FULL PRODUCT VERSION :
java version "9"
Java(TM) SE Runtime Environment (build 9+178)
Java HotSpot(TM) 64-Bit Server VM (build 9+178, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
Putting a "var" declaration in a for-loop produces only part of the expected tree and ignores the rest of the script code.

I have no clue about ECMA Script 6, but according to the spec 13.7.4.4 a VariableDeclarationList is a valid element in a for loop.

The parser should never fail quietly. It should either give a full tree or throw an exception.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Parse this script and use jdk.nashorn.api.tree.SimpleTreeVisitorES6 to inspect the tree.

for (var i = 0; i < c.length; i++) {
    console.log(c[i]);
}


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
0-61 jdk.nashorn.api.tree.ForLoopTreeImpl


Note: this is the tree for a version without the "var"
for (i = 0; i < c.length; i++) {
    console.log(c[i]);
}

The actual expected result should either have VARIABLE instead of ASSIGNMENT or show an ErroneousTree node.

Tree:
@0-0 COMPILATION_UNIT
 @0-57 FOR_LOOP for (i = 0; i < c.length; i++) { console.log(c[i]); }
  @5-10 ASSIGNMENT i = 0
   @5-6 IDENTIFIER i
   @9-10 NUMBER_LITERAL 0
  @12-24 LESS_THAN i < c.length
   @12-13 IDENTIFIER i
   @16-24 MEMBER_SELECT c.length
    @16-17 IDENTIFIER c
  @26-29 POSTFIX_INCREMENT i++
   @26-27 IDENTIFIER i
  @31-57 BLOCK { console.log(c[i]); }
   @37-54 EXPRESSION_STATEMENT console.log(c[i])
    @37-54 FUNCTION_INVOCATION console.log(c[i])
     @37-48 MEMBER_SELECT console.log
      @37-44 IDENTIFIER console
     @49-53 ARRAY_ACCESS c[i]
      @49-50 IDENTIFIER c
      @51-52 IDENTIFIER i

ACTUAL -
5-14 jdk.nashorn.api.tree.VariableTreeImpl

Tree:
@0-0 COMPILATION_UNIT
 @5-14 VARIABLE var i = 0
  @9-10 IDENTIFIER i
  @13-14 NUMBER_LITERAL 0

No other nodes in CompilationUnit.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public static void main(String[] args) {
String script = "for (var i = 0; i < c.length; i++) {\n console.log(c[i]);\n}\n";
        DiagnosticListener listener = (Diagnostic diag) -> { System.err.println(diag.toString()); };

Parser parser = Parser.create("--language=es6", "--empty-statements");
Tree astRoot = parser.parse("unknown", script, listener);
astRoot.accept(new SimpleTreeVisitorES6<Boolean, Void>() {
@Override
public Boolean visitCompilationUnit(CompilationUnitTree stmt, Void none) {
for (Tree item : stmt.getSourceElements()) {
System.out.println(item.getStartPosition() + "-" + item.getEndPosition() + " " + item.getClass().getName());
}
return super.visitCompilationUnit(stmt, none);
}

}, null);
}

---------- END SOURCE ----------