Reduce strong mode errors and warnings

pkg/front_end/lib/src/fasta/analyzer/mock_type.dart

Index: pkg/front_end/lib/src/fasta/analyzer/mock_type.dart
diff --git a/pkg/front_end/lib/src/fasta/analyzer/mock_type.dart b/pkg/front_end/lib/src/fasta/analyzer/mock_type.dart
index ce34190cd9d8900ff910e3078d3d10a92988ade4..bf55d3766c4dc80415b79297f2c218ded09b9ae3 100644
--- a/pkg/front_end/lib/src/fasta/analyzer/mock_type.dart
+++ b/pkg/front_end/lib/src/fasta/analyzer/mock_type.dart
@@ -36,7 +36,9 @@ abstract class MockType extends DartType {
 
   String get name => internalError("not supported.");
 
-  DartType flattenFutures(TypeSystem typeSystem) => internalError("not supported.");
+  DartType flattenFutures(TypeSystem typeSystem) {
+    return internalError("not supported.");
+  }
 
   bool isAssignableTo(DartType type) => internalError("not supported.");
 
@@ -46,20 +48,32 @@ abstract class MockType extends DartType {
 
   bool isSupertypeOf(DartType type) => internalError("not supported.");
 
-  DartType resolveToBound(DartType objectType) => internalError("not supported.");
+  DartType resolveToBound(DartType objectType) {
+    return internalError("not supported.");
+  }
 
   DartType substitute2(
-      List<DartType> argumentTypes, List<DartType> parameterTypes) => internalError("not supported.");
+      List<DartType> argumentTypes, List<DartType> parameterTypes) {
+    return internalError("not supported.");
+  }
 
   List<DartType> get typeArguments => internalError("not supported.");
 
-  List<TypeParameterElement> get typeParameters => internalError("not supported.");
+  List<TypeParameterElement> get typeParameters {
+    return internalError("not supported.");
+  }
 
-  ParameterizedType instantiate(List<DartType> argumentTypes) => internalError("not supported.");
+  ParameterizedType instantiate(List<DartType> argumentTypes) {
+    return internalError("not supported.");
+  }
 }
 
 abstract class MockInterfaceType extends MockType implements InterfaceType {
-  List<PropertyAccessorElement> get accessors => internalError("not supported.");
+  ClassElement get element => internalError("not supported.");
+
+  List<PropertyAccessorElement> get accessors {
+    return internalError("not supported.");
+  }
 
   List<ConstructorElement> get constructors => internalError("not supported.");
 
@@ -71,44 +85,77 @@ abstract class MockInterfaceType extends MockType implements InterfaceType {
 
   InterfaceType get superclass => internalError("not supported.");
 
-  PropertyAccessorElement getGetter(String name) => internalError("not supported.");
+  PropertyAccessorElement getGetter(String name) {
+    return internalError("not supported.");
+  }
 
   MethodElement getMethod(String name) => internalError("not supported.");
 
-  PropertyAccessorElement getSetter(String name) => internalError("not supported.");
+  PropertyAccessorElement getSetter(String name) {
+    return internalError("not supported.");
+  }
 
-  bool isDirectSupertypeOf(InterfaceType type) => internalError("not supported.");
+  bool isDirectSupertypeOf(InterfaceType type) {
+    return internalError("not supported.");
+  }
 
 
-  ConstructorElement lookUpConstructor(String name, LibraryElement library) => internalError("not supported.");
+  ConstructorElement lookUpConstructor(String name, LibraryElement library) {
+    return internalError("not supported.");
+  }
 
-  PropertyAccessorElement lookUpGetter(String name, LibraryElement library) => internalError("not supported.");
+  PropertyAccessorElement lookUpGetter(String name, LibraryElement library) {
+    return internalError("not supported.");
+  }
 
   PropertyAccessorElement lookUpGetterInSuperclass(
       String name, LibraryElement library) => internalError("not supported.");
 
   PropertyAccessorElement lookUpInheritedGetter(String name,
-      {LibraryElement library, bool thisType: true}) => internalError("not supported.");
+      {LibraryElement library, bool thisType: true}) {
+    return internalError("not supported.");
+  }
 
   ExecutableElement lookUpInheritedGetterOrMethod(String name,
       {LibraryElement library}) => internalError("not supported.");
 
   MethodElement lookUpInheritedMethod(String name,
-      {LibraryElement library, bool thisType: true}) => internalError("not supported.");
+      {LibraryElement library, bool thisType: true}) {
+    return internalError("not supported.");
+  }
 
   PropertyAccessorElement lookUpInheritedSetter(String name,
-      {LibraryElement library, bool thisType: true}) => internalError("not supported.");
+      {LibraryElement library, bool thisType: true}) {
+    return internalError("not supported.");
+  }
 
-  MethodElement lookUpMethod(String name, LibraryElement library) => internalError("not supported.");
+  MethodElement lookUpMethod(String name, LibraryElement library) {
+    return internalError("not supported.");
+  }
 
-  MethodElement lookUpMethodInSuperclass(String name, LibraryElement library) => internalError("not supported.");
+  MethodElement lookUpMethodInSuperclass(String name, LibraryElement library) {
+    return internalError("not supported.");
+  }
 
-  PropertyAccessorElement lookUpSetter(String name, LibraryElement library) => internalError("not supported.");
+  PropertyAccessorElement lookUpSetter(String name, LibraryElement library) {
+    return internalError("not supported.");
+  }
 
   PropertyAccessorElement lookUpSetterInSuperclass(
       String name, LibraryElement library) => internalError("not supported.");
 
-  InterfaceType substitute4(List<DartType> argumentTypes) => internalError("not supported.");
+  InterfaceType instantiate(List<DartType> argumentTypes) {
+    return internalError("not supported.");
+  }
+
+  InterfaceType substitute2(
+      List<DartType> argumentTypes, List<DartType> parameterTypes) {
+    return internalError("not supported.");
+  }
+
+  InterfaceType substitute4(List<DartType> argumentTypes) {
+    return internalError("not supported.");
+  }
 
   get isDartCoreNull => internalError("not supported.");
 }