[GROOVY-6050] [Static type checking] - Inconvertible types: cannot cast java.io.Writer to SomeInterface

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.1.2
• Component/s: Static Type Checker
• Labels: CompileStatic
• Environment: Java 1.7.0_17
• Assignee: Cédric Champeau
• Reporter: Lari Hotari
• Created: 13/Mar/13 07:29
• Updated: 19/Mar/13 05:11
• Resolved: 13/Mar/13 08:10

Description

Similar to GROOVY-5870, but that has been marked fixed.

Compiling this code:

import groovy.transform.CompileStatic;

import java.io.IOException;

class CastingBugTest {

    
    public void testCastingToInterface() {
        Writer myWriter=MyTester.createWriter()
        MyTester.sayHelloIfSomeInterface(myWriter)
    }
}

@CompileStatic
class MyTester {
    static Writer createWriter() {
        return new MyWriter()
    }
    
    static void sayHelloIfSomeInterface(Writer writer) {
        if(writer instanceof SomeInterface) {
            ((SomeInterface)writer).sayHello()
        }
    }
}

@CompileStatic
interface SomeInterface {
    public void sayHello();
}

@CompileStatic
class MyWriter extends Writer implements SomeInterface {
    public void sayHello() {
        println "Hello"
        
    }

    @Override
    public void write(char[] cbuf, int off, int len) throws IOException {
        
    }

    @Override
    public void flush() throws IOException {
        
    }

    @Override
    public void close() throws IOException {
        
    }
}

Causes this error:

org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
CastingBugTest.groovy: 22: [Static type checking] - Inconvertible types: cannot cast java.io.Writer to SomeInterface
 @ line 22, column 13.
               ((SomeInterface)writer).sayHello()
               ^

1 error