[GROOVY-11450] flow typing can lead to type unsafe results when having nested ifs

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.23, 4.0.23, 5.0.0-alpha-10
• Component/s: Static Type Checker

Language

groovy

• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 09/Aug/24 10:17
• Updated: 04/Sep/24 18:49
• Resolved: 04/Sep/24 18:03

Description

I have the following program

class A {
  Object clone() { return null; }
}
class Main {
  public static void main(Object y) {
    def x
    x = new A()
    if (false ){
      x = new A()
    } else {
      if (true) {
        x = 1
      }
    }
    x.clone();
  }
} 

Actual behavior

The program compiles, but I receive the following error at runtime:

Exception in thread "main" java.lang.ClassCastException: class java.lang.Integer cannot be cast to class A (java.lang.Integer is in module java.base of loader 'bootstrap'; A is in unnamed module of loader 'app')
    at Main.main(test.groovy:16) 

Expected behavior

The code should have been rejected with

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
test.groovy: 12: Cannot access method: clone() of class: java.lang.Object @ line 12, column 5.
       x.clone();
       ^1 error
 

 

Issue Links

• is related to: GROOVY-9786 SC: cast exception for variable assigned within conditional blocks