Assignments in closures can introduce issues in flow typing

class Test {
  public static void main(String[] args) {
    def x = 1
    Closure m = null
    if (true) {
      m = {x = ""}
    }
    x = 1
    m()
  }
} 

 Exception in thread "main" org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '' with class 'java.lang.String' to class 'java.lang.Integer'
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToNumber(DefaultTypeTransformation.java:177)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnNumber(DefaultTypeTransformation.java:294)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToType(DefaultTypeTransformation.java:248)
        at org.codehaus.groovy.vmplugin.v8.IndyInterface.fromCache(IndyInterface.java:336)
        at Test$_main_closure1.doCall(test.groovy:6)
        at Test$_main_closure1.call(test.groovy)
        at Test.main(test.groovy:9)