Collection literals

Collection literals directly return Result[collection, AllocError]:

def build() -> Result[list[list[i64]], AllocError]:
    [[1, 2]?, [3]?]

def main() -> Result[(), AllocError | IoError]:
    print({"answer": 42}?)?
    print(build()?)?
    Ok(())

{"answer": 42}
[[1, 2], [3]]

Construction stops at its first allocation failure, drops the partial collection, and skips later entries. The nested ? operations extract each inner list and propagate its failure to build. Empty displays need context: values: Result[list[i64], AllocError] = [], or values: list[i64] = []? inside a function returning Result[..., AllocError].

Byte keys and iterable conversion

Byte literals and tuples of hashable values can be dictionary keys or set members. Call-style list constructors can collect text scalars or literal bytes:

def main() -> Result[(), AllocError | IoError]:
    names = {b"GIF8": "gif"}?
    seen = {(b"tag", 1), (b"tag", 1)}?
    print(names[b"GIF8"], len(seen))?
    print(list("aé")?)?
    print(list[u8](b"AB")?)?
    Ok(())

gif 1
["a", "é"]
[65, 66]

The .from(...) methods accept collections, ranges, and generators, but not text or bytes. See collection conversion for the supported constructor forms.