Rollup of 5 pull requests

src/libcore/alloc.rs

@@ -17,7 +17,7 @@ use crate::num::NonZeroUsize;
 #[derive(Debug)]
 pub struct Excess(pub NonNull<u8>, pub usize);
 
-fn size_align<T>() -> (usize, usize) {
+const fn size_align<T>() -> (usize, usize) {
     (mem::size_of::<T>(), mem::align_of::<T>())
 }
 
@@ -118,14 +118,14 @@ impl Layout {
 
     /// Constructs a `Layout` suitable for holding a value of type `T`.
     #[stable(feature = "alloc_layout", since = "1.28.0")]
+    #[rustc_const_stable(feature = "alloc_layout_const_new", since = "1.42.0")]
     #[inline]
-    pub fn new<T>() -> Self {
+    pub const fn new<T>() -> Self {
         let (size, align) = size_align::<T>();
         // Note that the align is guaranteed by rustc to be a power of two and
         // the size+align combo is guaranteed to fit in our address space. As a
         // result use the unchecked constructor here to avoid inserting code
         // that panics if it isn't optimized well enough.
-        debug_assert!(Layout::from_size_align(size, align).is_ok());
         unsafe {
             Layout::from_size_align_unchecked(size, align)
         }

src/librustc/hir/intravisit.rs

@@ -1056,9 +1056,9 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
             walk_list!(visitor, visit_label, opt_label);
             visitor.visit_block(block);
         }
-        ExprKind::Assign(ref left_hand_expression, ref right_hand_expression) => {
-            visitor.visit_expr(right_hand_expression);
-            visitor.visit_expr(left_hand_expression)
+        ExprKind::Assign(ref lhs, ref rhs, _) => {
+            visitor.visit_expr(rhs);
+            visitor.visit_expr(lhs)
         }
         ExprKind::AssignOp(_, ref left_expression, ref right_expression) => {
             visitor.visit_expr(right_expression);

src/librustc/hir/lowering.rs

@@ -3437,65 +3437,3 @@ fn body_ids(bodies: &BTreeMap<hir::BodyId, hir::Body<'hir>>) -> Vec<hir::BodyId>
     body_ids.sort_by_key(|b| bodies[b].value.span);
     body_ids
 }
-
-/// Checks if the specified expression is a built-in range literal.
-/// (See: `LoweringContext::lower_expr()`).
-pub fn is_range_literal(sess: &Session, expr: &hir::Expr) -> bool {
-    use hir::{Path, QPath, ExprKind, TyKind};
-
-    // Returns whether the given path represents a (desugared) range,
-    // either in std or core, i.e. has either a `::std::ops::Range` or
-    // `::core::ops::Range` prefix.
-    fn is_range_path(path: &Path) -> bool {
-        let segs: Vec<_> = path.segments.iter().map(|seg| seg.ident.to_string()).collect();
-        let segs: Vec<_> = segs.iter().map(|seg| &**seg).collect();
-
-        // "{{root}}" is the equivalent of `::` prefix in `Path`.
-        if let ["{{root}}", std_core, "ops", range] = segs.as_slice() {
-            (*std_core == "std" || *std_core == "core") && range.starts_with("Range")
-        } else {
-            false
-        }
-    };
-
-    // Check whether a span corresponding to a range expression is a
-    // range literal, rather than an explicit struct or `new()` call.
-    fn is_lit(sess: &Session, span: &Span) -> bool {
-        let source_map = sess.source_map();
-        let end_point = source_map.end_point(*span);
-
-        if let Ok(end_string) = source_map.span_to_snippet(end_point) {
-            !(end_string.ends_with("}") || end_string.ends_with(")"))
-        } else {
-            false
-        }
-    };
-
-    match expr.kind {
-        // All built-in range literals but `..=` and `..` desugar to `Struct`s.
-        ExprKind::Struct(ref qpath, _, _) => {
-            if let QPath::Resolved(None, ref path) = **qpath {
-                return is_range_path(&path) && is_lit(sess, &expr.span);
-            }
-        }
-
-        // `..` desugars to its struct path.
-        ExprKind::Path(QPath::Resolved(None, ref path)) => {
-            return is_range_path(&path) && is_lit(sess, &expr.span);
-        }
-
-        // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
-        ExprKind::Call(ref func, _) => {
-            if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.kind {
-                if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.kind {
-                    let new_call = segment.ident.name == sym::new;
-                    return is_range_path(&path) && is_lit(sess, &expr.span) && new_call;
-                }
-            }
-        }
-
-        _ => {}
-    }
-
-    false
-}

