map/flatMap/filter/filterWith causes non-termination

[tonymorris]

At the sbt console, occasionally using some methods would fail to produce a result

scala> myFunctor.map(x)(f)
// fails to terminate

scala> val q = myFunctor.map(x) _
scala> q(f) // however, this terminates just fine

However, this behaviour goes way if the method is not called map.

scala> myFunctor.mapmap(x)(f) // terminates

We also saw this behaviour for a method named filter.

@S11001001 has pointed out that this is due to having -optimise turned on, which we do as seen in build.sbt. The inliner bumps up the inliner score for methods name map, foreach, flatMap, filter or withFilter.

Here is a link to the source code to isMonadicMethod which is later referenced in the file.

https://github.com/scala/scala/blob/v2.10.3/src/compiler/scala/tools/nsc/backend/opt/Inliners.scala#L153-L158

[markhibberd]

Yeh, removing -optimise does fix it. Thanks @S11001001.

[markhibberd]

Fixed in b8c4e3a.

[S11001001]

Now you too can share in the joy of knowing about isMonadicMethod. 😃