Replace TypeMask.isEmpty by isEmptyOrNull, use isEmpty when it's really empty.

pkg/compiler/lib/src/cps_ir/inline.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library cps_ir.optimization.inline;
 
 import 'cps_fragment.dart';
 import 'cps_ir_builder.dart' show ThisParameterLocal;
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
@@ skipping 413 matching lines @@
     if (target.asyncMarker != AsyncMarker.SYNC) return null;
     // V8 does not optimize functions containing a try statement.  Inlining
     // code containing a try statement will make the optimizable calling code
     // become unoptimizable.
     if (target.resolvedAst.elements.containsTryStatement) {
       return null;
     }
 
     // Don't inline methods that never return. They are usually helper functions
     // that throw an exception.
-    if (invoke.type.isEmpty && !invoke.type.isNullable) {
+    if (invoke.type.isEmpty) {
       // TODO(sra): It would be ok to inline if doing so was shrinking.
       return null;
     }
 
     if (isBlacklisted(target)) return null;
 
     if (invoke.callingConvention == CallingConvention.OneShotIntercepted) {
       // One-shot interceptor calls with a known target are only inserted on
       // uncommon code paths, so they should not be inlined.
       return null;
     }
 
     Reference<Primitive> dartReceiver = invoke.dartReceiverRef;
     TypeMask abstractReceiver =
         dartReceiver == null ? null : abstractType(dartReceiver);
     // The receiver is non-null in a method body, unless the receiver is known
     // to be `null` (isEmpty covers `null` and unreachable).
     TypeMask abstractReceiverInMethod = abstractReceiver == null
         ? null
-        : abstractReceiver.isEmpty
+        : abstractReceiver.isEmptyOrNull
             ? abstractReceiver
             : abstractReceiver.nonNullable();
     List<TypeMask> abstractArguments =
         invoke.argumentRefs.map(abstractType).toList();
     var cachedResult = _inliner.cache.get(target, callStructure,
         abstractReceiverInMethod,
         abstractArguments);
 
     // Negative inlining result in the cache.
     if (cachedResult == InliningCache.NO_INLINE) return null;
@@ skipping 154 matching lines @@
         (enclosingClass == backend.helpers.jsNumberClass ||
          enclosingClass == backend.helpers.jsDoubleClass ||
          enclosingClass == backend.helpers.jsIntClass)) {
       // These should be handled by operator specialization.
       return true;
     }
     if (target == backend.helpers.stringInterpolationHelper) return true;
     return false;
   }
 }