question: public TypeVariable typeVariable ( TypeNode typeNode ) { TypeVariable result = typeVariableMap . get ( typeNode ) ; if ( result == null ) { int id = typeVariableList . size ( ) ; typeVariableList . add ( null ) ; result = new TypeVariable ( id , this , typeNode ) ; typeVariableList . set ( id , result ) ; typeVariableMap . put ( typeNode , result ) ; } return result ; }
target:  Get type variable for the given type node. 