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

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

Index: pkg/analyzer/lib/src/summary/link.dart
diff --git a/pkg/analyzer/lib/src/summary/link.dart b/pkg/analyzer/lib/src/summary/link.dart
index ea25920c1156c792e894a411b3760042c0c6183e..87828c393b44993dd6d8f2e77ba6b275536bea97 100644
--- a/pkg/analyzer/lib/src/summary/link.dart
+++ b/pkg/analyzer/lib/src/summary/link.dart
@@ -3104,8 +3104,10 @@ class FunctionElementForLink_Local_NonSynthetic extends ExecutableElementForLink
    * 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);
     }