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Extend conformance tests for dataclass hashability #2201

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a912053
Extend tests for dataclass hashability
AlexWaygood Feb 28, 2026
b5baab9
Merge branch 'main' into more-hash-tests
JelleZijlstra Feb 28, 2026
4c5db27
Jelle's suggestion
AlexWaygood Feb 28, 2026
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14 changes: 11 additions & 3 deletions conformance/results/mypy/dataclasses_hash.toml
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Original file line number Diff line number Diff line change
@@ -1,11 +1,19 @@
conformant = "Partial"
conformant = "Unsupported"
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@AlexWaygood AlexWaygood Feb 28, 2026

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It's not clear to me that mypy has implemented support for any of the functionality tested in dataclasses_hash.py, so I downgraded its score from "Partial" to "Unsupported". I'm very happy to revert this change if anybody feels this is unfair or if I've missed something!

notes = """
Does not synthesize `__hash__ = None` as a class attribute for unhashable dataclasses.
Does not report when an unhashable dataclass has `__hash__` called directly on an instance.
Does not report when dataclass is not compatible with Hashable protocol.
"""
output = """
dataclasses_hash.py:14: error: Expression is of type "Callable[[object], int]", not "None" [assert-type]
dataclasses_hash.py:36: error: Expression is of type "Callable[[object], int]", not "None" [assert-type]
"""
conformance_automated = "Fail"
errors_diff = """
Line 15: Expected 1 errors
Line 32: Expected 1 errors
Line 17: Expected 1 errors
Line 18: Expected 1 errors
Line 39: Expected 1 errors
Line 40: Expected 1 errors
Line 14: Unexpected errors ['dataclasses_hash.py:14: error: Expression is of type "Callable[[object], int]", not "None" [assert-type]']
Line 36: Unexpected errors ['dataclasses_hash.py:36: error: Expression is of type "Callable[[object], int]", not "None" [assert-type]']
"""
6 changes: 4 additions & 2 deletions conformance/results/pyrefly/dataclasses_hash.toml
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Expand Up @@ -3,6 +3,8 @@ conformance_automated = "Pass"
errors_diff = """
"""
output = """
ERROR dataclasses_hash.py:15:16-22: `DC1` is not assignable to `Hashable` [bad-assignment]
ERROR dataclasses_hash.py:32:16-22: `DC3` is not assignable to `Hashable` [bad-assignment]
ERROR dataclasses_hash.py:17:1-16: Expected a callable, got `None` [not-callable]
ERROR dataclasses_hash.py:18:16-22: `DC1` is not assignable to `Hashable` [bad-assignment]
ERROR dataclasses_hash.py:39:1-16: Expected a callable, got `None` [not-callable]
ERROR dataclasses_hash.py:40:16-22: `DC3` is not assignable to `Hashable` [bad-assignment]
"""
6 changes: 4 additions & 2 deletions conformance/results/pyright/dataclasses_hash.toml
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Original file line number Diff line number Diff line change
@@ -1,10 +1,12 @@
conformant = "Pass"
output = """
dataclasses_hash.py:15:16 - error: Type "DC1" is not assignable to declared type "Hashable"
dataclasses_hash.py:17:1 - error: Object of type "None" cannot be called (reportOptionalCall)
dataclasses_hash.py:18:16 - error: Type "DC1" is not assignable to declared type "Hashable"
  "DC1" is incompatible with protocol "Hashable"
    "__hash__" is an incompatible type
      Type "None" is not assignable to type "() -> int" (reportAssignmentType)
dataclasses_hash.py:32:16 - error: Type "DC3" is not assignable to declared type "Hashable"
dataclasses_hash.py:39:1 - error: Object of type "None" cannot be called (reportOptionalCall)
dataclasses_hash.py:40:16 - error: Type "DC3" is not assignable to declared type "Hashable"
  "DC3" is incompatible with protocol "Hashable"
    "__hash__" is an incompatible type
      Type "None" is not assignable to type "() -> int" (reportAssignmentType)
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4 changes: 2 additions & 2 deletions conformance/results/results.html
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Expand Up @@ -737,9 +737,9 @@ <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;dataclasses_hash</th>
<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not report when dataclass is not compatible with Hashable protocol.</p></span></div></th>
<th class="column col2 conformant">Pass</th>
<th class="column col2 not-conformant"><div class="hover-text">Unsupported<span class="tooltip-text" id="bottom"><p>Does not synthesize `__hash__ = None` as a class attribute for unhashable dataclasses.</p><p>Does not report when an unhashable dataclass has `__hash__` called directly on an instance.</p><p>Does not report when dataclass is not compatible with Hashable protocol.</p></span></div></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 synthesize a `__hash__ = None` class attribute for unhashable dataclasses.</p></span></div></th>
<th class="column col2 conformant">Pass</th>
</tr>
<tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dataclasses_inheritance</th>
Expand Down
16 changes: 13 additions & 3 deletions conformance/results/zuban/dataclasses_hash.toml
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@@ -1,7 +1,17 @@
conformance_automated = "Pass"
conformance_automated = "Fail"
conformant = "Partial"
notes = """
Does not synthesize a `__hash__ = None` class attribute for unhashable dataclasses.
"""
errors_diff = """
Line 14: Unexpected errors ['dataclasses_hash.py:14: error: Expression is of type "Callable[[object], int]", not "None" [misc]']
Line 36: Unexpected errors ['dataclasses_hash.py:36: error: Expression is of type "Callable[[object], int]", not "None" [misc]']
"""
output = """
dataclasses_hash.py:15: error: Incompatible types in assignment (expression has type "DC1", variable has type "Hashable") [assignment]
dataclasses_hash.py:32: error: Incompatible types in assignment (expression has type "DC3", variable has type "Hashable") [assignment]
dataclasses_hash.py:14: error: Expression is of type "Callable[[object], int]", not "None" [misc]
dataclasses_hash.py:17: error: "DC1" has no attribute "__hash__" [attr-defined]
dataclasses_hash.py:18: error: Incompatible types in assignment (expression has type "DC1", variable has type "Hashable") [assignment]
dataclasses_hash.py:36: error: Expression is of type "Callable[[object], int]", not "None" [misc]
dataclasses_hash.py:39: error: "DC3" has no attribute "__hash__" [attr-defined]
dataclasses_hash.py:40: error: Incompatible types in assignment (expression has type "DC3", variable has type "Hashable") [assignment]
"""
32 changes: 24 additions & 8 deletions conformance/tests/dataclasses_hash.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,15 +3,18 @@
"""

