diff --git a/pkg/compiler/lib/src/dump_info.dart b/pkg/compiler/lib/src/dump_info.dart
index acf302a..75010fd 100644
--- a/pkg/compiler/lib/src/dump_info.dart
+++ b/pkg/compiler/lib/src/dump_info.dart
@@ -20,11 +20,9 @@
 import 'elements/entities.dart';
 import 'js/js.dart' as jsAst;
 import 'js_backend/js_backend.dart' show JavaScriptBackend;
+import 'types/masks.dart';
 import 'types/types.dart'
-    show
-        GlobalTypeInferenceElementResult,
-        GlobalTypeInferenceMemberResult,
-        TypeMask;
+    show GlobalTypeInferenceElementResult, GlobalTypeInferenceMemberResult;
 import 'universe/world_builder.dart'
     show CodegenWorldBuilder, ReceiverConstraint;
 import 'universe/world_impact.dart'
diff --git a/pkg/compiler/lib/src/inferrer/builder_kernel.dart b/pkg/compiler/lib/src/inferrer/builder_kernel.dart
index 85a0795..2998bbf 100644
--- a/pkg/compiler/lib/src/inferrer/builder_kernel.dart
+++ b/pkg/compiler/lib/src/inferrer/builder_kernel.dart
@@ -18,6 +18,7 @@
 import '../native/behavior.dart';
 import '../options.dart';
 import '../types/constants.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/selector.dart';
 import '../universe/side_effects.dart';
diff --git a/pkg/compiler/lib/src/inferrer/closure_tracer.dart b/pkg/compiler/lib/src/inferrer/closure_tracer.dart
index 1c131cb..8f785fb 100644
--- a/pkg/compiler/lib/src/inferrer/closure_tracer.dart
+++ b/pkg/compiler/lib/src/inferrer/closure_tracer.dart
@@ -7,7 +7,7 @@
 import '../common/names.dart' show Names;
 import '../elements/entities.dart';
 import '../js_backend/backend.dart' show JavaScriptBackend;
-import '../types/types.dart' show TypeMask;
+import '../types/masks.dart' show TypeMask;
 import '../universe/selector.dart' show Selector;
 import 'debug.dart' as debug;
 import 'inferrer_engine.dart';
diff --git a/pkg/compiler/lib/src/inferrer/inferrer_engine.dart b/pkg/compiler/lib/src/inferrer/inferrer_engine.dart
index 07aa78b..9a5fdc1 100644
--- a/pkg/compiler/lib/src/inferrer/inferrer_engine.dart
+++ b/pkg/compiler/lib/src/inferrer/inferrer_engine.dart
@@ -19,6 +19,7 @@
 import '../options.dart';
 import '../types/abstract_value_domain.dart';
 import '../types/constants.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/call_structure.dart';
 import '../universe/selector.dart';
diff --git a/pkg/compiler/lib/src/inferrer/node_tracer.dart b/pkg/compiler/lib/src/inferrer/node_tracer.dart
index b1ed67d..032b254 100644
--- a/pkg/compiler/lib/src/inferrer/node_tracer.dart
+++ b/pkg/compiler/lib/src/inferrer/node_tracer.dart
@@ -6,7 +6,7 @@
 
