Changelog for mypy 2.0 (#21422)

This will be the final changelog for mypy 2.0.0.

Related issue: #20726

Author: JukkaL

CHANGELOG.md

@@ -2,7 +2,18 @@
 
 ## Next Release
 
-### Enabling `--local-partial-types` by Default
+## Mypy 2.0
+
+We’ve just uploaded mypy 2.0.0 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).
+Mypy is a static type checker for Python. This release includes new features, performance
+improvements and bug fixes. There are also changes to options and defaults.
+You can install it as follows:
+
+    python3 -m pip install -U mypy
+
+You can read the full documentation for this release on [Read the Docs](http://mypy.readthedocs.io).
+
+### Enable `--local-partial-types` by Default
 
 This flag affects the inference of types based on assignments in other scopes.
 For now, explicitly disabling this continues to be supported, but this support will be removed
@@ -11,7 +22,7 @@ in mypy, like the daemon or the new implementation of flexible redefinitions.
 
 Contributed by Ivan Levkivskyi, Jukka Lehtosalo, Shantanu in [PR 21163](https://github.com/python/mypy/pull/21163).
 
-### Enabling `--strict-bytes` by Default
+### Enable `--strict-bytes` by Default
 
 Per [PEP 688](https://peps.python.org/pep-0688), mypy no longer treats `bytearray` and `memoryview`
 values as assignable to the `bytes` type.
@@ -72,6 +83,25 @@ in future mypy releases.
 Contributed by Ivan Levkivskyi, with additional contributions from Emma Smith and Jukka
 Lehtosalo.
 
+Recent related changes since the last release:
+
+- Freeze garbage collection in parallel workers for 4-5% speedup (Ivan Levkivskyi, PR [21302](https://github.com/python/mypy/pull/21302))
+- Expose `--num-workers` and `--native-parser` (Ivan Levkivskyi, PR [21387](https://github.com/python/mypy/pull/21387))
+- Split type checking into interface and implementation in parallel workers (Ivan Levkivskyi, PR [21119](https://github.com/python/mypy/pull/21119))
+- Batch module groups for parallel processing (Ivan Levkivskyi, PR [21287](https://github.com/python/mypy/pull/21287))
+- Optimize parallel worker startup (Ivan Levkivskyi, PR [21203](https://github.com/python/mypy/pull/21203))
+- Parse files in parallel when possible (Ivan Levkivskyi, PR [21175](https://github.com/python/mypy/pull/21175))
+- Use parallel parsing at all stages (Ivan Levkivskyi, PR [21266](https://github.com/python/mypy/pull/21266))
+- Fix sequential bottleneck in parallel parsing (Jukka Lehtosalo, PR [21291](https://github.com/python/mypy/pull/21291))
+- Fail fast when a user tries to generate reports with parallel workers (Ivan Levkivskyi, PR [21341](https://github.com/python/mypy/pull/21341))
+- Partially support old NumPy plugin in parallel type checking (Ivan Levkivskyi, PR [21324](https://github.com/python/mypy/pull/21324))
+- Handle reachability consistently in parallel type checking (Ivan Levkivskyi, PR [21322](https://github.com/python/mypy/pull/21322))
+- Always respect `@no_type_check` in parallel type checking (Ivan Levkivskyi, PR [21320](https://github.com/python/mypy/pull/21320))
+- Minor fixes in parallel checking (Ivan Levkivskyi, PR [21319](https://github.com/python/mypy/pull/21319))
+- Fix plugin logic in parallel type checking (Ivan Levkivskyi, PR [21252](https://github.com/python/mypy/pull/21252))
+- Fix Windows IPC race condition when using parallel checking (Jukka Lehtosalo, PR [21228](https://github.com/python/mypy/pull/21228))
+- Report parallel worker exit status on receive failure (Jukka Lehtosalo, PR [21224](https://github.com/python/mypy/pull/21224))
+
 ### Drop Support for Targeting Python 3.9
 
 Mypy no longer supports type checking code with `--python-version 3.9`.
@@ -111,6 +141,114 @@ the details.
 
 Contributed by Jukka Lehtosalo.
 
