Ensure that element handles never refer to Member objects.

pkg/analyzer/lib/src/dart/element/member.dart

Index: pkg/analyzer/lib/src/dart/element/member.dart
diff --git a/pkg/analyzer/lib/src/dart/element/member.dart b/pkg/analyzer/lib/src/dart/element/member.dart
index 57cbcb91d44f57a45c2e3d724f8121d0f185176d..f3689e4dbcbf4106dd7a01bf4194dad3c66b327c 100644
--- a/pkg/analyzer/lib/src/dart/element/member.dart
+++ b/pkg/analyzer/lib/src/dart/element/member.dart
@@ -128,8 +128,7 @@ class ConstructorMember extends ExecutableMember implements ConstructorElement {
  * type parameters are known.
  */
 abstract class ExecutableMember extends Member implements ExecutableElement {
-  @override
-  final FunctionType type;
+  FunctionType _type;
 
   /**
    * Initialize a newly created element to represent a callable element (like a
@@ -139,9 +138,7 @@ abstract class ExecutableMember extends Member implements ExecutableElement {
    */
   ExecutableMember(ExecutableElement baseElement, InterfaceType definingType,
       [FunctionType type])

[scheglov, 2016/02/10 21:53:26]

[FunctionType this._type] maybe?
OTOH this is not the most nice name to expose to clients.

[Paul Berry, 2016/02/10 22:10:59]

Yeah, I had a similar thought.  I think I'd prefer to leave as is so that the
documentation can still refer to [type].

-      : type = type ??
-            baseElement.type.substitute2(definingType.typeArguments,
-                TypeParameterTypeImpl.getTypes(definingType.typeParameters)),
+      : _type = type,
         super(baseElement, definingType);
 
   @override
@@ -201,6 +198,12 @@ abstract class ExecutableMember extends Member implements ExecutableElement {
   DartType get returnType => type.returnType;
 
   @override
+  FunctionType get type {
+    return _type ??= baseElement.type.substitute2(definingType.typeArguments,
+        TypeParameterTypeImpl.getTypes(definingType.typeParameters));
+  }
+
+  @override
   List<TypeParameterElement> get typeParameters => baseElement.typeParameters;
 
   @override