The reference ambiguous checking is too broad in dotty 0.24

[esse-byte]

Minimized code

class A(val i: Int)

def a(i: Int): A = new A(i) { println(i) }

Output

Reference to i is ambiguous,
it is both defined in method a
and inherited subsequently in anonymous class A {...}

Expectation

The code compiles in both dotty 0.23 and scala 2.3.1

[smarter]

The stricter checks are intentional: #8622, not sure if we could relax them in this particular case.

[odersky]

The only way to relax them would be to somehow detect that the parameter to A ends up as the initializer of the field a. But we could detect that only after type checking. So, I don't think that would be practical.

[som-snytt]

Even if the aliasing were detected, it's not obvious that the usage is intended without more explicit syntax.

This belongs to the class of "pass-thru" init, class X(_) extends Y(_). Whatever the hypothetical syntax, "apply incoming params directly to a thing." (Without danger of alias.)

[som-snytt]

Fixing code in Scala 2 project, similar example with tree, which is assumed to mean the only possible tree under consideration. Hypothetical syntax new C(tree' = tree) to mean the arg must be aliased to member of that name, and refchecked.