Explicitly upcast intermediate result to aid program elaboration #230
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| @@ -89,7 +89,7 @@ class ParserJVM private[parser] (pattern: String) extends Parser(pattern) { | |||
| * `"[abc]"` | |||
| */ | |||
| override def charClass[A: P]: P[CharacterClass] = | |||
| Indexed("[" ~ "^".!.? ~ (charClassIntersection.rep(exactly = 1) | classItem.rep(minCharClassItem)) ~ "]") | |||
| Indexed("[" ~ "^".!.? ~ ((charClassIntersection.rep(exactly = 1): P[Seq[RegexTree]]) | classItem.rep(minCharClassItem)) ~ "]") | |||
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May I ask why this particular rep needs an upcast, but not others?
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Hello, thank you for having a look at the PR!
In scala/scala3#17924, I made a change in the compiler that affects program elaboration (ie, implicits resolution). The consequence is that the compiler may give up earlier than what it used to do in the past. Here, the type ascription helps the compiler figure out the least upper bound of both sides of the | operator, which in turn simplifies the resolution of implicit parameter for the second rep call.
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Thanks for the explanation! This rep comes from fastparse so I would imagine there’re more projects that depend on fastparse that are affected by this problem. Should this issue be elevated to fastparse?
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I am not sure what would be a good fix in fastparse, though…
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@julienrf Could you run scalafmt or give me push access to this PR so I can run it and make formatting happy? |
See scala/scala3#18130 for context. We add an explicit type ascription to help the compiler infer contextual arguments.
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Sorry for the delay. This is done! |
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Arguably the formatting is less legible, but I dare not go against scalafmt. Thanks for the contribution! |
See scala/scala3#18130 for context.
We add an explicit type ascription to help the compiler infer contextual arguments. This make the code future-proof against the next versions of the compiler. I have successfully compiled the project locally with Scala 3.3.2-RC1-bin-20230703-0a21ecf-NIGHTLY.