CC Language Reference: Make Code Snippets Checkable

[bracevac]

It'd be good to have the code snippets inside the language reference
type checked, e.g., through mdoc.

Scaladoc can check snippets, so we should have that enabled for the CC language reference.

[WojciechMazur]

Doesn't it work already?
In #24734 checkable code snippets are one of the main functionalities, it seemed to work for some of experimental features (see screenshot below)
There was in fact one fix needed when running scaladoc/generateReferenceDocumentation - it crashed previously when we tried to compile code snippets in markdown files b6368e7

Details

Markdown source: https://raw.githubusercontent.com/scala/scala3/b76b88993631a2146b6705904833ff7e706848b3/docs/_docs/reference/error-codes/E218.md

[bracevac]

Thanks, I didn't know this already worked. Is it also possible to hide certain lines in a code from rendering? Say:

import language.experimental.captureChecking // hide this
import caps.* // hide this

foo() // only show this

[WojciechMazur]

It should be possible, but I have not tried it yet
https://docs.scala-lang.org/scala3/guides/scaladoc/snippet-compiler.html#hiding-code