 import '../common/names.dart' show Identifiers;
 import '../elements/entities.dart';
-import '../types/types.dart' show ContainerTypeMask, MapTypeMask;
+import '../types/masks.dart' show ContainerTypeMask, MapTypeMask;
 import '../util/util.dart' show Setlet;
 import 'debug.dart' as debug;
 import 'inferrer_engine.dart';
diff --git a/pkg/compiler/lib/src/inferrer/type_graph_dump.dart b/pkg/compiler/lib/src/inferrer/type_graph_dump.dart
index f4ec50f..d8242e9 100644
--- a/pkg/compiler/lib/src/inferrer/type_graph_dump.dart
+++ b/pkg/compiler/lib/src/inferrer/type_graph_dump.dart
@@ -6,7 +6,7 @@
 import '../../compiler_new.dart';
 import '../elements/entities.dart';
 import '../elements/entity_utils.dart' as utils;
-import '../types/types.dart';
+import '../types/masks.dart';
 import 'inferrer_engine.dart';
 import 'type_graph_nodes.dart';
 import 'debug.dart';
diff --git a/pkg/compiler/lib/src/js_backend/backend.dart b/pkg/compiler/lib/src/js_backend/backend.dart
index 00fe50c..7188cf6 100644
--- a/pkg/compiler/lib/src/js_backend/backend.dart
+++ b/pkg/compiler/lib/src/js_backend/backend.dart
@@ -37,7 +37,7 @@
 import '../native/native.dart' as native;
 import '../ssa/ssa.dart' show SsaFunctionCompiler;
 import '../tracer.dart';
-import '../types/types.dart';
+import '../types/masks.dart';
 import '../universe/call_structure.dart' show CallStructure;
 import '../universe/class_hierarchy_builder.dart'
     show ClassHierarchyBuilder, ClassQueries;
diff --git a/pkg/compiler/lib/src/js_backend/interceptor_data.dart b/pkg/compiler/lib/src/js_backend/interceptor_data.dart
index 87fc04e..079aa91 100644
--- a/pkg/compiler/lib/src/js_backend/interceptor_data.dart
+++ b/pkg/compiler/lib/src/js_backend/interceptor_data.dart
@@ -9,7 +9,7 @@
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../js/js.dart' as jsAst;
-import '../types/types.dart' show TypeMask;
+import '../types/masks.dart' show TypeMask;
 import '../universe/selector.dart';
 import '../world.dart' show ClosedWorld;
 import 'namer.dart';
diff --git a/pkg/compiler/lib/src/kernel/element_map.dart b/pkg/compiler/lib/src/kernel/element_map.dart
index fe468dd..13adcc4 100644
--- a/pkg/compiler/lib/src/kernel/element_map.dart
+++ b/pkg/compiler/lib/src/kernel/element_map.dart
@@ -20,7 +20,7 @@
 import '../js_model/elements.dart' show JGeneratorBody;
 import '../native/native.dart' as native;
 import '../ssa/type_builder.dart';
-import '../types/types.dart';
+import '../types/masks.dart';
 import '../universe/call_structure.dart';
 import '../universe/selector.dart';
 import '../world.dart';
diff --git a/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart b/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
index 3c3f6bf..ae1b004 100644
--- a/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
+++ b/pkg/compiler/lib/src/kernel/kernel_backend_strategy.dart
@@ -25,6 +25,7 @@
 import '../ssa/nodes.dart';
 import '../ssa/ssa.dart';
 import '../ssa/types.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/selector.dart';
 import '../universe/world_impact.dart';
@@ -173,7 +174,7 @@
         !mask.satisfies(closedWorld.commonElements.jsStringClass, closedWorld);
   }
 
-  bool isFixedLength(TypeMask mask, ClosedWorld closedWorld) {
+  bool isFixedLength(covariant TypeMask mask, ClosedWorld closedWorld) {
     if (mask.isContainer && (mask as ContainerTypeMask).length != null) {
       // A container on which we have inferred the length.
       return true;
@@ -204,7 +205,7 @@
         parameter, _globalInferenceResults);
   }
 
