Extract CallStructure from Selector.

pkg/compiler/lib/src/closure.dart

Index: pkg/compiler/lib/src/closure.dart
diff --git a/pkg/compiler/lib/src/closure.dart b/pkg/compiler/lib/src/closure.dart
index 175ca25b47159c2eae98fc7ab29d5e3ce236362f..4aaa293a517a487019f9f1d0da5edbc01a2695fe 100644
--- a/pkg/compiler/lib/src/closure.dart
+++ b/pkg/compiler/lib/src/closure.dart
@@ -93,7 +93,7 @@ abstract class CapturedVariable {}
 // TODO(ahe): These classes continuously cause problems.  We need to
 // find a more general solution.
 class ClosureFieldElement extends ElementX
-    implements VariableElement, CapturedVariable {
+    implements FieldElement, CapturedVariable {
   /// The [BoxLocal] or [LocalElement] being accessed through the field.
   final Local local;
 
@@ -146,6 +146,9 @@ class ClosureFieldElement extends ElementX
   accept(ElementVisitor visitor) => visitor.visitClosureFieldElement(this);
 
   Element get analyzableElement => closureClass.methodElement.analyzableElement;
+
+  @override
+  List<FunctionElement> get nestedClosures => const <FunctionElement>[];
 }
 
 // TODO(ahe): These classes continuously cause problems.  We need to find
@@ -226,7 +229,7 @@ class BoxLocal extends Local {
 // TODO(ngeoffray, ahe): These classes continuously cause problems.  We need to
 // find a more general solution.
 class BoxFieldElement extends ElementX
-    implements TypedElement, CapturedVariable {
+    implements TypedElement, CapturedVariable, FieldElement {
   final BoxLocal box;
 
   BoxFieldElement(String name, this.variableElement, BoxLocal box)
@@ -240,6 +243,33 @@ class BoxFieldElement extends ElementX
   final VariableElement variableElement;
 
   accept(ElementVisitor visitor) => visitor.visitBoxFieldElement(this);
+
+  @override
+  bool get hasNode => false;
+
+  @override
+  bool get hasResolvedAst => false;
+
+  @override
+  Expression get initializer {
+    throw new UnsupportedError("BoxFieldElement.initializer");
+  }
+
+  @override
+  MemberElement get memberContext => box.executableContext.memberContext;
+
+  @override
+  List<FunctionElement> get nestedClosures => const <FunctionElement>[];
+
+  @override
+  Node get node {
+    throw new UnsupportedError("BoxFieldElement.node");
+  }
+
+  @override
+  ResolvedAst get resolvedAst {
+    throw new UnsupportedError("BoxFieldElement.resolvedAst");
+  }
 }
 
 /// A local variable used encode the direct (uncaptured) references to [this].
@@ -254,7 +284,8 @@ class ThisLocal extends Local {
 }
 
 /// Call method of a closure class.
-class SynthesizedCallMethodElementX extends BaseFunctionElementX {
+class SynthesizedCallMethodElementX extends BaseFunctionElementX
+    implements MethodElement {
   final LocalFunctionElement expression;
 
   SynthesizedCallMethodElementX(String name,