shrink ty::PredicateKind again

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>),