-  TypeMask selectorTypeOf(Selector selector, TypeMask mask) {
+  TypeMask selectorTypeOf(Selector selector, covariant TypeMask mask) {
     return TypeMaskFactory.inferredTypeForSelector(
         selector, mask, _globalInferenceResults);
   }
diff --git a/pkg/compiler/lib/src/ssa/codegen.dart b/pkg/compiler/lib/src/ssa/codegen.dart
index 843957a..5d70634 100644
--- a/pkg/compiler/lib/src/ssa/codegen.dart
+++ b/pkg/compiler/lib/src/ssa/codegen.dart
@@ -26,7 +26,7 @@
 import '../native/native.dart' as native;
 import '../options.dart';
 import '../types/abstract_value_domain.dart';
-import '../types/types.dart';
+import '../types/masks.dart';
 import '../universe/call_structure.dart' show CallStructure;
 import '../universe/selector.dart' show Selector;
 import '../universe/use.dart'
diff --git a/pkg/compiler/lib/src/ssa/codegen_helpers.dart b/pkg/compiler/lib/src/ssa/codegen_helpers.dart
index d7194b8..bfa7fb2 100644
--- a/pkg/compiler/lib/src/ssa/codegen_helpers.dart
+++ b/pkg/compiler/lib/src/ssa/codegen_helpers.dart
@@ -8,7 +8,7 @@
 import '../js_backend/interceptor_data.dart';
 import '../options.dart';
 import '../types/abstract_value_domain.dart';
-import '../types/types.dart';
+import '../types/masks.dart';
 import '../universe/selector.dart' show Selector;
 import '../world.dart' show ClosedWorld;
 import 'nodes.dart';
diff --git a/pkg/compiler/lib/src/ssa/graph_builder.dart b/pkg/compiler/lib/src/ssa/graph_builder.dart
index 832bb52..6dc7c0a 100644
--- a/pkg/compiler/lib/src/ssa/graph_builder.dart
+++ b/pkg/compiler/lib/src/ssa/graph_builder.dart
@@ -24,6 +24,7 @@
 import '../js_emitter/code_emitter_task.dart';
 import '../options.dart';
 import '../types/abstract_value_domain.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../world.dart' show ClosedWorld;
 import 'jump_handler.dart';
diff --git a/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart b/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
index 11b98a0..a3ec846 100644
--- a/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
+++ b/pkg/compiler/lib/src/ssa/interceptor_simplifier.dart
@@ -8,7 +8,7 @@
 import '../elements/entities.dart';
 import '../js_backend/interceptor_data.dart';
 import '../types/abstract_value_domain.dart';
-import '../types/types.dart';
+import '../types/masks.dart';
 import '../universe/selector.dart' show Selector;
 import '../world.dart' show ClosedWorld;
 import 'nodes.dart';
diff --git a/pkg/compiler/lib/src/ssa/invoke_dynamic_specializers.dart b/pkg/compiler/lib/src/ssa/invoke_dynamic_specializers.dart
index 0ca17d5..ac8576f 100644
--- a/pkg/compiler/lib/src/ssa/invoke_dynamic_specializers.dart
+++ b/pkg/compiler/lib/src/ssa/invoke_dynamic_specializers.dart
@@ -8,6 +8,7 @@
 import '../elements/entities.dart';
 import '../elements/names.dart';
 import '../options.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/call_structure.dart';
 import '../universe/selector.dart';
diff --git a/pkg/compiler/lib/src/ssa/locals_handler.dart b/pkg/compiler/lib/src/ssa/locals_handler.dart
index 408e089..bf5b34b 100644
--- a/pkg/compiler/lib/src/ssa/locals_handler.dart
+++ b/pkg/compiler/lib/src/ssa/locals_handler.dart
@@ -11,6 +11,8 @@
 import '../js_backend/interceptor_data.dart';
 import '../js_model/closure.dart' show JRecordField, JClosureField;
 import '../js_model/locals.dart' show JLocal;
+import '../types/abstract_value_domain.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../world.dart' show ClosedWorld;
 
@@ -66,7 +68,8 @@
 
   ClosedWorld get closedWorld => builder.closedWorld;
 
-  CommonMasks get commonMasks => closedWorld.abstractValueDomain;
+  AbstractValueDomain get _abstractValueDomain =>
+      closedWorld.abstractValueDomain;
 
   GlobalTypeInferenceResults get _globalInferenceResults =>
       builder.globalInferenceResults;
@@ -116,7 +119,7 @@
   }
 