from dataclasses import dataclass
from typing import Hashable
from typing import Callable, Hashable, assert_type


@dataclass
class DC1:
a: int


# This should generate an error because DC1 isn't hashable.
assert_type(DC1.__hash__, None)

# These should generate errors because DC1 isn't hashable.
DC1(0).__hash__() # E
v1: Hashable = DC1(0) # E


Expand All @@ -20,15 +23,20 @@ class DC2:
a: int


v2: Hashable = DC2(0)
dc2_hash: Callable[..., int] = DC2.__hash__ # OK
DC2(0).__hash__() # OK
v2: Hashable = DC2(0) # OK


@dataclass(eq=True)
class DC3:
a: int


# This should generate an error because DC3 isn't hashable.
assert_type(DC3.__hash__, None)

# These should generate errors because DC3 isn't hashable.
DC3(0).__hash__() # E
v3: Hashable = DC3(0) # E


Expand All @@ -37,15 +45,19 @@ class DC4:
a: int


v4: Hashable = DC4(0)
dc4_hash: Callable[..., int] = DC4.__hash__ # OK
DC4(0).__hash__() # OK
v4: Hashable = DC4(0) # OK


@dataclass(eq=True, unsafe_hash=True)
class DC5:
a: int


v5: Hashable = DC5(0)
dc5_hash: Callable[..., int] = DC5.__hash__ # OK
DC5(0).__hash__() # OK
v5: Hashable = DC5(0) # OK


@dataclass(eq=True)
Expand All @@ -56,7 +68,9 @@ def __hash__(self) -> int:
return 0


v6: Hashable = DC6(0)
dc6_hash: Callable[..., int] = DC6.__hash__ # OK
DC6(0).__hash__() # OK
v6: Hashable = DC6(0) # OK


@dataclass(frozen=True)
Expand All @@ -67,4 +81,6 @@ def __eq__(self, other) -> bool:
return self.a == other.a


v7: Hashable = DC7(0)
dc7_hash: Callable[..., int] = DC7.__hash__ # OK
DC7(0).__hash__() # OK
v7: Hashable = DC7(0) # OK