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

Inizia eseguendo la riproduzione main.py dell’issue o il relativo link mypy-play e confronta i due risultati di reveal_type. Traccia il punto di ingresso della sintesi del costruttore di dataclass_transform e i test esistenti, quindi aggiungi la copertura per la classe derivata senza campi; il lavoro è completato quando DerivedNoFields.__init__ contiene solo self, mentre il caso con campi rimane invariato.