Fix analyzer's handling of import prefixes not followed by '.'.

tests/language/prefix_unqualified_invocation_test.dart

+// Copyright (c) 2015, 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.
+
+// Validate that an attempt to invoke a prefix is handled consistently with the
+// following spec text from section 16.14.3 (Unqualified invocation):
+//     An unqualifiedfunction invocation i has the form
+//     id(a1, ..., an, xn+1 : an+1, ..., xn+k : an+k),
+//     where id is an identifier.
+//     If there exists a lexically visible declaration named id, let fid be the
+//   innermost such declaration.  Then
+//     - If fid isa local function, a library function, a library or static
+//       getter or a variable then ...
+//     - Otherwise, if fid is a static method of the enclosing class C, ...
+//     - Otherwise, fid is considered equivalent to the ordinary method
+//       invocation this.id(a1, ..., an, xn+1 : an+1, ..., xn+k : an+k).
+//
+// Therefore, if p is an import prefix, evaluation of "p()" should be
+// equivalent to "this.p()".  That is, it should call the method "p"
+// dynamically if inside a method, and should produce a NoSucMethodError (and a
+// static warning) outside a method.
+
+import "package:expect/expect.dart";
+import "empty_library.dart" as p;
+
+class Base {
+  var pCalled = false;
+
+  void p() {
+    pCalled = true;
+  }
+}
+
+class Derived extends Base {
+  void f() {
+    p(); Expect.isTrue(pCalled); /// 01: ok
+  }
+}
+
+noMethod(e) => e is NoSuchMethodError;
+
+main() {
+  new Derived().f();
+  Expect.throws(() { p(); }, noMethod); /// 02: static type warning
+}