diff --git a/pkg/compiler/lib/src/common_elements.dart b/pkg/compiler/lib/src/common_elements.dart
index 0c7edc97a9f6..86d62ea491d0 100644
--- a/pkg/compiler/lib/src/common_elements.dart
+++ b/pkg/compiler/lib/src/common_elements.dart
@@ -1329,9 +1329,12 @@ abstract class ElementEnvironment {
   /// `Object`.
   DartType getTypeVariableBound(TypeVariableEntity typeVariable);
 
-  /// Returns the type if [function].
+  /// Returns the type of [function].
   FunctionType getFunctionType(FunctionEntity function);
 
+  /// Returns the type of [field].
+  DartType getFieldType(FieldEntity field);
+
   /// Returns the type of the [local] function.
   FunctionType getLocalFunctionType(Local local);
 
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart b/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart
index ee71c76bc0a5..245d50be5fb4 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder/collector.dart
@@ -48,7 +48,7 @@ class Collector {
   /// This flag is updated in [computeNeededConstants].
   bool outputContainsConstantList = false;
 
-  final List<ClassElement> nativeClassesAndSubclasses = <ClassElement>[];
+  final List<ClassEntity> nativeClassesAndSubclasses = <ClassEntity>[];
 
   List<TypedefEntity> typedefsNeededForReflection;
 
@@ -88,7 +88,7 @@ class Collector {
    */
   Function computeClassFilter() {
     if (_mirrorsData.isTreeShakingDisabled) {
-      return (ClassElement cls) => true;
+      return (ClassEntity cls) => true;
     }
 
     Set<ClassEntity> unneededClasses = new Set<ClassEntity>();
@@ -136,17 +136,24 @@ class Collector {
     if (_mirrorsData.mustRetainMetadata) {
       // TODO(floitsch): verify that we don't run through the same elements
       // multiple times.
-      for (MemberElement element in _generatedCode.keys) {
+      for (MemberEntity element in _generatedCode.keys) {
         if (_mirrorsData.isMemberAccessibleByReflection(element)) {
           _mirrorsData.retainMetadataOfMember(element);
         }
       }
-      for (ClassElement cls in neededClasses) {
+      for (ClassEntity cls in neededClasses) {
         final onlyForRti = classesOnlyNeededForRti.contains(cls);
         if (!onlyForRti) {
           _mirrorsData.retainMetadataOfClass(cls);
-          new FieldVisitor(_options, _elementEnvironment, _worldBuilder,
-                  _nativeData, _mirrorsData, _namer, _closedWorld)
+          new FieldVisitor(
+                  _options,
+                  _elementEnvironment,
+                  _commonElements,
+                  _worldBuilder,
+                  _nativeData,
+                  _mirrorsData,
+                  _namer,
+                  _closedWorld)
               .visitFields((FieldEntity member,
                   js.Name name,
                   js.Name accessorName,
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder/field_visitor.dart b/pkg/compiler/lib/src/js_emitter/program_builder/field_visitor.dart
index f85f1a38c801..39c0107c529f 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder/field_visitor.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder/field_visitor.dart
@@ -28,6 +28,7 @@ typedef void AcceptField(FieldEntity member, js.Name name, js.Name accessorName,
 class FieldVisitor {
   final CompilerOptions _options;
   final ElementEnvironment _elementEnvironment;
+  final CommonElements _commonElements;
   final CodegenWorldBuilder _codegenWorldBuilder;
   final NativeData _nativeData;
   final MirrorsData _mirrorsData;
@@ -37,6 +38,7 @@ class FieldVisitor {
   FieldVisitor(
       this._options,
       this._elementEnvironment,
+      this._commonElements,
       this._codegenWorldBuilder,
       this._nativeData,
       this._mirrorsData,
@@ -46,13 +48,13 @@ class FieldVisitor {
   /**
    * Invokes [f] for each of the fields of [element].
    *
-   * [element] must be a [ClassElement] or a [LibraryElement].
+   * [element] must be a [ClassEntity] or a [LibraryEntity].
    *
-   * If [element] is a [ClassElement], the static fields of the class are
+   * If [element] is a [ClassEntity], the static fields of the class are
    * visited if [visitStatics] is true and the instance fields are visited if
    * [visitStatics] is false.
    *
-   * If [element] is a [LibraryElement], [visitStatics] must be true.
+   * If [element] is a [LibraryEntity], [visitStatics] must be true.
    *
    * When visiting the instance fields of a class, the fields of its superclass
    * are also visited if the class is instantiated.
@@ -79,8 +81,8 @@ class FieldVisitor {
       isLibrary = true;
       assert(visitStatics, failedAt(library));
     } else {
-      failedAt(NO_LOCATION_SPANNABLE,
-          'Expected a ClassElement or a LibraryElement.');
+      failedAt(
+          NO_LOCATION_SPANNABLE, 'Expected a ClassEntity or a LibraryEntity.');
     }
 
