Rollup of 14 pull requests

compiler/rustc_ast_pretty/src/pp.rs

@@ -132,6 +132,9 @@
 //! methods called `Printer::scan_*`, and the 'PRINT' process is the
 //! method called `Printer::print`.
 
+mod ring;
+
+use ring::RingBuffer;
 use std::borrow::Cow;
 use std::collections::VecDeque;
 use std::fmt;
@@ -190,8 +193,7 @@ impl fmt::Display for Token {
     }
 }
 
-fn buf_str(buf: &[BufEntry], left: usize, right: usize, lim: usize) -> String {
-    let n = buf.len();
+fn buf_str(buf: &RingBuffer<BufEntry>, left: usize, right: usize, lim: usize) -> String {
     let mut i = left;
     let mut l = lim;
     let mut s = String::from("[");
@@ -202,7 +204,6 @@ fn buf_str(buf: &[BufEntry], left: usize, right: usize, lim: usize) -> String {
         }
         s.push_str(&format!("{}={}", buf[i].size, &buf[i].token));
         i += 1;
-        i %= n;
     }
     s.push(']');
     s
@@ -224,7 +225,6 @@ const SIZE_INFINITY: isize = 0xffff;
 
 pub struct Printer {
     out: String,
-    buf_max_len: usize,
     /// Width of lines we're constrained to
     margin: isize,
     /// Number of spaces left on line
@@ -234,7 +234,7 @@ pub struct Printer {
     /// Index of right side of input stream
     right: usize,
     /// Ring-buffer of tokens and calculated sizes
-    buf: Vec<BufEntry>,
+    buf: RingBuffer<BufEntry>,
     /// Running size of stream "...left"
     left_total: isize,
     /// Running size of stream "...right"
@@ -267,19 +267,16 @@ impl Default for BufEntry {
 impl Printer {
     pub fn new() -> Self {
         let linewidth = 78;
-        // Yes 55, it makes the ring buffers big enough to never fall behind.
-        let n: usize = 55 * linewidth;
         debug!("Printer::new {}", linewidth);
+        let mut buf = RingBuffer::new();
+        buf.advance_right();
         Printer {
             out: String::new(),
-            buf_max_len: n,
             margin: linewidth as isize,
             space: linewidth as isize,
             left: 0,
             right: 0,
-            // Initialize a single entry; advance_right() will extend it on demand
-            // up to `buf_max_len` elements.
-            buf: vec![BufEntry::default()],
+            buf,
             left_total: 0,
             right_total: 0,
             scan_stack: VecDeque::new(),
@@ -308,8 +305,8 @@ impl Printer {
         if self.scan_stack.is_empty() {
             self.left_total = 1;
             self.right_total = 1;
-            self.left = 0;
-            self.right = 0;
+            self.right = self.left;
+            self.buf.truncate(1);
         } else {
             self.advance_right();
         }
@@ -332,8 +329,8 @@ impl Printer {
         if self.scan_stack.is_empty() {
             self.left_total = 1;
             self.right_total = 1;
-            self.left = 0;
-            self.right = 0;
+            self.right = self.left;
+            self.buf.truncate(1);
         } else {
             self.advance_right();
         }
@@ -400,12 +397,7 @@ impl Printer {
 
     fn advance_right(&mut self) {
         self.right += 1;
-        self.right %= self.buf_max_len;
-        // Extend the buf if necessary.
-        if self.right == self.buf.len() {
-            self.buf.push(BufEntry::default());
-        }
-        assert_ne!(self.right, self.left);
+        self.buf.advance_right();
     }
 
     fn advance_left(&mut self) {
@@ -437,8 +429,8 @@ impl Printer {
                 break;
             }
 
+            self.buf.advance_left();
             self.left += 1;
-            self.left %= self.buf_max_len;
 
             left_size = self.buf[self.left].size;
         }

compiler/rustc_ast_pretty/src/pp/ring.rs

@@ -0,0 +1,53 @@
+use std::collections::VecDeque;
+use std::ops::{Index, IndexMut};
+
+/// A view onto a finite range of an infinitely long sequence of T.
+///
+/// The Ts are indexed 0..infinity. A RingBuffer begins as a view of elements
+/// 0..0 (i.e. nothing). The user of the RingBuffer advances its left and right
+/// position independently, although only in the positive direction, and only
+/// with left <= right at all times.
+///
+/// Holding a RingBuffer whose view is elements left..right gives the ability to
+/// use Index and IndexMut to access elements i in the infinitely long queue for
+/// which left <= i < right.
+pub struct RingBuffer<T> {
+    data: VecDeque<T>,
+    // Abstract index of data[0] in the infinitely sized queue.
+    offset: usize,
+}
+
+impl<T> RingBuffer<T> {
+    pub fn new() -> Self {
+        RingBuffer { data: VecDeque::new(), offset: 0 }
+    }
+
+    pub fn advance_right(&mut self)
+    where
+        T: Default,
+    {
+        self.data.push_back(T::default());
+    }
+
+    pub fn advance_left(&mut self) {
+        self.data.pop_front().unwrap();
+        self.offset += 1;
+    }
+
+    pub fn truncate(&mut self, len: usize) {
+        self.data.truncate(len);
+    }
+}
+
+impl<T> Index<usize> for RingBuffer<T> {
+    type Output = T;
+    fn index(&self, index: usize) -> &Self::Output {
+        &self.data[index.checked_sub(self.offset).unwrap()]
+    }
+}
+
+impl<T> IndexMut<usize> for RingBuffer<T> {
+    fn index_mut(&mut self, index: usize) -> &mut Self::Output {
+        &mut self.data[index.checked_sub(self.offset).unwrap()]
+    }
+}

