Conformance: test @override checks on __init__ and __new__

conformance/results/mypy/classes_override.toml

@@ -1,11 +1,17 @@
-conformant = "Pass"
+conformant = "Partial"
+notes = """
+Does not honor `@override` compatibility checks for `__init__` and `__new__`:
+the incompatible constructor overrides in `ChildC2` are not flagged.
+"""
 output = """
 classes_override.py:53: error: Method "method3" is marked as an override, but no base method was found with this name  [misc]
 classes_override.py:56: error: Method "method4" is marked as an override, but no base method was found with this name  [misc]
 classes_override.py:79: error: Method "static_method1" is marked as an override, but no base method was found with this name  [misc]
 classes_override.py:84: error: Method "class_method1" is marked as an override, but no base method was found with this name  [misc]
 classes_override.py:89: error: Method "property1" is marked as an override, but no base method was found with this name  [misc]
 """
-conformance_automated = "Pass"
+conformance_automated = "Fail"
 errors_diff = """
+Lines 134, 135: Expected error (tag 'init')
+Lines 137, 138: Expected error (tag 'new')
 """

conformance/results/pycroscope/classes_override.toml

@@ -1,5 +1,12 @@
-conformance_automated = "Pass"
+conformant = "Partial"
+notes = """
+Does not honor `@override` compatibility checks for `__init__` and `__new__`:
+the incompatible constructor overrides in `ChildC2` are not flagged.
+"""
+conformance_automated = "Fail"
 errors_diff = """
+Lines 134, 135: Expected error (tag 'init')
+Lines 137, 138: Expected error (tag 'new')
 """
 output = """
 ./classes_override.py:53:4: Method does not override any base method [override_does_not_override]

conformance/results/pyrefly/classes_override.toml

@@ -8,4 +8,6 @@ ERROR classes_override.py:57:9-16: Class member `ChildA.method4` is marked as an
 ERROR classes_override.py:79:9-23: Class member `ChildA.static_method1` is marked as an override, but no parent class has a matching attribute [bad-override]
 ERROR classes_override.py:84:9-22: Class member `ChildA.class_method1` is marked as an override, but no parent class has a matching attribute [bad-override]
 ERROR classes_override.py:89:9-18: Class member `ChildA.property1` is marked as an override, but no parent class has a matching attribute [bad-override]
+ERROR classes_override.py:135:9-17: Class member `ChildC2.__init__` overrides parent class `ParentC` in an inconsistent manner [bad-override]
+ERROR classes_override.py:138:9-16: Class member `ChildC2.__new__` overrides parent class `ParentC` in an inconsistent manner [bad-override]
 """

conformance/results/pyright/classes_override.toml

@@ -1,11 +1,17 @@
-conformant = "Pass"
+conformant = "Partial"
+notes = """
+Does not honor `@override` compatibility checks for `__init__` and `__new__`:
+the incompatible constructor overrides in `ChildC2` are not flagged.
+"""
 output = """
 classes_override.py:53:9 - error: Method "method3" is marked as override, but no base method of same name is present (reportGeneralTypeIssues)
 classes_override.py:65:9 - error: Method "method4" is marked as override, but no base method of same name is present (reportGeneralTypeIssues)
 classes_override.py:79:9 - error: Method "static_method1" is marked as override, but no base method of same name is present (reportGeneralTypeIssues)
 classes_override.py:84:9 - error: Method "class_method1" is marked as override, but no base method of same name is present (reportGeneralTypeIssues)
 classes_override.py:89:9 - error: Method "property1" is marked as override, but no base method of same name is present (reportGeneralTypeIssues)
 """
-conformance_automated = "Pass"
+conformance_automated = "Fail"
 errors_diff = """
+Lines 134, 135: Expected error (tag 'init')
+Lines 137, 138: Expected error (tag 'new')
 """