src/librustc/hir/lowering/expr.rs

@@ -112,8 +112,8 @@ impl LoweringContext<'_, '_> {
                                                       opt_label.is_some()),
                                                       self.lower_label(opt_label))
             }
-            ExprKind::Assign(ref el, ref er) => {
-                hir::ExprKind::Assign(P(self.lower_expr(el)), P(self.lower_expr(er)))
+            ExprKind::Assign(ref el, ref er, span) => {
+                hir::ExprKind::Assign(P(self.lower_expr(el)), P(self.lower_expr(er)), span)
             }
             ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
                 self.lower_binop(op),
@@ -1084,7 +1084,7 @@ impl LoweringContext<'_, '_> {
             let next_expr = P(self.expr_ident(pat.span, next_ident, next_pat_hid));
             let assign = P(self.expr(
                 pat.span,
-                hir::ExprKind::Assign(next_expr, val_expr),
+                hir::ExprKind::Assign(next_expr, val_expr, pat.span),
                 ThinVec::new(),
             ));
             let some_pat = self.pat_some(pat.span, val_pat);

src/librustc/hir/mod.rs

@@ -24,9 +24,10 @@ use syntax::ast::{AttrVec, Attribute, Label, LitKind, StrStyle, FloatTy, IntTy,
 pub use syntax::ast::{Mutability, Constness, Unsafety, Movability, CaptureBy};
 pub use syntax::ast::{IsAuto, ImplPolarity, BorrowKind};
 use syntax::attr::{InlineAttr, OptimizeAttr};
-use syntax::symbol::{Symbol, kw};
 use syntax::tokenstream::TokenStream;
 use syntax::util::parser::ExprPrecedence;
+use syntax_pos::symbol::{Symbol, kw, sym};
+use syntax_pos::source_map::SourceMap;
 use rustc_target::spec::abi::Abi;
 use rustc_data_structures::sync::{par_for_each_in, Send, Sync};
 use rustc_macros::HashStable;
@@ -1595,6 +1596,68 @@ impl fmt::Debug for Expr {
     }
 }
 
+/// Checks if the specified expression is a built-in range literal.
+/// (See: `LoweringContext::lower_expr()`).
+///
+/// FIXME(#60607): This function is a hack. If and when we have `QPath::Lang(...)`,
+/// we can use that instead as simpler, more reliable mechanism, as opposed to using `SourceMap`.
+pub fn is_range_literal(sm: &SourceMap, expr: &Expr) -> bool {
+    // Returns whether the given path represents a (desugared) range,
+    // either in std or core, i.e. has either a `::std::ops::Range` or
+    // `::core::ops::Range` prefix.
+    fn is_range_path(path: &Path) -> bool {
+        let segs: Vec<_> = path.segments.iter().map(|seg| seg.ident.to_string()).collect();
+        let segs: Vec<_> = segs.iter().map(|seg| &**seg).collect();
+
+        // "{{root}}" is the equivalent of `::` prefix in `Path`.
+        if let ["{{root}}", std_core, "ops", range] = segs.as_slice() {
+            (*std_core == "std" || *std_core == "core") && range.starts_with("Range")
+        } else {
+            false
+        }
+    };
+
+    // Check whether a span corresponding to a range expression is a
+    // range literal, rather than an explicit struct or `new()` call.
+    fn is_lit(sm: &SourceMap, span: &Span) -> bool {
+        let end_point = sm.end_point(*span);
+
+        if let Ok(end_string) = sm.span_to_snippet(end_point) {
+            !(end_string.ends_with("}") || end_string.ends_with(")"))
+        } else {
+            false
+        }
+    };
+
+    match expr.kind {
+        // All built-in range literals but `..=` and `..` desugar to `Struct`s.
+        ExprKind::Struct(ref qpath, _, _) => {
+            if let QPath::Resolved(None, ref path) = **qpath {
+                return is_range_path(&path) && is_lit(sm, &expr.span);
+            }
+        }
+
+        // `..` desugars to its struct path.
+        ExprKind::Path(QPath::Resolved(None, ref path)) => {
+            return is_range_path(&path) && is_lit(sm, &expr.span);
+        }
+
+        // `..=` desugars into `::std::ops::RangeInclusive::new(...)`.
+        ExprKind::Call(ref func, _) => {
+            if let ExprKind::Path(QPath::TypeRelative(ref ty, ref segment)) = func.kind {
+                if let TyKind::Path(QPath::Resolved(None, ref path)) = ty.kind {
+                    let new_call = segment.ident.name == sym::new;
+                    return is_range_path(&path) && is_lit(sm, &expr.span) && new_call;
+                }
+            }
+        }
+
+        _ => {}
+    }
+
+    false
+}
+
 #[derive(RustcEncodable, RustcDecodable, Debug, HashStable)]
 pub enum ExprKind {
     /// A `box x` expression.
@@ -1659,7 +1722,8 @@ pub enum ExprKind {
     Block(P<Block>, Option<Label>),
 
