Improve REPL display of method types

[bishabosha]

The following examples are implemented, my main question is should methodTypeAsDef stay in the IMain class or go elsewhere - it currently computes the type String as if it will be appended to a method name.

Current behaviour:

val/var

scala> lazy val x = ""
lazy val x: String // unevaluated

scala> val (a, b) = (true, false)
val a: Boolean = true
val b: Boolean = false

scala> var mut = 0
var mut: Int = 0

scala> mut = 1
// mutated mut

def/macro

scala> def foo = ""
def foo: String

scala> def foo[T: ClassTag, A: ClassTag](x: T): String = x.toString
def foo[T, A](x: T)(implicit evidence$1: ClassTag[T], evidence$2: ClassTag[A]): String

scala> def m(x: => Int): Int = macro ???
def m(x: => Int): Int

definitions - I'd prefer to comment // defined class A to make it clear information is lost

scala> object A
object A

scala> trait B
trait B

scala> class C
class C

scala> type D = Unit
type D

Fixes scala/bug#10024

[hrhino]

Mostly bikeshedding, but that's the nature of the bug.

Thanks for taking this on!

[bishabosha]

also it would be quite good if printedName from scala.reflect.internal.Printers.CodePrinter could be lifted elsewhere, as it decodes names and restores backticks if necessary.

protected def printedName(name: Name, decoded: Boolean = true) = {
  import Chars._
  val decName = name.decoded
  val bslash = '\\'
  val isDot = (x: Char) => x == '.'
  val brackets = List('[',']','(',')','{','}')

  def addBackquotes(s: String) =
    if (decoded && (decName.exists(ch => brackets.contains(ch) || isWhitespace(ch) || isDot(ch)) ||
      (name.isOperatorName && decName.exists(isOperatorPart) && decName.exists(isScalaLetter) && !decName.contains(bslash))))
      s"`$s`" else s

  if (name == nme.CONSTRUCTOR) "this"
  else addBackquotes(quotedName(name, decoded))
}

[som-snytt]

I love the cartoon quality of the long eyebrow, but maybe these lines could be clearer? Anything that doesn't entail counting quotes.

[som-snytt]

Oh, I can't tell by looking if it helps me understand what lazy val i = 27 means.

[bishabosha]

I've cleaned up the quotes, but right now the repl would print

scala> lazy val i = 27
lazy val i: Int

scala> 

is = <lazy> noise or useful?

[SethTisue]

= ???, perhaps

[bishabosha]

what about

scala> lazy val x = 0
lazy val x: Int // unevaluated

[bishabosha]

= ???, perhaps

I'm concerned with triple question mark as a beginner could see that as the value in Predef and be confused.

[som-snytt]

This is more like what people ask for ("something I can cut/paste"), but I'm not sure about output for class C. Maybe I'd also miss the sense of "running commentary" like in "// mutated x", such as "defined macro m".

Just speculating, but what if class C -> class C extends AnyRef, that is, fill in the missing parts. Why doesn't class C { def i = 42 } say

class C extends AnyRef {
  def i: Int = 42
}

[bishabosha]

But then if there are too many members to a definition wouldn’t that be polluting to print them out?

[som-snytt]

For things like highlighting lazy or verbose class printing, I'm thinking of the beginner use case. I don't have an answer, but I've often thought that beginner mode would be useful. I assumed that printing "val i" so it looks like code was also a beginner feature.

Also, the jalapeno bagel at the office this morning is really hot, so I have to go get some water now.

[adriaanm]

Very nice work! I think it's best to omit members from class definitions and generally the right-hand side of definitions. I like that everything echo'ed is valid syntax. We already have a way to print the tree after type checking (add // print at the end of a line and hit tab). Maybe we could make that more easily discoverable? (For example, add // members omitted, use :print to show in full)

[bishabosha]

// members omitted, use :print to show in full

I can't see an option to :print in the :help, is this something new?,

edit: or most likely you mean make a new Issue for it 😀

[adriaanm]

Sorry, it's not there yet. I meant we could make the secret // print <TAB> feature more public with a :print command that exposes its functionality and prints a fully desugared & type checked version of the last line.

[adriaanm]

Also, this could definitely be left for a follow-up PR.

[som-snytt]

For future ref, I was futzing with repl recently and I thought verbose print could be a mode. print-tab is handy but going into print mode, I can try out a few things and just see it printed verbosely. It could also be a regular setting, :se -Vrepl for verbose repl.

[SethTisue]

// members omitted, use :print to show in full

(It seems like more noise/annoyance than benefit to me. Separate PR, please, if someone still wants to do it.)

[som-snytt]

// ask @SethTisue to explain this to you

[SethTisue]

needs rebase (probably very minor)

I suggest we push this to 2.13.2

[bishabosha]

Squashed and rebased

[lrytz]

Very nice, thanks @bishabosha!

[dwijnand]

This is awesome. Thanks, @bishabosha!