shrink `ty::PredicateKind` again

6 files changed, 54 insertions, 10 deletions

diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 9b3de6710ec..f8e0d910a54 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -303,7 +303,7 @@ rustc_queries! {
     }
 
     query try_unify_abstract_consts(key: (
-        ty::Unevaluated<'tcx>, ty::Unevaluated<'tcx>
+        ty::Unevaluated<'tcx, ()>, ty::Unevaluated<'tcx, ()>
     )) -> bool {
         desc {
             |tcx| "trying to unify the generic constants {} and {}",
diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index b1f6a612776..e6a6b7f8556 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -1,4 +1,5 @@
 use std::convert::TryInto;
+use std::fmt;
 
 use crate::mir::interpret::{AllocId, ConstValue, Scalar};
 use crate::mir::Promoted;
@@ -20,20 +21,38 @@ use super::ScalarInt;
 /// so refer to that check for more info.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, TyEncodable, TyDecodable, Lift)]
 #[derive(Hash, HashStable)]
-pub struct Unevaluated<'tcx> {
+pub struct Unevaluated<'tcx, P = Option<Promoted>> {
     pub def: ty::WithOptConstParam<DefId>,
     pub substs_: Option<SubstsRef<'tcx>>,
-    pub promoted: Option<Promoted>,
+    pub promoted: P,
 }
 
 impl<'tcx> Unevaluated<'tcx> {
-    pub fn new(def: ty::WithOptConstParam<DefId>, substs: SubstsRef<'tcx>) -> Unevaluated<'tcx> {
-        Unevaluated { def, substs_: Some(substs), promoted: None }
+    pub fn shrink(self) -> Unevaluated<'tcx, ()> {
+        debug_assert_eq!(self.promoted, None);
+        Unevaluated { def: self.def, substs_: self.substs_, promoted: () }
     }
+}
+
+impl<'tcx> Unevaluated<'tcx, ()> {
+    pub fn expand(self) -> Unevaluated<'tcx> {
+        Unevaluated { def: self.def, substs_: self.substs_, promoted: None }
+    }
+}
+
+impl<'tcx, P: Default> Unevaluated<'tcx, P> {
+    pub fn new(def: ty::WithOptConstParam<DefId>, substs: SubstsRef<'tcx>) -> Unevaluated<'tcx, P> {
+        Unevaluated { def, substs_: Some(substs), promoted: Default::default() }
+    }
+}
 
+impl<'tcx, P: Default + PartialEq + fmt::Debug> Unevaluated<'tcx, P> {
     pub fn substs(self, tcx: TyCtxt<'tcx>) -> SubstsRef<'tcx> {
         self.substs_.unwrap_or_else(|| {
-            debug_assert_eq!(self.promoted, None);
+            // We must not use the parents default substs for promoted constants
+            // as that can result in incorrect substs and calls the `default_anon_const_substs`
+            // for something that might not actually be a constant.
+            debug_assert_eq!(self.promoted, Default::default());
             tcx.default_anon_const_substs(self.def.did)
         })
     }
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index 1c4f24cdf39..763da7e82c8 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -310,7 +310,7 @@ impl FlagComputation {
         }
     }
 
-    fn add_unevaluated_const(&mut self, ct: ty::Unevaluated<'tcx>) {
+    fn add_unevaluated_const<P>(&mut self, ct: ty::Unevaluated<'tcx, P>) {
         if let Some(substs) = ct.substs_ {
             self.add_substs(substs);
         } else {
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index b1ebe43c491..8f814a84b49 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -406,7 +406,7 @@ crate struct PredicateInner<'tcx> {
 }
 
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
-static_assert_size!(PredicateInner<'_>, 56);
+static_assert_size!(PredicateInner<'_>, 48);
 
 #[derive(Clone, Copy, Lift)]
 pub struct Predicate<'tcx> {
@@ -502,7 +502,7 @@ pub enum PredicateKind<'tcx> {
     Coerce(CoercePredicate<'tcx>),
 
     /// Constant initializer must evaluate successfully.
-    ConstEvaluatable(ty::Unevaluated<'tcx>),
+    ConstEvaluatable(ty::Unevaluated<'tcx, ()>),
 
     /// Constants must be equal. The first component is the const that is expected.
     ConstEquate(&'tcx Const<'tcx>, &'tcx Const<'tcx>),
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index b64d507e0b8..4a2c8349fdc 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -579,7 +579,7 @@ pub fn super_relate_consts<R: TypeRelation<'tcx>>(
         (ty::ConstKind::Unevaluated(au), ty::ConstKind::Unevaluated(bu))
             if tcx.features().const_evaluatable_checked =>
         {
-            tcx.try_unify_abstract_consts((au, bu))
+            tcx.try_unify_abstract_consts((au.shrink(), bu.shrink()))
         }
 
         // While this is slightly incorrect, it shouldn't matter for `min_const_generics`
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 31088423efa..2ab25c83970 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -1105,3 +1105,28 @@ impl<'tcx> TypeFoldable<'tcx> for ty::Unevaluated<'tcx> {
         }
     }
 }
+
+impl<'tcx> TypeFoldable<'tcx> for ty::Unevaluated<'tcx, ()> {
+    fn super_fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
+        ty::Unevaluated {
+            def: self.def,
+            substs_: Some(self.substs(folder.tcx()).fold_with(folder)),
+            promoted: self.promoted,
+        }
+    }
+
+    fn visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        visitor.visit_unevaluated_const(self.expand())
+    }
+
+    fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        if let Some(tcx) = visitor.tcx_for_anon_const_substs() {
+            self.substs(tcx).visit_with(visitor)
+        } else if let Some(substs) = self.substs_ {
+            substs.visit_with(visitor)
+        } else {
+            debug!("ignoring default substs of `{:?}`", self.def);
+            ControlFlow::CONTINUE
+        }
+    }
+}