Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Class constructor parameter with default value causes companion object initializer to fail #5000

Open
scabug opened this issue Sep 17, 2011 · 7 comments
Open

Class constructor parameter with default value causes companion object initializer to fail #5000

scabug opened this issue Sep 17, 2011 · 7 comments
Labels
language spec named/default args

Comments

@scabug
Copy link

scabug commented Sep 17, 2011

The following code fails to compile,

class Foo(t: Any)
class Bar(x: String = "bar")
object Bar extends Foo(new Bar())

The error message is: "super constructor cannot be passed a self reference unless parameter is declared by-name". I would expect either the code to compile or a more informative error message.

javap reveals that the zero-parameter constructor for class Bar with default value x = "bar" is actually defined as init$default$1 in the companion object Bar. I assume the problem is that extends Foo(new Bar()) is trying to access Bar.init$default$1 before object Bar has been constructed.

I couldn't find this restriction in the SLS. If the compile error is correct, perhaps the error message could be improved? Thanks.

Possibly related: #4278
Source: http://stackoverflow.com/questions/7448931/extending-a-class-with-many-implementation-that-each-have-main-methods-in-scala
@scabug
Copy link
Author

scabug commented Sep 17, 2011

Imported From: https://issues.scala-lang.org/browse/SI-5000?orig=1
Reporter: Kipton Barros (kbarros)
Affected Versions: 2.9.1

@scabug
Copy link
Author

scabug commented Sep 23, 2011

Michael Schmitz (schmmd) said (edited on Sep 23, 2011 1:09:21 AM UTC):
This also causes the same error.

class Foo(t: Any)
class Bar(x: String)
object Bar extends Foo(Bar.param) {
    val param = "bar"
}

error: super constructor cannot be passed a self reference unless parameter is declared by-name

@scabug
Copy link
Author

scabug commented Oct 11, 2011

@paulp said:
More interesting corners arise when classes and their companions reference one another.

@scabug
Copy link
Author

scabug commented Mar 15, 2013

@adriaanm said:
Un-assigning to foster work stealing, as announced in https://groups.google.com/forum/?fromgroups=#!topic/scala-internals/o8WG4plpNkw

@scabug
Copy link
Author

scabug commented Jul 10, 2013

@adriaanm said:
Unassigning and rescheduling to M6 as previous deadline was missed.

@scabug
Copy link
Author

scabug commented Aug 5, 2014

@gkossakowski said:
The 2.11.2 is out so I'm rescheduling the issue for 2.11.3.

@scabug
Copy link
Author

scabug commented Nov 4, 2014

@retronym said:
Updating fix-by version to 2.11.5.

@scabug scabug mentioned this issue Apr 7, 2017
Open
@aaabramov aaabramov mentioned this issue Oct 3, 2017
Closed
wajda added a commit to AbsaOSS/commons that referenced this issue Jan 27, 2020
@wajda
Place a workaround for scala/bug#5000
0174fc3
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Assignees
No one assigned
Labels
language spec named/default args
Projects
None yet
Milestone
No milestone
Development

No branches or pull requests
1 participant
@scabug