+### Mypyc Improvements
+
+- Document `librt.time` (Jukka Lehtosalo, PR [21372](https://github.com/python/mypy/pull/21372))
+- Mark `librt.time.time()` non-experimental (Ivan Levkivskyi, PR [21310](https://github.com/python/mypy/pull/21310))
+- Fix `librt.time` primitive now that it is no longer experimental (Ivan Levkivskyi, PR [21318](https://github.com/python/mypy/pull/21318))
+- Fix `librt` API/ABI version checks (Jukka Lehtosalo, PR [21311](https://github.com/python/mypy/pull/21311))
+- Generate more type methods for classes with attribute dictionaries (Piotr Sawicki, PR [21290](https://github.com/python/mypy/pull/21290))
+- Fix reference counting for tuple items during deallocation (Shantanu, PR [21245](https://github.com/python/mypy/pull/21245))
+- Release new instances when `__init__` raises (Shantanu, PR [21248](https://github.com/python/mypy/pull/21248))
+- Fix `@property` getter memory leak (Vaggelis Danias, PR [21230](https://github.com/python/mypy/pull/21230))
+- Fix semantics for walrus expression in tuple (Shantanu, PR [21249](https://github.com/python/mypy/pull/21249))
+- Fix crash on import errors during cleanup (Shantanu, PR [21247](https://github.com/python/mypy/pull/21247))
+- Fix reference leak in str index (Shantanu, PR [21251](https://github.com/python/mypy/pull/21251))
+- Fix memory leak in integer true division (Shantanu, PR [21246](https://github.com/python/mypy/pull/21246))
+- Fix reference leaks in `list.clear()`/`dict.clear()` (Shantanu, PR [21244](https://github.com/python/mypy/pull/21244))
+- Resolve type aliases in function specialization (esarp, PR [21233](https://github.com/python/mypy/pull/21233))
+- Report an error if an acyclic class inherits from non-acyclic (Piotr Sawicki, PR [21227](https://github.com/python/mypy/pull/21227))
+- Fix `b64decode` to match new CPython behavior (Piotr Sawicki, PR [21200](https://github.com/python/mypy/pull/21200))
+
+### Fixes to Crashes
+
+- Fix crash when a file does not exist during semantic analysis (Ivan Levkivskyi, PR [21379](https://github.com/python/mypy/pull/21379))
+- Fix parallel worker crash on syntax error (Ivan Levkivskyi, PR [21202](https://github.com/python/mypy/pull/21202))
+
+### Changes to Messages
+
+- Improve error messages for unexpected keyword arguments in overloaded functions (Kevin Kannammalil, PR [20592](https://github.com/python/mypy/pull/20592))
+- Don't suggest `Foo[...]` when `Foo(arg=...)` is used in annotation (Yosof Badr, PR [21238](https://github.com/python/mypy/pull/21238))
+- Mention what codes are actually ignored in "not covered by type: ignore comment" note (wyattscarpenter, PR [19904](https://github.com/python/mypy/pull/19904))
+- Improve error messages when positional argument is missing (Kevin Kannammalil, PR [20591](https://github.com/python/mypy/pull/20591))
+- Improve "name is not defined" errors with fuzzy matching (Kevin Kannammalil, PR [20693](https://github.com/python/mypy/pull/20693))
+- Add suggestions for misspelled module imports (Kevin Kannammalil, PR [20695](https://github.com/python/mypy/pull/20695))
+
+### Performance Improvements
+
+- Replace `NamedTuple` with faster regular classes in hot paths (Shantanu, PR [21326](https://github.com/python/mypy/pull/21326))
+- Avoid calling best-match suggestions unless the message is shown (Ivan Levkivskyi, PR [21307](https://github.com/python/mypy/pull/21307))
+- Order cases in native parser based on AST node frequency (Jukka Lehtosalo, PR [21219](https://github.com/python/mypy/pull/21219))
+
+### Stubtest Improvements
+
+- Basic support for unpack kwargs (Shantanu, PR [21024](https://github.com/python/mypy/pull/21024))
+- Fix false positive for properties with a deleter (Pranav Manglik, PR [21259](https://github.com/python/mypy/pull/21259))
+
+### Documentation Updates
+
+- Rename "value restriction" to "value-constrained type variable" (Leo Ji, PR [21112](https://github.com/python/mypy/pull/21112))
+- Clarify that invariant-by-default applies to legacy `TypeVar` syntax (Leo Ji, PR [21108](https://github.com/python/mypy/pull/21108))
