Fix summarization of inferred types which are function-typed params of typedefs.

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

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index f3aef149697be333b805a9b53d4c28cca29fd78b..3bebefa4e23ad0cdcbbfa534c420c5d4c30d7e11 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -1051,7 +1051,7 @@ class _CompilationUnitSerializer {
         ParameterElement parameterElement = typeElement.enclosingElement;
         while (true) {
           Element parent = parameterElement.enclosingElement;
-          if (parent is ExecutableElement) {
+          if (parent is FunctionTypedElement) {
             Element grandParent = parent.enclosingElement;
             b.implicitFunctionTypeIndices
                 .insert(0, parent.parameters.indexOf(parameterElement));