malformed union type not caught at compile time

I (mis)defined a union as this (missing 'type' keywords inside the union):

leaf datapath-id {
type union

The parser did not complain, but at run time i got the following exception:

2015-09-14 19:41:54,787 | WARN | bundle-tracker-0 | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 89: Failed to resolve node urn:ietf:params:xml:ns:yang:ietf-yang-types:hex-string : no such extension definition found.
2015-09-14 19:41:54,787 | WARN | bundle-tracker-0 | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 90: Failed to resolve node urn:opendaylight:openflow-pce-topology:uint64 : no such extension definition found.
2015-09-14 19:41:55,054 | WARN | bundle-tracker-0 | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 89: Failed to resolve node urn:ietf:params:xml:ns:yang:ietf-yang-types:hex-string : no such extension definition found.
2015-09-14 19:41:55,054 | WARN | bundle-tracker-0 | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 90: Failed to resolve node urn:opendaylight:openflow-pce-topology:uint64 : no such extension definition found.
2015-09-14 19:41:55,386 | WARN | bundle-tracker-0 | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 89: Failed to resolve node urn:ietf:params:xml:ns:yang:ietf-yang-types:hex-string : no such extension definition found.
2015-09-14 19:41:55,386 | WARN | bundle-tracker-0 | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 90: Failed to resolve node urn:opendaylight:openflow-pce-topology:uint64 : no such extension definition found.
2015-09-14 19:41:55,878 | WARN | ty-notifications | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 89: Failed to resolve node urn:ietf:params:xml:ns:yang:ietf-yang-types:hex-string : no such extension definition found.
2015-09-14 19:41:55,878 | WARN | ty-notifications | YangParserImpl | 79 - org.opendaylight.yangtools.yang-parser-impl - 0.8.0.SNAPSHOT | Error in module of-l3-topology at line 90: Failed to resolve node urn:opendaylight:openflow-pce-topology:uint64 : no such extension definition found.

The parser should catch this syntax error.