[GROOVY-10972] Issue in resolving overloaded method reference

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.0.18, 4.0.12
• Component/s: Static Type Checker
• Assignee: Eric Milles
• Reporter: Thodoris Sotiropoulos
• Created: 09/Mar/23 15:51
• Updated: 23/Aug/23 09:07
• Resolved: 19/Apr/23 15:30

Description

I have the following program

import java.util.function.Function;
import java.util.LinkedList;

class Foo {}


class Test {

    public static void main(String[] args) {
        LinkedList<Foo> x = new LinkedList();
        x.add(new Foo());

        Function<Integer, Foo> z = x::remove;
        Foo k = z.apply(0); // ClassCastException boolean cannot be cast to Foo.
    }

}

Actual behavior

The compiler accepts the code, but the following exception is triggered at runtime.

Exception in thread "main" org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object 'false' with class 'java.lang.Boolean' to class 'Foo'
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnSAM(DefaultTypeTransformation.java:425)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.continueCastOnNumber(DefaultTypeTransformation.java:336)
        at org.codehaus.groovy.runtime.typehandling.DefaultTypeTransformation.castToType(DefaultTypeTransformation.java:256)
        at org.codehaus.groovy.vmplugin.v8.IndyInterface.fromCache(IndyInterface.java:321)
        at Test.main(test.groovy:14)

There problem happens because there are two overloaded methods inside LinkedList:

• E remove(int x)
• boolean remove(Object d)

The compiler seems to resolve the second method (i.e., boolean remove (Object)) although its return type does not match with Function<Integer, Foo>.

Based only on the argument type, both methods are applicable. If the second "remove" method is more specific than the first one, then a compiler error should be raised at compile-time, because boolean does not match Foo. If this is not the case, then the program should call the first "remove" method.