Error message cursor at wrong position for packed struct containing packed union

[wooster0]

Zig Version

0.14.0-dev.2273+73dcd1914

Steps to Reproduce and Observed Behavior

const X = packed struct {
    a: packed union {
        b: u8,
    },
};

test {
    const y: X = undefined;
    y.a = .{ .b = 0 };
}

x.zig:9:19: error: cannot assign to constant
    y.a = .{ .b = 0 };
                  ^

Expected Behavior

x.zig:9:19: error: cannot assign to constant
    y.a = .{ .b = 0 };
    ^