Refactor handling of compounds.

pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart

Index: pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
diff --git a/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart b/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
index 941d64dc244c32518b622804d651b4e810144358..63ceb308f5613925e40ada0be75fdcd001645b17 100644
--- a/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
+++ b/pkg/compiler/lib/src/inferrer/simple_types_inferrer.dart
@@ -1007,8 +1007,8 @@ class SimpleTypeInferrerVisitor<T>
   @override
   T visitSuperCompoundIndexSet(
       ast.SendSet node,
-      FunctionElement getter,
-      FunctionElement setter,
+      MethodElement getter,
+      MethodElement setter,
       ast.Node index,
       op.AssignmentOperator operator,
       ast.Node rhs,
@@ -1020,6 +1020,7 @@ class SimpleTypeInferrerVisitor<T>
   T visitUnresolvedSuperGetterCompoundIndexSet(
       ast.SendSet node,
       Element element,
+      MethodElement setter,
       ast.Node index,
       op.AssignmentOperator operator,
       ast.Node rhs,
@@ -1030,7 +1031,7 @@ class SimpleTypeInferrerVisitor<T>
   @override
   T visitUnresolvedSuperSetterCompoundIndexSet(
       ast.SendSet node,
-      FunctionElement getter,
+      MethodElement getter,
       Element element,
       ast.Node index,
       op.AssignmentOperator operator,
@@ -1043,6 +1044,7 @@ class SimpleTypeInferrerVisitor<T>
   T visitUnresolvedSuperGetterIndexPrefix(
       ast.SendSet node,
       Element element,
+      MethodElement setter,
       ast.Node index,
       op.IncDecOperator operator,
       _) {
@@ -1053,7 +1055,7 @@ class SimpleTypeInferrerVisitor<T>
   @override
   T visitUnresolvedSuperSetterIndexPrefix(
       ast.SendSet node,
-      FunctionElement getter,
+      MethodElement getter,
       Element element,
       ast.Node index,
       op.IncDecOperator operator,
@@ -1066,6 +1068,7 @@ class SimpleTypeInferrerVisitor<T>
   T visitUnresolvedSuperGetterIndexPostfix(
       ast.SendSet node,
       Element element,
+      MethodElement setter,
       ast.Node index,
       op.IncDecOperator operator,
       _) {
@@ -1076,7 +1079,7 @@ class SimpleTypeInferrerVisitor<T>
   @override
   T visitUnresolvedSuperSetterIndexPostfix(
       ast.SendSet node,
-      FunctionElement getter,
+      MethodElement getter,
       Element element,
       ast.Node index,
       op.IncDecOperator operator,