Cannot do a map on a Map with Scala 3, with Scala 2.13 it works ok about dotty

[SethTisue]

A consider a bug to behave differently just for defining an intermediate variable

That's an incorrect expectation, at least in general. It can perhaps be defended in specific cases, but it has to specifically defended, you can't just point at the general principle and be done, since the general principle does not exist. Type inference in Scala 3 processes entire expressions. It's normal that the overall result might be different if you first give the type checker only part of the expression to work with, forcing it to decide on an answer based on partial information, and then only later give it the rest.

[DavidPerezIngeniero]

A workaorund is to define an intermediate variable:

val p2 = (p: Map[?, ?]).asScala
p2.map { case (k, v) => (k, v) }

I consider a bug to behave differently just for defining an intermediate variable.

[SethTisue]

Is the issue reproducible without involving an external dependency...?

[DavidPerezIngeniero]

Is the issue reproducible without involving an external dependency...?

I don't know, but the code I've shown it is quite simple and minimalistic.

[DavidPerezIngeniero]

A consider a bug to behave differently just for defining an intermediate variable

That's an incorrect expectation, at least in general. It can perhaps be defended in specific cases, but it has to specifically defended, you can't just point at the general principle and be done, since the general principle does not exist. Type inference in Scala 3 processes entire expressions. It's normal that the overall result might be different if you first give the type checker only part of the expression to work with, forcing it to decide on an answer based on partial information, and then only later give it the rest.

At least I don´t expect different results if I split an expression using an intermediate variable.

[SethTisue]

I don't know, but the code I've shown it is quite simple and minimalistic.

Regardless, reproducing a bug without an external dependency is considered the standard for bug reporting in this repository, for two main reasons:

1. It's what we need in order to turn the report into a test case that can be added to our test suite

(but perhaps even more importantly:)

2. it often gives considerable additional insight into the nature of the problem (including insight into whether the problem is in fact a bug in Scala itself, or somehow the external dependency's fault)