   HInstruction createBox(SourceInformation sourceInformation) {
-    HInstruction box = new HCreateBox(commonMasks.nonNullType)
+    HInstruction box = new HCreateBox(_abstractValueDomain.nonNullType)
       ..sourceInformation = sourceInformation;
     builder.add(box);
     return box;
@@ -135,7 +138,8 @@
     if (forGenerativeConstructorBody) {
       // The box is passed as a parameter to a generative
       // constructor body.
-      box = builder.addParameter(closureInfo.context, commonMasks.nonNullType);
+      box = builder.addParameter(
+          closureInfo.context, _abstractValueDomain.nonNullType);
     } else {
       box = createBox(sourceInformation);
     }
@@ -226,7 +230,7 @@
       });
       // Inside closure redirect references to itself to [:this:].
       HThis thisInstruction =
-          new HThis(closureData.thisLocal, commonMasks.nonNullType);
+          new HThis(closureData.thisLocal, _abstractValueDomain.nonNullType);
       builder.graph.thisInstruction = thisInstruction;
       builder.graph.entry.addAtEntry(thisInstruction);
       updateLocal(closureData.closureEntity, thisInstruction);
@@ -338,7 +342,7 @@
       FieldEntity redirect = redirectionMapping[local];
       HInstruction receiver = readLocal(closureData.closureEntity);
       TypeMask type = local is BoxLocal
-          ? commonMasks.nonNullType
+          ? _abstractValueDomain.nonNullType
           : getTypeOfCapturedVariable(redirect);
       HInstruction fieldGet = new HFieldGet(redirect, receiver, type);
       builder.add(fieldGet);
@@ -364,8 +368,8 @@
     } else {
       assert(_isUsedInTryOrGenerator(local));
       HLocalValue localValue = getLocal(local);
-      HInstruction instruction = new HLocalGet(
-          local, localValue, commonMasks.dynamicType, sourceInformation);
+      HInstruction instruction = new HLocalGet(local, localValue,
+          _abstractValueDomain.dynamicType, sourceInformation);
       builder.add(instruction);
       return instruction;
     }
@@ -391,8 +395,9 @@
     }
 
     return activationVariables.putIfAbsent(local, () {
-      HLocalValue localValue = new HLocalValue(local, commonMasks.nonNullType)
-        ..sourceInformation = sourceInformation;
+      HLocalValue localValue =
+          new HLocalValue(local, _abstractValueDomain.nonNullType)
+            ..sourceInformation = sourceInformation;
       builder.graph.entry.addAtExit(localValue);
       return localValue;
     });
@@ -509,8 +514,8 @@
       if (isAccessedDirectly(local)) {
         // We know 'this' cannot be modified.
         if (local != scopeInfo.thisLocal) {
-          HPhi phi =
-              new HPhi.singleInput(local, instruction, commonMasks.dynamicType);
+          HPhi phi = new HPhi.singleInput(
+              local, instruction, _abstractValueDomain.dynamicType);
           loopEntry.addPhi(phi);
           directLocals[local] = phi;
         } else {
@@ -577,8 +582,10 @@
         if (identical(instruction, mine)) {
           joinedLocals[local] = instruction;
         } else {
-          HInstruction phi = new HPhi.manyInputs(local,
-              <HInstruction>[mine, instruction], commonMasks.dynamicType);
+          HInstruction phi = new HPhi.manyInputs(
+              local,
+              <HInstruction>[mine, instruction],
+              _abstractValueDomain.dynamicType);
           joinBlock.addPhi(phi);
           joinedLocals[local] = phi;
         }
@@ -600,7 +607,7 @@
     HInstruction thisValue = null;
     directLocals.forEach((Local local, HInstruction instruction) {
       if (local != scopeInfo.thisLocal) {
-        HPhi phi = new HPhi.noInputs(local, commonMasks.dynamicType);
+        HPhi phi = new HPhi.noInputs(local, _abstractValueDomain.dynamicType);
         joinedLocals[local] = phi;
         joinBlock.addPhi(phi);
       } else {
diff --git a/pkg/compiler/lib/src/ssa/optimize.dart b/pkg/compiler/lib/src/ssa/optimize.dart
index 170afb3..f521421 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -18,6 +18,7 @@
 import '../native/native.dart' as native;
 import '../options.dart';
 import '../types/abstract_value_domain.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/selector.dart' show Selector;
 import '../universe/side_effects.dart' show SideEffects;
diff --git a/pkg/compiler/lib/src/ssa/type_builder.dart b/pkg/compiler/lib/src/ssa/type_builder.dart
index a60c98e..81268b8 100644
--- a/pkg/compiler/lib/src/ssa/type_builder.dart
+++ b/pkg/compiler/lib/src/ssa/type_builder.dart
@@ -7,7 +7,7 @@
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../io/source_information.dart';
-import '../types/types.dart';
+import '../types/masks.dart';
 import '../universe/use.dart' show TypeUse;
 
