REPL gives stack overflow during too eager syntax highlighting, e.g. when multiplying string

[bjornregnell]

Compiler version

3.3.0-RC2

Minimized code

$ scala-cli repl -S 3.3.0-RC2
Welcome to Scala 3.3.0-RC2 (17.0.4.1, Java OpenJDK 64-Bit Server VM).
Type in expressions for evaluation. Or try :help.
                                                                                                                                                                       
scala> "works fine" * 100
val res0: String = works fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks fineworks ...
                                                                                                                                                                       
scala> "works not fine"* 1000
Exception in thread "main" java.lang.StackOverflowError
    at dotty.tools.dotc.ast.untpd$UntypedTreeAccumulator.foldMoreCases(untpd.scala:799)
    at dotty.tools.dotc.ast.Trees$Instance$TreeAccumulator.foldOver(Trees.scala:1641)
    at dotty.tools.dotc.ast.untpd$UntypedTreeTraverser.traverseChildren(untpd.scala:809)
    at dotty.tools.dotc.printing.SyntaxHighlighting$TreeHighlighter$2$.traverse(SyntaxHighlighting.scala:123)
    at dotty.tools.dotc.ast.untpd$UntypedTreeTraverser.apply(untpd.scala:808)
    at dotty.tools.dotc.ast.untpd$UntypedTreeTraverser.apply(untpd.scala:808)
 

Expectation

Should work and not give stack overflow (as in e.g. 2.13)

[som-snytt]

This is the highlight of my day.

[mpilquist]

Note this isn't unique to string multiplication - it's a bug in syntax highlighting of very long strings.

[som-snytt]

it's not trying to highlight a string but a huge infix expression.

val res0: String = works fineworks fineworks

The fix is to put the string in quotes for parsing, as in scala/scala#8885

Then, to pun further, the fix is in.

I was curious about ellipsis output:

ending in the ellipsis, so it must abort highlighting on parse error.

[WojciechMazur]

Bisect points to 1475a6f

[prolativ]

It looks like the problem is that the limit of characters used for truncation got raised from 1000 to 50000. I think we should make the default 1000 again (3000 seem to work for me but I'm not sure if this would work universally). If users wanted to have a higher limit, they could use the setting explicitly now.
CC @mpollmeier

[mpollmeier]

Sure we can change the default back to 1000, but that's only covering the underlying issue, doesn't it?
As @mpilquist mentioned, it's a bug in the syntax highlighting. So if users configure a higher limit for their session, they're still going to run into this...

[som-snytt]

My point was ignored.

This is already wrong color, string would be red:

It's parsing that text to know how to colorize it, and works fineworks fineworks is an infix expression, not a string.

There are other workarounds besides putting quotes around the string, namely, not attempting to highlight the RHS or using the type to pick a color.

[bjornregnell]

Why is the interior of a string syntax highlighted in the first place? It is just a string... (sorry if I'm missing something here and asking a strange question)

[bjornregnell]

I mean: this is the algorithm that I (perhaps simplistically) assumed:

• val replInput: String = """"works fine" * 1000"""
• val code: FancyAST = intepret(replInput)
• aha code is just a string (although loooong), so no further highlighting is necessary and just print (parts of) it

(But again, I am perhaps missing something obvious... )