     void visitField(FieldEntity field, {ClassEntity holder}) {
@@ -175,10 +177,10 @@ class FieldVisitor {
         field is ClosureFieldElement;
   }
 
-  bool canAvoidGeneratedCheckedSetter(FieldElement member) {
+  bool canAvoidGeneratedCheckedSetter(FieldEntity member) {
     // We never generate accessors for top-level/static fields.
     if (!member.isInstanceMember) return true;
-    ResolutionDartType type = member.type;
-    return type.treatAsDynamic || type.isObject;
+    DartType type = _elementEnvironment.getFieldType(member);
+    return type.treatAsDynamic || type == _commonElements.objectType;
   }
 }
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart b/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
index e50a7d7ee1ea..f0290b08eb0f 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder/program_builder.dart
@@ -15,16 +15,8 @@ import '../../constants/values.dart'
 import '../../common_elements.dart' show CommonElements, ElementEnvironment;
 import '../../deferred_load.dart' show DeferredLoadTask, OutputUnit;
 import '../../elements/elements.dart'
-    show
-        ClassElement,
-        FieldElement,
-        FunctionSignature,
-        LibraryElement,
-        MemberElement,
-        MethodElement,
-        ParameterElement;
+    show ClassElement, FieldElement, LibraryElement, MethodElement;
 import '../../elements/entities.dart';
-import '../../elements/resolution_types.dart' show ResolutionDartType;
 import '../../elements/types.dart';
 import '../../js/js.dart' as js;
 import '../../js_backend/backend.dart' show SuperMemberData;
@@ -192,7 +184,7 @@ class ProgramBuilder {
   ///
   /// Also contains classes that are not tracked by the profile run (like
   /// interceptors, ...).
-  Set<ClassElement> _notSoftDeferred;
+  Set<ClassEntity> _notSoftDeferred;
 
   Program buildProgram({bool storeFunctionTypesInMetadata: false}) {
     collector.collect();
@@ -326,16 +318,17 @@ class ProgramBuilder {
 
       String data = new File(allocatedClassesPath).readAsStringSync();
       Set<String> allocatedClassesKeys = JSON.decode(data).keys.toSet();
-      Set<ClassElement> allocatedClasses = new Set<ClassElement>();
+      Set<ClassEntity> allocatedClasses = new Set<ClassEntity>();
 
       // Collects all super and mixin classes of a class.
-      void collect(ClassElement element) {
+      void collect(ClassEntity element) {
         allocatedClasses.add(element);
-        if (element.isMixinApplication) {
+        if (_elementEnvironment.isMixinApplication(element)) {
           collect(_elementEnvironment.getEffectiveMixinClass(element));
         }
-        if (element.superclass != null) {
-          collect(element.superclass);
+        ClassEntity superclass = _elementEnvironment.getSuperClass(element);
+        if (superclass != null) {
+          collect(superclass);
         }
       }
 
