lang/zig/error-set.zig


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const expect = @import("std").testing.expect;
const FileOpenError = error { AccessDenied, OutOfMemory, FileNotFound };
const AllocationError = error { OutOfMemory };

fn foo(err: AllocationError) FileOpenError {
    return err;
}

test "coerce subset to superset" {
    const err = foo(AllocationError.OutOfMemory);
    expect(err == FileOpenError.OutOfMemory);
    expect(err == AllocationError.OutOfMemory);
    expect(err == error.OutOfMemory);
}

fn bar(err: FileOpenError) AllocationError {
    return err;
}

test "coerce superset to subset" {
    bar(FileOpenError.OutOfMemory) catch {};
}