compiler/rustc_feature/src/builtin_attrs.rs

@@ -352,15 +352,15 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
 
     // Runtime
     ungated!(
-        windows_subsystem, Normal,
+        windows_subsystem, CrateLevel,
         template!(NameValueStr: "windows|console"), FutureWarnFollowing
     ),
     ungated!(panic_handler, Normal, template!(Word), WarnFollowing), // RFC 2070
 
     // Code generation:
     ungated!(inline, Normal, template!(Word, List: "always|never"), FutureWarnFollowing),
     ungated!(cold, Normal, template!(Word), WarnFollowing),
-    ungated!(no_builtins, Normal, template!(Word), WarnFollowing),
+    ungated!(no_builtins, CrateLevel, template!(Word), WarnFollowing),
     ungated!(target_feature, Normal, template!(List: r#"enable = "name""#), DuplicatesOk),
     ungated!(track_caller, Normal, template!(Word), WarnFollowing),
     gated!(

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -425,7 +425,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
                         // FIXME: perf problem described in #55921.
                         ui = ty::UniverseIndex::ROOT;
                         return self.canonicalize_const_var(
-                            CanonicalVarInfo { kind: CanonicalVarKind::Const(ui) },
+                            CanonicalVarInfo { kind: CanonicalVarKind::Const(ui, ct.ty) },
                             ct,
                         );
                     }

compiler/rustc_infer/src/infer/canonical/mod.rs

@@ -137,12 +137,9 @@ impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> {
                 self.tcx.mk_region(ty::RePlaceholder(placeholder_mapped)).into()
             }
 
-            CanonicalVarKind::Const(ui) => self
+            CanonicalVarKind::Const(ui, ty) => self
                 .next_const_var_in_universe(
-                    self.next_ty_var_in_universe(
-                        TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span },
-                        universe_map(ui),
-                    ),
+                    ty,
                     ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span },
                     universe_map(ui),
                 )

compiler/rustc_middle/src/infer/canonical.rs

@@ -23,7 +23,7 @@
 
 use crate::infer::MemberConstraint;
 use crate::ty::subst::GenericArg;
-use crate::ty::{self, BoundVar, List, Region, TyCtxt};
+use crate::ty::{self, BoundVar, List, Region, Ty, TyCtxt};
 use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable;
 use smallvec::SmallVec;
@@ -104,7 +104,7 @@ impl<'tcx> CanonicalVarInfo<'tcx> {
             CanonicalVarKind::PlaceholderTy(_) => false,
             CanonicalVarKind::Region(_) => true,
             CanonicalVarKind::PlaceholderRegion(..) => false,
-            CanonicalVarKind::Const(_) => true,
+            CanonicalVarKind::Const(..) => true,
             CanonicalVarKind::PlaceholderConst(_) => false,
         }
     }
@@ -130,7 +130,7 @@ pub enum CanonicalVarKind<'tcx> {
     PlaceholderRegion(ty::PlaceholderRegion),
 
     /// Some kind of const inference variable.
-    Const(ty::UniverseIndex),
+    Const(ty::UniverseIndex, Ty<'tcx>),
 
     /// A "placeholder" that represents "any const".
     PlaceholderConst(ty::PlaceholderConst<'tcx>),
@@ -147,7 +147,7 @@ impl<'tcx> CanonicalVarKind<'tcx> {
             CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.universe,
             CanonicalVarKind::Region(ui) => ui,
             CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.universe,
-            CanonicalVarKind::Const(ui) => ui,
+            CanonicalVarKind::Const(ui, _) => ui,
             CanonicalVarKind::PlaceholderConst(placeholder) => placeholder.universe,
         }
     }

compiler/rustc_passes/src/check_attr.rs

@@ -126,6 +126,7 @@ impl CheckAttrVisitor<'_> {
             // lint-only checks
             match attr.name_or_empty() {
                 sym::cold => self.check_cold(hir_id, attr, span, target),
+                sym::link => self.check_link(hir_id, attr, span, target),
                 sym::link_name => self.check_link_name(hir_id, attr, span, target),
                 sym::link_section => self.check_link_section(hir_id, attr, span, target),
                 sym::no_mangle => self.check_no_mangle(hir_id, attr, span, target),
@@ -1157,6 +1158,26 @@ impl CheckAttrVisitor<'_> {
         }
     }
 
