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ruff/crates/red_knot_python_semantic/resources/mdtest/unpacking.md
Shaygan Hooshyari 03ff883626
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Display Union of Literals as a Literal (#14993) 
## Summary

Resolves #14988

Display union of Literals like other type checkers do.

With this change we lose the sorting behavior. And we show the types as
they appeared. So it's deterministic and tests should not be flaky.
This is similar to how Mypy [reveals the
type](https://mypy-play.net/?mypy=latest&python=3.12&gist=51ad03b153bfca3b940d5084345e230f).

In some cases this makes it harder to know what is the order in revealed
type when writing tests but since it's consistent after the test fails
we know the order.

## Test Plan

I adjusted mdtests for this change. Basically merged the int and string
types of the unions.

In cases where we have types other than numbers and strings like this
[one](https://github.com/astral-sh/ruff/pull/14993/files#diff-ac50bce02b9f0ad4dc7d6b8e1046d60dad919ac52d0aeb253e5884f89ea42bfeL51).
We only group the strings and numbers as the issue suggsted.

```
def _(flag: bool, flag2: bool):
    if flag:
        f = 1
    elif flag2:
        f = "foo"
    else:
        def f() -> int:
            return 1
    # error: "Object of type `Literal[1, "foo", f]` is not callable (due to union elements Literal[1], Literal["foo"])"
    # revealed: Unknown | int
    reveal_type(f())
```

[pyright
example](https://pyright-play.net/?code=GYJw9gtgBALgngBwJYDsDmUkQWEMoAySMApiAIYA2AUNQCYnBQD6AFMJeWgFxQBGYMJQA0UDlwBMvAUICU3alCWYm4nouWamAXigBGDUpKUkqzmimHNYqLoBEwQXavGAziQXXlDVa1lQAWgA%2BTBQYTy9rEBIYAFcQFH0rAGIoMnAQXjsAeT4AKxIAY3wwJngEEigAAyJSCkoAbT1RBydRYABdKsxXKBQwfEKqTj5KStY6WMqYMChYlCQwROMSCBIw3tqyKiaO0S36htawOw7ZZ01U6IA3EioSOl4AVRQAa36Ad0SAH1CYKxud0ozHKJHYflk1CAA)

[mypy
example](https://mypy-play.net/?mypy=latest&python=3.12&gist=31c8bdaa5521860cfeca4b92841cb3b7)

---------

Co-authored-by: Carl Meyer <carl@oddbird.net>
2025-01-08 00:58:38 +00:00

13 KiB
Raw Blame History

Unpacking

Tuple

Simple tuple

(a, b, c) = (1, 2, 3)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]
reveal_type(c)  # revealed: Literal[3]

Simple list

[a, b, c] = (1, 2, 3)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]
reveal_type(c)  # revealed: Literal[3]

Simple mixed

[a, (b, c), d] = (1, (2, 3), 4)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]
reveal_type(c)  # revealed: Literal[3]
reveal_type(d)  # revealed: Literal[4]

Multiple assignment

a, b = c = 1, 2
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]
reveal_type(c)  # revealed: tuple[Literal[1], Literal[2]]

Nested tuple with unpacking

(a, (b, c), d) = (1, (2, 3), 4)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]
reveal_type(c)  # revealed: Literal[3]
reveal_type(d)  # revealed: Literal[4]

Nested tuple without unpacking

(a, b, c) = (1, (2, 3), 4)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: tuple[Literal[2], Literal[3]]
reveal_type(c)  # revealed: Literal[4]

Uneven unpacking (1)

# error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
(a, b, c) = (1, 2)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]
reveal_type(c)  # revealed: Unknown

Uneven unpacking (2)

# error: [invalid-assignment] "Too many values to unpack (expected 2, got 3)"
(a, b) = (1, 2, 3)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]

Starred expression (1)

# error: [invalid-assignment] "Not enough values to unpack (expected 3 or more, got 2)"
[a, *b, c, d] = (1, 2)
reveal_type(a)  # revealed: Literal[1]
# TODO: Should be list[Any] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: Literal[2]
reveal_type(d)  # revealed: Unknown

Starred expression (2)

[a, *b, c] = (1, 2)
reveal_type(a)  # revealed: Literal[1]
# TODO: Should be list[Any] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: Literal[2]

Starred expression (3)

[a, *b, c] = (1, 2, 3)
reveal_type(a)  # revealed: Literal[1]
# TODO: Should be list[int] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: Literal[3]

Starred expression (4)

[a, *b, c, d] = (1, 2, 3, 4, 5, 6)
reveal_type(a)  # revealed: Literal[1]
# TODO: Should be list[int] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: Literal[5]
reveal_type(d)  # revealed: Literal[6]

Starred expression (5)

[a, b, *c] = (1, 2, 3, 4)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Literal[2]
# TODO: Should be list[int] once support for assigning to starred expression is added
reveal_type(c)  # revealed: @Todo(starred unpacking)

Starred expression (6)

