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

pkg/compiler/lib/src/ssa/builder.dart

 // Copyright (c) 2012, 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.
 
 part of ssa;
 
 class SsaFunctionCompiler implements FunctionCompiler {
   final SsaCodeGeneratorTask generator;
   final SsaBuilderTask builder;
   final SsaOptimizerTask optimizer;
@@ skipping 1383 matching lines @@
         return false;
       }
 
       // A generative constructor body is not seen by global analysis,
       // so we should not query for its type.
       if (!element.isGenerativeConstructorBody) {
         // Don't inline if the return type was inferred to be non-null empty.
         // This means that the function always throws an exception.
         TypeMask returnType =
             compiler.typesTask.getGuaranteedReturnTypeOfElement(element);
-        if (returnType != null
-            && returnType.isEmpty
-            && !returnType.isNullable) {
+        if (returnType != null && returnType.isEmpty) {
           isReachable = false;
           return false;
         }
       }
 
       return true;
     }
 
     bool doesNotContainCode() {
       // A function with size 1 does not contain any code.
@@ skipping 264 matching lines @@
               closeAndGotoExit(new HReturn(
                   graph.addConstantBool(false, compiler),
                   sourceInformationBuilder
                       .buildImplicitReturn(functionElement)));
             },
             visitElse: null,
             sourceInformation: sourceInformationBuilder.buildIf(function.body));
       }
     }
     if (const bool.fromEnvironment('unreachable-throw') == true) {
-      var emptyParameters = parameters.values.where((p) =>
-          p.instructionType.isEmpty && !p.instructionType.isNullable);
+      var emptyParameters = parameters.values
+          .where((p) => p.instructionType.isEmpty);
       if (emptyParameters.length > 0) {
         addComment('${emptyParameters} inferred as [empty]');
         pushInvokeStatic(function.body, helpers.assertUnreachableMethod, []);
         pop();
         return closeFunction();
       }
     }
     function.body.accept(this);
     return closeFunction();
   }
@@ skipping 7536 matching lines @@
     if (unaliased is TypedefType) throw 'unable to unalias $type';
     unaliased.accept(this, builder);
   }
 
   void visitDynamicType(DynamicType type, SsaBuilder builder) {
     JavaScriptBackend backend = builder.compiler.backend;
     ClassElement cls = backend.helpers.DynamicRuntimeType;
     builder.push(new HDynamicType(type, new TypeMask.exact(cls, classWorld)));
   }
 }