GROOVY-9239 pre-work: add support at grammar level

We still need to do something with the generics term

src/antlr/GroovyParser.g4

@@ -964,7 +964,7 @@ pathElement returns [int t]
             |
                 METHOD_POINTER nls      // Method pointer operator: foo.&y == foo.metaClass.getMethodPointer(foo, "y")
             |
-                METHOD_REFERENCE nls    // Method reference: System.out::println
+                METHOD_REFERENCE nls (nonWildcardTypeArguments)?  // Method reference: System.out::println
             )
             namePart
             { $t = 1; }

src/test-resources/core/MethodReference_01x.groovy

@@ -16,6 +16,8 @@
  *  specific language governing permissions and limitations
  *  under the License.
  */
+import java.util.function.Function
+import java.util.function.Supplier
 import java.util.stream.Stream
 
 import static java.util.stream.Collectors.toList
@@ -109,3 +111,9 @@ assert a.class == b.class && a == b
 a = String[][][][]::new(1, 2)
 b = new String[1][2][][]
 assert a.class == b.class && a == b
+
+static <T extends CharSequence> T chars() { 'foo' }
+Supplier foo = this::<String>chars
+assert foo() == 'foo'
+Function sz = ArrayList::<Integer>size
+assert sz([1, 2, 3, 4]) == 4