+
+### Improvements to the Native Parser
+
+The new native parser is still experimental.
+
+- Make new parser consistent with the old one (Ivan Levkivskyi, PR [21377](https://github.com/python/mypy/pull/21377))
+- Support `--package-root` with the native parser (Ivan Levkivskyi, PR [21321](https://github.com/python/mypy/pull/21321))
+- Improve call expressions in type annotations with the native parser (Jukka Lehtosalo, PR [21300](https://github.com/python/mypy/pull/21300))
+- Depend on `ast-serialize` by default (Jukka Lehtosalo, PR [21297](https://github.com/python/mypy/pull/21297))
+
+### Other Notable Fixes and Improvements
+
+- Fix narrowing for `AbstractSet` and `Mapping` (Shantanu, PR [21352](https://github.com/python/mypy/pull/21352))
+- Preserve gradual guarantee when narrowing `Any` union via equality (Shantanu, PR [21368](https://github.com/python/mypy/pull/21368))
+- Make type variable upper bound narrowing symmetric (Ivan Levkivskyi, PR [21350](https://github.com/python/mypy/pull/21350))
+- Behave consistently when type-checking a stub package directly (Ivan Levkivskyi, PR [21330](https://github.com/python/mypy/pull/21330))
+- Add support for `Final[...]` in dataclasses (Ivan Levkivskyi, PR [21334](https://github.com/python/mypy/pull/21334))
+- Narrow more sequence parents (Shantanu, PR [21327](https://github.com/python/mypy/pull/21327))
+- Better narrowing for enums and other types with known equality (Shantanu, PR [21281](https://github.com/python/mypy/pull/21281))
+- Fix pathspec error (Ivan Levkivskyi, PR [21296](https://github.com/python/mypy/pull/21296))
+- Use sharding for the SQLite cache (Jukka Lehtosalo, PR [21292](https://github.com/python/mypy/pull/21292))
+- Limit type inference context fallback to the walrus operator only (Ivan Levkivskyi, PR [21294](https://github.com/python/mypy/pull/21294))
+- Support `.git/info/exclude` for `--exclude-gitignore` (RogerJinIS, PR [21286](https://github.com/python/mypy/pull/21286))
+- Let `--allow-redefinition` widen a global in a function with `None` initialization (Jukka Lehtosalo, PR [21285](https://github.com/python/mypy/pull/21285))
+- Delete Python 2 extra (Shantanu, PR [18374](https://github.com/python/mypy/pull/18374))
+- No longer narrow final globals in functions (Ivan Levkivskyi, PR [21241](https://github.com/python/mypy/pull/21241))
+- Narrow unions containing `Any` in conditional branches (Shantanu, PR [21231](https://github.com/python/mypy/pull/21231))
+- Propagate narrowing within chained comparisons (Shantanu, PR [21160](https://github.com/python/mypy/pull/21160))
+- Add proper lazy deserialization (Ivan Levkivskyi, PR [21198](https://github.com/python/mypy/pull/21198))
+- Add `install_types` to options affecting cache (Brian Schubert, PR [21070](https://github.com/python/mypy/pull/21070))
+- Narrow `Any` in conditional type checks (Shantanu, PR [21167](https://github.com/python/mypy/pull/21167))
+- Fix exception handler target location in new parser (Ivan Levkivskyi, PR [21185](https://github.com/python/mypy/pull/21185))
+- Improve traceback display (Shantanu, PR [21155](https://github.com/python/mypy/pull/21155))
+- Include two more files in the sdist: `CREDITS` and the typeshed `README` (Michael R. Crusoe, PR [21131](https://github.com/python/mypy/pull/21131))
+
+### Typeshed Updates
+
+Please see [git log](https://github.com/python/typeshed/commits/main?after=c5e47faeda2cf9d233f91bc1dc95814b0cc7ccba+0&branch=main&path=stdlib) for full list of standard library typeshed stub changes.
+
+### Acknowledgements
+
+Thanks to all mypy contributors who contributed to this release:
+- Brian Schubert
+- Ethan Sarp
+- Ivan Levkivskyi
+- Jukka Lehtosalo
+- Kevin Kannammalil
+- Leo Ji
+- Marc Mueller
+- Michael R. Crusoe
+- Piotr Sawicki
+- Pranav Manglik
+- RogerJinIS
+- Shantanu
+- Vaggelis Danias
+- wyattscarpenter
+- Yosof Badr
+
+I’d also like to thank my employer, Dropbox, for supporting mypy development.
+
 ## Mypy 1.20
 
 We’ve just uploaded mypy 1.20.0 to the Python Package Index ([PyPI](https://pypi.org/project/mypy/)).