from typing_extensions import Generic, TypeVar

T1 = TypeVar("T1")
T2 = TypeVar("T2", default=T1)

class MyClass(Generic[T1, T2]): ...

reveal_type(MyClass[int])  # N: Revealed type is "def [T2 = builtins.int] () -> __main__.MyClass[builtins.int, T2`2 = builtins.int]"

# `T2` now defaults to `int` for `MyClass` from now on
reveal_type(MyClass[str])  # N: Revealed type is "def [T2 = builtins.int] () -> __main__.MyClass[builtins.str, T2`2 = builtins.int]"
reveal_type(MyClass[bytes])  # N: Revealed type is "def [T2 = builtins.int] () -> __main__.MyClass[builtins.bytes, T2`2 = builtins.int]"

reveal_type(MyClass[str])  # N: Revealed type is "def [T2 = builtins.str] () -> __main__.MyClass[builtins.str, T2`2 = builtins.str]"
reveal_type(MyClass[bytes])  # N: Revealed type is "def [T2 = builtins.bytes] () -> __main__.MyClass[builtins.bytes, T2`2 = builtins.bytes]"