Merging upstream version 1.66.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

12 files changed, 168 insertions, 112 deletions

diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index e4039cc7c..b5a50cc15 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -479,12 +479,7 @@ impl<T: Any> AsAny for T {
 }
 
 /// A trait for machine-specific errors (or other "machine stop" conditions).
-pub trait MachineStopType: AsAny + fmt::Display + Send {
-    /// If `true`, emit a hard error instead of going through the `CONST_ERR` lint
-    fn is_hard_err(&self) -> bool {
-        false
-    }
-}
+pub trait MachineStopType: AsAny + fmt::Display + Send {}
 
 impl dyn MachineStopType {
     #[inline(always)]
@@ -543,16 +538,4 @@ impl InterpError<'_> {
                 | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::Ub(_))
         )
     }
-
-    /// Should this error be reported as a hard error, preventing compilation, or a soft error,
-    /// causing a deny-by-default lint?
-    pub fn is_hard_err(&self) -> bool {
-        use InterpError::*;
-        match *self {
-            MachineStop(ref err) => err.is_hard_err(),
-            UndefinedBehavior(_) => true,
-            ResourceExhaustion(ResourceExhaustionInfo::MemoryExhausted) => true,
-            _ => false,
-        }
-    }
 }
diff --git a/compiler/rustc_middle/src/mir/interpret/pointer.rs b/compiler/rustc_middle/src/mir/interpret/pointer.rs
index 95e52e391..23c2ce647 100644
--- a/compiler/rustc_middle/src/mir/interpret/pointer.rs
+++ b/compiler/rustc_middle/src/mir/interpret/pointer.rs
@@ -43,7 +43,7 @@ pub trait PointerArithmetic: HasDataLayout {
         let val = val as i64;
         // Now wrap-around into the machine_isize range.
         if val > self.machine_isize_max() {
-            // This can only happen the the ptr size is < 64, so we know max_usize_plus_1 fits into
+            // This can only happen if the ptr size is < 64, so we know max_usize_plus_1 fits into
             // i64.
             debug_assert!(self.pointer_size().bits() < 64);
             let max_usize_plus_1 = 1u128 << self.pointer_size().bits();
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs
index 4207988d7..473894ac1 100644
--- a/compiler/rustc_middle/src/mir/interpret/queries.rs
+++ b/compiler/rustc_middle/src/mir/interpret/queries.rs
@@ -4,7 +4,9 @@ use crate::mir;
 use crate::ty::subst::InternalSubsts;
 use crate::ty::visit::TypeVisitable;
 use crate::ty::{self, query::TyCtxtAt, query::TyCtxtEnsure, TyCtxt};
+use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
+use rustc_session::lint;
 use rustc_span::{Span, DUMMY_SP};
 
 impl<'tcx> TyCtxt<'tcx> {
@@ -36,7 +38,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn const_eval_resolve(
         self,
         param_env: ty::ParamEnv<'tcx>,
-        ct: ty::Unevaluated<'tcx>,
+        ct: mir::UnevaluatedConst<'tcx>,
         span: Option<Span>,
     ) -> EvalToConstValueResult<'tcx> {
         // Cannot resolve `Unevaluated` constants that contain inference
@@ -45,11 +47,15 @@ impl<'tcx> TyCtxt<'tcx> {
         //
         // When trying to evaluate constants containing inference variables,
         // use `Infcx::const_eval_resolve` instead.
-        if ct.substs.has_infer_types_or_consts() {
+        if ct.substs.has_non_region_infer() {
             bug!("did not expect inference variables here");
         }
 
-        match ty::Instance::resolve_opt_const_arg(self, param_env, ct.def, ct.substs) {
+        match ty::Instance::resolve_opt_const_arg(
+            self, param_env,
+            // FIXME: maybe have a separate version for resolving mir::UnevaluatedConst?
+            ct.def, ct.substs,
+        ) {
             Ok(Some(instance)) => {
                 let cid = GlobalId { instance, promoted: ct.promoted };
                 self.const_eval_global_id(param_env, cid, span)
@@ -63,7 +69,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn const_eval_resolve_for_typeck(
         self,
         param_env: ty::ParamEnv<'tcx>,
-        ct: ty::Unevaluated<'tcx, ()>,
+        ct: ty::UnevaluatedConst<'tcx>,
         span: Option<Span>,
     ) -> EvalToValTreeResult<'tcx> {
         // Cannot resolve `Unevaluated` constants that contain inference
@@ -72,14 +78,36 @@ impl<'tcx> TyCtxt<'tcx> {
         //
         // When trying to evaluate constants containing inference variables,
         // use `Infcx::const_eval_resolve` instead.
-        if ct.substs.has_infer_types_or_consts() {
+        if ct.substs.has_non_region_infer() {
             bug!("did not expect inference variables here");
         }
 
