Classes org.jboss.as.weld.WeldJBossAll10Parser and org.jboss.as.weld.WeldJBossAll11Parser are incorrect. They do not parse <weld> element as XML, they just check attributes.

As a result, everything that comes after </weld> is ignored.

This jboss-all.xml fails, as expected: 

<jboss xmlns="urn:jboss:1.0">
    <some-stupid-element/>
    <weld xmlns="urn:jboss:weld:1.1"/>
</jboss>

 This one is successfully parsed (but must also fail):

<jboss xmlns="urn:jboss:1.0">
    <weld xmlns="urn:jboss:weld:1.1"/>
    <some-stupid-element/>
</jboss>

Now imagine that "some-stupid-element" is in fact "jboss-deployment-structure" which gets ignored...