[GROOVY-7888] Type checker infers wrong type on compound assignment (e.g. += for collection) for property

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.4.7
• Fix Version/s: 2.4.8
• Component/s: Static Type Checker
• Assignee: Paul King
• Reporter: Stefan Wolf
• Created: 20/Jul/16 10:51
• Updated: 01/Feb/17 23:19
• Resolved: 24/Aug/16 07:40

Description

Given the Java class

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;
    }
}

the following Groovy code will not type check:

@TypeChecked
private Set<File> modifyIdeaModel() {
    set.files += new File('foo')
}

The failure is:

Error: Groovyc: [Static type checking] - Cannot assign value of type java.io.File to variable of type java.util.Set <java.io.File>

Without the @TypeChecked the code runs with dynamic Groovy.

Using the following Groovy class type checking the code above works.

class ContainsSet {
    Set<File> files = new HashSet<>()
}

Issue Links

• links to: GitHub Pull Request #390