Constant fold `toInt`, `toLong`, `toDouble`, `toFloat`, `toByte` and `toShort`

[nicolasstucki]

Compiler version

3.1.0

Minimized code

inline val myIntMask = 1 << 4
inline val myLongMask = myIntMask.toLong

Output

2 |inline val myLongMask = myIntMask.toLong
  |                        ^^^^^^^^^^^^^^^^
  |                        inline value must have a literal constant type

Expectation

We should be able to constant fold toInt, toLong, toDouble, toFloat, toByte and toShort.

This would also alow us to write inline vals with Short and Byte types as shown bellow

inline val myByteMask = 2.toByte

This is currently impossible as we do not possess a byte or short numerical postfix in the syntax.

[mbovel]

Seems like this should be relatively straightforward to extends foldUnop to support constant-folding these methods?

https://github.com/lampepfl/dotty/blob/d02ecd02b7acde957600649ad41a1a1b33572f4d/compiler/src/dotty/tools/dotc/typer/ConstFold.scala#L76-L90

Would that be appropriate for a spree?

[scala-center-bot]

This issue was picked for the Issue Spree No. 30 of 09 May 2023 which takes place in a week from now. @KuceraMartin, @eugenefle, @TheElectronWill will be working on it. If you have any insight into the issue or guidance on how to fix it, please leave it here.

[mbovel]

@KuceraMartin, @eugenefle, @TheElectronWill: In case your team is super fast and manage to fix this issue in less than 1.5 hours, you can then try to tackle #17188 😉

[mbovel]

Please ignore the 2 previous message from the Scala Center bot. Teams for the next spree can be found here: https://airtable.com/shrSni1OItSuErosU/tblLEWc2ISeGHPbsc. Sorry for the spam!