Fixes #309: [java] Parse error on method reference

pmd-java/etc/grammar/Java.jjt

@@ -1,4 +1,9 @@
 /**
+ * Allow method references to specify generics also for
+ * constructor references ("new").
+ * Bug #309
+ * Andreas Dangel 03/2017
+ *====================================================================
  * Provide a better fix for CastExpression, getting rid of most hacks.
  * Bug #257
  *
@@ -1831,7 +1836,7 @@ Token t;
 void MethodReference() :
 {Token t; checkForBadMethodReferenceUsage();}
 {
-  "::" ("new" {jjtThis.setImage("new");} | [TypeArguments()] t=<IDENTIFIER> {jjtThis.setImage(t.image);} )
+  "::" [TypeArguments()] ( "new" {jjtThis.setImage("new");} | t=<IDENTIFIER> {jjtThis.setImage(t.image);} )
 }
 
 void PrimaryPrefix() :

pmd-java/src/test/java/net/sourceforge/pmd/lang/java/ast/ParserCornersTest.java

@@ -4,6 +4,7 @@
 package net.sourceforge.pmd.lang.java.ast;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.fail;
 
 import java.io.IOException;
@@ -172,6 +173,13 @@ public class ParserCornersTest extends ParserTst {
         assertEquals("A cast was found when none expected", 0, compilationUnit.findDescendantsOfType(ASTCastExpression.class).size());
     }
 
+    @Test
+    public void testGitHubBug309() throws Exception {
+        String code = readAsString("GitHubBug309.java");
+        ASTCompilationUnit compilationUnit = parseJava18(code);
+        assertNotNull(compilationUnit);
+    }
+
     /**
      * This triggered bug #1484 UnusedLocalVariable - false positive - parenthesis
      * @throws Exception

pmd-java/src/test/resources/net/sourceforge/pmd/lang/java/ast/GitHubBug309.java

@@ -0,0 +1,8 @@
+import java.util.*;
+
+public class GitHubBug309 {
+    public static void main(String[] args) {
+        Runnable r11 = Main::<String>new;
+        IntFunction<int[]> r13 = int[]::<String>new; // produces the same results
+    }
+}

src/site/markdown/overview/changelog.md

@@ -20,6 +20,7 @@ This is a bug fixing release.
 *   general:
     *   [#305](https://github.com/pmd/pmd/issues/305): \[core] PMD not executing under git bash
 *   java-design:
+    *   [#309](https://github.com/pmd/pmd/issues/309): \[java] Parse error on method reference
     *   [#275](https://github.com/pmd/pmd/issues/275): \[java] FinalFieldCouldBeStatic: Constant in @interface incorrectly reported as "could be made static"
 *   java-junit
     *   [#285](https://github.com/pmd/pmd/issues/285): \[java] JUnitTestsShouldIncludeAssertRule should support @Rule as well as @Test(expected = ...)