Rollup of 7 pull requests

src/liballoc/str.rs

@@ -28,7 +28,7 @@
 // It's cleaner to just turn off the unused_imports warning than to fix them.
 #![allow(unused_imports)]
 
-use core::borrow::Borrow;
+use core::borrow::{Borrow, BorrowMut};
 use core::str::pattern::{Pattern, Searcher, ReverseSearcher, DoubleEndedSearcher};
 use core::mem;
 use core::ptr;
@@ -190,6 +190,14 @@ impl Borrow<str> for String {
     }
 }
 
+#[stable(feature = "string_borrow_mut", since = "1.36.0")]
+impl BorrowMut<str> for String {
+    #[inline]
+    fn borrow_mut(&mut self) -> &mut str {
+        &mut self[..]
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl ToOwned for str {
     type Owned = String;

src/libprofiler_builtins/build.rs

@@ -44,6 +44,19 @@ fn main() {
         cfg.define("COMPILER_RT_HAS_UNAME", Some("1"));
     }
 
+    // Assume that the Unixes we are building this for have fnctl() available
+    if env::var_os("CARGO_CFG_UNIX").is_some() {
+        cfg.define("COMPILER_RT_HAS_FCNTL_LCK", Some("1"));
+    }
+
+    // This should be a pretty good heuristic for when to set
+    // COMPILER_RT_HAS_ATOMICS
+    if env::var_os("CARGO_CFG_TARGET_HAS_ATOMIC").map(|features| {
+        features.to_string_lossy().to_lower_case().contains("cas")
+    }).unwrap_or(false) {
+        cfg.define("COMPILER_RT_HAS_ATOMICS", Some("1"));
+    }
+
     // The source for `compiler-rt` comes from the `compiler-builtins` crate, so
     // load our env var set by cargo to find the source code.
     let root = env::var_os("DEP_COMPILER_RT_COMPILER_RT").unwrap();

src/librustc/arena.rs

@@ -144,6 +144,14 @@ impl<'tcx> Arena<'tcx> {
         }
     }
 
+    #[inline]
+    pub fn alloc_slice<T: Copy>(&self, value: &[T]) -> &mut [T] {
+        if value.len() == 0 {
+            return &mut []
+        }
+        self.dropless.alloc_slice(value)
+    }
+
     pub fn alloc_from_iter<
         T: ArenaAllocatable,
         I: IntoIterator<Item = T>

src/librustc/cfg/construct.rs

@@ -369,7 +369,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
             hir::ExprKind::AddrOf(_, ref e) |
             hir::ExprKind::Cast(ref e, _) |
             hir::ExprKind::Type(ref e, _) |
-            hir::ExprKind::Use(ref e) |
+            hir::ExprKind::DropTemps(ref e) |
             hir::ExprKind::Unary(_, ref e) |
             hir::ExprKind::Field(ref e, _) |
             hir::ExprKind::Yield(ref e) |

src/librustc/hir/intravisit.rs

@@ -1029,7 +1029,7 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
             visitor.visit_expr(subexpression);
             visitor.visit_ty(typ)
         }
-        ExprKind::Use(ref subexpression) => {
+        ExprKind::DropTemps(ref subexpression) => {
             visitor.visit_expr(subexpression);
         }
         ExprKind::If(ref head_expression, ref if_block, ref optional_else) => {

src/librustc/hir/lowering.rs

@@ -4671,7 +4671,7 @@ impl<'a> LoweringContext<'a> {
                 // The construct was introduced in #21984.
                 // FIXME(60253): Is this still necessary?
                 // Also, add the attributes to the outer returned expr node.
-                return self.expr_use(head_sp, match_expr, e.attrs.clone())
+                return self.expr_drop_temps(head_sp, match_expr, e.attrs.clone())
             }
 
             // Desugar `ExprKind::Try`
@@ -5030,15 +5030,19 @@ impl<'a> LoweringContext<'a> {
         )
     }
 
