The protected keyword makes it impossible for the subclass to use the default value of the superclass constructor #16814
Description
Compiler version
I was able to narrow down the time when the bug originated to somewhere between 3.3.0-RC1-bin-20221122-794818b-NIGHTLY and 3.3.0-RC1. The bug is still present in 3.3.0-RC2.
Minimized code
class Foo protected (foo: Int = 0) { }
class Bar extends Foo
Output
In Scala 3.2.1 the above code compiles.
Bar extends Foo without providing a value for foo, but there is the default value 0 in the superclass constructor so all is good.
In Scala 3.3.0-RC1/RC2 (but not yet in the nightly I specified above) it fails with:
[error] | class Bar extends Foo
[error] | ^^^
[error] |missing argument for parameter foo of constructor Foo in class Foo: (foo: Int):
[error] one error found
It compiles again either if I remove protected from the superclass constructor, or if I provide the value for foo explicitly:
class Foo(foo: Int = 0) { } // this is ok
class Bar extends Foo
// ---
class Foo protected (foo: Int = 0) { }
class Bar extends Foo(0) // this is ok
Expectation
The original minimized code should compile.