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type alias and object with the same name cause type mismatch #7139

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scabug opened this issue Feb 15, 2013 · 7 comments
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type alias and object with the same name cause type mismatch #7139

scabug opened this issue Feb 15, 2013 · 7 comments
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@lrytz
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2.12.1

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@scabug
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scabug commented Feb 15, 2013 •
edited by retronym 

// test/A.scala
package test {
  object A
}
package object test {
  type A = Int
}
scala> val a = test.A
<console>:10: error: type mismatch;
 found   : test.A.type
 required: Any
Note that A extends Any, not AnyRef.
Such types can participate in value classes, but instances
cannot appear in singleton types or in reference comparisons.
 + "a: test.A.type = " + scala.runtime.ScalaRunTime.replStringOf(`a`, 1000)
                                                                                      ^
@scabug
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scabug commented Feb 15, 2013

Imported From: https://issues.scala-lang.org/browse/SI-7139?orig=1
Reporter: @rjolly
Affected Versions: 2.10.0
See #5031

@scabug
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scabug commented Mar 14, 2013 •
edited by retronym

@rjolly said:
Variation:

// A.scala

package test {
  object A {
    def apply(n: A) = n
  }
}
package object test {
  type A = Int
}
scala> import test._
import test._

scala> A(0)
res0: test.A = 0

scala> A(0)
<console>:11: error: test.A.type does not take parameters
              A(0)
               ^

@scabug
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scabug commented Dec 2, 2014

Jed Wesley-Smith (jedws) said:
This issue isn't limited to the REPL, it also causes compilation issues in multi-module builds. We saw the following symptom:

[error] bad symbolic reference to io.atlassian.aws.AwsAction.Functions encountered in class file 'SQSAction.class'.
[error] Cannot access type Functions in object io.atlassian.aws.AwsAction. The current classpath may be
[error] missing a definition for io.atlassian.aws.AwsAction.Functions, or SQSAction.class may have been compiled against a version that's
[error] incompatible with the one found on the current classpath.
[error] /work/aws-scala/sqs/src/test/scala/io/atlassian/aws/sqs/SQSSpec.scala:48: value ok is not a member of object io.atlassian.aws.sqs.SQSAction
[error]         _ <- handles.headOption.map { h => SQS.changeVisibility(url, h, Duration(5, TimeUnit.SECONDS)) } getOrElse SQSAction.ok(())
[error]                                                                                                                              ^

@scabug
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scabug commented Dec 3, 2014

@retronym said:
A workaround should be:

package test {
  object A0
}
package object test {
  type A = Int
  val A: A0.type = A0
}

@scabug
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scabug commented Apr 15, 2015

@retronym said:
Reproduction with the resident compiler:

% scalac sandbox/test.scala
% scalac -Xresident

nsc> sandbox/test2.scala

nsc> sandbox/test2.scala
sandbox/test2.scala:2: error: type mismatch;
 found   : p.X.type
 required: AnyRef
Note that X extends Any, not AnyRef.
Such types can participate in value classes, but instances
cannot appear in singleton types or in reference comparisons.
  private[this] val res1 = (null: p.X.type)
                                    ^

@scabug
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scabug commented Apr 15, 2015

@retronym said:
At the start of the second run, someone is setting the info of the module class of X to NoType. Find that someone, and we'll be closer to understanding this.

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scabug commented Oct 27, 2016

@lrytz said:
fixed in scala/scala#5482

@scabug scabug closed this as completed Oct 31, 2016
@scabug scabug added the repl label Apr 7, 2017
@scabug scabug added this to the 2.12.1 milestone Apr 7, 2017
This was referenced Apr 7, 2017
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Closed
@eed3si9n eed3si9n mentioned this issue Jul 14, 2017
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