Bug in the behavior of select/deselect in configuration with a XOR

[surli]

I just try to run the following script:

fm = FM(A: (B|C);)
c = configuration fm
select B in c
result = select C in c
print "Should be false : "
println result

Should be false: true

print "Should have B and C selected : "
println selectedF c

Should have B and C selected : {A}

I don't understand why when I try to select C, the command returns true, but everything is deselected...