+    /// Checks if `#[link]` is applied to an item other than a foreign module.
+    fn check_link(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
+        match target {
+            Target::ForeignMod => {}
+            _ => {
+                self.tcx.struct_span_lint_hir(UNUSED_ATTRIBUTES, hir_id, attr.span, |lint| {
+                    let mut diag = lint.build("attribute should be applied to an `extern` block");
+                    diag.warn(
+                        "this was previously accepted by the compiler but is \
+                         being phased out; it will become a hard error in \
+                         a future release!",
+                    );
+
+                    diag.span_label(*span, "not an `extern` block");
+                    diag.emit();
+                });
+            }
+        }
+    }
+
     /// Checks if `#[link_name]` is applied to an item other than a foreign function or static.
     fn check_link_name(&self, hir_id: HirId, attr: &Attribute, span: &Span, target: Target) {
         match target {

compiler/rustc_traits/src/chalk/mod.rs

@@ -85,7 +85,7 @@ crate fn evaluate_goal<'tcx>(
                         chalk_ir::VariableKind::Lifetime,
                         chalk_ir::UniverseIndex { counter: ui.index() },
                     ),
-                    CanonicalVarKind::Const(_ui) => unimplemented!(),
+                    CanonicalVarKind::Const(_ui, _ty) => unimplemented!(),
                     CanonicalVarKind::PlaceholderConst(_pc) => unimplemented!(),
                 }),
             ),
@@ -127,9 +127,9 @@ crate fn evaluate_goal<'tcx>(
                     chalk_ir::VariableKind::Lifetime => CanonicalVarKind::Region(
                         ty::UniverseIndex::from_usize(var.skip_kind().counter),
                     ),
-                    chalk_ir::VariableKind::Const(_) => CanonicalVarKind::Const(
-                        ty::UniverseIndex::from_usize(var.skip_kind().counter),
-                    ),
+                    // FIXME(compiler-errors): We don't currently have a way of turning
+                    // a Chalk ty back into a rustc ty, right?
+                    chalk_ir::VariableKind::Const(_) => todo!(),
                 };
                 CanonicalVarInfo { kind }
             })

compiler/rustc_typeck/src/check/method/confirm.rs

@@ -149,7 +149,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // time writing the results into the various typeck results.
         let mut autoderef =
             self.autoderef_overloaded_span(self.span, unadjusted_self_ty, self.call_expr.span);
-        let (_, n) = match autoderef.nth(pick.autoderefs) {
+        let (ty, n) = match autoderef.nth(pick.autoderefs) {
             Some(n) => n,
             None => {
                 return self.tcx.ty_error_with_message(
@@ -161,14 +161,15 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         assert_eq!(n, pick.autoderefs);
 
         let mut adjustments = self.adjust_steps(&autoderef);
+        let mut target = self.structurally_resolved_type(autoderef.span(), ty);
 
-        let mut target =
-            self.structurally_resolved_type(autoderef.span(), autoderef.final_ty(false));
-
-        match &pick.autoref_or_ptr_adjustment {
+        match pick.autoref_or_ptr_adjustment {
             Some(probe::AutorefOrPtrAdjustment::Autoref { mutbl, unsize }) => {
                 let region = self.next_region_var(infer::Autoref(self.span));
-                target = self.tcx.mk_ref(region, ty::TypeAndMut { mutbl: *mutbl, ty: target });
+                // Type we're wrapping in a reference, used later for unsizing
+                let base_ty = target;
+
+                target = self.tcx.mk_ref(region, ty::TypeAndMut { mutbl, ty: target });
                 let mutbl = match mutbl {
                     hir::Mutability::Not => AutoBorrowMutability::Not,
                     hir::Mutability::Mut => AutoBorrowMutability::Mut {
@@ -182,10 +183,18 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                     target,
                 });
 
-                if let Some(unsize_target) = unsize {
+                if unsize {
+                    let unsized_ty = if let ty::Array(elem_ty, _) = base_ty.kind() {
+                        self.tcx.mk_slice(elem_ty)
+                    } else {
+                        bug!(
+                            "AutorefOrPtrAdjustment's unsize flag should only be set for array ty, found {}",
+                            base_ty
+                        )
+                    };
                     target = self
                         .tcx
-                        .mk_ref(region, ty::TypeAndMut { mutbl: mutbl.into(), ty: unsize_target });
+                        .mk_ref(region, ty::TypeAndMut { mutbl: mutbl.into(), ty: unsized_ty });
                     adjustments
                         .push(Adjustment { kind: Adjust::Pointer(PointerCast::Unsize), target });
                 }