         match ty::Instance::resolve_opt_const_arg(self, param_env, ct.def, ct.substs) {
             Ok(Some(instance)) => {
                 let cid = GlobalId { instance, promoted: None };
-                self.const_eval_global_id_for_typeck(param_env, cid, span)
+                self.const_eval_global_id_for_typeck(param_env, cid, span).inspect(|_| {
+                    // We are emitting the lint here instead of in `is_const_evaluatable`
+                    // as we normalize obligations before checking them, and normalization
+                    // uses this function to evaluate this constant.
+                    //
+                    // @lcnr believes that successfully evaluating even though there are
+                    // used generic parameters is a bug of evaluation, so checking for it
+                    // here does feel somewhat sensible.
+                    if !self.features().generic_const_exprs && ct.substs.has_non_region_param() {
+                        assert!(matches!(self.def_kind(ct.def.did), DefKind::AnonConst));
+                        let mir_body = self.mir_for_ctfe_opt_const_arg(ct.def);
+                        if mir_body.is_polymorphic {
+                            let Some(local_def_id) = ct.def.did.as_local() else { return };
+                            self.struct_span_lint_hir(
+                                lint::builtin::CONST_EVALUATABLE_UNCHECKED,
+                                self.hir().local_def_id_to_hir_id(local_def_id),
+                                self.def_span(ct.def.did),
+                                "cannot use constants which depend on generic parameters in types",
+                                |err| err,
+                            )
+                        }
+                    }
+                })
             }
             Ok(None) => Err(ErrorHandled::TooGeneric),
             Err(error_reported) => Err(ErrorHandled::Reported(error_reported)),
@@ -211,7 +239,7 @@ impl<'tcx> TyCtxt<'tcx> {
         self,
         param_env: ty::ParamEnv<'tcx>,
         constant: mir::ConstantKind<'tcx>,
-    ) -> mir::DestructuredMirConstant<'tcx> {
+    ) -> mir::DestructuredConstant<'tcx> {
         self.try_destructure_mir_constant(param_env.and(constant)).unwrap()
     }
 }
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 3d7a6230e..79db35a76 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -7,12 +7,12 @@ use crate::mir::interpret::{
 };
 use crate::mir::visit::MirVisitable;
 use crate::ty::codec::{TyDecoder, TyEncoder};
-use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeSuperFoldable};
+use crate::ty::fold::{FallibleTypeFolder, TypeFoldable};
 use crate::ty::print::{FmtPrinter, Printer};
-use crate::ty::subst::{GenericArg, InternalSubsts, Subst, SubstsRef};
-use crate::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
+use crate::ty::visit::{TypeVisitable, TypeVisitor};
 use crate::ty::{self, List, Ty, TyCtxt};
 use crate::ty::{AdtDef, InstanceDef, ScalarInt, UserTypeAnnotationIndex};
+use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
 
 use rustc_data_structures::captures::Captures;
 use rustc_errors::ErrorGuaranteed;
@@ -116,11 +116,6 @@ pub trait MirPass<'tcx> {
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
 
-    /// If this pass causes the MIR to enter a new phase, return that phase.
-    fn phase_change(&self) -> Option<MirPhase> {
-        None
-    }
-
     fn is_mir_dump_enabled(&self) -> bool {
         true
     }
@@ -145,6 +140,35 @@ impl MirPhase {
     }
 }
 
+impl Display for MirPhase {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            MirPhase::Built => write!(f, "built"),
+            MirPhase::Analysis(p) => write!(f, "analysis-{}", p),
+            MirPhase::Runtime(p) => write!(f, "runtime-{}", p),
+        }
+    }
+}
+
+impl Display for AnalysisPhase {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            AnalysisPhase::Initial => write!(f, "initial"),
+            AnalysisPhase::PostCleanup => write!(f, "post_cleanup"),
+        }
+    }
+}
+
+impl Display for RuntimePhase {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            RuntimePhase::Initial => write!(f, "initial"),
+            RuntimePhase::PostCleanup => write!(f, "post_cleanup"),
+            RuntimePhase::Optimized => write!(f, "optimized"),
+        }
+    }
+}
+
 /// Where a specific `mir::Body` comes from.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 #[derive(HashStable, TyEncodable, TyDecodable, TypeFoldable, TypeVisitable)]
@@ -207,6 +231,9 @@ pub struct Body<'tcx> {
     /// us to see the difference and forego optimization on the inlined promoted items.
     pub phase: MirPhase,
 
