import java

class InstantiatedType extends ParameterizedType {

InstantiatedType() { typeArgs(_, _, this) }

}

Type getAMentionedType(RefType type) {

result = type

or

result = getAMentionedType(type).(Array).getElementType()

or

result = getAMentionedType(type).(InstantiatedType).getATypeArgument()

or

result = getAMentionedType(type).(NestedType).getEnclosingType()

or

result = getAMentionedType(type).(Wildcard).getATypeBound().getType()

}

Type getATypeUsedInClass(RefType type) {

// Base cases:

result = type.getAField().getType()

or

result = type.getAMethod().getReturnType()

or

result = type.getAMethod().getParameterType(_)

or

result = any(Expr e | e.getEnclosingCallable().getDeclaringType() = type).getType()

or

// Structural recursion over types:

result = getAMentionedType(getATypeUsedInClass(type))

}

Element getEnclosingElementStar(RefType e) {

result = e

or

result.contains(e)

}

TypeVariable getATypeVariableInScope(RefType type) {

exists(Element e | e = getEnclosingElementStar(type) |

result = e.(RefType).getACallable().(GenericCallable).getATypeParameter()

or

result = e.(GenericType).getATypeParameter()

or

result = e.(GenericCallable).getATypeParameter()

or

result = getAMentionedType(e.(InstantiatedType).getATypeArgument())

)

}

from ClassOrInterface typeUser, TypeVariable outOfScope

where

outOfScope = getATypeUsedInClass(typeUser) and not outOfScope = getATypeVariableInScope(typeUser)

select "Type " + typeUser + " uses out-of-scope type variable " + outOfScope +

". Note the Java extractor is known to sometimes do this; the Kotlin extractor should not."