--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/api/JavacTrees.java	Wed Feb 08 13:35:42 2017 -0800
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/api/JavacTrees.java	Wed Feb 08 19:42:24 2017 -0800
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2005, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2005, 2017, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -418,6 +418,7 @@
 
     private Symbol attributeDocReference(TreePath path, DCReference ref) {
         Env<AttrContext> env = getAttrContext(path);
+        if (env == null) return null;
 
         Log.DeferredDiagnosticHandler deferredDiagnosticHandler =
                 new Log.DeferredDiagnosticHandler(log);
@@ -881,6 +882,7 @@
                 case INTERFACE:
 //                    System.err.println("CLASS: " + ((JCClassDecl)tree).sym.getSimpleName());
                     env = enter.getClassEnv(((JCClassDecl)tree).sym);
+                    if (env == null) return null;
                     break;
                 case METHOD:
 //                    System.err.println("METHOD: " + ((JCMethodDecl)tree).sym.getSimpleName());

--- a/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Enter.java	Wed Feb 08 13:35:42 2017 -0800
+++ b/langtools/src/jdk.compiler/share/classes/com/sun/tools/javac/comp/Enter.java	Wed Feb 08 19:42:24 2017 -0800
@@ -156,6 +156,7 @@
 
     public Env<AttrContext> getClassEnv(TypeSymbol sym) {
         Env<AttrContext> localEnv = getEnv(sym);
+        if (localEnv == null) return null;
         Env<AttrContext> lintEnv = localEnv;
         while (lintEnv.info.lint == null)
             lintEnv = lintEnv.next;

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/langtools/test/tools/javac/doclint/NPEDuplicateClassNamesTest.java	Wed Feb 08 19:42:24 2017 -0800
@@ -0,0 +1,97 @@
+/*
+ * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8174073
+ * @summary NPE caused by link reference to class
+ * @modules jdk.compiler/com.sun.tools.javac.api
+ *          jdk.compiler/com.sun.tools.javac.main
+ * @library /tools/lib
+ * @build toolbox.JavacTask toolbox.TestRunner toolbox.ToolBox
+ * @run main NPEDuplicateClassNamesTest
+ */
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+
+import toolbox.JavacTask;
+import toolbox.Task;
+import toolbox.TestRunner;
+import toolbox.ToolBox;
+
+public class NPEDuplicateClassNamesTest extends TestRunner {
+
+    public static void main(String... args) throws Exception {
+        NPEDuplicateClassNamesTest t = new NPEDuplicateClassNamesTest();
+        t.runTests();
+    }
+
+    private final ToolBox tb = new ToolBox();
+    private final String class1 =
+            "package com;\n" +
+            "/***/\n" +
+            "public class MyClass {}";
+    private final String class2 =
+            "package com;\n" +
+            "/**\n" +
+            " * The following link tag causes a NullPointerException: {@link Requirements}. \n" +
+            " */\n" +
+            "public class MyClass {}";
+
+    NPEDuplicateClassNamesTest() throws IOException {
+        super(System.err);
+    }
+
+    @Test
+    public void testDuplicateClassNames() throws IOException {
+        Path src = Paths.get("src");
+        Path one = src.resolve("one");
+        Path two = src.resolve("two");
+        Path classes = Paths.get("classes");
+        Files.createDirectories(classes);
+        tb.writeJavaFiles(one, class1);
+        tb.writeJavaFiles(two, class2);
+
+        List<String> expected = Arrays.asList(
+                "MyClass.java:5:8: compiler.err.duplicate.class: com.MyClass",
+                "MyClass.java:3:65: compiler.err.proc.messager: reference not found",
+                "2 errors");
+        List<String> output = new JavacTask(tb)
+                  .outdir(classes)
+                  .options("-XDrawDiagnostics", "-Xdoclint:all", "-XDdev")
+                  .files(tb.findJavaFiles(src))
+                  .run(Task.Expect.FAIL)
+                  .writeAll()
+                  .getOutputLines(Task.OutputKind.DIRECT);
+
+        if (!Objects.equals(output, expected)) {
+            throw new IllegalStateException("incorrect output; actual=" + output + "; expected=" + expected);
+        }
+    }
+}