[rules-users] [Bug] 5.5.0 Correctly compiled DRL runs into run time error: "incompatible types"

[Wolfgang Laun]

Below is a fully self-contained DRL that compiles correctly but runs
into a runtime error when the LHS of rule "match" is evaluated. The
"culprit" is the test "this != $c", but one would expect simply a true
result from the comparison.

declare Person
  name: String
end
declare Customer
extends Person
  rating: int
end
declare Employee
extends Person
  wage: int
end

rule initphone
salience 100
when
then
    insert( new Customer( "Joe", 100 ) );
    insert( new Employee( "Paul", 2100 ) );
end

rule match
when
    $c: Customer()
    $e: Employee( this != $c )
then
    System.out.println( "c/e " + $c + " " + $e );
end

Exception in thread "main" Exception executing consequence for rule
"initphone" in express: [Error: incompatible types in statement: class
express.Customer (compared from: class express.Employee)]
[Near : {... this != $c ....}]
             ^
[Line: 1, Column: 1]
	at org.drools.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)
	at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1297)
	at org.drools.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1221)
	at org.drools.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1456)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:710)
	at org.drools.common.AbstractWorkingMemory.fireAllRules(AbstractWorkingMemory.java:674)
	at org.drools.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:230)
	at express.Main.execute(Main.java:92)
	at express.Main.main(Main.java:126)
Caused by: [Error: incompatible types in statement: class
express.Customer (compared from: class express.Employee)]
[Near : {... this != $c ....}]
             ^
[Line: 1, Column: 1]
	at org.mvel2.ast.BinaryOperation.<init>(BinaryOperation.java:84)
	at org.mvel2.util.CompilerTools.finalizePayload(CompilerTools.java:118)
	at org.mvel2.compiler.ExpressionCompiler._compile(ExpressionCompiler.java:287)
	at org.mvel2.compiler.ExpressionCompiler.compile(ExpressionCompiler.java:62)
	at org.mvel2.MVEL.compileExpression(MVEL.java:810)
	at org.drools.base.mvel.MVELCompilationUnit.compile(MVELCompilationUnit.java:435)
	at org.drools.base.mvel.MVELCompilationUnit.getCompiledExpression(MVELCompilationUnit.java:238)
	at org.drools.rule.constraint.MvelConstraint.createMvelConditionEvaluator(MvelConstraint.java:206)
	at org.drools.rule.constraint.MvelConstraint.evaluate(MvelConstraint.java:190)
	at org.drools.rule.constraint.MvelConstraint.isAllowedCachedRight(MvelConstraint.java:184)
	at org.drools.common.SingleBetaConstraints.isAllowedCachedRight(SingleBetaConstraints.java:134)
	at org.drools.reteoo.JoinNode.propagateFromRight(JoinNode.java:156)
	at org.drools.reteoo.JoinNode.assertObject(JoinNode.java:148)
	at org.drools.reteoo.SingleObjectSinkAdapter.propagateAssertObject(SingleObjectSinkAdapter.java:59)
	at org.drools.reteoo.ObjectTypeNode.assertObject(ObjectTypeNode.java:235)
	at org.drools.reteoo.EntryPointNode.assertObject(EntryPointNode.java:240)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:350)
	at org.drools.common.NamedEntryPoint.insert(NamedEntryPoint.java:311)
	at org.drools.common.AbstractWorkingMemory.insert(AbstractWorkingMemory.java:903)
	at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:192)
	at org.drools.base.DefaultKnowledgeHelper.insert(DefaultKnowledgeHelper.java:186)
	at express.Rule_initphone_aea184dfceb14326841c37daadabfdbc.defaultConsequence(Rule_initphone_aea184dfceb14326841c37daadabfdbc.java:8)
	at express.Rule_initphone_aea184dfceb14326841c37daadabfdbcDefaultConsequenceInvokerGenerated.evaluate(Unknown
Source)
	at express.Rule_initphone_aea184dfceb14326841c37daadabfdbcDefaultConsequenceInvoker.evaluate(Unknown
Source)
	at org.drools.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1287)
	... 7 more