     /// An assignment (e.g., `a = foo()`).
-    Assign(P<Expr>, P<Expr>),
+    /// The `Span` argument is the span of the `=` token.
+    Assign(P<Expr>, P<Expr>, Span),
     /// An assignment with an operator.
     ///
     /// E.g., `a += 1`.

src/librustc/hir/print.rs

@@ -1312,7 +1312,7 @@ impl<'a> State<'a> {
                 self.ibox(0);
                 self.print_block(&blk);
             }
-            hir::ExprKind::Assign(ref lhs, ref rhs) => {
+            hir::ExprKind::Assign(ref lhs, ref rhs, _) => {
                 let prec = AssocOp::Assign.precedence() as i8;
                 self.print_expr_maybe_paren(&lhs, prec + 1);
                 self.s.space();
@@ -2282,7 +2282,7 @@ fn contains_exterior_struct_lit(value: &hir::Expr) -> bool {
     match value.kind {
         hir::ExprKind::Struct(..) => true,
 
-        hir::ExprKind::Assign(ref lhs, ref rhs) |
+        hir::ExprKind::Assign(ref lhs, ref rhs, _) |
         hir::ExprKind::AssignOp(_, ref lhs, ref rhs) |
         hir::ExprKind::Binary(_, ref lhs, ref rhs) => {
             // `X { y: 1 } + X { y: 2 }`

src/librustc_lint/types.rs

@@ -1,8 +1,6 @@
 #![allow(non_snake_case)]
 
-use rustc::hir::{ExprKind, Node};
-use crate::hir::def_id::DefId;
-use rustc::hir::lowering::is_range_literal;
+use rustc::hir::{ExprKind, Node, is_range_literal, def_id::DefId};
 use rustc::ty::subst::SubstsRef;
 use rustc::ty::{self, AdtKind, ParamEnv, Ty, TyCtxt};
 use rustc::ty::layout::{self, IntegerExt, LayoutOf, VariantIdx, SizeSkeleton};
@@ -275,7 +273,7 @@ fn lint_int_literal<'a, 'tcx>(
         let par_id = cx.tcx.hir().get_parent_node(e.hir_id);
         if let Node::Expr(par_e) = cx.tcx.hir().get(par_id) {
             if let hir::ExprKind::Struct(..) = par_e.kind {
-                if is_range_literal(cx.sess(), par_e)
+                if is_range_literal(cx.sess().source_map(), par_e)
                     && lint_overflowing_range_endpoint(cx, lit, v, max, e, par_e, t.name_str())
                 {
                     // The overflowing literal lint was overridden.
@@ -328,7 +326,7 @@ fn lint_uint_literal<'a, 'tcx>(
                     }
                 }
                 hir::ExprKind::Struct(..)
-                    if is_range_literal(cx.sess(), par_e) => {
+                    if is_range_literal(cx.sess().source_map(), par_e) => {
                         let t = t.name_str();
                         if lint_overflowing_range_endpoint(cx, lit, lit_val, max, e, par_e, t) {
                             // The overflowing literal lint was overridden.

src/librustc_lint/unused.rs

@@ -512,7 +512,7 @@ impl EarlyLintPass for UnusedParens {
                 (value, "`return` value", false, Some(left), None)
             }
 
