[GROOVY-9907] Type tracked from instanceof condition is not captured in closure

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.7
• Fix Version/s: 3.0.8, 4.0.0-alpha-3, 2.5.19
• Component/s: Static compilation
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 25/Jan/21 15:14
• Updated: 27/Aug/22 15:40
• Resolved: 02/Mar/21 15:12

Description

I have the following Groovy program

 

 

@groovy.transform.TypeChecked
class Test {
  public static void main(String[] args) {
    println(foo(10));
  }

  static Integer foo(Object x) {
    if (x instanceof Integer) {
      def bar = {x};
      return bar();
    }
    return 100;
    
  }
}

 

 

Actual Behavior

The program does not compile, and I get the following error

 

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
program.groovy: 10: [Static type checking] - Cannot return value of type java.lang.Object on method returning type java.lang.Integer
 @ line 10, column 14.
         return bar();
                ^1 error

Expected Behavior

Compile successfully.

In particular I would expect that the inferred type of the return type of closure is "Integer" and not "Object", as the closure is defined inside a block where the following condition holds.

x instanceof Integer