Rollup merge of #111366 - obeis:ascribe-user-type-variance, r=lcnr

Make `NonUseContext::AscribeUserTy` carry `ty::Variance`

Close #108267

compiler/rustc_borrowck/src/def_use.rs

@@ -55,7 +55,7 @@ pub fn categorize(context: PlaceContext) -> Option<DefUse> {
         // `PlaceMention` and `AscribeUserType` both evaluate the place, which must not
         // contain dangling references.
         PlaceContext::NonMutatingUse(NonMutatingUseContext::PlaceMention) |
-        PlaceContext::NonUse(NonUseContext::AscribeUserTy) |
+        PlaceContext::NonUse(NonUseContext::AscribeUserTy(_)) |
 
         PlaceContext::MutatingUse(MutatingUseContext::AddressOf) |
         PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf) |

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -777,7 +777,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                 Inspect | Copy | Move | PlaceMention | SharedBorrow | ShallowBorrow | UniqueBorrow
                 | AddressOf | Projection,
             ) => ty::Covariant,
-            PlaceContext::NonUse(AscribeUserTy) => ty::Covariant,
+            PlaceContext::NonUse(AscribeUserTy(variance)) => variance,
         }
     }