fix type errors, add type tests

.github/workflows/test.yml

@@ -6,7 +6,7 @@ on:
   pull_request:
 
 jobs:
-  pyright:
+  typing:
     strategy:
       fail-fast: false
       matrix:
@@ -23,9 +23,13 @@ jobs:
         path: ~/.cache/pip
         key: pip-pyright
     - name: Install dependencies
-      run: pip install -e . pyright
-    - name: Run pyright
+      run: pip install -e . pyright mypy
+    - name: Run pyright verifytypes
       run: pyright --verifytypes exceptiongroup --verbose
+    - name: Run pyright type test
+      run: pyright tests/check_types.py
+    - name: Run mypy type test
+      run: mypy tests/check_types.py
 
   test:
     strategy:

pyproject.toml

@@ -45,7 +45,7 @@ version_scheme = "post-release"
 local_scheme = "dirty-tag"
 write_to = "src/exceptiongroup/_version.py"
 
-[tool.ruff]
+[tool.ruff.lint]
 select = [
     "E", "F", "W",  # default flake-8
     "I",            # isort
@@ -55,11 +55,11 @@ select = [
     "UP",           # pyupgrade
 ]
 
-[tool.ruff.pyupgrade]
+[tool.ruff.lint.pyupgrade]
 # Preserve types, even if a file imports `from __future__ import annotations`.
 keep-runtime-typing = true
 
-[tool.ruff.isort]
+[tool.ruff.lint.isort]
 known-first-party = ["exceptiongroup"]
 
 [tool.pytest.ini_options]
@@ -76,6 +76,14 @@ exclude_also = [
     "@overload",
 ]
 
+[tool.pyright]
+# for type tests, the code itself isn't type checked in CI
+reportUnnecessaryTypeIgnoreComment = true
+
+[tool.mypy]
+# for type tests, the code itself isn't type checked in CI
+warn_unused_ignores = true
+
 [tool.tox]
 legacy_tox_ini = """
 [tox]
@@ -90,8 +98,13 @@ extras = test
 commands = python -m pytest {posargs}
 usedevelop = true
 
-[testenv:{py37-,py38-,py39-,py310-,py311-,py312-,}pyright]
-deps = pyright
-commands = pyright --verifytypes exceptiongroup
+[testenv:{py37-,py38-,py39-,py310-,py311-,py312-,}typing]
+deps =
+    pyright
+    mypy
+commands =
+    pyright --verifytypes exceptiongroup
+    pyright tests/check_types.py
+    mypy tests/check_types.py
 usedevelop = true
 """

src/exceptiongroup/_exceptions.py

@@ -57,7 +57,7 @@ class BaseExceptionGroup(BaseException, Generic[_BaseExceptionT_co]):
     """A combination of multiple unrelated exceptions."""
 
     def __new__(
-        cls: _BaseExceptionGroupSelf,
+        cls: type[_BaseExceptionGroupSelf],
         __message: str,
         __exceptions: Sequence[_BaseExceptionT_co],
     ) -> _BaseExceptionGroupSelf:
@@ -265,7 +265,9 @@ def __repr__(self) -> str:
 
 class ExceptionGroup(BaseExceptionGroup[_ExceptionT_co], Exception):
     def __new__(
-        cls, __message: str, __exceptions: Sequence[_ExceptionT_co]
+        cls: type[_ExceptionGroupSelf],
+        __message: str,
+        __exceptions: Sequence[_ExceptionT_co],
     ) -> _ExceptionGroupSelf:
         return super().__new__(cls, __message, __exceptions)
 

src/exceptiongroup/_suppress.py

@@ -1,7 +1,9 @@
+from __future__ import annotations
+
 import sys
 from contextlib import AbstractContextManager
 from types import TracebackType
-from typing import TYPE_CHECKING, Optional, Type
+from typing import TYPE_CHECKING, Optional, Type, cast
 
 if sys.version_info < (3, 11):
     from ._exceptions import BaseExceptionGroup
@@ -16,7 +18,7 @@
 class suppress(BaseClass):
     """Backport of :class:`contextlib.suppress` from Python 3.12.1."""
 
-    def __init__(self, *exceptions: BaseException):
+    def __init__(self, *exceptions: type[BaseException]):
         self._exceptions = exceptions
 
     def __enter__(self) -> None:
@@ -44,7 +46,7 @@ def __exit__(
             return True
 
         if issubclass(exctype, BaseExceptionGroup):
-            match, rest = excinst.split(self._exceptions)
+            match, rest = cast(BaseExceptionGroup, excinst).split(self._exceptions)
             if rest is None:
                 return True
 

tests/check_types.py

@@ -0,0 +1,36 @@
+from typing_extensions import assert_type
+
+from exceptiongroup import BaseExceptionGroup, ExceptionGroup, catch, suppress
+
+# issue 117
+a = BaseExceptionGroup("", (KeyboardInterrupt(),))
+assert_type(a, BaseExceptionGroup[KeyboardInterrupt])
+b = BaseExceptionGroup("", (ValueError(),))
+assert_type(b, BaseExceptionGroup[ValueError])
+c = ExceptionGroup("", (ValueError(),))
+assert_type(c, ExceptionGroup[ValueError])
+
+# expected type error when passing a BaseException to ExceptionGroup
+ExceptionGroup("", (KeyboardInterrupt(),))  # type: ignore[type-var]
+
+
+# code snippets from the README
+
+
+def value_key_err_handler(excgroup: BaseExceptionGroup) -> None:
+    for exc in excgroup.exceptions:
+        print("Caught exception:", type(exc))
+
+
+def runtime_err_handler(exc: BaseExceptionGroup) -> None:
+    print("Caught runtime error")
+
+
+with catch(
+    {(ValueError, KeyError): value_key_err_handler, RuntimeError: runtime_err_handler}
+):
+    ...
+
+
+with suppress(RuntimeError):
+    raise ExceptionGroup("", [RuntimeError("boo")])