-            Assign(_, ref value) => (value, "assigned value", false, None, None),
+            Assign(_, ref value, _) => (value, "assigned value", false, None, None),
             AssignOp(.., ref value) => (value, "assigned value", false, None, None),
             // either function/method call, or something this lint doesn't care about
             ref call_or_other => {

src/librustc_mir/borrow_check/diagnostics/mod.rs

@@ -32,7 +32,7 @@ mod explain_borrow;
 
 crate use mutability_errors::AccessKind;
 crate use region_name::{RegionName, RegionNameSource, RegionErrorNamingCtx};
-crate use region_errors::{ErrorReportingCtx, ErrorConstraintInfo};
+crate use region_errors::{ErrorReportingCtx, ErrorConstraintInfo, RegionErrors, RegionErrorKind};
 crate use outlives_suggestion::OutlivesSuggestionBuilder;
 
 pub(super) struct IncludingDowncast(pub(super) bool);

src/librustc_mir/borrow_check/diagnostics/outlives_suggestion.rs

@@ -250,7 +250,9 @@ impl OutlivesSuggestionBuilder<'a> {
 
         // If there is only one constraint to suggest, then we already suggested it in the
         // intermediate suggestion above.
-        if self.constraints_to_add.len() == 1 {
+        if self.constraints_to_add.len() == 1
+            && self.constraints_to_add.values().next().unwrap().len() == 1
+        {
             debug!("Only 1 suggestion. Skipping.");
             return;
         }

src/librustc_mir/borrow_check/diagnostics/region_errors.rs

@@ -3,12 +3,13 @@
 use rustc::hir::def_id::DefId;
 use rustc::infer::{
     error_reporting::nice_region_error::NiceRegionError,
+    region_constraints::GenericKind,
     InferCtxt, NLLRegionVariableOrigin,
 };
 use rustc::mir::{
     ConstraintCategory, Local, Location, Body,
 };
-use rustc::ty::{self, RegionVid};
+use rustc::ty::{self, RegionVid, Ty};
 use rustc_index::vec::IndexVec;
 use rustc_errors::DiagnosticBuilder;
 use std::collections::VecDeque;
@@ -53,13 +54,74 @@ impl ConstraintDescription for ConstraintCategory {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Eq)]
+#[derive(Copy, Clone, PartialEq, Eq, Debug)]
 enum Trace {
     StartRegion,
     FromOutlivesConstraint(OutlivesConstraint),
     NotVisited,
 }
 
+/// A collection of errors encountered during region inference. This is needed to efficiently
+/// report errors after borrow checking.
+///
+/// Usually we expect this to either be empty or contain a small number of items, so we can avoid
+/// allocation most of the time.
+crate type RegionErrors<'tcx> = Vec<RegionErrorKind<'tcx>>;
+
+#[derive(Clone, Debug)]
+crate enum RegionErrorKind<'tcx> {
+    /// An error for a type test: `T: 'a` does not live long enough.
+    TypeTestDoesNotLiveLongEnough {
+        /// The span of the type test.
+        span: Span,
+        /// The generic type of the type test.
+        generic: GenericKind<'tcx>,
+    },
+
+    /// A generic bound failure for a type test.
+    TypeTestGenericBoundError {
+        /// The span of the type test.
+        span: Span,
+        /// The generic type of the type test.
+        generic: GenericKind<'tcx>,
+        /// The lower bound region.
+        lower_bound_region: ty::Region<'tcx>,
+    },
+
+    /// An unexpected hidden region for an opaque type.
+    UnexpectedHiddenRegion {
+        /// The def id of the opaque type.
+        opaque_type_def_id: DefId,
+        /// The hidden type.
+        hidden_ty: Ty<'tcx>,
+        /// The unexpected region.
+        member_region: ty::Region<'tcx>,
+    },
+
+    /// Higher-ranked subtyping error.
+    BoundUniversalRegionError {
+        /// The placeholder free region.
+        longer_fr: RegionVid,
+        /// The region that erroneously must be outlived by `longer_fr`.
+        error_region: RegionVid,
+        /// The origin of the placeholder region.
+        fr_origin: NLLRegionVariableOrigin,
+    },
+
+    /// Any other lifetime error.
+    RegionError {
+        /// The origin of the region.
+        fr_origin: NLLRegionVariableOrigin,
+        /// The region that should outlive `shorter_fr`.
+        longer_fr: RegionVid,
+        /// The region that should be shorter, but we can't prove it.
+        shorter_fr: RegionVid,
+        /// Indicates whether this is a reported error. We currently only report the first error
+        /// encountered and leave the rest unreported so as not to overwhelm the user.
+        is_reported: bool,
+    },
+}
+
 /// Various pieces of state used when reporting borrow checker errors.
 pub struct ErrorReportingCtx<'a, 'b, 'tcx> {
     /// The region inference context used for borrow chekcing this MIR body.