-    /// Wrap the given `expr` in `hir::ExprKind::Use`.
+    /// Wrap the given `expr` in a terminating scope using `hir::ExprKind::DropTemps`.
     ///
-    /// In terms of drop order, it has the same effect as
-    /// wrapping `expr` in `{ let _t = $expr; _t }` but
-    /// should provide better compile-time performance.
+    /// In terms of drop order, it has the same effect as wrapping `expr` in
+    /// `{ let _t = $expr; _t }` but should provide better compile-time performance.
     ///
     /// The drop order can be important in e.g. `if expr { .. }`.
-    fn expr_use(&mut self, span: Span, expr: P<hir::Expr>, attrs: ThinVec<Attribute>) -> hir::Expr {
-        self.expr(span, hir::ExprKind::Use(expr), attrs)
+    fn expr_drop_temps(
+        &mut self,
+        span: Span,
+        expr: P<hir::Expr>,
+        attrs: ThinVec<Attribute>
+    ) -> hir::Expr {
+        self.expr(span, hir::ExprKind::DropTemps(expr), attrs)
     }
 
     fn expr_match(

src/librustc/hir/mod.rs

@@ -1366,7 +1366,7 @@ impl Expr {
             ExprKind::Unary(..) => ExprPrecedence::Unary,
             ExprKind::Lit(_) => ExprPrecedence::Lit,
             ExprKind::Type(..) | ExprKind::Cast(..) => ExprPrecedence::Cast,
-            ExprKind::Use(ref expr, ..) => expr.precedence(),
+            ExprKind::DropTemps(ref expr, ..) => expr.precedence(),
             ExprKind::If(..) => ExprPrecedence::If,
             ExprKind::While(..) => ExprPrecedence::While,
             ExprKind::Loop(..) => ExprPrecedence::Loop,
@@ -1438,7 +1438,7 @@ impl Expr {
             ExprKind::Binary(..) |
             ExprKind::Yield(..) |
             ExprKind::Cast(..) |
-            ExprKind::Use(..) |
+            ExprKind::DropTemps(..) |
             ExprKind::Err => {
                 false
             }
@@ -1488,10 +1488,12 @@ pub enum ExprKind {
     Cast(P<Expr>, P<Ty>),
     /// A type reference (e.g., `Foo`).
     Type(P<Expr>, P<Ty>),
-    /// Semantically equivalent to `{ let _t = expr; _t }`.
-    /// Maps directly to `hair::ExprKind::Use`.
-    /// Only exists to tweak the drop order in HIR.
-    Use(P<Expr>),
+    /// Wraps the expression in a terminating scope.
+    /// This makes it semantically equivalent to `{ let _t = expr; _t }`.
+    ///
+    /// This construct only exists to tweak the drop order in HIR lowering.
+    /// An example of that is the desugaring of `for` loops.
+    DropTemps(P<Expr>),
     /// An `if` block, with an optional else block.
     ///
     /// I.e., `if <expr> { <expr> } else { <expr> }`.

src/librustc/hir/print.rs

@@ -1388,7 +1388,7 @@ impl<'a> State<'a> {
                 self.word_space(":")?;
                 self.print_type(&ty)?;
             }
-            hir::ExprKind::Use(ref init) => {
+            hir::ExprKind::DropTemps(ref init) => {
                 // Print `{`:
                 self.cbox(indent_unit)?;
                 self.ibox(0)?;

src/librustc/middle/expr_use_visitor.rs

@@ -520,7 +520,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                 self.consume_expr(&base);
             }
 
-            hir::ExprKind::Use(ref expr) => {
+            hir::ExprKind::DropTemps(ref expr) => {
                 self.consume_expr(&expr);
             }
 

src/librustc/middle/liveness.rs

@@ -521,7 +521,7 @@ fn visit_expr<'a, 'tcx>(ir: &mut IrMaps<'a, 'tcx>, expr: &'tcx Expr) {
       hir::ExprKind::Binary(..) |
       hir::ExprKind::AddrOf(..) |
       hir::ExprKind::Cast(..) |
-      hir::ExprKind::Use(..) |
+      hir::ExprKind::DropTemps(..) |
       hir::ExprKind::Unary(..) |
       hir::ExprKind::Break(..) |
       hir::ExprKind::Continue(_) |
@@ -1222,7 +1222,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
             hir::ExprKind::AddrOf(_, ref e) |
             hir::ExprKind::Cast(ref e, _) |
             hir::ExprKind::Type(ref e, _) |
-            hir::ExprKind::Use(ref e) |
+            hir::ExprKind::DropTemps(ref e) |
             hir::ExprKind::Unary(_, ref e) |
             hir::ExprKind::Yield(ref e) |
             hir::ExprKind::Repeat(ref e, _) => {
@@ -1526,7 +1526,7 @@ fn check_expr<'a, 'tcx>(this: &mut Liveness<'a, 'tcx>, expr: &'tcx Expr) {
         hir::ExprKind::Match(..) | hir::ExprKind::While(..) | hir::ExprKind::Loop(..) |
         hir::ExprKind::Index(..) | hir::ExprKind::Field(..) |
         hir::ExprKind::Array(..) | hir::ExprKind::Tup(..) | hir::ExprKind::Binary(..) |
-        hir::ExprKind::Cast(..) | hir::ExprKind::Use(..) | hir::ExprKind::Unary(..) |
+        hir::ExprKind::Cast(..) | hir::ExprKind::DropTemps(..) | hir::ExprKind::Unary(..) |
         hir::ExprKind::Ret(..) | hir::ExprKind::Break(..) | hir::ExprKind::Continue(..) |
         hir::ExprKind::Lit(_) | hir::ExprKind::Block(..) | hir::ExprKind::AddrOf(..) |
         hir::ExprKind::Struct(..) | hir::ExprKind::Repeat(..) |

