Rollup of 9 pull requests

src/libcore/any.rs

@@ -164,7 +164,7 @@ impl dyn Any {
         // Get `TypeId` of the type this function is instantiated with.
         let t = TypeId::of::<T>();
 
-        // Get `TypeId` of the type in the trait object.
+        // Get `TypeId` of the type in the trait object (`self`).
         let concrete = self.type_id();
 
         // Compare both `TypeId`s on equality.

src/librustc/ich/impls_ty.rs

@@ -92,9 +92,6 @@ impl<'a> HashStable<StableHashingContext<'a>> for ty::RegionKind {
             ty::ReFree(ref free_region) => {
                 free_region.hash_stable(hcx, hasher);
             }
-            ty::ReClosureBound(vid) => {
-                vid.hash_stable(hcx, hasher);
-            }
             ty::ReVar(..) | ty::RePlaceholder(..) => {
                 bug!("StableHasher: unexpected region {:?}", *self)
             }

src/librustc/mir/interpret/error.rs

@@ -14,7 +14,7 @@ use rustc_hir as hir;
 use rustc_macros::HashStable;
 use rustc_session::CtfeBacktrace;
 use rustc_span::{def_id::DefId, Pos, Span};
-use std::{any::Any, fmt};
+use std::{any::Any, fmt, mem};
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, RustcEncodable, RustcDecodable)]
 pub enum ErrorHandled {
@@ -449,9 +449,6 @@ impl fmt::Debug for UndefinedBehaviorInfo {
 pub enum UnsupportedOpInfo {
     /// Free-form case. Only for errors that are never caught!
     Unsupported(String),
-    /// When const-prop encounters a situation it does not support, it raises this error.
-    /// This must not allocate for performance reasons (hence `str`, not `String`).
-    ConstPropUnsupported(&'static str),
     /// Accessing an unsupported foreign static.
     ReadForeignStatic(DefId),
     /// Could not find MIR for a function.
@@ -470,9 +467,6 @@ impl fmt::Debug for UnsupportedOpInfo {
         use UnsupportedOpInfo::*;
         match self {
             Unsupported(ref msg) => write!(f, "{}", msg),
-            ConstPropUnsupported(ref msg) => {
-                write!(f, "Constant propagation encountered an unsupported situation: {}", msg)
-            }
             ReadForeignStatic(did) => {
                 write!(f, "tried to read from foreign (extern) static {:?}", did)
             }
@@ -494,8 +488,10 @@ impl fmt::Debug for UnsupportedOpInfo {
 pub enum ResourceExhaustionInfo {
     /// The stack grew too big.
     StackFrameLimitReached,
-    /// The program ran into an infinite loop.
-    InfiniteLoop,
+    /// The program ran for too long.
+    ///
+    /// The exact limit is set by the `const_eval_limit` attribute.
+    StepLimitReached,
 }
 
 impl fmt::Debug for ResourceExhaustionInfo {
@@ -505,15 +501,36 @@ impl fmt::Debug for ResourceExhaustionInfo {
             StackFrameLimitReached => {
                 write!(f, "reached the configured maximum number of stack frames")
             }
-            InfiniteLoop => write!(
-                f,
-                "duplicate interpreter state observed here, const evaluation will never \
-                    terminate"
-            ),
+            StepLimitReached => {
+                write!(f, "exceeded interpreter step limit (see `#[const_eval_limit]`)")
+            }
         }
     }
 }
 
+/// A trait to work around not having trait object upcasting.
+pub trait AsAny: Any {
+    fn as_any(&self) -> &dyn Any;
+}
+
+impl<T: Any> AsAny for T {
+    #[inline(always)]
+    fn as_any(&self) -> &dyn Any {
+        self
+    }
+}
+
+/// A trait for machine-specific errors (or other "machine stop" conditions).
+pub trait MachineStopType: AsAny + fmt::Debug + Send {}
+impl MachineStopType for String {}
+
+impl dyn MachineStopType {
+    #[inline(always)]
+    pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
+        self.as_any().downcast_ref()
+    }
+}
+
 pub enum InterpError<'tcx> {
     /// The program caused undefined behavior.
     UndefinedBehavior(UndefinedBehaviorInfo),
@@ -527,7 +544,7 @@ pub enum InterpError<'tcx> {
     ResourceExhaustion(ResourceExhaustionInfo),
     /// Stop execution for a machine-controlled reason. This is never raised by
     /// the core engine itself.
-    MachineStop(Box<dyn Any + Send>),
+    MachineStop(Box<dyn MachineStopType>),
 }
 