 /// Enum that defines how a member has access to the current type variables.
diff --git a/pkg/compiler/lib/src/ssa/types.dart b/pkg/compiler/lib/src/ssa/types.dart
index d93488d..9e938c4 100644
--- a/pkg/compiler/lib/src/ssa/types.dart
+++ b/pkg/compiler/lib/src/ssa/types.dart
@@ -5,6 +5,7 @@
 import '../common_elements.dart' show CommonElements;
 import '../elements/entities.dart';
 import '../native/native.dart' as native;
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/selector.dart' show Selector;
 import '../world.dart' show ClosedWorld;
diff --git a/pkg/compiler/lib/src/ssa/types_propagation.dart b/pkg/compiler/lib/src/ssa/types_propagation.dart
index f5e50bb..d0a0f44 100644
--- a/pkg/compiler/lib/src/ssa/types_propagation.dart
+++ b/pkg/compiler/lib/src/ssa/types_propagation.dart
@@ -6,6 +6,7 @@
 import '../elements/entities.dart';
 import '../options.dart';
 import '../types/abstract_value_domain.dart';
+import '../types/masks.dart';
 import '../types/types.dart';
 import '../universe/selector.dart' show Selector;
 import '../world.dart' show ClosedWorld;
diff --git a/pkg/compiler/lib/src/types/types.dart b/pkg/compiler/lib/src/types/types.dart
index 26ad97d..704157c 100644
--- a/pkg/compiler/lib/src/types/types.dart
+++ b/pkg/compiler/lib/src/types/types.dart
@@ -13,8 +13,6 @@
 import '../world.dart' show ClosedWorld, ClosedWorldRefiner;
 import 'abstract_value_domain.dart';
 
-export 'masks.dart';
-
 /// Results about a single element (e.g. a method, parameter, or field)
 /// produced by the global type-inference algorithm.
 ///
diff --git a/pkg/compiler/lib/src/universe/function_set.dart b/pkg/compiler/lib/src/universe/function_set.dart
index 01f27b2..4d64297 100644
--- a/pkg/compiler/lib/src/universe/function_set.dart
+++ b/pkg/compiler/lib/src/universe/function_set.dart
@@ -6,7 +6,7 @@
 
 import '../common/names.dart' show Identifiers, Selectors;
 import '../elements/entities.dart';
-import '../types/types.dart';
+import '../types/masks.dart';
 import '../util/util.dart' show Hashing, Setlet;
 import '../world.dart' show ClosedWorld;
 import 'selector.dart' show Selector;
diff --git a/tests/compiler/dart2js/codegen/expect_annotations_test.dart b/tests/compiler/dart2js/codegen/expect_annotations_test.dart
index bff2af5..e5d0770f 100644
--- a/tests/compiler/dart2js/codegen/expect_annotations_test.dart
+++ b/tests/compiler/dart2js/codegen/expect_annotations_test.dart
@@ -7,6 +7,7 @@
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/elements/entities.dart';
 import 'package:compiler/src/js_backend/annotations.dart' as optimizerHints;
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/types/types.dart';
 import 'package:compiler/src/world.dart' show ClosedWorld;
 import '../inference/type_mask_test_helper.dart';
diff --git a/tests/compiler/dart2js/codegen/trust_type_annotations_test.dart b/tests/compiler/dart2js/codegen/trust_type_annotations_test.dart
index 4e8b777..615226b 100644
--- a/tests/compiler/dart2js/codegen/trust_type_annotations_test.dart
+++ b/tests/compiler/dart2js/codegen/trust_type_annotations_test.dart
@@ -6,7 +6,7 @@
 import "package:async_helper/async_helper.dart";
 import 'package:compiler/src/commandline_options.dart';
 import 'package:compiler/src/elements/entities.dart';
-import '../compiler_helper.dart';
+import 'package:compiler/src/types/masks.dart';
 import '../memory_compiler.dart';
 