src/librustc/middle/mem_categorization.rs

@@ -677,7 +677,7 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             hir::ExprKind::Assign(..) | hir::ExprKind::AssignOp(..) |
             hir::ExprKind::Closure(..) | hir::ExprKind::Ret(..) |
             hir::ExprKind::Unary(..) | hir::ExprKind::Yield(..) |
-            hir::ExprKind::MethodCall(..) | hir::ExprKind::Cast(..) | hir::ExprKind::Use(..) |
+            hir::ExprKind::MethodCall(..) | hir::ExprKind::Cast(..) | hir::ExprKind::DropTemps(..) |
             hir::ExprKind::Array(..) | hir::ExprKind::Tup(..) | hir::ExprKind::If(..) |
             hir::ExprKind::Binary(..) | hir::ExprKind::While(..) |
             hir::ExprKind::Block(..) | hir::ExprKind::Loop(..) | hir::ExprKind::Match(..) |

src/librustc/middle/region.rs

@@ -908,8 +908,8 @@ fn resolve_expr<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>, expr:
                 visitor.cx.var_parent = visitor.cx.parent;
             }
 
-            hir::ExprKind::Use(ref expr) => {
-                // `Use(expr)` does not denote a conditional scope.
+            hir::ExprKind::DropTemps(ref expr) => {
+                // `DropTemps(expr)` does not denote a conditional scope.
                 // Rather, we want to achieve the same behavior as `{ let _t = expr; _t }`.
                 terminating(expr.hir_id.local_id);
             }

src/librustc/query/mod.rs

@@ -245,13 +245,13 @@ rustc_queries! {
 
         /// Get a map with the variance of every item; use `item_variance`
         /// instead.
-        query crate_variances(_: CrateNum) -> Lrc<ty::CrateVariancesMap> {
+        query crate_variances(_: CrateNum) -> Lrc<ty::CrateVariancesMap<'tcx>> {
             desc { "computing the variances for items in this crate" }
         }
 
         /// Maps from def-id of a type or region parameter to its
         /// (inferred) variance.
-        query variances_of(_: DefId) -> Lrc<Vec<ty::Variance>> {}
+        query variances_of(_: DefId) -> &'tcx [ty::Variance] {}
     }
 
     TypeChecking {

src/librustc/ty/mod.rs

@@ -332,15 +332,11 @@ pub enum Variance {
 /// `tcx.variances_of()` to get the variance for a *particular*
 /// item.
 #[derive(HashStable)]
-pub struct CrateVariancesMap {
+pub struct CrateVariancesMap<'tcx> {
     /// For each item with generics, maps to a vector of the variance
     /// of its generics. If an item has no generics, it will have no
     /// entry.
-    pub variances: FxHashMap<DefId, Lrc<Vec<ty::Variance>>>,
-
-    /// An empty vector, useful for cloning.
-    #[stable_hasher(ignore)]
-    pub empty_variance: Lrc<Vec<ty::Variance>>,
+    pub variances: FxHashMap<DefId, &'tcx [ty::Variance]>,
 }
 
 impl Variance {

src/librustc/ty/relate.rs

@@ -60,7 +60,7 @@ pub trait TypeRelation<'a, 'gcx: 'a+'tcx, 'tcx: 'a> : Sized {
                b_subst);
 
         let opt_variances = self.tcx().variances_of(item_def_id);
-        relate_substs(self, Some(&opt_variances), a_subst, b_subst)
+        relate_substs(self, Some(opt_variances), a_subst, b_subst)
     }
 