+    /// How many passses we have executed since starting the current phase. Used for debug output.
+    pub pass_count: usize,
+
     pub source: MirSource<'tcx>,
 
     /// A list of source scopes; these are referenced by statements
@@ -292,6 +319,7 @@ impl<'tcx> Body<'tcx> {
 
         let mut body = Body {
             phase: MirPhase::Built,
+            pass_count: 1,
             source,
             basic_blocks: BasicBlocks::new(basic_blocks),
             source_scopes,
@@ -313,7 +341,7 @@ impl<'tcx> Body<'tcx> {
             is_polymorphic: false,
             tainted_by_errors,
         };
-        body.is_polymorphic = body.has_param_types_or_consts();
+        body.is_polymorphic = body.has_non_region_param();
         body
     }
 
@@ -325,6 +353,7 @@ impl<'tcx> Body<'tcx> {
     pub fn new_cfg_only(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self {
         let mut body = Body {
             phase: MirPhase::Built,
+            pass_count: 1,
             source: MirSource::item(CRATE_DEF_ID.to_def_id()),
             basic_blocks: BasicBlocks::new(basic_blocks),
             source_scopes: IndexVec::new(),
@@ -339,7 +368,7 @@ impl<'tcx> Body<'tcx> {
             is_polymorphic: false,
             tainted_by_errors: None,
         };
-        body.is_polymorphic = body.has_param_types_or_consts();
+        body.is_polymorphic = body.has_non_region_param();
         body
     }
 
@@ -1380,6 +1409,7 @@ impl<V, T> ProjectionElem<V, T> {
 
             Self::Field(_, _)
             | Self::Index(_)
+            | Self::OpaqueCast(_)
             | Self::ConstantIndex { .. }
             | Self::Subslice { .. }
             | Self::Downcast(_, _) => false,
@@ -1574,7 +1604,9 @@ impl Debug for Place<'_> {
     fn fmt(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
         for elem in self.projection.iter().rev() {
             match elem {
-                ProjectionElem::Downcast(_, _) | ProjectionElem::Field(_, _) => {
+                ProjectionElem::OpaqueCast(_)
+                | ProjectionElem::Downcast(_, _)
+                | ProjectionElem::Field(_, _) => {
                     write!(fmt, "(").unwrap();
                 }
                 ProjectionElem::Deref => {
@@ -1590,6 +1622,9 @@ impl Debug for Place<'_> {
 
         for elem in self.projection.iter() {
             match elem {
+                ProjectionElem::OpaqueCast(ty) => {
+                    write!(fmt, " as {})", ty)?;
+                }
                 ProjectionElem::Downcast(Some(name), _index) => {
                     write!(fmt, " as {})", name)?;
                 }
@@ -1818,7 +1853,6 @@ impl<'tcx> Rvalue<'tcx> {
             // While the model is undecided, we should be conservative. See
             // <https://www.ralfj.de/blog/2022/04/11/provenance-exposed.html>
             Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => false,
-            Rvalue::Cast(CastKind::DynStar, _, _) => false,
 
             Rvalue::Use(_)
             | Rvalue::CopyForDeref(_)
@@ -1828,7 +1862,15 @@ impl<'tcx> Rvalue<'tcx> {
             | Rvalue::AddressOf(_, _)
             | Rvalue::Len(_)
             | Rvalue::Cast(
-                CastKind::Misc | CastKind::Pointer(_) | CastKind::PointerFromExposedAddress,
+                CastKind::IntToInt
+                | CastKind::FloatToInt
+                | CastKind::FloatToFloat
+                | CastKind::IntToFloat
+                | CastKind::FnPtrToPtr
+                | CastKind::PtrToPtr
+                | CastKind::Pointer(_)
+                | CastKind::PointerFromExposedAddress
+                | CastKind::DynStar,
                 _,
                 _,
             )
@@ -2043,13 +2085,13 @@ pub struct Constant<'tcx> {
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable, Debug)]
-#[derive(Lift)]
+#[derive(Lift, TypeFoldable, TypeVisitable)]
 pub enum ConstantKind<'tcx> {
     /// This constant came from the type system
     Ty(ty::Const<'tcx>),
 
