[GROOVY-11008] incorrect type inference after (instanceof || instanceof)

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Duplicate
• Affects Version/s: 3.0.17
• Component/s: Compiler
• Assignee: Eric Milles
• Reporter: Jason Garrett
• Created: 10/Apr/23 21:13
• Updated: 22/Dec/23 11:38
• Resolved: 29/Apr/23 17:02

Description

Under static compilation, inside an "if" condition that checks if either of two variables are an instance of a class, both variables are inferred to be that class.  If one of them is not, accessing it results in a ClassCastException.

import groovy.transform.CompileStatic

@CompileStatic
class InstanceofTypeInference {
    static abstract class BaseClass {
       abstract String getMyString()
    }

    static class ClassA extends BaseClass {
       String getMyString() {
          return "Class A String"
       }
    }

    static class ClassB extends BaseClass {
       String getMyString() {
          return "Class B String"
       }
    }

    void doStuff(BaseClass foo, BaseClass bar) {
       if((foo instanceof ClassA) || (bar instanceof ClassA)) {
          println foo.myString
          println bar.myString  // cannot cast ClassB to ClassA
       }
    }

    static void main(args) {
       def example = new InstanceofTypeInference()
       example.doStuff(new ClassA(), new ClassB())
    }
} 

Running this example fails with a ClassCastException.

Issue Links

• duplicates: GROOVY-7971 @CS flow typing incorrectly casting to map at runtime
• is related to: GROOVY-8965 instanceof with || inserts wrong cast