 pub type InterpResult<'tcx, T = ()> = Result<T, InterpErrorInfo<'tcx>>;
@@ -547,7 +564,7 @@ impl fmt::Debug for InterpError<'_> {
             InvalidProgram(ref msg) => write!(f, "{:?}", msg),
             UndefinedBehavior(ref msg) => write!(f, "{:?}", msg),
             ResourceExhaustion(ref msg) => write!(f, "{:?}", msg),
-            MachineStop(_) => bug!("unhandled MachineStop"),
+            MachineStop(ref msg) => write!(f, "{:?}", msg),
         }
     }
 }
@@ -558,8 +575,9 @@ impl InterpError<'_> {
     /// waste of resources.
     pub fn allocates(&self) -> bool {
         match self {
-            InterpError::MachineStop(_)
-            | InterpError::Unsupported(UnsupportedOpInfo::Unsupported(_))
+            // Zero-sized boxes do not allocate.
+            InterpError::MachineStop(b) => mem::size_of_val::<dyn MachineStopType>(&**b) > 0,
+            InterpError::Unsupported(UnsupportedOpInfo::Unsupported(_))
             | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::ValidationFailure(_))
             | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::Ub(_)) => true,
             _ => false,

src/librustc/mir/interpret/mod.rs

@@ -97,8 +97,8 @@ mod value;
 
 pub use self::error::{
     struct_error, ConstEvalErr, ConstEvalRawResult, ConstEvalResult, ErrorHandled, FrameInfo,
-    InterpError, InterpErrorInfo, InterpResult, InvalidProgramInfo, ResourceExhaustionInfo,
-    UndefinedBehaviorInfo, UnsupportedOpInfo,
+    InterpError, InterpErrorInfo, InterpResult, InvalidProgramInfo, MachineStopType,
+    ResourceExhaustionInfo, UndefinedBehaviorInfo, UnsupportedOpInfo,
 };
 
 pub use self::value::{get_slice_bytes, ConstValue, RawConst, Scalar, ScalarMaybeUndef};

src/librustc/mir/query.rs

@@ -88,34 +88,35 @@ pub struct ConstQualifs {
 /// requirements are then verified and proved by the closure's
 /// creating function. This struct encodes those requirements.
 ///
-/// The requirements are listed as being between various
-/// `RegionVid`. The 0th region refers to `'static`; subsequent region
-/// vids refer to the free regions that appear in the closure (or
-/// generator's) type, in order of appearance. (This numbering is
-/// actually defined by the `UniversalRegions` struct in the NLL
-/// region checker. See for example
-/// `UniversalRegions::closure_mapping`.) Note that we treat the free
-/// regions in the closure's type "as if" they were erased, so their
-/// precise identity is not important, only their position.
+/// The requirements are listed as being between various `RegionVid`. The 0th
+/// region refers to `'static`; subsequent region vids refer to the free
+/// regions that appear in the closure (or generator's) type, in order of
+/// appearance. (This numbering is actually defined by the `UniversalRegions`
+/// struct in the NLL region checker. See for example
+/// `UniversalRegions::closure_mapping`.) Note the free regions in the
+/// closure's signature and captures are erased.
 ///
 /// Example: If type check produces a closure with the closure substs:
 ///
 /// ```text
 /// ClosureSubsts = [
-///     i8,                                  // the "closure kind"
-///     for<'x> fn(&'a &'x u32) -> &'x u32,  // the "closure signature"
-///     &'a String,                          // some upvar
+///     'a,                                         // From the parent.
+///     'b,
+///     i8,                                         // the "closure kind"
+///     for<'x> fn(&'<erased> &'x u32) -> &'x u32,  // the "closure signature"
+///     &'<erased> String,                          // some upvar
 /// ]
 /// ```
 ///
-/// here, there is one unique free region (`'a`) but it appears
-/// twice. We would "renumber" each occurrence to a unique vid, as follows:
+/// We would "renumber" each free region to a unique vid, as follows:
 ///
 /// ```text
 /// ClosureSubsts = [
-///     i8,                                  // the "closure kind"
-///     for<'x> fn(&'1 &'x u32) -> &'x u32,  // the "closure signature"
-///     &'2 String,                          // some upvar
+///     '1,                                         // From the parent.
+///     '2,
+///     i8,                                         // the "closure kind"
+///     for<'x> fn(&'3 &'x u32) -> &'x u32,         // the "closure signature"
+///     &'4 String,                                 // some upvar
 /// ]
 /// ```
 ///
@@ -124,14 +125,12 @@ pub struct ConstQualifs {
 /// can be extracted from its type and constrained to have the given
 /// outlives relationship.
 ///
-/// In some cases, we have to record outlives requirements between
-/// types and regions as well. In that case, if those types include
-/// any regions, those regions are recorded as `ReClosureBound`
-/// instances assigned one of these same indices. Those regions will
-/// be substituted away by the creator. We use `ReClosureBound` in
-/// that case because the regions must be allocated in the global
-/// `TyCtxt`, and hence we cannot use `ReVar` (which is what we use
-/// internally within the rest of the NLL code).
+/// In some cases, we have to record outlives requirements between types and
+/// regions as well. In that case, if those types include any regions, those
+/// regions are recorded using their external names (`ReStatic`,
+/// `ReEarlyBound`, `ReFree`). We use these because in a query response we
+/// cannot use `ReVar` (which is what we use internally within the rest of the
+/// NLL code).
 #[derive(Clone, Debug, RustcEncodable, RustcDecodable, HashStable)]
 pub struct ClosureRegionRequirements<'tcx> {
     /// The number of external regions defined on the closure. In our

