[GROOVY-11474] flow typing on loops can introduce type unsafety

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 5.0.0-alpha-11
• Component/s: Static Type Checker

Language

groovy

• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 10/Sep/24 09:05
• Updated: 12/Nov/24 11:39
• Resolved: 10/Sep/24 18:38

Description

I have the following program

class Test {
  public static void main(String[] args) {
    def x = 1
    while (true) {
      Integer y = x
      x = ""
      
    }
  }
}

Actual behavior

The code compiles, but I get a CCE at runtime:

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(test.groovy:5)
 

Expected behavior

The code should have been rejected.