Pyrefly: vanhemmat versiot ja versiohistoria

*Release date：September 28, 2026*

Pyrefly v1.3.2 is a patch release that fixes regressions in how Pyrefly infers the type of a variable after it is assigned a value of type `Any`.

---

## 🐛 Bug fixes

• **#4846:** Fixed several regressions from v1.3.0 in type inference after a variable is reassigned to `Any`:
• Assigning an implicit `Any` (a value with no known type, such as the result of an unannotated function or an unresolved import) to an annotated variable once again produces `Unknown`. It no longer turns into an explicit `Any`.
• When a variable annotated as `Optional[T]` or `T | None` is narrowed to `None` and then reassigned inside that branch, Pyrefly no longer adds the annotation's `None` back after the branch. For example, `x：Any | None` followed by `if x is None: x = get_any()` now gives `Any` instead of `Any | None`.
• When a variable's annotation is a union that contains `Any`, assigning `Any` to it now narrows the variable to `Any`. For example, `x：Any | None` followed by `x = x or get_any()` now gives `Any` instead of `Any | None`, so later attribute access no longer reports a false `missing-attribute` error on `None`.

Thank-you to all our contributors who found these bugs and reported them! Did you know this is one of the most helpful contributions you can make to an open-source project? If you find any bugs in Pyrefly we want to know about them! Please open a bug report issue [here](https://github.com/facebook/pyrefly/issues).

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## 📦 Upgrade

```bash
pip install --upgrade pyrefly==1.3.2
```

### How to safely upgrade your codebase

Upgrading the version of Pyrefly you're using or a third-party library you depend on can reveal new type errors in your code. Fixing them all at once is often unrealistic. We've written scripts to help you temporarily silence them. After upgrading, follow these steps:

1. `pyrefly check --suppress-errors`
2. Run your code formatter of choice
3. `pyrefly check --remove-unused-ignores`
4. Repeat until you achieve a clean formatting run and a clean type check.

This will add `# pyrefly：ignore` comments to your code, enabling you to silence errors and return to fix them later. This can make the process of upgrading a large codebase much more manageable.

Read more about error suppressions in the [Pyrefly documentation](https://pyrefly.org/en/docs/error-suppressions/).

*Release date: July 31, 2026*

Pyrefly v1.2.0 bundles **901 commits** from **59 contributors**.

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## ✨ New & Improved

### Type Checking

Attrs classes are now fully supported with comprehensive field synthesis, validation, and special-method generation. Pyrefly recognizes `@attr.s`, `@define`, `@frozen`, and their variants, handling field specifiers (`attr.ib()`, `field()`), converters, validators, defaults, and private-field aliasing. Converters are typed from their real input type rather than `Any`, including the `@<field>.converter` decorator, `attrs.converters.pipe`, `attrs.converters.default_if_none`, and generic converters like `copy.deepcopy`. See the new [attrs documentation](https://pyrefly.org/en/docs/attrs/) for details.
`functools.partial` is now type-checked instead of treated as opaque. Bound arguments are validated at construction and Pyrefly synthesizes a precise residual signature for the remaining parameters, so errors surface at both the `partial(...)` call and the later invocation. Generic functions, overloads, constructors, bound methods, and `**Unpack[TypedDict]` parameters are supported, and results expose `.func`, `.args`, and `.keywords`. Precise residual callable assignment is enabled by the `strict` and `all` presets or explicitly with `strict-partial-subtyping`.
Functions decorated with `functools.singledispatch` now type-check calls using the signature of the function you decorated, and registered implementations are checked against that function's first parameter. Generic `singledispatch` functions infer from call arguments instead of reporting `Unknown`.
Pyrefly can now warn when a function declared to return a concrete type returns `Any`, with separate diagnostics for explicit and inferred cases. Off by default, and migrated automatically from mypy's `warn_return_any`.
Pattern matching is substantially more precise: positional class patterns resolve attribute names from `__match_args__` at solve time, sequence element captures read from the narrowed subject so sibling constraints refine them, and `isinstance` on a facet filters the parent union to matching members. Fully covered class and sequence patterns now subtract their union member from later cases.
Unpacking a variadic tuple with a fixed prefix and suffix no longer smears those elements into the starred capture, so `a, *rest, b = t` where `t: tuple[int, *tuple[bool, ...], str]` types `rest` as `list[bool]`.
TypedDict classes now synthesize `__required_keys__` and `__optional_keys__`, so protocols requiring them (like those in langgraph) satisfy structural checks. `.get()` and `.pop()` with literal defaults preserve the field type.
Overload handling improved throughout: constrained TypeVar arguments expand during resolution, rejected overloads no longer leak argument errors into diagnostics, and exact callback-forwarding signatures resolve overloaded callbacks against forwarded arguments for helpers like `asyncio.to_thread`.
Enum `.value` on an enum type now infers as the union of member literal values instead of widening to the mixed-in data type.
Lambda parameters are contextually typed more thoroughly. Types are stored directly rather than resolved through inference variables, and `*args`/`**kwargs` resolve from callable hints to `tuple[...]` and `dict[str, ...]` inside the body while preserving element types in the signature.
All properties are now treated as data descriptors, and reflected binary-operation dunders are tried first for proper subclasses, fixing a class of incorrect attribute and operator results.
Cyclic type aliases reachable from an annotation are now detected instead of hanging, and class finality is taken into account when deciding whether a condition is redundant.
Continued basedpyright parity work: class instance truthiness is recognized, code under `if TYPE_CHECKING` is handled consistently, `typing_extensions.sentinel` is supported with relaxed naming restrictions, and `super(cls, cls)` is accepted.
`copy.re

Release date: June 18, 2026

Pyrefly v1.1.1 is a patch release with a single bug fix.

-----

## 🐛 Bug fixes

- #3867: Fixed a regression introduced in 1.1.0 where isinstance() narrowing of a union variable
silently stopped working when an earlier sibling branch in the same if/elif/else chain narrowed
a different variable with isinstance() and returned. The later narrowing left the union
untouched, producing false missing-attribute errors on code that checked correctly in 1.0.0.

Thank-you to all our contributors who found these bugs and reported them! Did you know this is one
of the most helpful contributions you can make to an open-source project? If you find any bugs in
Pyrefly we want to know about them! Please open a bug report issue here.