Unable to Deserialize Model with BaseModel as Dictionary Keys

[gvariable]

Initial Checks

• I confirm that I'm using Pydantic V2

Description

I am encountering an issue when trying to serialize and deserialize a Pydantic model that uses another BaseModel as dictionary keys. The deserialization process fails. Below is the code that reproduces the problem

Example Code

from pydantic import BaseModel, ConfigDict

class Cell(BaseModel):
    value: str

    model_config = ConfigDict(
        # make it hashable
        frozen=True,
    )

class WeightedSeeds(BaseModel):
    seeds: dict[Cell, int]

c = Cell(value="Hello World")
seed = WeightedSeeds(seeds={c: 100})
print(WeightedSeeds.model_validate_json(seed.model_dump_json())) # Fail

Python, Pydantic & OS Version

pydantic version: 2.7.1
        pydantic-core version: 2.18.2
          pydantic-core build: profile=release pgo=true
                 install path: /opt/homebrew/Caskroom/miniconda/base/envs/synthesis/lib/python3.12/site-packages/pydantic
               python version: 3.12.0 | packaged by conda-forge | (main, Oct  3 2023, 08:36:57) [Clang 15.0.7 ]
                     platform: macOS-14.1.1-arm64-arm-64bit
             related packages: typing_extensions-4.9.0 mypy-1.7.1 fastapi-0.111.0
                       commit: unknown

[sydney-runkle]

@gvariable,

Looks like a bug, will probably require some fixes in core. Thanks for reporting this!