Don't serialize elements of top-level function/constructor/method bodies.

pkg/analyzer/lib/src/summary/link.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * This library is capable of producing linked summaries from unlinked
  * ones (or prelinked ones).  It functions by building a miniature
  * element model to represent the contents of the summaries, and then
  * scanning the element model to gather linked information and adding
  * it to the summary data structures.
@@ skipping 3086 matching lines @@
   @override
   FunctionElementForLink_Local getLocalFunction(int index) {
     List<FunctionElementForLink_Local_NonSynthetic> functions = this.functions;
     return index < functions.length ? functions[index] : null;
   }
 
   /**
    * Store the results of type inference for this function in [compilationUnit].
    */
   void link(CompilationUnitElementInBuildUnit compilationUnit) {
-    compilationUnit._storeLinkedType(
-        _unlinkedExecutable.inferredReturnTypeSlot, inferredReturnType, this);
+    if (_unlinkedExecutable.returnType == null) {
+      compilationUnit._storeLinkedType(
+          _unlinkedExecutable.inferredReturnTypeSlot, inferredReturnType, this);
+    }
     for (FunctionElementForLink_Local_NonSynthetic function in functions) {
       function.link(compilationUnit);
     }
   }
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 
   @override
   void _setInferredType(DartType type) {
@@ skipping 1940 matching lines @@
    * there are no type parameters in scope.
    */
   TypeParameterizedElementMixin get _typeParameterContext;
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 
   @override
   String toString() => '$enclosingElement.$name';
 }