closure calls (just the invocation part).

frog/leg/elements/elements.dart

Index: frog/leg/elements/elements.dart
diff --git a/frog/leg/elements/elements.dart b/frog/leg/elements/elements.dart
index 437c819ed233101092b7f8680ff14a22ac06ea08..3f0f6ecc5470f5e0ee82aafbce3084eaa735b585 100644
--- a/frog/leg/elements/elements.dart
+++ b/frog/leg/elements/elements.dart
@@ -54,6 +54,8 @@ class Element implements Hashable {
   bool isInstanceMember() => false;
   bool isFactoryConstructor() => modifiers != null && modifiers.isFactory();
   bool isGenerativeConstructor() => kind == ElementKind.GENERATIVE_CONSTRUCTOR;
+  bool isVariable() => kind == ElementKind.VARIABLE;
+  bool isParameter() => kind == ElementKind.PARAMETER;
 
   bool isAssignable() {
     if (modifiers != null && modifiers.isFinal()) return false;
@@ -356,4 +358,14 @@ class Elements {
            && element.isInstanceMember()
            && (element.kind === ElementKind.FUNCTION);
   }
+
+  static bool isClosureSend(Send send, TreeElements elements) {
+    if (send.isPropertyAccess) return false;
+    if (send.receiver !== null) return false;
+    Element element = elements[send];
+    // (o)() or foo()().
+    if (element === null && send.selector.asIdentifier() === null) return true;
+    // foo() with foo a local or a parameter.
+    return element.isVariable() || element.isParameter();
+  }
 }