GitLab

Submitted by Lim Jongrok

Link to original bug (#764440)

Description

Null Coalescing Operator "??" evaluates both of left and right side of expression, when right side throws Error.

This code:

public errordomain SomeError {
    DUMMY_CODE
}

public class Something {
    private int value;

    public Something (int value = 0) {
        message ("Construction: %d", value);
    }

    public Something.throws_error (int value = 0) throws SomeError {
        this (value);
    }
}

public Something create_throwing (int value = 0) throws SomeError {
    return new Something (value);
}

public Something? create_nullable (int value = 0) {
    return new Something (value);
}

public void main () {
    try {
        Something? a = new Something (10);
        Something b = a ?? create_throwing (11);
    
        Something? c = new Something (101);
        Something? d = c ?? create_nullable (102);
    }

    catch (SomeError e) {
        assert_not_reached ();
    }
}

Results in:

** Message: something.vala:9: Construction: 10
** Message: something.vala:9: Construction: 11
** Message: something.vala:9: Construction: 101

which means, create_throwing (11) is evaluated even a is not null. create_nullable (102) isn't evaluated as c is not null.