@@ -343,7 +336,7 @@ class ProgramBuilder {
       // collect its dependencies (supers and mixins) and mark them as
       // not-soft-deferrable.
       collector.outputClassLists.forEach((_, List<ClassEntity> elements) {
-        for (ClassElement element in elements) {
+        for (ClassEntity element in elements) {
           // TODO(29574): share the encoding of the element with the code
           // that emits the profile-run.
           var key = "${element.library.canonicalUri}:${element.name}";
@@ -562,7 +555,7 @@ class ProgramBuilder {
 
             if (member.isFunction) {
               MethodElement fn = member;
-              functionType = fn.type;
+              functionType = _elementEnvironment.getFunctionType(fn);
             } else if (member.isGetter) {
               if (_options.trustTypeAnnotations) {
                 DartType returnType =
@@ -786,7 +779,7 @@ class ProgramBuilder {
       for (Field field in instanceFields) {
         if (field.needsCheckedSetter) {
           assert(!field.needsUncheckedSetter);
-          FieldElement element = field.element;
+          FieldEntity element = field.element;
           js.Expression code = _generatedCode[element];
           assert(code != null);
           js.Name name = _namer.deriveSetterName(field.accessorName);
@@ -863,23 +856,28 @@ class ProgramBuilder {
         _closedWorld.getMightBePassedToApply(method);
   }
 
-  /* Map | List */ _computeParameterDefaultValues(FunctionSignature signature) {
+  /* Map | List */ _computeParameterDefaultValues(FunctionEntity method) {
     var /* Map | List */ optionalParameterDefaultValues;
-    if (signature.optionalParametersAreNamed) {
+    ParameterStructure parameterStructure = method.parameterStructure;
+    if (parameterStructure.namedParameters.isNotEmpty) {
       optionalParameterDefaultValues = new Map<String, ConstantValue>();
-      signature.forEachOptionalParameter((_parameter) {
-        ParameterElement parameter = _parameter;
-        ConstantValue def =
-            _constantHandler.getConstantValue(parameter.constant);
-        optionalParameterDefaultValues[parameter.name] = def;
+      _worldBuilder.forEachParameter(method,
+          (DartType type, String name, ConstantValue defaultValue) {
+        if (parameterStructure.namedParameters.contains(name)) {
+          assert(defaultValue != null);
+          optionalParameterDefaultValues[name] = defaultValue;
+        }
       });
     } else {
       optionalParameterDefaultValues = <ConstantValue>[];
-      signature.forEachOptionalParameter((_parameter) {
-        ParameterElement parameter = _parameter;
-        ConstantValue def =
-            _constantHandler.getConstantValue(parameter.constant);
-        optionalParameterDefaultValues.add(def);
+      int index = 0;
+      _worldBuilder.forEachParameter(method,
+          (DartType type, String name, ConstantValue defaultValue) {
+        if (index >= parameterStructure.requiredParameters) {
+          assert(defaultValue != null);
+          optionalParameterDefaultValues.add(defaultValue);
+        }
+        index++;
       });
     }
     return optionalParameterDefaultValues;
@@ -945,11 +943,10 @@ class ProgramBuilder {
     var /* List | Map */ optionalParameterDefaultValues;
     if (canBeApplied || canBeReflected) {
       // TODO(redemption): Handle function entities.
-      MethodElement method = element;
-      FunctionSignature signature = method.functionSignature;
-      requiredParameterCount = signature.requiredParameterCount;
-      optionalParameterDefaultValues =
-          _computeParameterDefaultValues(signature);
+      FunctionEntity method = element;
+      ParameterStructure parameterStructure = method.parameterStructure;
+      requiredParameterCount = parameterStructure.requiredParameters;
+      optionalParameterDefaultValues = _computeParameterDefaultValues(method);
     }
 
     return new InstanceMethod(element, name, code,
@@ -995,7 +992,7 @@ class ProgramBuilder {
   /// Stub methods may have an element that can be used for code-size
   /// attribution.
   Method _buildStubMethod(js.Name name, js.Expression code,
-      {MemberElement element}) {
+      {MemberEntity element}) {
     return new StubMethod(name, code, element: element);
   }
 
@@ -1085,8 +1082,15 @@ class ProgramBuilder {
           needsCheckedSetter));
     }
 
-    FieldVisitor visitor = new FieldVisitor(_options, _elementEnvironment,
-        _worldBuilder, _nativeData, _mirrorsData, _namer, _closedWorld);
+    FieldVisitor visitor = new FieldVisitor(
+        _options,
+        _elementEnvironment,
+        _commonElements,
+        _worldBuilder,
+        _nativeData,
+        _mirrorsData,
+        _namer,
+        _closedWorld);
     visitor.visitFields(visitField,
         visitStatics: visitStatics, library: library, cls: cls);
 
