
             local_decl.ty = self.by_move_coroutine_ty;
         }
+        self.super_local_decl(local, local_decl);
     }
 }

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -1115,6 +1115,7 @@ impl<'a, 'ra, 'tcx> BuildReducedGraphVisitor<'a, 'ra, 'tcx> {
                 }
             });
         } else {
+            #[allow(rustc::potential_query_instability)] // FIXME
             for ident in single_imports.iter().cloned() {
                 let result = self.r.maybe_resolve_ident_in_module(
                     ModuleOrUniformRoot::Module(module),

compiler/rustc_resolve/src/diagnostics.rs

@@ -6,6 +6,7 @@ use rustc_ast::{
 };
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::unord::UnordSet;
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, Diag, DiagCtxtHandle, ErrorGuaranteed, MultiSpan, SuggestionStyle,
@@ -1467,6 +1468,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             return;
         }
 
+        #[allow(rustc::potential_query_instability)] // FIXME
         let unused_macro = self.unused_macros.iter().find_map(|(def_id, (_, unused_ident))| {
             if unused_ident.name == ident.name { Some((def_id, unused_ident)) } else { None }
         });
@@ -2863,18 +2865,11 @@ fn show_candidates(
             } else {
                 // Get the unique item kinds and if there's only one, we use the right kind name
                 // instead of the more generic "items".
-                let mut kinds = accessible_path_strings
+                let kinds = accessible_path_strings
                     .iter()
                     .map(|(_, descr, _, _, _)| *descr)
-                    .collect::<FxHashSet<&str>>()
-                    .into_iter();
-                let kind = if let Some(kind) = kinds.next()
-                    && let None = kinds.next()
-                {
-                    kind
-                } else {
-                    "item"
-                };
+                    .collect::<UnordSet<&str>>();
+                let kind = if let Some(kind) = kinds.get_only() { kind } else { "item" };
                 let s = if kind.ends_with('s') { "es" } else { "s" };
 
                 ("one of these", kind, s, String::new(), "")

compiler/rustc_resolve/src/ident.rs

@@ -946,6 +946,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
 
         // Check if one of single imports can still define the name,
         // if it can then our result is not determined and can be invalidated.
+        #[allow(rustc::potential_query_instability)] // FIXME
         for single_import in &resolution.single_imports {
             if ignore_import == Some(*single_import) {
                 // This branch handles a cycle in single imports.

compiler/rustc_resolve/src/late.rs

@@ -18,6 +18,7 @@ use rustc_ast::visit::{
 };
 use rustc_ast::*;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
+use rustc_data_structures::unord::{UnordMap, UnordSet};
 use rustc_errors::codes::*;
 use rustc_errors::{
     Applicability, DiagArgValue, ErrorGuaranteed, IntoDiagArg, StashKey, Suggestions,
@@ -47,8 +48,6 @@ mod diagnostics;
 
 type Res = def::Res<NodeId>;
 
-type IdentMap<T> = FxHashMap<Ident, T>;
-
 use diagnostics::{ElisionFnParameter, LifetimeElisionCandidate, MissingLifetime};
 
 #[derive(Copy, Clone, Debug)]
@@ -273,8 +272,8 @@ impl RibKind<'_> {
 /// resolving, the name is looked up from inside out.
 #[derive(Debug)]
 pub(crate) struct Rib<'ra, R = Res> {
-    pub bindings: IdentMap<R>,
-    pub patterns_with_skipped_bindings: FxHashMap<DefId, Vec<(Span, Result<(), ErrorGuaranteed>)>>,
+    pub bindings: FxHashMap<Ident, R>,
+    pub patterns_with_skipped_bindings: UnordMap<DefId, Vec<(Span, Result<(), ErrorGuaranteed>)>>,
     pub kind: RibKind<'ra>,
 }
 
@@ -1605,12 +1604,12 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         // for better diagnostics.
         let mut forward_ty_ban_rib_const_param_ty = Rib {
             bindings: forward_ty_ban_rib.bindings.clone(),
-            patterns_with_skipped_bindings: FxHashMap::default(),
+            patterns_with_skipped_bindings: Default::default(),
             kind: RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::ConstParamTy),
         };
         let mut forward_const_ban_rib_const_param_ty = Rib {
             bindings: forward_const_ban_rib.bindings.clone(),
-            patterns_with_skipped_bindings: FxHashMap::default(),
+            patterns_with_skipped_bindings: Default::default(),
             kind: RibKind::ForwardGenericParamBan(ForwardGenericParamBanReason::ConstParamTy),
         };
         // We'll ban these with a `ConstParamTy` rib, so just clear these ribs for better
@@ -2334,7 +2333,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
             let local_candidates = self.lifetime_elision_candidates.take();
 
             if let Some(candidates) = local_candidates {
-                let distinct: FxHashSet<_> = candidates.iter().map(|(res, _)| *res).collect();
+                let distinct: UnordSet<_> = candidates.iter().map(|(res, _)| *res).collect();
                 let lifetime_count = distinct.len();
                 if lifetime_count != 0 {
                     parameter_info.push(ElisionFnParameter {
@@ -2358,14 +2357,13 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         }
                     }));
                 }
-                let mut distinct_iter = distinct.into_iter();
-                if let Some(res) = distinct_iter.next() {
+                if !distinct.is_empty() {
                     match elision_lifetime {
                         // We are the first parameter to bind lifetimes.
                         Elision::None => {
-                            if distinct_iter.next().is_none() {
+                            if let Some(res) = distinct.get_only() {
                                 // We have a single lifetime => success.
-                                elision_lifetime = Elision::Param(res)
+                                elision_lifetime = Elision::Param(*res)
                             } else {
                                 // We have multiple lifetimes => error.
                                 elision_lifetime = Elision::Err;
@@ -2890,6 +2888,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
                         break;
                     }
 
+                    #[allow(rustc::potential_query_instability)] // FIXME
                     seen_bindings
                         .extend(parent_rib.bindings.keys().map(|ident| (*ident, ident.span)));
                 }
@@ -4004,7 +4003,7 @@ impl<'a, 'ast, 'ra: 'ast, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
         }
     }
 
-    fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut IdentMap<Res> {
+    fn innermost_rib_bindings(&mut self, ns: Namespace) -> &mut FxHashMap<Ident, Res> {
         &mut self.ribs[ns].last_mut().unwrap().bindings
     }
 
@@ -5202,6 +5201,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         let mut late_resolution_visitor = LateResolutionVisitor::new(self);
         late_resolution_visitor.resolve_doc_links(&krate.attrs, MaybeExported::Ok(CRATE_NODE_ID));
         visit::walk_crate(&mut late_resolution_visitor, krate);
+        #[allow(rustc::potential_query_instability)] // FIXME
         for (id, span) in late_resolution_visitor.diag_metadata.unused_labels.iter() {
             self.lint_buffer.buffer_lint(
                 lint::builtin::UNUSED_LABELS,