Implementing generic trait for dyn T is not allowed when a supertrait with different type parameter is present

[alrz]

I tried this code:

mod supertrait {
    trait V<T> {}
    trait A : V<u32> {}
    struct T {}
    impl A for T {}
    impl V<u32> for T {}
    impl V<i32> for dyn A {} // `(dyn A + 'static)` automatically implements trait `V`
}

mod nosupertrait {
    trait V<T> {}
    trait A {}
    struct T {}
    impl A for T {}
    impl V<u32> for T {}
    impl V<i32> for dyn A {} // ok
}

I expected to see this happen: No error in either case.

Instead, this happened: Using a supertrait causes the compiler to complain about auto implemented trait as if type parameters are not being taken into account.

Meta

rustc --version --verbose:

rustc 1.88.0 (6b00bc388 2025-06-23)
binary: rustc
commit-hash: 6b00bc3880198600130e1cf62b8f8a93494488cc
commit-date: 2025-06-23
host: x86_64-pc-windows-msvc
release: 1.88.0
LLVM version: 20.1.5

Backtrace

<backtrace>

[aviralgarg05]

I would like to solve this issue