No-field class derived from `dataclass_transform` base class uses base class's constructor signature

Bug Report

When a class derives from a base class marked with dataclass_transform and the derived class has no fields, mypy incorrectly infers that the derived class does not provide its own constructor. This issue does not happen if the derived class has any fields.

Pyright infers the correct constructor signature here.

To Reproduce

from typing import dataclass_transform, reveal_type

@dataclass_transform()
class Base:
   def __init__( self, a: int ) -> None:
      pass

class DerivedNoFields( Base ):
   pass

class DerivedWithFields( Base ):
   b: str

reveal_type( DerivedNoFields.__init__ )
reveal_type( DerivedWithFields.__init__ )

Playground link

Expected Behavior

main.py:14: note: Revealed type is "def (self: __main__.DerivedNoFields)"
main.py:15: note: Revealed type is "def (self: __main__.DerivedWithFields, b: builtins.str)"

Actual Behavior

main.py:14: note: Revealed type is "def (self: __main__.Base, a: builtins.int)"
main.py:15: note: Revealed type is "def (self: __main__.DerivedWithFields, b: builtins.str)"

Your Environment

• Mypy version used: 3.16.1
• Python version used: 3.13
• No command-line flags or configuration options

Beginne damit, die main.py-Reproduktion aus dem Issue oder dessen mypy-play-Link auszuführen, und vergleiche die beiden reveal_type-Ergebnisse. Verfolge den Einstiegspunkt für die Konstruktor-Synthese von dataclass_transform und die vorhandenen Tests. Füge anschließend Abdeckung für die abgeleitete Klasse ohne Felder hinzu; fertig ist es, wenn DerivedNoFields.__init__ nur self enthält, während der Fall mit Feldern unverändert bleibt.