src/librustc/ty/print/pretty.rs

@@ -1574,7 +1574,7 @@ impl<F: fmt::Write> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx, F> {
 
             ty::ReVar(_) | ty::ReScope(_) | ty::ReErased => false,
 
-            ty::ReStatic | ty::ReEmpty(_) | ty::ReClosureBound(_) => true,
+            ty::ReStatic | ty::ReEmpty(_) => true,
         }
     }
 
@@ -1686,12 +1686,6 @@ impl<F: fmt::Write> FmtPrinter<'_, '_, F> {
                 p!(write("'<empty:{:?}>", ui));
                 return Ok(self);
             }
-
-            // The user should never encounter these in unsubstituted form.
-            ty::ReClosureBound(vid) => {
-                p!(write("{:?}", vid));
-                return Ok(self);
-            }
         }
 
         p!(write("'_"));

src/librustc/ty/structural_impls.rs

@@ -81,8 +81,6 @@ impl fmt::Debug for ty::RegionKind {
         match *self {
             ty::ReEarlyBound(ref data) => write!(f, "ReEarlyBound({}, {})", data.index, data.name),
 
-            ty::ReClosureBound(ref vid) => write!(f, "ReClosureBound({:?})", vid),
-
             ty::ReLateBound(binder_id, ref bound_region) => {
                 write!(f, "ReLateBound({:?}, {:?})", binder_id, bound_region)
             }

src/librustc/ty/sty.rs

@@ -1352,12 +1352,6 @@ pub enum RegionKind {
 
     /// Erased region, used by trait selection, in MIR and during codegen.
     ReErased,
-
-    /// These are regions bound in the "defining type" for a
-    /// closure. They are used ONLY as part of the
-    /// `ClosureRegionRequirements` that are produced by MIR borrowck.
-    /// See `ClosureRegionRequirements` for more details.
-    ReClosureBound(RegionVid),
 }
 
 impl<'tcx> rustc_serialize::UseSpecializedDecodable for Region<'tcx> {}
@@ -1567,7 +1561,6 @@ impl RegionKind {
             RegionKind::RePlaceholder(placeholder) => placeholder.name.is_named(),
             RegionKind::ReEmpty(_) => false,
             RegionKind::ReErased => false,
-            RegionKind::ReClosureBound(..) => false,
         }
     }
 
@@ -1648,9 +1641,6 @@ impl RegionKind {
             ty::ReEmpty(_) | ty::ReStatic => {
                 flags = flags | TypeFlags::HAS_FREE_REGIONS;
             }
-            ty::ReClosureBound(..) => {
-                flags = flags | TypeFlags::HAS_FREE_REGIONS;
-            }
             ty::ReLateBound(..) => {
                 flags = flags | TypeFlags::HAS_RE_LATE_BOUND;
             }

src/librustc/ty/util.rs

@@ -1047,10 +1047,7 @@ pub fn needs_drop_components(
         // Foreign types can never have destructors.
         ty::Foreign(..) => Ok(SmallVec::new()),
 
