Reject common phrases like "guten morgen"

[emlautarom1]

In German, "morgen" is used for "tomorrow" and there is a rule for that:

duckling/Duckling/Time/DE/Rules.hs

Line 40 in 7520daa

, ( "tomorrow" , TG.Day , 1, "morgen" )

Unfortunately, this means that phrases like "guten morgen" are interpreted as "tomorrow", despite it being a common phrase that has nothing to do with time. I would like to add some kind of rule that detects this pattern and always rejects it.

My initial attempt used negative lookbehinds like (?<!guten\s+)morgen, but this is not supported by the engine. A second approach was to create a rule that matched on the guten\s+morgen regex and has a production of const Nothing, but this does not work either because the morgen rule gets used instead.

How can I force Duckling to always ignore this phrase?