 const String TEST = """
diff --git a/tests/compiler/dart2js/codegen/type_inference8_test.dart b/tests/compiler/dart2js/codegen/type_inference8_test.dart
index 502aa96..7940d5e 100644
--- a/tests/compiler/dart2js/codegen/type_inference8_test.dart
+++ b/tests/compiler/dart2js/codegen/type_inference8_test.dart
@@ -7,7 +7,7 @@
 import "package:async_helper/async_helper.dart";
 import "package:compiler/src/commandline_options.dart";
 import "package:compiler/src/constants/values.dart";
-import "package:compiler/src/types/types.dart";
+import "package:compiler/src/types/masks.dart";
 import "package:expect/expect.dart";
 import '../memory_compiler.dart';
 
diff --git a/tests/compiler/dart2js/compiler_helper.dart b/tests/compiler/dart2js/compiler_helper.dart
index 7e8faba..50d9225 100644
--- a/tests/compiler/dart2js/compiler_helper.dart
+++ b/tests/compiler/dart2js/compiler_helper.dart
@@ -21,8 +21,6 @@
 export 'package:compiler/src/diagnostics/source_span.dart';
 export 'package:compiler/src/diagnostics/spannable.dart';
 
-export 'package:compiler/src/types/types.dart' show TypeMask;
-
 import 'package:compiler/src/util/util.dart';
 export 'package:compiler/src/util/util.dart';
 
diff --git a/tests/compiler/dart2js/inference/data/field_type.dart b/tests/compiler/dart2js/inference/data/field_type.dart
index 44168f3..51b672d 100644
--- a/tests/compiler/dart2js/inference/data/field_type.dart
+++ b/tests/compiler/dart2js/inference/data/field_type.dart
@@ -202,8 +202,7 @@
 
   /*element: A9.:[exact=A9]*/
   A9(/*[exact=JSBool]*/ x) {
-    if (x) {
-    } else {
+    if (x) {} else {
       /*update: [exact=A9]*/ f9 = "1";
     }
   }
@@ -728,8 +727,7 @@
   /*element: A29.:[exact=A29]*/
   A29(/*[exact=JSUInt31]*/ x) {
     this. /*update: [exact=A29]*/ f29a = x;
-    if (x /*invoke: [exact=JSUInt31]*/ == 0) {
-    } else {
+    if (x /*invoke: [exact=JSUInt31]*/ == 0) {} else {
       return;
     }
     this. /*update: [exact=A29]*/ f29b = x;
diff --git a/tests/compiler/dart2js/inference/data/general.dart b/tests/compiler/dart2js/inference/data/general.dart
index 1b2d806..ea317d5 100644
--- a/tests/compiler/dart2js/inference/data/general.dart
+++ b/tests/compiler/dart2js/inference/data/general.dart
@@ -306,8 +306,7 @@
 
 /*element: testIsCheck26:[subclass=JSInt]*/
 testIsCheck26(/*[null|subclass=Object]*/ a) {
-  if (a is int) {
-  } else {
+  if (a is int) {} else {
     throw 42;
   }
   return a;
@@ -315,8 +314,7 @@
 
 /*element: testIsCheck27:[subclass=JSInt]*/
 testIsCheck27(/*[null|subclass=Object]*/ a) {
-  if (a is int) {
-  } else {
+  if (a is int) {} else {
     return 42;
   }
   return a;
@@ -324,8 +322,7 @@
 
 /*element: testIsCheck28:[null|subclass=Object]*/
 testIsCheck28(/*[null|subclass=Object]*/ a) {
-  if (a is int) {
-  } else {}
+  if (a is int) {} else {}
   return a;
 }
 
