[jira] [Created] (GROOVY-10480) Closure that assigns null to object changes the type of variable

["Thodoris Sotiropoulos (Jira)" <ji...@apache.org>]

Thodoris Sotiropoulos created GROOVY-10480:
----------------------------------------------

             Summary: Closure that assigns null to object changes the type of variable
                 Key: GROOVY-10480
                 URL: https://issues.apache.org/jira/browse/GROOVY-10480
             Project: Groovy
          Issue Type: Bug
          Components: Static Type Checker
            Reporter: Thodoris Sotiropoulos


I have the following Groovy program


{code:java}
class Foo {
  void foo() {}
}


class Main  {

  static void bar() {
    def x = new Foo();
    if (false) {
      x = null;
    }
    x.foo(); // works
  }

  static void baz() {
    def x  = new Foo();
    def clos = { -> {
      x = null;
      
    }}
    x.foo(); // fails
  }

}
{code}

h3. Actual behaviour

The assignment that takes inside closure changes the type of variable `x`, even though closure is never being called.
The compilerthen rejects the program by raising the following error message.

{code}
org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 22: [Static type checking] - A closure shared variable [x] has been assigned with various types and the method [foo()] does not exist in the lowest upper bound of those types: [java.lang.Object]. In general, this is a bad practice (variable reuse) because the compiler cannot determine safely what is the type of the variable at the moment of the call in a multithreaded context.
 @ line 22, column 5.
       x.foo();
       ^

1 error
{code}

h3. Expected behaviour

Compile successfully

Tested against master (https://github.com/apache/groovy/commit/5601ea14304b67e71586b0196e38f90fa1a46f5b).



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