Closures shouldn't have fuzzy arrow type.

pkg/analyzer/lib/src/task/strong/info.dart

Index: pkg/analyzer/lib/src/task/strong/info.dart
diff --git a/pkg/analyzer/lib/src/task/strong/info.dart b/pkg/analyzer/lib/src/task/strong/info.dart
index f39efffd4eb1fb08e7ea6b1396c489ab3cd681b9..41703e12a13f9ba325536ab51ca59d45ff62c30c 100644
--- a/pkg/analyzer/lib/src/task/strong/info.dart
+++ b/pkg/analyzer/lib/src/task/strong/info.dart
@@ -518,7 +518,9 @@ abstract class StaticInfo {
 
   static bool isKnownFunction(Expression expression) {
     Element element = null;
-    if (expression is PropertyAccess) {
+    if (expression is FunctionExpression) {
+      return true;
+    } else if (expression is PropertyAccess) {
       element = expression.propertyName.staticElement;
     } else if (expression is Identifier) {
       element = expression.staticElement;