@@ -347,8 +344,7 @@
 /*element: testIf2:[null|exact=JSUInt31]*/
 testIf2(/*[null|subclass=Object]*/ a) {
   var c = null;
-  if (a) {
-  } else {
+  if (a) {} else {
     c = 10;
   }
   return c;
diff --git a/tests/compiler/dart2js/inference/inference_test_helper.dart b/tests/compiler/dart2js/inference/inference_test_helper.dart
index 7796132..a116e44 100644
--- a/tests/compiler/dart2js/inference/inference_test_helper.dart
+++ b/tests/compiler/dart2js/inference/inference_test_helper.dart
@@ -9,6 +9,7 @@
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/diagnostics/diagnostic_listener.dart';
 import 'package:compiler/src/elements/entities.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/types/types.dart';
 import 'package:compiler/src/js_model/locals.dart';
 import 'package:compiler/src/kernel/element_map.dart';
diff --git a/tests/compiler/dart2js/inference/list_tracer_test.dart b/tests/compiler/dart2js/inference/list_tracer_test.dart
index 4e3b241..e7713ce 100644
--- a/tests/compiler/dart2js/inference/list_tracer_test.dart
+++ b/tests/compiler/dart2js/inference/list_tracer_test.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:async_helper/async_helper.dart';
-import 'package:compiler/src/types/types.dart' show ContainerTypeMask, TypeMask;
+import 'package:compiler/src/types/masks.dart' show ContainerTypeMask, TypeMask;
 import 'package:expect/expect.dart';
 
 import 'type_mask_test_helper.dart';
diff --git a/tests/compiler/dart2js/inference/load_deferred_library_test.dart b/tests/compiler/dart2js/inference/load_deferred_library_test.dart
index 78a0ea5..62d1b4a 100644
--- a/tests/compiler/dart2js/inference/load_deferred_library_test.dart
+++ b/tests/compiler/dart2js/inference/load_deferred_library_test.dart
@@ -11,7 +11,7 @@
 import 'package:compiler/src/js_model/js_strategy.dart';
 import 'package:compiler/src/kernel/element_map.dart';
 import 'package:compiler/src/types/abstract_value_domain.dart';
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/world.dart';
 import 'package:expect/expect.dart';
 import 'package:kernel/ast.dart' as ir;
diff --git a/tests/compiler/dart2js/inference/map_tracer_test.dart b/tests/compiler/dart2js/inference/map_tracer_test.dart
index c450698..4336589 100644
--- a/tests/compiler/dart2js/inference/map_tracer_test.dart
+++ b/tests/compiler/dart2js/inference/map_tracer_test.dart
@@ -6,7 +6,8 @@
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/elements/entities.dart';
 import 'package:compiler/src/inferrer/type_graph_inferrer.dart';
-import 'package:compiler/src/types/types.dart' show MapTypeMask, TypeMask;
+import 'package:compiler/src/types/abstract_value_domain.dart';
+import 'package:compiler/src/types/masks.dart' show MapTypeMask, TypeMask;
 import 'package:compiler/src/world.dart';
 import 'package:expect/expect.dart';
 
@@ -233,7 +234,7 @@
   TypeGraphInferrer typesInferrer =
       compiler.globalInference.typesInferrerInternal;
   ClosedWorld closedWorld = typesInferrer.closedWorld;
-  CommonMasks commonMasks = closedWorld.abstractValueDomain;
+  AbstractValueDomain commonMasks = closedWorld.abstractValueDomain;
   TypeMask emptyType = new TypeMask.nonNullEmpty();
   MemberEntity aKey = findMember(closedWorld, 'aKey');
   TypeMask aKeyType = typesInferrer.getTypeOfMember(aKey);
diff --git a/tests/compiler/dart2js/inference/type_combination_test.dart b/tests/compiler/dart2js/inference/type_combination_test.dart
index 2d84f97..64216dc 100644
--- a/tests/compiler/dart2js/inference/type_combination_test.dart
+++ b/tests/compiler/dart2js/inference/type_combination_test.dart
@@ -7,10 +7,9 @@
 import 'package:compiler/src/common_elements.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/elements/entities.dart';
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/world.dart';
 import 'type_mask_test_helper.dart';
-import '../compiler_helper.dart';
 import '../memory_compiler.dart';
 