# error: [invalid-assignment] "Not enough values to unpack (expected 5 or more, got 1)"
(a, b, c, *d, e, f) = (1,)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: Unknown
reveal_type(c)  # revealed: Unknown
reveal_type(d)  # revealed: @Todo(starred unpacking)
reveal_type(e)  # revealed: Unknown
reveal_type(f)  # revealed: Unknown

Non-iterable unpacking

# error: "Object of type `Literal[1]` is not iterable"
a, b = 1
reveal_type(a)  # revealed: Unknown
reveal_type(b)  # revealed: Unknown

Custom iterator unpacking

class Iterator:
    def __next__(self) -> int:
        return 42

class Iterable:
    def __iter__(self) -> Iterator:
        return Iterator()

(a, b) = Iterable()
reveal_type(a)  # revealed: int
reveal_type(b)  # revealed: int

Custom iterator unpacking nested

class Iterator:
    def __next__(self) -> int:
        return 42

class Iterable:
    def __iter__(self) -> Iterator:
        return Iterator()

(a, (b, c), d) = (1, Iterable(), 2)
reveal_type(a)  # revealed: Literal[1]
reveal_type(b)  # revealed: int
reveal_type(c)  # revealed: int
reveal_type(d)  # revealed: Literal[2]

String

Simple unpacking

a, b = "ab"
reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: LiteralString

Uneven unpacking (1)

# error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
a, b, c = "ab"
reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: LiteralString
reveal_type(c)  # revealed: Unknown

Uneven unpacking (2)

# error: [invalid-assignment] "Too many values to unpack (expected 2, got 3)"
a, b = "abc"
reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: LiteralString

Starred expression (1)

# error: [invalid-assignment] "Not enough values to unpack (expected 3 or more, got 2)"
(a, *b, c, d) = "ab"
reveal_type(a)  # revealed: LiteralString
# TODO: Should be list[LiteralString] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: LiteralString
reveal_type(d)  # revealed: Unknown

Starred expression (2)

(a, *b, c) = "ab"
reveal_type(a)  # revealed: LiteralString
# TODO: Should be list[Any] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: LiteralString

Starred expression (3)

(a, *b, c) = "abc"
reveal_type(a)  # revealed: LiteralString
# TODO: Should be list[LiteralString] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: LiteralString

Starred expression (4)

(a, *b, c, d) = "abcdef"
reveal_type(a)  # revealed: LiteralString
# TODO: Should be list[LiteralString] once support for assigning to starred expression is added
reveal_type(b)  # revealed: @Todo(starred unpacking)
reveal_type(c)  # revealed: LiteralString
reveal_type(d)  # revealed: LiteralString

Starred expression (5)

(a, b, *c) = "abcd"
reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: LiteralString
# TODO: Should be list[int] once support for assigning to starred expression is added
reveal_type(c)  # revealed: @Todo(starred unpacking)

Unicode

# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
(a, b) = "é"

reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: Unknown

Unicode escape (1)

# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
(a, b) = "\u9E6C"

reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: Unknown

Unicode escape (2)

# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
(a, b) = "\U0010FFFF"

reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: Unknown

Surrogates

(a, b) = "\uD800\uDFFF"

reveal_type(a)  # revealed: LiteralString
reveal_type(b)  # revealed: LiteralString

Union

Same types

Union of two tuples of equal length and each element is of the same type.

def _(arg: tuple[int, int] | tuple[int, int]):
    (a, b) = arg
    reveal_type(a)  # revealed: int
    reveal_type(b)  # revealed: int

Mixed types (1)

Union of two tuples of equal length and one element differs in its type.

def _(arg: tuple[int, int] | tuple[int, str]):
    a, b = arg
    reveal_type(a)  # revealed: int
    reveal_type(b)  # revealed: int | str

Mixed types (2)

Union of two tuples of equal length and both the element types are different.

def _(arg: tuple[int, str] | tuple[str, int]):
    a, b = arg
    reveal_type(a)  # revealed: int | str
    reveal_type(b)  # revealed: str | int

Mixed types (3)

Union of three tuples of equal length and various combination of element types:

  1. All same types
  2. One different type
  3. All different types
def _(arg: tuple[int, int, int] | tuple[int, str, bytes] | tuple[int, int, str]):
    a, b, c = arg
    reveal_type(a)  # revealed: int
    reveal_type(b)  # revealed: int | str
    reveal_type(c)  # revealed: int | bytes | str

Nested

def _(arg: tuple[int, tuple[str, bytes]] | tuple[tuple[int, bytes], Literal["ab"]]):
    a, (b, c) = arg
    reveal_type(a)  # revealed: int | tuple[int, bytes]
    reveal_type(b)  # revealed: str
    reveal_type(c)  # revealed: bytes | LiteralString

Starred expression

def _(arg: tuple[int, bytes, int] | tuple[int, int, str, int, bytes]):
    a, *b, c = arg
    reveal_type(a)  # revealed: int
    # TODO: Should be `list[bytes | int | str]`
    reveal_type(b)  # revealed: @Todo(starred unpacking)
    reveal_type(c)  # revealed: int | bytes

