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Date: Thu, 3 Mar 2016 14:17:16 -0600
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 <CAGosAErMa=A7tvmCnmfej7=Fc7pv5yJ8GAepVwFj2Z79C_=dfg@mail.gmail.com>
Subject: Re: Compilation error with Scala case class with private constructor
From: Andrew Whitaker <andrew.whitaker@braintreepayments.com>
To: user@flink.apache.org
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Thanks for the quick response, Stephen, that makes sense.

> Is it a problem for your use case to make the constructor public?

It's not a huge problem, I was mostly just curious as to what the problem
was exactly.

On Thu, Mar 3, 2016 at 2:14 PM, Stephan Ewen <sewen@apache.org> wrote:

> Hi!
>
> My guess is that this error is indirectly reporting that no
> TypeInformation could be generated for the case class. That TypeInformation
> is generated using macros during program compilation.
>
> The generated TypeInformation will contain a partially code-generated
> serializer including the code to instantiate the case class upon
> deserialization. That generated code at some point calls the constructor
> and thus probably fails to compile when the constructor is private. As a
> result, no TypeInformation will be created, and then Scala cannot provide
> one for the implicit parameter.
>
> I think Aljoscha can probably give a deeper insight into the
> TypeInformation generator for Scala.
>
> Is it a problem for your use case to make the constructor public?
>
> Greetings,
> Stephan
>
>
> On Thu, Mar 3, 2016 at 9:06 PM, Andrew Whitaker <
> andrew.whitaker@braintreepayments.com> wrote:
>
>> Hi,
>>
>> I've run up against a compilation error involving a case class with a
>> private constructor:
>>
>> [error]
>> /Users/anwhitaker/code/flink-fold-issue/src/main/scala/TestApp.scala:18:
>> could not find implicit value for evidence parameter of type
>> org.apache.flink.api.common.typeinfo.TypeInformation[List[scala.util.Try[TestApp.Wrapper]]]
>> [error]       .fold(List[Try[Wrapper]](), new FoldFunction[Tuple2[Int,
>> Int], List[Try[Wrapper]]] {
>> [error]            ^
>> [error] one error found
>> [error] (compile:compileIncremental) Compilation failed
>>
>> If I make the constructor public again, the error goes away. I've set up
>> a simple example that demonstrates the problem here:
>> https://github.com/AndrewWhitaker/flink-case-class-private-ctor
>> I've read this article on Flink's website:
>> https://flink.apache.org/faq.html#why-am-i-getting-a-nonserializableexception-
>> but I think my issue is slightly different.
>>
>> I'm just trying to understand this behavior and if there's a way I can
>> work around it.
>>
>> Thanks!
>>
>> --
>> Andrew Whitaker | andrew.whitaker@braintreepayments.com
>>
>
>


-- 
Andrew Whitaker | andrew.whitaker@braintreepayments.com
--
Note: this information is confidential. It is prohibited to share, post
online or otherwise publicize without Braintree's prior written consent.

