Warn if type argument was inferred as union type #24258
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| em"""|A type argument was inferred to be union type ${tpt.tpe.stripTypeVar} | ||
| |This may indicate a programming error. | ||
| |""", tpt.srcPos) | ||
| ) |
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It could reside in a miniphase following CheckUnused. There's not a "framework" for lints. The only policy there is that trees are not transformed. (I don't know if CheckUnused will always rely on miniphase.) In particular, CheckUnused doesn't look at InferredTypeTrees. To say more, it keeps warnings out of core code if possible, a drumbeat heard from on high. Also helps composition.
| val inferredOrTypes = args.filter(tpt => | ||
| tpt.isInstanceOf[InferredTypeTree] && tpt.tpe.stripTypeVar.isInstanceOf[OrType] | ||
| ) | ||
| inferredOrTypes.headOption.foreach(tpt => |
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Since you're going through Option, you mean args.find. Or args.iterator.filter(p).take(1). I was actually going to point out args.filter: tpt => if you haven't tried the style.
| List(new Parser) :: // Compiler frontend: scanner, parser | ||
| List(new TyperPhase) :: // Compiler frontend: namer, typer | ||
| List(CheckUnused.PostTyper(), CheckShadowing()) :: // Check for unused, shadowed elements | ||
| List(new WInferUnion) :: // Winfer-union |
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Since you use the mini-phase idea, it must be part of a megaphase, and I think putting it with CheckUnused and CheckShadowing would be fine. It could go in front. That means the megaphase walks the tree once to dispatch to all three miniphases.
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If this is too much work, or doesn't work for some reason, reverting to post-typer would be OK, but it's good if it just works.
Also please squash the commits.
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Also please squash the commits.
Doesn't github allow squash and merge?
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| object WInferUnion: | ||
| val name = "Winfer-union" | ||
| val description = "warn if type argument inferred as union type" |
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The name and description could be more generic for -Vphases (as opposed to settings help), such as lintInferredTypes and checks inferred types for undesirable results or something. That's not a blocker.
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Okay, I'll keep that in mind. I changed the description a bit.
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Thanks, I think I'm the only one who ever reads -Vphases.
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Thanks, nice to "normalize" adding warnings in a place which doesn't impact core features or code. (This was a modest impact in any case.) |
Alex1005a
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Seem like "squash and merge" squashes all commits into a single one. Just in case, I made squash by hand. |
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Scala 2 has a
-Xlint:infer-anyoption that warns if a type argument was inferred asAny. In Scala 3 instead of union type arguments will be inferred as union types. In Scala 3, a union type will be inferred instead of Any. So to replaceinfer-anyyou need to warn that a union type has been inferred.