 TypeMask nullType;
diff --git a/tests/compiler/dart2js/inference/type_mask2_test.dart b/tests/compiler/dart2js/inference/type_mask2_test.dart
index 3cd3137..c5e075a 100644
--- a/tests/compiler/dart2js/inference/type_mask2_test.dart
+++ b/tests/compiler/dart2js/inference/type_mask2_test.dart
@@ -8,7 +8,7 @@
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/elements/entities.dart';
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/world.dart' show ClosedWorld;
 import '../type_test_helper.dart';
 
diff --git a/tests/compiler/dart2js/inference/type_mask_disjoint_test.dart b/tests/compiler/dart2js/inference/type_mask_disjoint_test.dart
index b520387..a680f5b 100644
--- a/tests/compiler/dart2js/inference/type_mask_disjoint_test.dart
+++ b/tests/compiler/dart2js/inference/type_mask_disjoint_test.dart
@@ -7,7 +7,7 @@
 import 'package:compiler/src/common_elements.dart';
 import 'package:compiler/src/compiler.dart';
 import 'package:compiler/src/elements/entities.dart';
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/world.dart';
 
 import '../memory_compiler.dart';
diff --git a/tests/compiler/dart2js/inference/type_mask_test.dart b/tests/compiler/dart2js/inference/type_mask_test.dart
index 91b1968..4561962 100644
--- a/tests/compiler/dart2js/inference/type_mask_test.dart
+++ b/tests/compiler/dart2js/inference/type_mask_test.dart
@@ -4,7 +4,7 @@
 
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 
 import 'package:compiler/src/common_elements.dart';
 import 'package:compiler/src/compiler.dart';
diff --git a/tests/compiler/dart2js/inference/type_mask_test_helper.dart b/tests/compiler/dart2js/inference/type_mask_test_helper.dart
index a3b661b..f979741 100644
--- a/tests/compiler/dart2js/inference/type_mask_test_helper.dart
+++ b/tests/compiler/dart2js/inference/type_mask_test_helper.dart
@@ -4,7 +4,7 @@
 
 library type_mask_test_helper;
 
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/world.dart' show ClosedWorld;
 
 export 'package:compiler/src/types/types.dart';
diff --git a/tests/compiler/dart2js/inference/union_type_test.dart b/tests/compiler/dart2js/inference/union_type_test.dart
index 1890622..37f4e29 100644
--- a/tests/compiler/dart2js/inference/union_type_test.dart
+++ b/tests/compiler/dart2js/inference/union_type_test.dart
@@ -4,7 +4,7 @@
 
 import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
-import "package:compiler/src/types/types.dart";
+import "package:compiler/src/types/masks.dart";
 import "package:compiler/src/world.dart";
 import '../type_test_helper.dart';
 
diff --git a/tests/compiler/dart2js/model/enqueuer_test.dart b/tests/compiler/dart2js/model/enqueuer_test.dart
index 567a11f..1912168 100644
--- a/tests/compiler/dart2js/model/enqueuer_test.dart
+++ b/tests/compiler/dart2js/model/enqueuer_test.dart
@@ -13,7 +13,7 @@
 import 'package:compiler/src/elements/names.dart';
 import 'package:compiler/src/elements/types.dart';
 import 'package:compiler/src/enqueue.dart';
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/universe/call_structure.dart';
 import 'package:compiler/src/universe/selector.dart';
 import 'package:compiler/src/universe/world_impact.dart';
diff --git a/tests/compiler/dart2js/receiver_type_test.dart b/tests/compiler/dart2js/receiver_type_test.dart
index da0a7a2..ac1c71f 100644
--- a/tests/compiler/dart2js/receiver_type_test.dart
+++ b/tests/compiler/dart2js/receiver_type_test.dart
@@ -5,7 +5,7 @@
 import 'dart:async';
 import 'package:async_helper/async_helper.dart';
 import 'package:compiler/src/elements/entities.dart';
-import 'package:compiler/src/types/types.dart';
+import 'package:compiler/src/types/masks.dart';
 import 'package:compiler/src/universe/selector.dart';
 import 'package:compiler/src/world.dart';
 import 'package:expect/expect.dart';