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.setCondition(userDotNode, MapShortcut.class);
                            }
                            if (List.class.isAssignableFrom(prefixType)) {
                                try {
                                    scriptScope.putDecoration(userDotNode, new StandardConstant(Integer.parseInt(index)));
                                } catch (NumberFormatException nfe) {
                                    throw userDotNode.createError(new IllegalArgumentException("invalid list index [" + index + "]", nfe));
                                }
                                getter = scriptScope.getPainlessLookup().lookupPainlessMethod(prefixType, false, "get", 1);
                                setter = scriptScope.getPainlessLookup().lookupPainlessMethod(prefixType, false, "set", 2);
                                if (getter != null
                                    && (getter.returnType() == void.class
                                        || getter.typeParameters().size() != 1
                                        || getter.typeParameters().get(0) != int.class)) {
                                    throw userDotNode.createError(
                                        new IllegalArgumentException(
                                            "Illegal list get shortcut for type [" + prefixCanonicalTypeName + "]."
                                        )
                                    );
                                }
                                if (setter != null
                                    && (setter.typeParameters().size() != 2 || setter.typeParameters().get(0) != int.class)) {
                                    throw userDotNode.createError(
                                        new IllegalArgumentException(
                                            "Illegal list set shortcut for type [" + prefixCanonicalTypeName + "]."
                                        )
                                    );
                                }
                                if (getter != null