Attributes not correctly uplifted in combination with multiple supertypes

For the grammar

Model:
	Rule1 | Rule2 | Rule3;

Rule1:
	'Rule1' name=ID frag;

Rule2:
	'Rule2' name=ID frag;

Rule3:
	'Rule3' name=ID;

fragment frag:
	'frag' someattribute=STRING;

the generated class hierarchy is not correctly inferred as the common name attribute is not lifted into the Model class.

Interestingly, this behaviour is determined by the order of appearance in the Xtext file:

• If the non-fragment rule is the first or second, inference works correctly
• Switching the alternative options in Model (e.g. to "Rule1 | Rule3 | Rule2") however has no effect
• "Physically" moving Rule3 definition between Rule1 and Rule2 (not changing any numbers) does make inference work correctly again

Update @cdietrich

same problem with other supertypes as well

Model:
	Rule1 | Rule3 | Rule2;

Rule1:
	{Rule1}'Rule1' name=ID;

Rule2:
	{Rule2}'Rule2' name=ID;

Rule3:
	'Rule3' name=ID;

Frag: Rule1 | Rule2;

Start by reproducing the issue with the grammar shown in the report, including the alternate example with additional supertypes. Trace the inferred generated class hierarchy and compare results when Rule3 is moved or the alternatives are reordered. Done means the shared name attribute is consistently lifted into the common Model class regardless of rule order.