     /// Switch variance for the purpose of relating `a` and `b`.
@@ -122,7 +122,7 @@ impl<'tcx> Relate<'tcx> for ty::TypeAndMut<'tcx> {
 }
 
 pub fn relate_substs<'a, 'gcx, 'tcx, R>(relation: &mut R,
-                                        variances: Option<&Vec<ty::Variance>>,
+                                        variances: Option<&[ty::Variance]>,
                                         a_subst: SubstsRef<'tcx>,
                                         b_subst: SubstsRef<'tcx>)
                                         -> RelateResult<'tcx, SubstsRef<'tcx>>

src/librustc_metadata/cstore_impl.rs

@@ -106,7 +106,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
         let _ = cdata;
         tcx.calculate_dtor(def_id, &mut |_,_| Ok(()))
     }
-    variances_of => { Lrc::new(cdata.get_item_variances(def_id.index)) }
+    variances_of => { tcx.arena.alloc_from_iter(cdata.get_item_variances(def_id.index)) }
     associated_item_def_ids => {
         let mut result = vec![];
         cdata.each_child_of_item(def_id.index,

src/librustc_mir/hair/cx/expr.rs

@@ -759,7 +759,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
                 }
             }
         }
-        hir::ExprKind::Use(ref source) => {
+        hir::ExprKind::DropTemps(ref source) => {
             ExprKind::Use { source: source.to_ref() }
         }
         hir::ExprKind::Box(ref value) => {

src/librustc_passes/rvalue_promotion.rs

@@ -437,7 +437,7 @@ fn check_expr_kind<'a, 'tcx>(
         hir::ExprKind::AddrOf(_, ref expr) |
         hir::ExprKind::Repeat(ref expr, _) |
         hir::ExprKind::Type(ref expr, _) |
-        hir::ExprKind::Use(ref expr) => {
+        hir::ExprKind::DropTemps(ref expr) => {
             v.check_expr(&expr)
         }
 

src/librustc_typeck/check/mod.rs

@@ -4538,7 +4538,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 self.check_expr_eq_type(&e, ty);
                 ty
             }
-            ExprKind::Use(ref e) => {
+            ExprKind::DropTemps(ref e) => {
                 self.check_expr_with_expectation(e, expected)
             }
             ExprKind::Array(ref args) => {

src/librustc_typeck/coherence/builtin.rs

@@ -223,19 +223,22 @@ fn visit_implementation_of_dispatch_from_dyn<'a, 'tcx>(
                     let fields = &def_a.non_enum_variant().fields;
 
                     let coerced_fields = fields.iter().filter_map(|field| {
-                        if tcx.type_of(field.did).is_phantom_data() {
-                            // ignore PhantomData fields
-                            return None
-                        }
-
                         let ty_a = field.ty(tcx, substs_a);
                         let ty_b = field.ty(tcx, substs_b);
+
+                        if let Ok(layout) = tcx.layout_of(param_env.and(ty_a)) {
+                            if layout.is_zst() && layout.details.align.abi.bytes() == 1 {
+                                // ignore ZST fields with alignment of 1 byte
+                                return None;
+                            }
+                        }
+
                         if let Ok(ok) = infcx.at(&cause, param_env).eq(ty_a, ty_b) {
                             if ok.obligations.is_empty() {
                                 create_err(
                                     "the trait `DispatchFromDyn` may only be implemented \
                                      for structs containing the field being coerced, \
-                                     `PhantomData` fields, and nothing else"
+                                     ZST fields with 1 byte alignment, and nothing else"
                                 ).note(
                                     &format!(
                                         "extra field `{}` of type `{}` is not allowed",

src/librustc_typeck/variance/mod.rs

@@ -36,7 +36,7 @@ pub fn provide(providers: &mut Providers<'_>) {
 }
 
 fn crate_variances<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum)
-                             -> Lrc<CrateVariancesMap> {
+                             -> Lrc<CrateVariancesMap<'tcx>> {
     assert_eq!(crate_num, LOCAL_CRATE);
     let mut arena = arena::TypedArena::default();
     let terms_cx = terms::determine_parameters_to_be_inferred(tcx, &mut arena);
@@ -45,7 +45,7 @@ fn crate_variances<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, crate_num: CrateNum)
 }
 
 fn variances_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item_def_id: DefId)
-                          -> Lrc<Vec<ty::Variance>> {
+                          -> &'tcx [ty::Variance] {
     let id = tcx.hir().as_local_hir_id(item_def_id).expect("expected local def-id");
     let unsupported = || {
         // Variance not relevant.
@@ -88,6 +88,6 @@ fn variances_of<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, item_def_id: DefId)
 
     let crate_map = tcx.crate_variances(LOCAL_CRATE);
     crate_map.variances.get(&item_def_id)
-                       .unwrap_or(&crate_map.empty_variance)
-                       .clone()
+                       .map(|p| *p)
+                       .unwrap_or(&[])
 }