Uplift CanonicalVarInfo and friends

compiler/rustc_middle/src/ty/mod.rs

@@ -1517,8 +1517,36 @@ pub struct Placeholder<T> {
 
 pub type PlaceholderRegion = Placeholder<BoundRegion>;
 
+impl rustc_type_ir::Placeholder for PlaceholderRegion {
+    fn universe(&self) -> UniverseIndex {
+        self.universe
+    }
+
+    fn var(&self) -> BoundVar {
+        self.bound.var
+    }
+
+    fn with_updated_universe(self, ui: UniverseIndex) -> Self {
+        Placeholder { universe: ui, ..self }
+    }
+}
+
 pub type PlaceholderType = Placeholder<BoundTy>;
 
+impl rustc_type_ir::Placeholder for PlaceholderType {
+    fn universe(&self) -> UniverseIndex {
+        self.universe
+    }
+
+    fn var(&self) -> BoundVar {
+        self.bound.var
+    }
+
+    fn with_updated_universe(self, ui: UniverseIndex) -> Self {
+        Placeholder { universe: ui, ..self }
+    }
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, HashStable)]
 #[derive(TyEncodable, TyDecodable, PartialOrd, Ord)]
 pub struct BoundConst<'tcx> {
@@ -1528,6 +1556,20 @@ pub struct BoundConst<'tcx> {
 
 pub type PlaceholderConst = Placeholder<BoundVar>;
 
+impl rustc_type_ir::Placeholder for PlaceholderConst {
+    fn universe(&self) -> UniverseIndex {
+        self.universe
+    }
+
+    fn var(&self) -> BoundVar {
+        self.bound
+    }
+
+    fn with_updated_universe(self, ui: UniverseIndex) -> Self {
+        Placeholder { universe: ui, ..self }
+    }
+}
+
 /// When type checking, we use the `ParamEnv` to track
 /// details about the set of where-clauses that are in scope at this
 /// particular point.