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Do not propagate @tailrec to exported methods #19509

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Jan 23, 2024
Merged

Do not propagate @tailrec to exported methods #19509

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aad73c1
Do not propagate `@tailrec` to exported methods
nicolasstucki Jan 22, 2024
29deb05
Do not propagate macro annotations to exported methods
nicolasstucki Jan 23, 2024
ef4888b
Do not propagate `main` annotations to exported methods
nicolasstucki Jan 23, 2024
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5 changes: 4 additions & 1 deletion compiler/src/dotty/tools/dotc/typer/Namer.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1254,7 +1254,10 @@ class Namer { typer: Typer =>
newSymbol(cls, forwarderName, mbrFlags, mbrInfo, coord = span)

forwarder.info = avoidPrivateLeaks(forwarder)
forwarder.addAnnotations(sym.annotations.filterConserve(_.symbol != defn.BodyAnnot))
forwarder.addAnnotations(sym.annotations.filterConserve { annot =>
annot.symbol != defn.BodyAnnot
&& annot.symbol != defn.TailrecAnnot
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@bishabosha bishabosha Jan 22, 2024 •
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alternatively, could the TailRec check ignore exported methods? - this filtering approach might not be scalable for e.g. macro annotations

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Right, we also need to filter macro annotations.

I think that disabling the behavior where it is checked will be less scalable. For example, I disable the macro annotations on exports I have to find one or more places where this restriction needs to be taken into account. And those places are usually code generation details like exports.

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I also added @main. Might might still need to filter others.

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@nicolasstucki nicolasstucki Jan 23, 2024 •
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I wonder if we should have a whitelist approach with this one. This would make sure that we never accidentally keep an annotation we do not want.

I tested this on scala3-bootstrapped/testCompilation and it only required the @targetName annotation. Others that should be required are @experimental, @publicInBinary, and showAsInfix.

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The thing is that we will never know what should be the behavior for custom annotations.

The only holistic solution here is to have an @meta-based indication of what to do. This is the approach used to determine whether annotations should go to fields/getters/setters. It would also be appropriate to determine whether it should go to exports/bridges/etc.

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Maybe we need ExportableAnnotation trait that all such annotations should extend to get exported.

})

if forwarder.isType then
buf += tpd.TypeDef(forwarder.asType).withSpan(span)
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10 changes: 10 additions & 0 deletions tests/pos/i19505.scala
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
import scala.annotation.tailrec

object Foo:
@tailrec
def foo(n: Int): Int =
if n == 0 then 0
else foo(n-1)

object Bar:
export Foo.foo // def foo here should not have `@tailrec`
8 changes: 8 additions & 0 deletions tests/warn/i19505.scala
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@@ -0,0 +1,8 @@
import scala.annotation.tailrec

object Foo:
@tailrec
def foo: Int = foo // warn: Infinite recursive call

object Bar:
export Foo.foo // def foo here should not have `@tailrec`
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