If a hex literal has an 'd' of 'f' in it, such as '0xf' or '0xd', the compiler fails with illegal tree structure.

The other hex literals work.  The issue is probably related to using `f` and `d` in float and double literals.

```
    public void testHexCollisionDouble() {
        assertEquals(13, exec("return 0xd"));
    }

    public void testHexCollisionFloat() {
        assertEquals(15, exec("return 0xf"));
    }

    public void testHex() throws Exception {
        for (int i = 0; i <= 15; i++) {
            String hex = Integer.toHexString(i);
            if ("d".equals(hex) || "f".equals(hex)) {
                continue;
            }
            assertEquals(i, exec("return 0x" + hex));
            assertEquals(i, exec("return 0x" + hex.toUpperCase(Locale.ROOT)));
            assertEquals(i, exec("return 0X" + hex));
            assertEquals(i, exec("return 0X" + hex.toUpperCase(Locale.ROOT)));
        }
    }
```
modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultSemanticAnalysisPhase.java
semanticScope.putDecoration(userConditionNode, new TargetType(boolean.class));
            checkedVisit(userConditionNode, semanticScope);
            decorateWithCast(userConditionNode, semanticScope);
            if (userConditionNode instanceof EBooleanConstant) {
                continuous = ((EBooleanConstant) userConditionNode).getBool();
                if (continuous == false) {
                    throw userForNode.createError(new IllegalArgumentException("extraneous for loop"));
                }
                if (userBlockNode == null) {
                    throw userForNode.createError(new IllegalArgumentException("no paths escape from for loop"));
                }
            }
        } else {
            continuous = true;
        }
        AExpression userAfterthoughtNode = userForNode.getAfterthoughtNode();
        if (userAfterthoughtNode != null) {
            checkedVisit(userAfterthoughtNode, semanticScope);
        }
        if (userBlockNode != null) {
            semanticScope.setCondition(userBlockNode, BeginLoop.class);
            semanticScope.setCondition(userBlockNode, InLoop.class);
            visit(userBlockNode, semanticScope);
            if (semanticScope.getCondition(userBlockNode, LoopEscape.class)
                && semanticScope.getCondition(userBlockNode, AnyContinue.class) == false) {
                throw userForNode.createError(new IllegalArgumentException("extraneous for loop"));
            }
            if (continuous && semanticScope.getCondition(userBlockNode, AnyBreak.class) == false) {
                semanticScope.setCondition(userForNode, MethodEscape.class);
                semanticScope.setCondition(userForNode, AllEscape.class);