Introduce GeneratorWitnessMIR.

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -435,6 +435,7 @@ impl<'cx, 'tcx> TypeFolder<'tcx> for Canonicalizer<'cx, 'tcx> {
             ty::Closure(..)
             | ty::Generator(..)
             | ty::GeneratorWitness(..)
+            | ty::GeneratorWitnessMIR(..)
             | ty::Bool
             | ty::Char
             | ty::Int(..)

compiler/rustc_infer/src/infer/freshen.rs

@@ -209,6 +209,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
             | ty::Foreign(..)
             | ty::Param(..)
             | ty::Closure(..)
+            | ty::GeneratorWitnessMIR(..)
             | ty::GeneratorWitness(..) => t.super_fold_with(self),
 
             ty::Placeholder(..) | ty::Bound(..) => bug!("unexpected type {:?}", t),

compiler/rustc_infer/src/infer/outlives/components.rs

@@ -112,7 +112,7 @@ fn compute_components<'tcx>(
             }
 
             // All regions are bound inside a witness
-            ty::GeneratorWitness(..) => (),
+            ty::GeneratorWitness(..) | ty::GeneratorWitnessMIR(..) => (),
 
             // OutlivesTypeParameterEnv -- the actual checking that `X:'a`
             // is implied by the environment is done in regionck.