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

Start by running the main.py reproduction from the issue or its mypy-play link and compare the two reveal_type results. Trace the dataclass_transform constructor-synthesis entry point and existing tests, then add coverage for the no-field derived class; done means DerivedNoFields.__init__ has only self while the field-bearing case remains unchanged.