-        // Pessimistically assume that all generators will require destructors
-        // as we don't know if a destructor is a noop or not until after the MIR
-        // state transformation pass.
-        ty::Generator(..) | ty::Dynamic(..) | ty::Error => Err(AlwaysRequiresDrop),
+        ty::Dynamic(..) | ty::Error => Err(AlwaysRequiresDrop),
 
         ty::Slice(ty) => needs_drop_components(ty, target_layout),
         ty::Array(elem_ty, size) => {
@@ -1083,7 +1080,8 @@ pub fn needs_drop_components(
         | ty::Placeholder(..)
         | ty::Opaque(..)
         | ty::Infer(_)
-        | ty::Closure(..) => Ok(smallvec![ty]),
+        | ty::Closure(..)
+        | ty::Generator(..) => Ok(smallvec![ty]),
     }
 }
 

src/librustc_error_codes/error_codes/E0452.md

@@ -1,4 +1,6 @@
-An invalid lint attribute has been given. Erroneous code example:
+An invalid lint attribute has been given.
+
+Erroneous code example:
 
 ```compile_fail,E0452
 #![allow(foo = "")] // error: malformed lint attribute

src/librustc_infer/infer/canonical/canonicalizer.rs

@@ -336,10 +336,6 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
             | ty::ReEmpty(_)
             | ty::RePlaceholder(..)
             | ty::ReErased => self.canonicalize_region_mode.canonicalize_free_region(self, r),
-
-            ty::ReClosureBound(..) => {
-                bug!("closure bound region encountered during canonicalization");
-            }
         }
     }
 

src/librustc_infer/infer/combine.rs

@@ -581,10 +581,6 @@ impl TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
                 return Ok(r);
             }
 
-            ty::ReClosureBound(..) => {
-                span_bug!(self.span, "encountered unexpected ReClosureBound: {:?}", r,);
-            }
-
             ty::RePlaceholder(..)
             | ty::ReVar(..)
             | ty::ReEmpty(_)

src/librustc_infer/infer/error_reporting/mod.rs

@@ -152,11 +152,6 @@ pub(super) fn note_and_explain_region(
         ty::ReVar(_) | ty::ReLateBound(..) | ty::ReErased => {
             (format!("lifetime {:?}", region), None)
         }
-
-        // We shouldn't encounter an error message with ReClosureBound.
-        ty::ReClosureBound(..) => {
-            bug!("encountered unexpected ReClosureBound: {:?}", region,);
-        }
     };
 
     emit_msg_span(err, prefix, description, span, suffix);

src/librustc_infer/infer/freshen.rs

@@ -135,10 +135,6 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
                 // replace all free regions with 'erased
                 self.tcx().lifetimes.re_erased
             }
-
-            ty::ReClosureBound(..) => {
-                bug!("encountered unexpected region: {:?}", r,);
-            }
         }
     }
 

src/librustc_infer/infer/lexical_region_resolve/mod.rs

@@ -493,12 +493,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> {
     /// term "concrete regions").
     fn lub_concrete_regions(&self, a: Region<'tcx>, b: Region<'tcx>) -> Region<'tcx> {
         let r = match (a, b) {
-            (&ty::ReClosureBound(..), _)
-            | (_, &ty::ReClosureBound(..))
-            | (&ReLateBound(..), _)
-            | (_, &ReLateBound(..))
-            | (&ReErased, _)
-            | (_, &ReErased) => {
+            (&ReLateBound(..), _) | (_, &ReLateBound(..)) | (&ReErased, _) | (_, &ReErased) => {
                 bug!("cannot relate region: LUB({:?}, {:?})", a, b);
             }
 

src/librustc_infer/infer/region_constraints/mod.rs

@@ -798,7 +798,7 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
             | ty::ReEarlyBound(..) => ty::UniverseIndex::ROOT,
             ty::ReEmpty(ui) => ui,
             ty::RePlaceholder(placeholder) => placeholder.universe,
-            ty::ReClosureBound(vid) | ty::ReVar(vid) => self.var_universe(vid),
+            ty::ReVar(vid) => self.var_universe(vid),
             ty::ReLateBound(..) => bug!("universe(): encountered bound region {:?}", region),
         }
     }