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
}
            if (staticType != null) {
                if (write) {
                    throw userDotNode.createError(
                        new IllegalArgumentException(
                            "invalid assignment: "
                                + "cannot write a value to a static type ["
                                + PainlessLookupUtility.typeToCanonicalTypeName(staticType)
                                + "]"
                        )
                    );
                }
                semanticScope.putDecoration(userDotNode, new StaticType(staticType));
            } else {
                Class<?> valueType = null;
                if (prefixValueType != null && prefixValueType.valueType().isArray()) {
                    if ("length".equals(index)) {
                        if (write) {
                            throw userDotNode.createError(
                                new IllegalArgumentException(
                                    "invalid assignment: cannot assign a value write to read-only field [length] for an array."
                                )
                            );
                        }
                        valueType = int.class;
                    } else {
                        throw userDotNode.createError(
                            new IllegalArgumentException(
                                "Field [" + index + "] does not exist for type [" + prefixValueType.getValueCanonicalTypeName() + "]."
                            )