     /// An unevaluated mir constant which is not part of the type system.
-    Unevaluated(ty::Unevaluated<'tcx, Option<Promoted>>, Ty<'tcx>),
+    Unevaluated(UnevaluatedConst<'tcx>, Ty<'tcx>),
 
     /// This constant cannot go back into the type system, as it represents
     /// something the type system cannot handle (e.g. pointers).
@@ -2309,12 +2351,11 @@ impl<'tcx> ConstantKind<'tcx> {
             ty::InlineConstSubsts::new(tcx, ty::InlineConstSubstsParts { parent_substs, ty })
                 .substs;
 
-        let uneval = ty::Unevaluated {
+        let uneval = UnevaluatedConst {
             def: ty::WithOptConstParam::unknown(def_id).to_global(),
             substs,
             promoted: None,
         };
-
         debug_assert!(!uneval.has_free_regions());
 
         Self::Unevaluated(uneval, ty)
@@ -2398,7 +2439,7 @@ impl<'tcx> ConstantKind<'tcx> {
 
         let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
         let span = tcx.hir().span(hir_id);
-        let uneval = ty::Unevaluated::new(def.to_global(), substs);
+        let uneval = UnevaluatedConst::new(def.to_global(), substs);
         debug!(?span, ?param_env);
 
         match tcx.const_eval_resolve(param_env, uneval, Some(span)) {
@@ -2411,7 +2452,7 @@ impl<'tcx> ConstantKind<'tcx> {
                 // Error was handled in `const_eval_resolve`. Here we just create a
                 // new unevaluated const and error hard later in codegen
                 Self::Unevaluated(
-                    ty::Unevaluated {
+                    UnevaluatedConst {
                         def: def.to_global(),
                         substs: InternalSubsts::identity_for_item(tcx, def.did.to_def_id()),
                         promoted: None,
@@ -2434,6 +2475,34 @@ impl<'tcx> ConstantKind<'tcx> {
     }
 }
 
