Nightly docs are missing Scala 3 parts of standard library

[Florian3k]

Nightly docs https://dotty.epfl.ch/api/index.html are missing Scala 3 additions to stdlib (compiletime, deriving, quoted, Tuple, CanEqual, CanThrow etc)

Bisect points to #17526

[Florian3k]

Background:
Scaladoc (generateScalaDocumentation and generateStableScala3Documentation precisely) uses results of building stdlib-bootstrapped (and few others) to generate documentation:
Relevant fragments from Build.scala:
For generateScalaDocumentation:
https://github.com/lampepfl/dotty/blob/89de88126e19b31f7eb22a2bff22a7a780a6a973/project/Build.scala#L2016-L2020
For generateStableScala3Documentation:
https://github.com/lampepfl/dotty/blob/89de88126e19b31f7eb22a2bff22a7a780a6a973/project/Build.scala#L2075-L2079

After #17526 stdlib-bootstrapped no longer contains Scala 3 parts of stdlib, so we need another source of those.

[Florian3k]

I attempted to resolve this by adding scala3-library-bootstrapped to scaladoc input files:

val dottyJars: Seq[java.io.File] = Seq(
  (`stdlib-bootstrapped`/Compile/products).value,
  (`scala3-interfaces`/Compile/products).value,
  (`tasty-core-bootstrapped`/Compile/products).value,
+ (`scala3-library-bootstrapped`/Compile/products).value,
).flatten

Seq(
  s"out/bootstrap/stdlib-bootstrapped/scala-$version-bin-SNAPSHOT-nonbootstrapped/classes",
  s"tmp/interfaces/target/classes",
  s"out/bootstrap/tasty-core-bootstrapped/scala-$version-bin-SNAPSHOT-nonbootstrapped/classes",
+ s"out/bootstrap/scala3-library-bootstrapped/scala-$version-bin-SNAPSHOT-nonbootstrapped/classes",
)

But that fails with the following error after running scaladoc:

-- Error: library/src/scala/quoted/ToExpr.scala:425:27 -------------------------
425 |      '{ BigDecimal(${Expr(x.toString)}) }
    |                           ^^^^^^^^^^
    |          method toString in class BigDecimal does not take parameters

[Florian3k]

@nicolasstucki I was told that you are currently working on some things related to tasty and stdlib-bootstrapped. Do you have any ideas about how to proceed with this?

[nicolasstucki]

What I am working on is generating TASTy for the Scala 2 stdlib. What you seem to be missing the Scala 3 library. Adding scala3-library-bootstrapped seems to be the correct direction.

[nicolasstucki]

I see what happened. The docs are consuming the artifacts of stdlib-bootstrapped to get TASTy from the Scala 2 library. It used to compile all Scala 2 and Scala 3 sources together (before #17526). These TASTy were not supposed to be stable enough to be consumed by any tool. I guess that it was good enough for a first version of the docs. What I am currently working on is to make these TASTy stable (align perfectly with the Scala 2 signatures).

Now, to fix this issue we have two alternatives

1. (quick fix) we create a new version of stdlib-bootstrapped that includes the Scala 3 sources and compiles without -Yscala2-stdlib (signature patches).
2. Scaladoc depends on both stdlib-bootstrapped and scala3-library-bootstrapped

We need to get to (2) at some point. The question is if this is simple or if we should have a quick patch (1) to make the documentation work while we figure out the details. I will open a PR for (1) and we can merge it if needed.