Unexpected "recursive value needs type" error

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With scala-2.10.0.r25850-b20111019023417, compiling:

// RecursiveValueNeedsType.scala
object RecursiveValueNeedsType {

  def foo(param: String) = 42
  def bar(n: Int) = 42

  {
    val xxx = foo(param = null)
    val param = bar(xxx)
  }
  
}

Gives the error:

RecursiveValueNeedsType.scala:8: error: recursive value xxx needs type
    val param = bar(xxx)

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Imported From: https://issues.scala-lang.org/browse/SI-5091?orig=1
Reporter: Matt Russell (mattrussell)
See #8342, #5044, #6051

[scabug]

Freewind (freewind) said:
An example: http://stackoverflow.com/questions/9148339/why-this-scala-code-reports-compilation-error-recursive-value-x-needs-type

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@lrytz said (edited on Jul 12, 2012 7:45:30 AM UTC):
very similar symptom in #6051

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Przemek Sokół (falconepl) said:
If you wrap such a code with a ScalaTest test, instead of a type checker confusion you get a compiler error:

    [error] Unknown type: <error>, <error> [class scala.reflect.internal.Types$ErrorType$, class scala.reflect.internal.Types$ErrorType$] TypeRef? false
    [trace] Stack trace suppressed: run last test:compile for the full output.
    [error] (test:compile) scala.reflect.internal.FatalError: Unknown type: <error>, <error> [class scala.reflect.internal.Types$ErrorType$, class scala.reflect.internal.Types$ErrorType$] TypeRef? false

You can find exemplary code here.

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@retronym said:
This gives a pretty reasonable error message these days:

qscalac test/pending/pos/t5091.scala
test/pending/pos/t5091.scala:8: error: recursive value xxx needs type
    val param = bar(xxx)
                    ^
test/pending/pos/t5091.scala:7: warning: type-checking the invocation of method foo checks if the named argument expression 'param = ...' is a valid assignment
in the current scope. The resulting type inference error (see above) can be fixed by providing an explicit type in the local definition for param.
    val xxx = foo(param = null)
                        ^
one warning found
one error found

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@retronym said:
I'm planning to close this one with that error message in a neg test: scala/scala#4044

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Christopher (metch) said:
To fix this issue with the current Scala version (<= 2.11.4), the type of param must be added: val param: Int = bar(xxx).
The above code example will compile without warning or error in 2.11.5, right ?

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@som-snytt said:
No, Jason reports the messages above. For the record, the message strings are very long (more than twitter length).

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Ivan Suhinin (suhinini) said:
Guys this is still reproducible in Scala 2.11.6. Please check out sample project: https://github.com/suhinini/SI-5091-Scala-2-11-6-Reopen

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Przemek Sokół (falconepl) said:
@[~suhinini]
Actually, when I compile your project in SBT, this is what I get:

[error] /home/.../SI-5091-Scala-2-11-6-Reopen/Test.scala:6: recursive value x needs type
[error]     val id = x + 1
[error]              ^
[error] one error found
[error] (compile:compile) Compilation failed

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Ivan Suhinin (suhinini) said:
So my recursive value x needs type is different from bug's recursive value needs type? Sorry if it is a different bug, just seems exactly like this one.

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@retronym said:
Looks like a SBT bug, scalac outputs a diagnostic warning for that code, but this is swallowed by SBT in favour of the compile error.

I've lodged this as sbt/sbt#1928

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Przemek Sokół (falconepl) said (edited on Mar 19, 2015 7:11:33 PM UTC):
@[~suhinini]
No, it's not. They are the same. But, as far as I understand, this issue is closed as it has been concluded that such a message is enough for this wierd typechecking cycle. See other comments, especially those by @retronym: {quote}I'm planning to close this one with that error message in a neg test{quote}.
Update:
OK, as Jason pointed out, it's that additional warning (to the compile error) that is swallowed by SBT.

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Ivan Suhinin (suhinini) said:
Thanks guys, now I get the resolution of this. Just spent some time yesterday trying to understand what's going on, wasn't clear without warning.

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Netta Doron (nettad) said:
I have a service running on scala version 2.11.7 and I'm still experiencing this issue.
case class Foo(id: UUID)
class FooTest extends org.specs2.mutable.SpecificationWithJUnit {
"this should compile" in
{ val foo = Foo(id = UUID.randomUUID) val id = foo.id true must beTrue }
}
generates the error recursive value foo needs type.
val id = foo.id

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@lrytz said:
related to #8342. we plan to dis-ambiguate the foo(a = x) syntax so that it can only mean a named argument, not an assignment to a.

[aaabramov]

The same here: https://stackoverflow.com/questions/45814226/scala-named-argument-recursive-call/45816574#45816574

[xuwei-k]

fixed since Scala 2.13.0-M4

scala/scala@a992c83#diff-3828abb025ee93aa4f0b1d654200e5c9