[WIP] Add support for '''- delimited strings (dedented string literals) in Scala 3

[lihaoyi]

SIP language feature discussion https://contributors.scala-lang.org/t/sip-xx-dedented-multiline-string-literals/7197

• Add new token types: tDEDENTED_STRING, tINTERPOLATED_DEDENTED_STRING, tINTERPOLATED_DEDENTED_RAW_STRING
• Update lexer grammar to recognize ''' delimiters with extended delimiter support
• Add INSIDE_DEDENTED_INTERPOLATED_STRING state and DedentedLevel class
• Support string interpolation for dedented strings
• Add comprehensive test coverage for basic, extended, and interpolated dedented strings
• Regenerated _ScalaCoreLexer.java from updated flex grammar

🤖 Generated with Claude Code

[lihaoyi]

I'm having trouble testing this manually, it seems the head of intellij-scala doesn't work on the latest intellij 2025.2 (Plugin 'Scala' (version 'SNAPSHOT') is not compatible with the current version of the IDE, because it requires build 252.25557 or newer but the current build is IU-252.23892.409), and ./installers.cmd in intellij-community seems to be taking forever. Is there an easy way to test this out manually?

[lihaoyi]

Managed to get this working locally by building intellij-scala on a slightly older commit

[lihaoyi]

Now it works for extensible delimiters too, at least up to a point:

So far hardcoded to work up to length=6 ''''''. There is probably a better way to do this so it works with arbitrarily long delimiters, but this works in a pinch

[SrTobi]

Hey @lihaoyi. Cool that you got it to work. We also looked at the sip and came up with the following points that have to be investigated and potentially adjusted when the SIP is greenlighted:

• Auto-indent on Enter/Delete/Backspace
• Insert/delete complementary quote
• Don't modify the contents on Format
• Don't add .stripMargin
• Copy/Paste handling
• IntelliLang (language injection)

Features:

• Re-indent on indenting val
• Intention: convert between different literal kinds
• Additional inspections (preferable to lexer errors)

We'd like to wait for the sip to be accepted before we start working on it or merge any feature regarding it.

[lihaoyi]

Yes of course. This is just an initial proof of concept, I expect it'll take some work to polish but that can wait until the SIP is reviewed and accepted into the language