[GROOVY-9967] STC: Access to field/property is forbidden after instanceof.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 4.0.0-alpha-2
• Fix Version/s: 2.5.15, 3.0.8, 4.0.0-alpha-3
• Component/s: Static compilation, Static Type Checker
• Assignee: Eric Milles
• Reporter: Stefanos Chaliasos
• Created: 05/Mar/21 09:30
• Updated: 02/May/21 09:16
• Resolved: 07/Mar/21 02:37

Description

I have the following Groovy program.

class Test {
  static void main(String[] args) {
    println(C.func4(new B()))
  }
}

class A {}
class B extends A {
  // It has the same behavior if f is a field instead of a property.
  String f = "foo"
}

@groovy.transform.CompileStatic
class C {
  static String func1(Object x) {
    (x instanceof String) ? x : "foo" // Compiles
  }

  static String func2(B x) {
    x.f // Compiles
  }

  static String func3(B x) {
    (x instanceof B) ? x.f : "foo" // Compiles
  }

  static String func4(A x) {
    (x instanceof B) ? x.f : "foo" // Does not compile
  }
}

Actual Behavior

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

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
Test.groovy: 28: Access to A#f is forbidden @ line 28, column 24.
       (x instanceof B) ? x.f : "foo" 
                          ^

1 error

Expected Behavior

Compile successfully.

Comment

This should be a regression bug because it compiles with the 3.0.7 compiler.
If we declared classes A and B after C, then the program compiles successfully.
Specifically, the following program compiles without any errors.

class Test {
  static void main(String[] args) {
    println(C.func4(new B()))
  }
}

@groovy.transform.CompileStatic
class C {
  static String func1(Object x) {
    (x instanceof String) ? x : "foo" 
  }

  static String func2(B x) {
    x.f 
  }

  static String func3(B x) {
    (x instanceof B) ? x.f : "foo"
  }

  static String func4(A x) {
    (x instanceof B) ? x.f : "foo" 
  }
}

class A {}
class B extends A {
  String f = "foo"
}