Regression: value foreach is not a member of _ #7667

scabug · 2013-07-15T16:46:12Z

The following code can be compiled with no errors by 2.10.0

Welcome to Scala version 2.10.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_32).
Type in expressions to have them evaluated.
Type :help for more information.

scala>   def packAny(value: Any) {
     |     value match {
     |       case x: collection.GenMapLike[_,_,_]  =>
     |         for((k,v) <- x) { ??? }
     |     }
     |   }
packAny: (value: Any)Unit

But cannot be compiled by 2.10.1 and 2.10.2

Welcome to Scala version 2.10.1 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_32).
Type in expressions to have them evaluated.
Type :help for more information.

scala>   def packAny(value: Any) {
     |     value match {
     |       case x: collection.GenMapLike[_,_,_]  =>
     |         for((k,v) <- x) { ??? }
     |     }
     |   }
<console>:10: error: value foreach is not a member of _
               for((k,v) <- x) { ??? }
                            ^

scabug · 2013-07-15T16:46:12Z

Imported From: https://issues.scala-lang.org/browse/SI-7667?orig=1
Reporter: Denis Petrov (denis)
Affected Versions: 2.10.1
See #6968

scabug · 2013-07-16T04:37:59Z

@retronym said:
This is basically a duplicate of #7222.

In 2.10.0, the parser phase of the compiler desugared your for-comprehension as irrefutable, ie to x.foreach { case (k, v) => }.

However, it can't do that in general for tuple patterns; they are supposed to parse to a withFilter call. That's important for code like:

for ( (a, b) <- List[Any]((1, 2), "boo"))

That code should return a one element list; if we omit the withFilter we'll get a MatchError instead.

So now your example is desugared to:

x.withFilter { case (k, v) => (k, v) }.foreach(_ => ???)

{withFilter} returns Repr, the third type argument of GenMapLike, which you have bound to an existential type. As such, it doesn't support foreach.

I suggest in this case to call foreach directly:

x foreach {
  case (k, v) => ???
}

scabug closed this as completed Jul 16, 2013

scabug added duplicate typer labels Apr 7, 2017

scabug assigned retronym Apr 7, 2017

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Regression: value foreach is not a member of _ #7667

Regression: value foreach is not a member of _ #7667

scabug commented Jul 15, 2013

scabug commented Jul 15, 2013

scabug commented Jul 16, 2013

Regression: value foreach is not a member of _ #7667

Regression: value foreach is not a member of _ #7667

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scabug commented Jul 15, 2013

scabug commented Jul 15, 2013

scabug commented Jul 16, 2013