+/// An unevaluated (potentially generic) constant used in MIR.
+#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Lift)]
+#[derive(Hash, HashStable, TypeFoldable, TypeVisitable)]
+pub struct UnevaluatedConst<'tcx> {
+    pub def: ty::WithOptConstParam<DefId>,
+    pub substs: SubstsRef<'tcx>,
+    pub promoted: Option<Promoted>,
+}
+
+impl<'tcx> UnevaluatedConst<'tcx> {
+    // FIXME: probably should get rid of this method. It's also wrong to
+    // shrink and then later expand a promoted.
+    #[inline]
+    pub fn shrink(self) -> ty::UnevaluatedConst<'tcx> {
+        ty::UnevaluatedConst { def: self.def, substs: self.substs }
+    }
+}
+
+impl<'tcx> UnevaluatedConst<'tcx> {
+    #[inline]
+    pub fn new(
+        def: ty::WithOptConstParam<DefId>,
+        substs: SubstsRef<'tcx>,
+    ) -> UnevaluatedConst<'tcx> {
+        UnevaluatedConst { def, substs, promoted: Default::default() }
+    }
+}
+
 /// A collection of projections into user types.
 ///
 /// They are projections because a binding can occur a part of a
@@ -2727,7 +2796,7 @@ fn pretty_print_const_value<'tcx>(
             }
             // Aggregates, printed as array/tuple/struct/variant construction syntax.
             //
-            // NB: the `has_param_types_or_consts` check ensures that we can use
+            // NB: the `has_non_region_param` check ensures that we can use
             // the `destructure_const` query with an empty `ty::ParamEnv` without
             // introducing ICEs (e.g. via `layout_of`) from missing bounds.
             // E.g. `transmute([0usize; 2]): (u8, *mut T)` needs to know `T: Sized`
@@ -2735,7 +2804,7 @@ fn pretty_print_const_value<'tcx>(
             //
             // FIXME(eddyb) for `--emit=mir`/`-Z dump-mir`, we should provide the
             // correct `ty::ParamEnv` to allow printing *all* constant values.
-            (_, ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) if !ty.has_param_types_or_consts() => {
+            (_, ty::Array(..) | ty::Tuple(..) | ty::Adt(..)) if !ty.has_non_region_param() => {
                 let ct = tcx.lift(ct).unwrap();
                 let ty = tcx.lift(ty).unwrap();
                 if let Some(contents) = tcx.try_destructure_mir_constant(
@@ -2906,11 +2975,12 @@ impl Location {
 mod size_asserts {
     use super::*;
     use rustc_data_structures::static_assert_size;
-    // These are in alphabetical order, which is easy to maintain.
+    // tidy-alphabetical-start
     static_assert_size!(BasicBlockData<'_>, 144);
     static_assert_size!(LocalDecl<'_>, 56);
     static_assert_size!(Statement<'_>, 32);
     static_assert_size!(StatementKind<'_>, 16);
     static_assert_size!(Terminator<'_>, 112);
     static_assert_size!(TerminatorKind<'_>, 96);
+    // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index 21ae121e1..15a24aa4a 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -81,7 +81,7 @@ impl<'tcx> MonoItem<'tcx> {
             MonoItem::Fn(instance) => tcx.symbol_name(instance),
             MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
             MonoItem::GlobalAsm(item_id) => {
-                SymbolName::new(tcx, &format!("global_asm_{:?}", item_id.def_id))
+                SymbolName::new(tcx, &format!("global_asm_{:?}", item_id.owner_id))
             }
         }
     }
@@ -182,7 +182,7 @@ impl<'tcx> MonoItem<'tcx> {
         match *self {
             MonoItem::Fn(Instance { def, .. }) => def.def_id().as_local(),
             MonoItem::Static(def_id) => def_id.as_local(),
-            MonoItem::GlobalAsm(item_id) => Some(item_id.def_id),
+            MonoItem::GlobalAsm(item_id) => Some(item_id.owner_id.def_id),
         }
         .map(|def_id| tcx.def_span(def_id))
     }
@@ -373,7 +373,7 @@ impl<'tcx> CodegenUnit<'tcx> {
                         }
                     }
                     MonoItem::Static(def_id) => def_id.as_local().map(Idx::index),
-                    MonoItem::GlobalAsm(item_id) => Some(item_id.def_id.index()),
+                    MonoItem::GlobalAsm(item_id) => Some(item_id.owner_id.def_id.index()),
                 },
                 item.symbol_name(tcx),
             )
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index 0b42137d4..05dcfba77 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -466,10 +466,9 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
                     ty::ConstKind::Param(p) => format!("Param({})", p),
                     ty::ConstKind::Unevaluated(uv) => {
                         format!(
-                            "Unevaluated({}, {:?}, {:?})",
+                            "Unevaluated({}, {:?})",
                             self.tcx.def_path_str(uv.def.did),
                             uv.substs,
-                            uv.promoted,
                         )
                     }
                     ty::ConstKind::Value(val) => format!("Value({})", fmt_valtree(&val)),
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index d89efe2b3..efd7357af 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -392,16 +392,9 @@ pub enum ClosureOutlivesSubject<'tcx> {
     Region(ty::RegionVid),
 }
 
-/// The constituent parts of a type level constant of kind ADT or array.
-#[derive(Copy, Clone, Debug, HashStable)]
-pub struct DestructuredConst<'tcx> {
-    pub variant: Option<VariantIdx>,
-    pub fields: &'tcx [ty::Const<'tcx>],
-}
-
 /// The constituent parts of a mir constant of kind ADT or array.
 #[derive(Copy, Clone, Debug, HashStable)]
-pub struct DestructuredMirConstant<'tcx> {
+pub struct DestructuredConstant<'tcx> {
     pub variant: Option<VariantIdx>,
     pub fields: &'tcx [ConstantKind<'tcx>],
 }
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index c7d0283aa..85ef51f12 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -82,9 +82,10 @@ pub enum MirPhase {
     ///    access to. This occurs in generator bodies. Such locals do not behave like other locals,
     ///    because they eg may be aliased in surprising ways. Runtime MIR has no such special locals -
     ///    all generator bodies are lowered and so all places that look like locals really are locals.
-    ///  - Const prop lints: The lint pass which reports eg `200_u8 + 200_u8` as an error is run as a
-    ///    part of analysis to runtime MIR lowering. This means that transformations which may supress
-    ///    such errors may not run on analysis MIR.
+    ///
+    /// Also note that the lint pass which reports eg `200_u8 + 200_u8` as an error is run as a part
+    /// of analysis to runtime MIR lowering. To ensure lints are reported reliably, this means that
+    /// transformations which may supress such errors should not run on analysis MIR.
     Runtime(RuntimePhase),
 }
 