Size mismatch (1)

def _(arg: tuple[int, bytes, int] | tuple[int, int, str, int, bytes]):
    # error: [invalid-assignment] "Too many values to unpack (expected 2, got 3)"
    # error: [invalid-assignment] "Too many values to unpack (expected 2, got 5)"
    a, b = arg
    reveal_type(a)  # revealed: int
    reveal_type(b)  # revealed: bytes | int

Size mismatch (2)

def _(arg: tuple[int, bytes] | tuple[int, str]):
    # error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
    # error: [invalid-assignment] "Not enough values to unpack (expected 3, got 2)"
    a, b, c = arg
    reveal_type(a)  # revealed: int
    reveal_type(b)  # revealed: bytes | str
    reveal_type(c)  # revealed: Unknown

Same literal types

def _(flag: bool):
    if flag:
        value = (1, 2)
    else:
        value = (3, 4)

    a, b = value
    reveal_type(a)  # revealed: Literal[1, 3]
    reveal_type(b)  # revealed: Literal[2, 4]

Mixed literal types

def _(flag: bool):
    if flag:
        value = (1, 2)
    else:
        value = ("a", "b")

    a, b = value
    reveal_type(a)  # revealed: Literal[1, "a"]
    reveal_type(b)  # revealed: Literal[2, "b"]

Typing literal

from typing import Literal

def _(arg: tuple[int, int] | Literal["ab"]):
    a, b = arg
    reveal_type(a)  # revealed: int | LiteralString
    reveal_type(b)  # revealed: int | LiteralString

Custom iterator (1)

class Iterator:
    def __next__(self) -> tuple[int, int] | tuple[int, str]:
        return (1, 2)

class Iterable:
    def __iter__(self) -> Iterator:
        return Iterator()

((a, b), c) = Iterable()
reveal_type(a)  # revealed: int
reveal_type(b)  # revealed: int | str
reveal_type(c)  # revealed: tuple[int, int] | tuple[int, str]

Custom iterator (2)

class Iterator:
    def __next__(self) -> bytes:
        return b""

class Iterable:
    def __iter__(self) -> Iterator:
        return Iterator()

def _(arg: tuple[int, str] | Iterable):
    a, b = arg
    reveal_type(a)  # revealed: int | bytes
    reveal_type(b)  # revealed: str | bytes

For statement

Unpacking in a for statement.

Same types

def _(arg: tuple[tuple[int, int], tuple[int, int]]):
    for a, b in arg:
        reveal_type(a)  # revealed: int
        reveal_type(b)  # revealed: int

Mixed types (1)

def _(arg: tuple[tuple[int, int], tuple[int, str]]):
    for a, b in arg:
        reveal_type(a)  # revealed: int
        reveal_type(b)  # revealed: int | str

Mixed types (2)

def _(arg: tuple[tuple[int, str], tuple[str, int]]):
    for a, b in arg:
        reveal_type(a)  # revealed: int | str
        reveal_type(b)  # revealed: str | int

Mixed types (3)

def _(arg: tuple[tuple[int, int, int], tuple[int, str, bytes], tuple[int, int, str]]):
    for a, b, c in arg:
        reveal_type(a)  # revealed: int
        reveal_type(b)  # revealed: int | str
        reveal_type(c)  # revealed: int | bytes | str

Same literal values

for a, b in ((1, 2), (3, 4)):
    reveal_type(a)  # revealed: Literal[1, 3]
    reveal_type(b)  # revealed: Literal[2, 4]

Mixed literal values (1)

for a, b in ((1, 2), ("a", "b")):
    reveal_type(a)  # revealed: Literal[1, "a"]
    reveal_type(b)  # revealed: Literal[2, "b"]

Mixed literals values (2)

# error: "Object of type `Literal[1]` is not iterable"
# error: "Object of type `Literal[2]` is not iterable"
# error: "Object of type `Literal[4]` is not iterable"
# error: [invalid-assignment] "Not enough values to unpack (expected 2, got 1)"
for a, b in (1, 2, (3, "a"), 4, (5, "b"), "c"):
    reveal_type(a)  # revealed: Unknown | Literal[3, 5] | LiteralString
    reveal_type(b)  # revealed: Unknown | Literal["a", "b"]

Custom iterator (1)

class Iterator:
    def __next__(self) -> tuple[int, int]:
        return (1, 2)

class Iterable:
    def __iter__(self) -> Iterator:
        return Iterator()

for a, b in Iterable():
    reveal_type(a)  # revealed: int
    reveal_type(b)  # revealed: int

Custom iterator (2)

class Iterator:
    def __next__(self) -> bytes:
        return b""

class Iterable:
    def __iter__(self) -> Iterator:
        return Iterator()

def _(arg: tuple[tuple[int, str], Iterable]):
    for a, b in arg:
        reveal_type(a)  # revealed: int | bytes
        reveal_type(b)  # revealed: str | bytes