Inlining still breaks type checking

Compiler version

3.0.0-RC2-bin-20210325-ab2664f-NIGHTLY

Problem

It is not enough to special-case Nothing (type-ascribing only trees of this type as in https://github.com/lampepfl/dotty/pull/11917). In principle, all inlined parameters may require a type annotation. This is because removing type annotations in Scala can break type checking, as subtyping is not transitive.

Minimized code

type A
class B { def foo = 0 }
trait Ev { type T >: A <: B }

inline  // commenting this fixes the error
def test(ev: Ev)(x: ev.T): Int = x.foo

def trial(ev: Ev, a: A) = {
  test(ev)(a)  // foo cannot be accessed as a member of (a : A) from module class main$package$.
}

Expectation

If it type-checks without inline, it should type-check with inline too. In particular, I assume that non-transparent inline is not supposed to interfere with type checking in any way. Is that a correct assumption?

[odersky]

I think the crucial thing to make progress is really to make type ascriptions transparent in the quoted APIs. So let me reassign to @nicolasstucki.

[nicolasstucki]

Ascriptions are already transparent in the quoted patterns.