@@ -829,6 +830,9 @@ pub type AssertMessage<'tcx> = AssertKind<Operand<'tcx>>;
 ///    generator has more than one variant, the parent place's variant index must be set, indicating
 ///    which variant is being used. If it has just one variant, the variant index may or may not be
 ///    included - the single possible variant is inferred if it is not included.
+///  - [`OpaqueCast`](ProjectionElem::OpaqueCast): This projection changes the place's type to the
+///    given one, and makes no other changes. A `OpaqueCast` projection on any type other than an
+///    opaque type from the current crate is not well-formed.
 ///  - [`ConstantIndex`](ProjectionElem::ConstantIndex): Computes an offset in units of `T` into the
 ///    place as described in the documentation for the `ProjectionElem`. The resulting address is
 ///    the parent's address plus that offset, and the type is `T`. This is only legal if the parent
@@ -928,6 +932,10 @@ pub enum ProjectionElem<V, T> {
     ///
     /// The included Symbol is the name of the variant, used for printing MIR.
     Downcast(Option<Symbol>, VariantIdx),
+
+    /// Like an explicit cast from an opaque type to a concrete type, but without
+    /// requiring an intermediate variable.
+    OpaqueCast(T),
 }
 
 /// Alias for projections as they appear in places, where the base is a place
@@ -1141,8 +1149,12 @@ pub enum CastKind {
     Pointer(PointerCast),
     /// Cast into a dyn* object.
     DynStar,
-    /// Remaining unclassified casts.
-    Misc,
+    IntToInt,
+    FloatToInt,
+    FloatToFloat,
+    IntToFloat,
+    PtrToPtr,
+    FnPtrToPtr,
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
@@ -1233,11 +1245,11 @@ pub enum BinOp {
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 mod size_asserts {
     use super::*;
-    // These are in alphabetical order, which is easy to maintain.
-    #[cfg(not(bootstrap))]
+    // tidy-alphabetical-start
     static_assert_size!(AggregateKind<'_>, 40);
     static_assert_size!(Operand<'_>, 24);
     static_assert_size!(Place<'_>, 16);
     static_assert_size!(PlaceElem<'_>, 24);
     static_assert_size!(Rvalue<'_>, 40);
+    // tidy-alphabetical-end
 }
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 405003156..fa3adafd4 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -4,7 +4,6 @@
  */
 
 use crate::mir::*;
-use crate::ty::subst::Subst;
 use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir as hir;
 use rustc_target::abi::VariantIdx;
@@ -57,7 +56,7 @@ impl<'tcx> PlaceTy<'tcx> {
     /// `PlaceElem`, where we can just use the `Ty` that is already
     /// stored inline on field projection elems.
     pub fn projection_ty(self, tcx: TyCtxt<'tcx>, elem: PlaceElem<'tcx>) -> PlaceTy<'tcx> {
-        self.projection_ty_core(tcx, ty::ParamEnv::empty(), &elem, |_, _, ty| ty)
+        self.projection_ty_core(tcx, ty::ParamEnv::empty(), &elem, |_, _, ty| ty, |_, ty| ty)
     }
 
     /// `place_ty.projection_ty_core(tcx, elem, |...| { ... })`
@@ -71,6 +70,7 @@ impl<'tcx> PlaceTy<'tcx> {
         param_env: ty::ParamEnv<'tcx>,
         elem: &ProjectionElem<V, T>,
         mut handle_field: impl FnMut(&Self, Field, T) -> Ty<'tcx>,
+        mut handle_opaque_cast: impl FnMut(&Self, T) -> Ty<'tcx>,
     ) -> PlaceTy<'tcx>
     where
         V: ::std::fmt::Debug,
@@ -109,6 +109,7 @@ impl<'tcx> PlaceTy<'tcx> {
                 PlaceTy { ty: self.ty, variant_index: Some(index) }
             }
             ProjectionElem::Field(f, fty) => PlaceTy::from_ty(handle_field(&self, f, fty)),
+            ProjectionElem::OpaqueCast(ty) => PlaceTy::from_ty(handle_opaque_cast(&self, ty)),
         };
         debug!("projection_ty self: {:?} elem: {:?} yields: {:?}", self, elem, answer);
         answer
diff --git a/compiler/rustc_middle/src/mir/type_foldable.rs b/compiler/rustc_middle/src/mir/type_foldable.rs
index 9d098c808..4c0974f86 100644
--- a/compiler/rustc_middle/src/mir/type_foldable.rs
+++ b/compiler/rustc_middle/src/mir/type_foldable.rs
@@ -26,6 +26,12 @@ TrivialTypeTraversalAndLiftImpls! {
     GeneratorSavedLocal,
 }
 
