Type derivation/checking issue

[Bart Bogaerts]

Compare file http://dtai.cs.kuleuven.be/krr/idp-ide/?src=0a83deab385d86d30a17

with file

http://dtai.cs.kuleuven.be/krr/idp-ide/?src=d32a4c2bed17de6dddd9

In one of the two, a type error is thrown, in the other: no error (weird behaviour!)