@@ -1152,11 +1156,10 @@ class ProgramBuilder {
     var /* List | Map */ optionalParameterDefaultValues;
     if (canBeApplied || canBeReflected) {
       // TODO(redemption): Support entities;
-      MethodElement method = element;
-      FunctionSignature signature = method.functionSignature;
-      requiredParameterCount = signature.requiredParameterCount;
-      optionalParameterDefaultValues =
-          _computeParameterDefaultValues(signature);
+      FunctionEntity method = element;
+      ParameterStructure parameterStructure = method.parameterStructure;
+      requiredParameterCount = parameterStructure.requiredParameters;
+      optionalParameterDefaultValues = _computeParameterDefaultValues(method);
     }
 
     // TODO(floitsch): we shouldn't update the registry in the middle of
diff --git a/pkg/compiler/lib/src/js_emitter/program_builder/registry.dart b/pkg/compiler/lib/src/js_emitter/program_builder/registry.dart
index b0266dc08693..b448c7ad804e 100644
--- a/pkg/compiler/lib/src/js_emitter/program_builder/registry.dart
+++ b/pkg/compiler/lib/src/js_emitter/program_builder/registry.dart
@@ -12,7 +12,7 @@ class LibraryContents {
 /// Maps [LibraryEntity]s to their [ClassEntity]s and [MemberEntity]s.
 ///
 /// Fundamentally, this class nicely encapsulates a
-/// `Map<LibraryElement, Pair<List<ClassElement>, List<MemberElement>>>`.
+/// `Map<LibraryEntity, Pair<List<ClassEntity>, List<MemberEntity>>>`.
 ///
 /// There exists exactly one instance per [OutputUnit].
 class LibrariesMap {
diff --git a/pkg/compiler/lib/src/js_emitter/type_test_registry.dart b/pkg/compiler/lib/src/js_emitter/type_test_registry.dart
index 363164c0b613..20ec76ae9113 100644
--- a/pkg/compiler/lib/src/js_emitter/type_test_registry.dart
+++ b/pkg/compiler/lib/src/js_emitter/type_test_registry.dart
@@ -6,9 +6,7 @@ library dart2js.js_emitter.type_test_registry;
 
 import '../common.dart';
 import '../common_elements.dart';
-import '../elements/elements.dart' show MethodElement;
 import '../elements/entities.dart';
-import '../elements/types.dart' show DartType;
 import '../elements/types.dart';
 import '../js_backend/runtime_types.dart'
     show
@@ -168,9 +166,8 @@ class TypeTestRegistry {
     liveMembers.where((MemberEntity element) {
       return canBeReflectedAsFunction(element) && canBeReified(element);
     }).forEach((_function) {
-      // TODO(redemption): Support entities.
-      MethodElement function = _function;
-      FunctionType type = function.type;
+      FunctionEntity function = _function;
+      FunctionType type = _elementEnvironment.getFunctionType(function);
       for (ClassEntity cls in _rtiChecks.getReferencedClasses(type)) {
         while (cls != null) {
           _rtiNeededClasses.add(cls);
diff --git a/pkg/compiler/lib/src/js_model/closure.dart b/pkg/compiler/lib/src/js_model/closure.dart
index 153853ac9dc1..16cfea58c6bd 100644
--- a/pkg/compiler/lib/src/js_model/closure.dart
+++ b/pkg/compiler/lib/src/js_model/closure.dart
@@ -508,6 +508,12 @@ class ClosureFunctionData extends ClosureMemberData implements FunctionData {
 class ClosureFieldData extends ClosureMemberData implements FieldData {
   ClosureFieldData(MemberDefinition definition) : super(definition);
 
+  @override
+  DartType getFieldType(KernelToElementMap elementMap) {
+    // A closure field doesn't have a Dart type.
+    return null;
+  }
+
   @override
   ConstantExpression getFieldConstant(
       KernelToElementMap elementMap, FieldEntity field) {
diff --git a/pkg/compiler/lib/src/kernel/element_map_impl.dart b/pkg/compiler/lib/src/kernel/element_map_impl.dart
index 614fd9cce3e5..380853e75be6 100644
--- a/pkg/compiler/lib/src/kernel/element_map_impl.dart
+++ b/pkg/compiler/lib/src/kernel/element_map_impl.dart
@@ -619,6 +619,12 @@ abstract class KernelToElementMapBase extends KernelToElementMapBaseMixin {
     return data.getFunctionType(this);
   }
 
