remove unused imports

src/AssignmentTaxiRules.rsc

 module AssignmentTaxiRules
 
 import Message;
-import Set;
 import Relation;
 import lang::java::m3::Core;
 import lang::java::m3::AST;
-import IO;
 
 import ClassHierarchy;
-import Util;
 import StandardLocations;
 
 set[Message] allAssignmentTaxiRules(M3 model, set[Declaration] ast)
@@ -84,7 +81,7 @@ set[Message] aTaxi_no_synchronized_modifier(M3 model) =
   | synchronizedThing <- invert(model.modifiers)[synchronized()]
   };
 
-set[Message] aTaxi_no_synchronized_block(M3 model, set[Declaration] ast) =
+set[Message] aTaxi_no_synchronized_block(M3 _, set[Declaration] ast) =
   { error("synchronized should not be used in this assignment", m.decl)
   | /m:method(_,_,_,_,/synchronizedStatement(_,_)) <- ast
   };
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