Fix type parameter forwarding for inherited generics

[brentyi]

This PR fixes an edge case and adds test cases for inheritance structures that look like this:

class Base[T1]:
    field2: T1

class Subclass[T2](Base[T2]):
    field2: T2

where assignments for the T2 type parameter are applied to field2, but not correctly forwarded to field1.

cc #327

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.87%. Comparing base (19c7af4) to head (57da453).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #328      +/-   ##
==========================================
- Coverage   99.87%   99.87%   -0.01%     
==========================================
  Files          35       35              
  Lines        2347     2346       -1     
==========================================
- Hits         2344     2343       -1     
  Misses          3        3              

Flag	Coverage Δ
unittests	99.87% <100.00%> (-0.01%)	⬇️

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[mirceamironenco]

Hi @brentyi,

This seems to have broken something for me, it's a functionality I implemented replicating your tyro.conf.configure:

import dataclasses
from typing import Annotated, Union

import tyro


@dataclasses.dataclass(kw_only=True, frozen=True)
class OptimizerConfig:
    lr: float = 1e-5
    weight_decay: float = 0.0


@dataclasses.dataclass(kw_only=True, frozen=True)
class AdamConfig(OptimizerConfig):
    betas: tuple[float, float] = (0.9, 0.999)
    eps: float = 1e-8
    amsgrad: bool = False
    fused: bool | None = None


@dataclasses.dataclass(kw_only=True, frozen=True)
class SGDConfig(OptimizerConfig):
    momentum: float = 0
    dampening: float = 0
    nesterov = False
    fused: bool | None = None


# works
# OptimizerConfig = Annotated[
#     OptimizerConfig,
#     tyro.conf.arg(constructor_factory=lambda: Union[AdamConfig, SGDConfig]),  # type: ignore
# ]

# crashes
OptimizerConfig.__tyro_markers__ = (  # type: ignore
    tyro.conf.arg(
        constructor_factory=lambda: Union[AdamConfig, SGDConfig]  # type: ignore
    ),
)


@dataclasses.dataclass
class Config:
    optimizer: OptimizerConfig = AdamConfig()


def main(config: Config) -> None:
    print(config)


if __name__ == "__main__":
    config = tyro.cli(Config)
    main(config)

On 0.9.27 this crashes for the case where I'm setting __tyro_markers__ directly, however this was working on 0.9.26. Do I have to switch away from this or is there some additional corner case missed by this PR?