Case class companion objects extending FunctionN in line with SLS?

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Hi all

As far as I can see from usage and -print REPL output, the generated 
companion object for a case class with N parameters is a subclass of 
FunctionN (2.11.6 REPL):

scala> :set -print

scala> case class Foo()
[[syntax trees at end of                   cleanup]] // <console>
...
  <synthetic> object iw$Foo extends scala.runtime.AbstractFunction0 with 
Serializable {

scala> case class Bar(n: Int)
[[syntax trees at end of                   cleanup]] // <console>
...
  <synthetic> object iw$Bar extends scala.runtime.AbstractFunction1 with 
Serializable {

scala> List(1, 2) map Bar
res0: List[Bar] = List(Bar(1), Bar(2))

SLS 5.3.2 [1] does not, as far as I can make out, say anything about this. 
The extractor object as defined there behaves differently from the one 
generate by the compiler:

scala> :paste
// Entering paste mode (ctrl-D to finish)

// not a case class; define the extractor as described in SLS explicitly
class Baz(n: Int)
object Baz {
  def apply(n: Int): Baz = new Baz(n)
  // other stuff
}

// Exiting paste mode, now interpreting.

defined class Baz
defined object Baz

scala> List(1, 2) map Baz
<console>:12: error: type mismatch;
 found   : Baz.type
 required: Int => ?
              List(1, 2) map Baz
                             ^
Is this a misreading/-understanding? If not, would this be considered a 
compiler bug, a spec omission or something else?

Regards

ap

[1] 
https://www.scala-lang.org/files/archive/spec/2.13/05-classes-and-objects.html#case-classes

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<div dir=3D"ltr"><div>Hi all</div><div><br></div><div>As far as I can see f=
rom usage and <font face=3D"courier new, monospace">-print</font> REPL outp=
ut, the generated companion object for a case class with N parameters is a =
subclass of <font face=3D"courier new, monospace">FunctionN</font> (2.11.6 =
REPL):</div><div><br></div><div><font face=3D"courier new, monospace">scala=
&gt; :set -print</font></div><div><font face=3D"courier new, monospace"><br=
></font></div><div><font face=3D"courier new, monospace">scala&gt; case cla=
ss Foo()</font></div><div><font face=3D"courier new, monospace">[[syntax tr=
ees at end of =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 cleanup]] // &lt;console&gt;</font></div><div><font face=3D"courier new=
, monospace">...</font></div><div><font face=3D"courier new, monospace">=C2=
=A0 &lt;synthetic&gt; object iw$Foo extends scala.runtime.AbstractFunction0=
 with Serializable {</font></div><div><font face=3D"courier new, monospace"=
><br></font></div><div><font face=3D"courier new, monospace">scala&gt; case=
 class Bar(n: Int)</font></div><div><font face=3D"courier new, monospace">[=
[syntax trees at end of =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 cleanup]] // &lt;console&gt;</font></div><div><font face=3D"c=
ourier new, monospace">...</font></div><div><font face=3D"courier new, mono=
space">=C2=A0 &lt;synthetic&gt; object iw$Bar extends scala.runtime.Abstrac=
tFunction1 with Serializable {</font></div><div><font face=3D"courier new, =
monospace"><br></font></div><div><font face=3D"courier new, monospace">scal=
a&gt; List(1, 2) map Bar</font></div><div><font face=3D"courier new, monosp=
ace">res0: List[Bar] =3D List(Bar(1), Bar(2))</font></div><div><br></div><d=
iv>SLS 5.3.2 [1] does not, as far as I can make out, say anything about thi=
s. The extractor object as defined there behaves differently from the one g=
enerate by the compiler:</div><div><br></div><div><font face=3D"courier new=
, monospace">scala&gt; :paste</font></div><div><font face=3D"courier new, m=
onospace">// Entering paste mode (ctrl-D to finish)</font></div><div><font =
face=3D"courier new, monospace"><br></font></div><div><font face=3D"courier=
 new, monospace">// not a case class; define the extractor as described in =
SLS explicitly</font></div><div><font face=3D"courier new, monospace">class=
 Baz(n: Int)</font></div><div><font face=3D"courier new, monospace">object =
Baz {</font></div><div><font face=3D"courier new, monospace">=C2=A0 def app=
ly(n: Int): Baz =3D new Baz(n)</font></div><div><font face=3D"courier new, =
monospace">=C2=A0 // other stuff</font></div><div><font face=3D"courier new=
, monospace">}</font></div><div><font face=3D"courier new, monospace"><br><=
/font></div><div><font face=3D"courier new, monospace">// Exiting paste mod=
e, now interpreting.</font></div><div><font face=3D"courier new, monospace"=
><br></font></div><div><font face=3D"courier new, monospace">defined class =
Baz</font></div><div><font face=3D"courier new, monospace">defined object B=
az</font></div><div><font face=3D"courier new, monospace"><br></font></div>=
<div><font face=3D"courier new, monospace">scala&gt; List(1, 2) map Baz</fo=
nt></div><div><font face=3D"courier new, monospace">&lt;console&gt;:12: err=
or: type mismatch;</font></div><div><font face=3D"courier new, monospace">=
=C2=A0found =C2=A0 : Baz.type</font></div><div><font face=3D"courier new, m=
onospace">=C2=A0required: Int =3D&gt; ?</font></div><div><font face=3D"cour=
ier new, monospace">=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 List(1=
, 2) map Baz</font></div><div><font face=3D"courier new, monospace">=C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0^</font></div><div>Is this a misreading/-understand=
ing? If not, would this be considered a compiler bug, a spec omission or so=
mething else?<br></div><div><br></div><div>Regards</div><div><br></div><div=
>ap</div><div><br></div><div>[1] https://www.scala-lang.org/files/archive/s=
pec/2.13/05-classes-and-objects.html#case-classes</div></div>

<p></p>

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