[jira] [Created] (GROOVY-7888) Type checker infers wrong type collection plus assignment (+=) for property on Java class

["Stefan Wolf (JIRA)" <ji...@apache.org>]

Stefan Wolf created GROOVY-7888:
-----------------------------------

             Summary: Type checker infers wrong type collection plus assignment (+=) for property on Java class
                 Key: GROOVY-7888
                 URL: https://issues.apache.org/jira/browse/GROOVY-7888
             Project: Groovy
          Issue Type: Bug
          Components: Static Type Checker
    Affects Versions: 2.4.7
            Reporter: Stefan Wolf


Given the Java class
{code}
public class ContainsSet extends GroovyObjectSupport {
    private Set<File> files = new HashSet<File>();

    public Set<File> getFiles() {
        return files;
    }

    public void setFiles(Set<File> files) {
        this.files = files;
    }
}
{code}

the following Groovy code will not type check:
{code}
@TypeChecked
private Set<File> modifyIdeaModel() {
    set.files += new File('foo')
}
{code}

The failure is: 
{code}
Error: Groovyc: [Static type checking] - Cannot assign value of type java.io.File to variable of type java.util.Set <java.io.File>
{code}

Without the {{@TypeChecked}} the code runs with dynamic Groovy.

Using the following Groovy class type checking works, too:
{code}
class ContainsSet {
    Set<File> files = new HashSet<>()
}
{code}



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