+TrivialTypeTraversalImpls! {
+    for <'tcx> {
+        ConstValue<'tcx>,
+    }
+}
+
 impl<'tcx> TypeFoldable<'tcx> for &'tcx [InlineAsmTemplatePiece] {
     fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, _folder: &mut F) -> Result<Self, F::Error> {
         Ok(self)
@@ -49,25 +55,3 @@ impl<'tcx, R: Idx, C: Idx> TypeFoldable<'tcx> for BitMatrix<R, C> {
         Ok(self)
     }
 }
-
-impl<'tcx> TypeFoldable<'tcx> for ConstantKind<'tcx> {
-    #[inline(always)]
-    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
-        folder.try_fold_mir_const(self)
-    }
-}
-
-impl<'tcx> TypeSuperFoldable<'tcx> for ConstantKind<'tcx> {
-    fn try_super_fold_with<F: FallibleTypeFolder<'tcx>>(
-        self,
-        folder: &mut F,
-    ) -> Result<Self, F::Error> {
-        match self {
-            ConstantKind::Ty(c) => Ok(ConstantKind::Ty(c.try_fold_with(folder)?)),
-            ConstantKind::Val(v, t) => Ok(ConstantKind::Val(v, t.try_fold_with(folder)?)),
-            ConstantKind::Unevaluated(uv, t) => {
-                Ok(ConstantKind::Unevaluated(uv.try_fold_with(folder)?, t.try_fold_with(folder)?))
-            }
-        }
-    }
-}
diff --git a/compiler/rustc_middle/src/mir/type_visitable.rs b/compiler/rustc_middle/src/mir/type_visitable.rs
index be19bb486..e7cd497b2 100644
--- a/compiler/rustc_middle/src/mir/type_visitable.rs
+++ b/compiler/rustc_middle/src/mir/type_visitable.rs
@@ -7,22 +7,3 @@ impl<'tcx, R: Idx, C: Idx> TypeVisitable<'tcx> for BitMatrix<R, C> {
         ControlFlow::CONTINUE
     }
 }
-
-impl<'tcx> TypeVisitable<'tcx> for ConstantKind<'tcx> {
-    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        visitor.visit_mir_const(*self)
-    }
-}
-
-impl<'tcx> TypeSuperVisitable<'tcx> for ConstantKind<'tcx> {
-    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
-        match *self {
-            ConstantKind::Ty(c) => c.visit_with(visitor),
-            ConstantKind::Val(_, t) => t.visit_with(visitor),
-            ConstantKind::Unevaluated(uv, t) => {
-                uv.visit_with(visitor)?;
-                t.visit_with(visitor)
-            }
-        }
-    }
-}
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index d9b24566b..ddcf3711b 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -1084,6 +1084,11 @@ macro_rules! visit_place_fns {
                     self.visit_ty(&mut new_ty, TyContext::Location(location));
                     if ty != new_ty { Some(PlaceElem::Field(field, new_ty)) } else { None }
                 }
+                PlaceElem::OpaqueCast(ty) => {
+                    let mut new_ty = ty;
+                    self.visit_ty(&mut new_ty, TyContext::Location(location));
+                    if ty != new_ty { Some(PlaceElem::OpaqueCast(new_ty)) } else { None }
+                }
                 PlaceElem::Deref
                 | PlaceElem::ConstantIndex { .. }
                 | PlaceElem::Subslice { .. }
@@ -1153,7 +1158,7 @@ macro_rules! visit_place_fns {
             location: Location,
         ) {
             match elem {
-                ProjectionElem::Field(_field, ty) => {
+                ProjectionElem::OpaqueCast(ty) | ProjectionElem::Field(_, ty) => {
                     self.visit_ty(ty, TyContext::Location(location));
                 }
                 ProjectionElem::Index(local) => {