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Make Scala-3-style implicit resolution explicitly opt-in rather than bundled in -Xsource:3 #10012

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merged 1 commit into from Jul 7, 2022
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Make Scala-3-style implicit resolution explicitly opt-in rather than bundled in -Xsource:3 #10012

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1 change: 1 addition & 0 deletions src/compiler/scala/tools/nsc/Global.scala
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Expand Up @@ -1168,6 +1168,7 @@ class Global(var currentSettings: Settings, reporter0: Reporter)

// We hit these checks regularly. They shouldn't change inside the same run, so cache the comparisons here.
val isScala3 = settings.isScala3
val isScala3ImplicitResolution = settings.Yscala3ImplicitResolution
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This is a BooleanSetting, not a Boolean.


// used in sbt
def uncheckedWarnings: List[(Position, String)] = reporting.uncheckedWarnings
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1 change: 1 addition & 0 deletions src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
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Expand Up @@ -275,6 +275,7 @@ trait ScalaSettings extends StandardScalaSettings with Warnings { _: MutableSett
val YpickleWrite = StringSetting("-Ypickle-write", "directory|jar", "destination for generated .sig files containing type signatures.", "", None).internalOnly()
val YpickleWriteApiOnly = BooleanSetting("-Ypickle-write-api-only", "Exclude private members (other than those material to subclass compilation, such as private trait vals) from generated .sig files containing type signatures.").internalOnly()
val YtrackDependencies = BooleanSetting("-Ytrack-dependencies", "Record references to in unit.depends. Deprecated feature that supports SBT 0.13 with incOptions.withNameHashing(false) only.", default = true)
val Yscala3ImplicitResolution = BooleanSetting("-Yscala3-implicit-resolution", "Use Scala-3-style downwards comparisons for implicit search and overloading resolution (see https://github.com/scala/bug/issues/12437).", default = false)

sealed abstract class CachePolicy(val name: String, val help: String)
object CachePolicy {
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6 changes: 3 additions & 3 deletions src/compiler/scala/tools/nsc/typechecker/Infer.scala
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Expand Up @@ -903,9 +903,9 @@ trait Infer extends Checkable {
isAsSpecificValueType(rtpe1, tpe2, undef1 ::: tparams1, undef2)
case _ =>
tpe2 match {
case PolyType(tparams2, rtpe2) => isAsSpecificValueType(tpe1, rtpe2, undef1, undef2 ::: tparams2)
case _ if !currentRun.isScala3 => existentialAbstraction(undef1, tpe1) <:< existentialAbstraction(undef2, tpe2)
case _ =>
case PolyType(tparams2, rtpe2) => isAsSpecificValueType(tpe1, rtpe2, undef1, undef2 ::: tparams2)
case _ if !currentRun.isScala3ImplicitResolution => existentialAbstraction(undef1, tpe1) <:< existentialAbstraction(undef2, tpe2)
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@som-snytt som-snytt Jul 20, 2022 •
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This incurs the implicit conversion. I wonder why I don't see a warning currently. Edit: I catch this in that PR.

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@povder povder Jul 20, 2022 •
edited

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I saw your comment and I was going to quickly make a change to avoid the conversion but upon checking out the most recent code I realized the conversion doesn't happen anymore with your change 0d252f6#diff-7b7600384a160cb93e5eceff814f6aed9f5c7b72b752a18c3f61d895482e75fcR907

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Thanks for checking my check. (That's what I meant by I caught it in my PR, which was about the same time as yours.) I might change them to vars, except there were a lot of isScala3 calls, so removing the .value is not appealing. But that is why sed is the "scala editor".

case _ =>
// Backport of fix for https://github.com/scala/bug/issues/2509
// from Dotty https://github.com/lampepfl/dotty/commit/89540268e6c49fb92b9ca61249e46bb59981bf5a
//
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2 changes: 1 addition & 1 deletion test/files/neg/t2509-2.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution
class A
class B extends A
class C extends B
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2 changes: 1 addition & 1 deletion test/files/neg/t2509-3.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution
class A
class B extends A

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2 changes: 1 addition & 1 deletion test/files/neg/t2509-7b.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution
class Both[-A, +B]

trait Factory[A] {
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2 changes: 1 addition & 1 deletion test/files/pos/t2509-5.scala
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@@ -1,5 +1,5 @@
// See https://github.com/lampepfl/dotty/issues/2974
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution

trait Foo[-T]

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2 changes: 1 addition & 1 deletion test/files/pos/t2509-6.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution
class A
class B extends A

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2 changes: 1 addition & 1 deletion test/files/pos/t2509-7a.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution

class Both[-A, +B]

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2 changes: 1 addition & 1 deletion test/files/run/t2509-1.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution
import scala.language.implicitConversions

class A
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2 changes: 1 addition & 1 deletion test/files/run/t2509-4.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution
import scala.language.implicitConversions

class A
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2 changes: 1 addition & 1 deletion test/files/run/t7768.scala
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@@ -1,4 +1,4 @@
// scalac: -Xsource:3.0
// scalac: -Yscala3-implicit-resolution
class A
class B extends A
class C extends B
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14 changes: 7 additions & 7 deletions test/junit/scala/tools/nsc/typechecker/InferencerTest.scala
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Expand Up @@ -6,7 +6,6 @@ import org.junit.{After, Before, Test}
import org.junit.runner.RunWith
import org.junit.runners.JUnit4

import scala.tools.nsc.settings.ScalaVersion
import scala.tools.testkit.BytecodeTesting

class A
Expand All @@ -26,18 +25,19 @@ trait ZwC[-T] extends Z[T] with C
class InferencerTests extends BytecodeTesting {
import compiler.global._, analyzer._

var storedXsource: ScalaVersion = null
var storedYscala3ImplicitResolution: Boolean = false
@Before
def storeXsource(): Unit = {
storedXsource = settings.source.value
def storeYscala3ImplicitResolution(): Unit = {
storedYscala3ImplicitResolution = settings.Yscala3ImplicitResolution.value
}
@After
def restoreXsource(): Unit = {
settings.source.value = storedXsource
def restoreYscala3ImplicitResolution(): Unit = {
settings.Yscala3ImplicitResolution.value = storedYscala3ImplicitResolution
}

@Test
def isAsSpecificScala2(): Unit = {
settings.Yscala3ImplicitResolution.value = false
val run = new global.Run

enteringPhase(run.typerPhase) {
Expand Down Expand Up @@ -103,7 +103,7 @@ class InferencerTests extends BytecodeTesting {

@Test
def isAsSpecificScala3(): Unit = {
settings.source.value = ScalaVersion("3.0")
settings.Yscala3ImplicitResolution.value = true

val run = new global.Run

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