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<div dir=3D"ltr">Thanks for the quick response, Stephen, that makes sense.<=
div><br></div><div>&gt;=C2=A0<span style=3D"font-size:12.8px">Is it a probl=
em for your use case to make the constructor public?</span></div><div><span=
 style=3D"font-size:12.8px"><br></span></div><div><span style=3D"font-size:=
12.8px">It&#39;s not a huge problem, I was mostly just curious as to what t=
he problem was exactly.</span></div></div><div class=3D"gmail_extra"><br><d=
iv class=3D"gmail_quote">On Thu, Mar 3, 2016 at 2:14 PM, Stephan Ewen <span=
 dir=3D"ltr">&lt;<a href=3D"mailto:sewen@apache.org" target=3D"_blank">sewe=
n@apache.org</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" sty=
le=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div d=
ir=3D"ltr">Hi!<div><br></div><div>My guess is that this error is indirectly=
 reporting that no TypeInformation could be generated for the case class. T=
hat TypeInformation is generated using macros during program compilation.</=
div><div><br></div><div>The generated TypeInformation will contain a partia=
lly code-generated serializer including the code to instantiate the case cl=
ass upon deserialization. That generated code at some point calls the const=
ructor and thus probably fails to compile when the constructor is private. =
As a result, no TypeInformation will be created, and then Scala cannot prov=
ide one for the implicit parameter.</div><div><br></div><div>I think Aljosc=
ha can probably give a deeper insight into the TypeInformation generator fo=
r Scala.</div><div><br></div><div>Is it a problem for your use case to make=
 the constructor public?</div><div><br></div><div>Greetings,</div><div>Step=
han</div><div><br></div></div><div class=3D"HOEnZb"><div class=3D"h5"><div =
class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Thu, Mar 3, 2016 at=
 9:06 PM, Andrew Whitaker <span dir=3D"ltr">&lt;<a href=3D"mailto:andrew.wh=
itaker@braintreepayments.com" target=3D"_blank">andrew.whitaker@braintreepa=
yments.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=
=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir=
=3D"ltr">Hi,<div><br></div><div>I&#39;ve run up against a compilation error=
 involving a case class with a private constructor:</div><div><br></div><di=
v><div>[error] /Users/anwhitaker/code/flink-fold-issue/src/main/scala/TestA=
pp.scala:18: could not find implicit value for evidence parameter of type o=
rg.apache.flink.api.common.typeinfo.TypeInformation[List[scala.util.Try[Tes=
tApp.Wrapper]]]</div><div>[error] =C2=A0 =C2=A0 =C2=A0 .fold(List[Try[Wrapp=
er]](), new FoldFunction[Tuple2[Int, Int], List[Try[Wrapper]]] {</div><div>=
[error] =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0^</div><div>[error] one er=
ror found</div><div>[error] (compile:compileIncremental) Compilation failed=
</div></div><div><br></div><div>If I make the constructor public again, the=
 error goes away. I&#39;ve set up a simple example that demonstrates the pr=
oblem here:=C2=A0<a href=3D"https://github.com/AndrewWhitaker/flink-case-cl=
ass-private-ctor" target=3D"_blank">https://github.com/AndrewWhitaker/flink=
-case-class-private-ctor</a></div><div>I&#39;ve read this article on Flink&=
#39;s website:=C2=A0<a href=3D"https://flink.apache.org/faq.html#why-am-i-g=
etting-a-nonserializableexception-" target=3D"_blank">https://flink.apache.=
org/faq.html#why-am-i-getting-a-nonserializableexception-</a> but I think m=
y issue is slightly different.<br></div><div><br></div><div>I&#39;m just tr=
ying to understand this behavior and if there&#39;s a way I can work around=
 it.</div><div><br></div><div>Thanks!<span><font color=3D"#888888"><br clea=
r=3D"all"><div><br></div>-- <br><div><div dir=3D"ltr"><div><div><span style=
=3D"color:rgb(77,77,77);font-family:&#39;Helvetica Neue&#39;,Arial,Helvetic=
a,sans-serif;font-size:14px;line-height:18px">Andrew Whitaker | <a href=3D"=
mailto:andrew.whitaker@braintreepayments.com" target=3D"_blank">andrew.whit=
aker@braintreepayments.com</a></span></div></div></div></div>
</font></span></div></div>
</blockquote></div><br></div>
</div></div></blockquote></div><br><br clear=3D"all"><div><br></div>-- <br>=
<div class=3D"gmail_signature"><div dir=3D"ltr"><div><div><span style=3D"co=
lor:rgb(77,77,77);font-family:&#39;Helvetica Neue&#39;,Arial,Helvetica,sans=
-serif;font-size:14px;line-height:18px">Andrew Whitaker | <a href=3D"mailto=
:andrew.whitaker@braintreepayments.com" target=3D"_blank">andrew.whitaker@b=
raintreepayments.com</a></span></div><div><span style=3D"color:rgb(77,77,77=
);font-family:&#39;Helvetica Neue&#39;,Arial,Helvetica,sans-serif;font-size=
:14px;line-height:18px">--</span></div><div dir=3D"ltr"><span style=3D"colo=
r:rgb(77,77,77);font-family:&#39;Helvetica Neue&#39;,Arial,Helvetica,sans-s=
erif;font-size:14px;line-height:18px">Note: this information is confidentia=
l. It is prohibited to share, post online or otherwise publicize without Br=
aintree&#39;s prior written consent.</span><br></div></div></div></div>
</div>

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