> ## Documentation Index
> Fetch the complete documentation index at: https://fastql.vachagan.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Generic types

> Author reusable generic types and concretize them per parametrization.

`@Type`, `@Input`, and `@Interface` accept `Generic[T]`. Each unique parametrization
is synthesized into one concrete GraphQL type at build time and memoized, so the same
parametrization always resolves to the same named type.

```python theme={null}
from typing import Generic, TypeVar
from fastql import Field, Query, Schema, Type

T = TypeVar("T")


@Type
class Page(Generic[T]):
    total: int
    items: list[T]


@Type
class User:
    id: int


@Query
class Queries:
    @Field
    def users(self) -> Page[User]:
        return Page(total=1, items=[User(1)])
```

The example synthesizes a `UserPage` type whose `items` field is typed `[User!]!`.
Synthetic names are derived from the parameter (`User` + `Page` → `UserPage`); pass a
`name` template with a `{}` placeholder to override the naming scheme. `TypeVar`
fields are resolved against the concrete parameters at each parametrization site.