conformance/results/results.html

@@ -564,12 +564,12 @@ <h3>Python Type System Conformance Test Results</h3>
 <th class="column col2 conformant">Pass</th>
 </tr>
 <tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;classes_override</th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not honor `@override` compatibility checks for `__init__` and `__new__`:</p><p>the incompatible constructor overrides in `ChildC2` are not flagged.</p></span></div></th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not honor `@override` compatibility checks for `__init__` and `__new__`:</p><p>the incompatible constructor overrides in `ChildC2` are not flagged.</p></span></div></th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not honor `@override` compatibility checks for `__init__` and `__new__`:</p><p>the incompatible constructor overrides in `ChildC2` are not flagged.</p></span></div></th>
 <th class="column col2 conformant">Pass</th>
-<th class="column col2 conformant">Pass</th>
-<th class="column col2 conformant">Pass</th>
-<th class="column col2 conformant">Pass</th>
-<th class="column col2 conformant">Pass</th>
-<th class="column col2 conformant">Pass</th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not honor `@override` compatibility checks for `__init__` and `__new__`:</p><p>the incompatible constructor overrides in `ChildC2` are not flagged.</p></span></div></th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not honor `@override` compatibility checks for `__init__` and `__new__`:</p><p>the incompatible constructor overrides in `ChildC2` are not flagged.</p></span></div></th>
 </tr>
 <tr><th class="column" colspan="7">
 <a class="test_group" href="https://typing.readthedocs.io/en/latest/spec/aliases.html">Type aliases</a>

conformance/results/ty/classes_override.toml

@@ -1,5 +1,12 @@
-conformance_automated = "Pass"
+conformant = "Partial"
+notes = """
+Does not honor `@override` compatibility checks for `__init__` and `__new__`:
+the incompatible constructor overrides in `ChildC2` are not flagged.
+"""
+conformance_automated = "Fail"
 errors_diff = """
+Lines 134, 135: Expected error (tag 'init')
+Lines 137, 138: Expected error (tag 'new')
 """
 output = """
 classes_override.py:53:9: error[invalid-explicit-override] Method `method3` is decorated with `@override` but does not override anything

conformance/results/zuban/classes_override.toml

@@ -1,5 +1,12 @@
-conformance_automated = "Pass"
+conformant = "Partial"
+notes = """
+Does not honor `@override` compatibility checks for `__init__` and `__new__`:
+the incompatible constructor overrides in `ChildC2` are not flagged.
+"""
+conformance_automated = "Fail"
 errors_diff = """
+Lines 134, 135: Expected error (tag 'init')
+Lines 137, 138: Expected error (tag 'new')
 """
 output = """
 classes_override.py:53: error: Method "method3" is marked as an override, but no base method was found with this name  [misc]

conformance/tests/classes_override.py

@@ -100,3 +100,51 @@ class ChildB(ParentB):
     @override
     def method1(self) -> None:  # OK
         pass
+
+
+# > When type checkers encounter a method decorated with @typing.override they
+# > should treat it as a type error unless that method is overriding a method or
+# > attribute in some ancestor class, and the type of the overriding method is
+# > assignable to the type of the overridden method.
+
+# ``__init__`` and ``__new__`` are normally exempt from override compatibility
+# checks, since constructors are not subject to the Liskov substitution
+# principle. However, when they are explicitly decorated with ``@override`` the
+# decorator's assignability check should still be honored.
+# See https://github.com/python/typing/issues/2222
+
+
+class ParentC:
+    def __init__(self, x: int) -> None: ...
+
+    def __new__(cls, x: int) -> "ParentC":
+        raise NotImplementedError
+
+
+class ChildC1(ParentC):
+    @override
+    def __init__(self, x: int) -> None: ...  # OK
+
+    @override
+    def __new__(cls, x: int) -> "ChildC1":  # OK
+        raise NotImplementedError
+
+
+class ChildC2(ParentC):
+    @override  # E[init]
+    def __init__(self, x: str) -> None: ...  # E[init]: not assignable to "ParentC.__init__"
+
+    @override  # E[new]
+    def __new__(cls, x: str) -> "ChildC2":  # E[new]: not assignable to "ParentC.__new__"
+        raise NotImplementedError
+
+
+# Without ``@override`` an incompatible constructor signature is allowed, since
+# ``__init__`` and ``__new__`` are exempt from the usual override checks.
+
+
+class ChildC3(ParentC):
+    def __init__(self, x: str) -> None: ...  # OK
+
+    def __new__(cls, x: str) -> "ChildC3":  # OK
+        raise NotImplementedError