+  DartType _getFieldType(IndexedField field) {
+    assert(checkFamily(field));
+    FieldData data = _memberData[field.memberIndex];
+    return data.getFieldType(this);
+  }
+
   ClassEntity _getAppliedMixin(IndexedClass cls) {
     assert(checkFamily(cls));
     ClassData data = _classData[cls.classIndex];
@@ -1336,6 +1342,11 @@ class KernelElementEnvironment implements ElementEnvironment {
     return elementMap._getFunctionType(function);
   }
 
+  @override
+  DartType getFieldType(FieldEntity field) {
+    return elementMap._getFieldType(field);
+  }
+
   @override
   FunctionType getLocalFunctionType(covariant KLocalFunction function) {
     return function.functionType;
diff --git a/pkg/compiler/lib/src/kernel/env.dart b/pkg/compiler/lib/src/kernel/env.dart
index af566a0e9ab1..845feeec36a7 100644
--- a/pkg/compiler/lib/src/kernel/env.dart
+++ b/pkg/compiler/lib/src/kernel/env.dart
@@ -563,11 +563,14 @@ class ConstructorDataImpl extends FunctionDataImpl implements ConstructorData {
 }
 
 abstract class FieldData extends MemberData {
+  DartType getFieldType(KernelToElementMap elementMap);
+
   ConstantExpression getFieldConstant(
       KernelToElementMapBase elementMap, FieldEntity field);
 }
 
 class FieldDataImpl extends MemberDataImpl implements FieldData {
+  DartType _type;
   ConstantExpression _constant;
 
   FieldDataImpl(ir.Field node, MemberDefinition definition)
@@ -575,6 +578,10 @@ class FieldDataImpl extends MemberDataImpl implements FieldData {
 
   ir.Field get node => super.node;
 
+  DartType getFieldType(covariant KernelToElementMapBase elementMap) {
+    return _type ??= elementMap.getDartType(node.type);
+  }
+
   ConstantExpression getFieldConstant(
       KernelToElementMapBase elementMap, FieldEntity field) {
     if (_constant == null) {
diff --git a/pkg/compiler/lib/src/resolution/resolution_strategy.dart b/pkg/compiler/lib/src/resolution/resolution_strategy.dart
index 62b23ea93cd4..ee21ec0397a2 100644
--- a/pkg/compiler/lib/src/resolution/resolution_strategy.dart
+++ b/pkg/compiler/lib/src/resolution/resolution_strategy.dart
@@ -667,6 +667,12 @@ class _CompilerElementEnvironment implements ElementEnvironment {
     return type;
   }
 
+  @override
+  DartType getFieldType(covariant FieldElement field) {
+    field.computeType(_resolution);
+    return field.type;
+  }
+
   @override
   ResolutionFunctionType getLocalFunctionType(
       covariant LocalFunctionElement function) {
diff --git a/pkg/compiler/lib/src/ssa/optimize.dart b/pkg/compiler/lib/src/ssa/optimize.dart
index 5b544b34be2f..bf6e754e4d98 100644
--- a/pkg/compiler/lib/src/ssa/optimize.dart
+++ b/pkg/compiler/lib/src/ssa/optimize.dart
@@ -9,8 +9,7 @@ import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../common_elements.dart' show CommonElements;
-import '../elements/elements.dart'
-    show ClassElement, FieldElement, MethodElement;
+import '../elements/elements.dart' show ClassElement, MethodElement;
 import '../elements/entities.dart';
 import '../elements/resolution_types.dart';
 import '../elements/types.dart';
@@ -1031,8 +1030,7 @@ class SsaInstructionSimplifier extends HBaseVisitor
     HInstruction value = node.inputs.last;
     if (_options.enableTypeAssertions) {
       // TODO(redemption): Support field entities.
-      FieldElement element = field;
-      DartType type = element.type;
+      DartType type = _closedWorld.elementEnvironment.getFieldType(field);
       if (!type.treatAsRaw ||
           type.isTypeVariable ||
           type.unaliased.isFunctionType) {