Structs missing in generated go code

[nettnikl]

Description

Some simple types are not generated under given circumstances. The original XSD is not created by me, but is i understand, is old and widely used.

I have no clue of XML, but i managed to dumb the issue down to this short code.

Steps to reproduce the issue:

1. See reproducible minimal example code below.
2. xgen -l Go -p internal -i resources/xsd/ -o internal/model/
3. Check the output.

Describe the results you received: AAA has a struct in go code created.

Describe the results you expected: GGG and DDD has types in go code created as well.

Output of go version:

go version go1.22.5 linux/amd64

xgen version or commit ID:

xgen version: 0.1.0

<?xml version="1.0" encoding="UTF-8"?>
<xsd:schema
        xmlns:xsd="http://www.w3.org/2001/XMLSchema"
        targetNamespace="http://example.com/schemas"
        xmlns:ak="http://example.com/schemas"
        elementFormDefault="qualified">

    <xsd:complexType name="AAA">
        <xsd:annotation><xsd:documentation>BBB</xsd:documentation></xsd:annotation>
        <xsd:sequence>
            <xsd:element name="CCC">
                <xsd:simpleType>
                    <xsd:restriction base="ak:GGG">
                        <!-- This seems to be the issue, CCC is not generated with this restriction enabled -->
                        <xsd:minLength value = "4" fixed = "true" />
                    </xsd:restriction>
                </xsd:simpleType>
            </xsd:element>
        </xsd:sequence>
    </xsd:complexType>

    <xsd:simpleType name="DDD">
        <xsd:annotation><xsd:documentation>EEE</xsd:documentation></xsd:annotation>
        <xsd:restriction base="ak:GGG">
            <!-- While CCC is ok, this is okay as well. While CCC has the invalid restriction: if any of the following it commented in, DDD is not generated anymore as well. -->
<!--            <xsd:whiteSpace value="collapse" />
<!--            <xsd:minLength value="1" />-->
<!--            <xsd:maxLength value="43" />-->
        </xsd:restriction>
    </xsd:simpleType>

    <xsd:simpleType name="GGG">
        <xsd:annotation><xsd:documentation>FFF</xsd:documentation></xsd:annotation>
        <xsd:restriction base="xsd:string"/>
    </xsd:simpleType>
    
</xsd:schema>

Environment details (OS, physical, etc.):