decompiler: fixed incorrect method references from single letter classes

testData/src/pkg/TestMethodReferenceLetterClass.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2000-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import java.util.function.Consumer;
+
+public class TestMethodReferenceLetterClass {
+  void boo() {
+    Consumer<R> foo = R::foo;
+  }
+}
+
+class R {
+  void foo() {}
+}