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Merge pull request #9167 from dotty-staging/fix-#9160
Have a per-run time budget for import suggestions
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‎compiler/src/dotty/tools/dotc/Run.scala‎

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@@ -31,6 +31,20 @@ import scala.util.control.NonFatal
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/** A compiler run. Exports various methods to compile source files */
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class Run(comp: Compiler, ictx: Context) extends ImplicitRunInfo with ConstraintRunInfo {
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/** Default timeout to stop looking for further implicit suggestions, in ms.
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* This is usually for the first import suggestion; subsequent suggestions
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* may get smaller timeouts. @see ImportSuggestions.reduceTimeBudget
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*/
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private var myImportSuggestionBudget: Int =
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Int.MinValue // sentinel value; means whatever is set in command line option
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def importSuggestionBudget =
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if myImportSuggestionBudget == Int.MinValue then ictx.settings.XimportSuggestionTimeout.value
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else myImportSuggestionBudget
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def importSuggestionBudget_=(x: Int) =
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myImportSuggestionBudget = x
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/** If this variable is set to `true`, some core typer operations will
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* return immediately. Currently these early abort operations are
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* `Typer.typed` and `Implicits.typedImplicit`.

‎compiler/src/dotty/tools/dotc/config/ScalaSettings.scala‎

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@@ -87,6 +87,7 @@ class ScalaSettings extends Settings.SettingGroup {
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val XfatalWarnings: Setting[Boolean] = BooleanSetting("-Xfatal-warnings", "Fail the compilation if there are any warnings.")
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val XverifySignatures: Setting[Boolean] = BooleanSetting("-Xverify-signatures", "Verify generic signatures in generated bytecode.")
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val XignoreScala2Macros: Setting[Boolean] = BooleanSetting("-Xignore-scala2-macros", "Ignore errors when compiling code that calls Scala2 macros, these will fail at runtime.")
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val XimportSuggestionTimeout: Setting[Int] = IntSetting("-Ximport-suggestion-timeout", "Timeout (in ms) for searching for import suggestions when errors are reported.", 8000)
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val XmixinForceForwarders = ChoiceSetting(
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name = "-Xmixin-force-forwarders",

‎compiler/src/dotty/tools/dotc/typer/ImportSuggestions.scala‎

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@@ -27,9 +27,6 @@ trait ImportSuggestions:
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/** Timeout to test a single implicit value as a suggestion, in ms */
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private inline val testOneImplicitTimeOut = 500
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/** Global timeout to stop looking for further implicit suggestions, in ms */
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private inline val suggestImplicitTimeOut = 10000
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/** A list of TermRefs referring to the roots where suggestions for
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* imports of givens or extension methods that might fix a type error
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* are searched.
@@ -145,7 +142,11 @@ trait ImportSuggestions:
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*/
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private def importSuggestions(pt: Type)(using Context): (List[TermRef], List[TermRef]) =
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val timer = new Timer()
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val deadLine = System.currentTimeMillis() + suggestImplicitTimeOut
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val allotted = ctx.run.importSuggestionBudget
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if allotted <= 1 then return (Nil, Nil)
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implicits.println(i"looking for import suggestions, timeout = ${allotted}ms")
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val start = System.currentTimeMillis()
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val deadLine = start + allotted
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// Candidates that are already available without explicit import because they
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// are already provided by the context (imported or inherited) or because they
@@ -249,9 +250,18 @@ trait ImportSuggestions:
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println("caught exception when searching for suggestions")
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ex.printStackTrace()
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(Nil, Nil)
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finally timer.cancel()
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finally
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timer.cancel()
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reduceTimeBudget(((System.currentTimeMillis() - start) min Int.MaxValue).toInt)
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end importSuggestions
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/** Reduce next timeout for import suggestions by the amount of time it took
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* for current search, but but never less than to half of the previous budget.
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*/
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private def reduceTimeBudget(used: Int)(using Context) =
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ctx.run.importSuggestionBudget =
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(ctx.run.importSuggestionBudget - used) max (ctx.run.importSuggestionBudget / 2)
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/** The `ref` parts of this list of pairs, discarding subsequent elements that
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* have the same String part. Elements are sorted by their String parts.
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*/

‎tests/neg/i9160.scala‎

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‎tests/neg/missing-implicit-2.check‎

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-- Error: tests/neg/missing-implicit-2.scala:4:24 ----------------------------------------------------------------------
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4 |val f = Future[Unit] { } // error
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| ^
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| Cannot find an implicit ExecutionContext. You might pass
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| an (implicit ec: ExecutionContext) parameter to your method.
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|
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| The ExecutionContext is used to configure how and on which
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| thread pools Futures will run, so the specific ExecutionContext
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| that is selected is important.
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|
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| If your application does not define an ExecutionContext elsewhere,
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| consider using Scala's global ExecutionContext by defining
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| the following:
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|
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| implicit val ec: scala.concurrent.ExecutionContext = scala.concurrent.ExecutionContext.global
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|
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| The following import might fix the problem:
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|
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| import concurrent.ExecutionContext.Implicits.global
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|
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-- [E007] Type Mismatch Error: tests/neg/missing-implicit-2.scala:6:25 -------------------------------------------------
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6 |val b: java.lang.Byte = (1: Byte) // error, but no hint
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| ^^^^^^^
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| Found: Byte
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| Required: Byte²
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|
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| where: Byte is a class in package scala
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| Byte² is a class in package java.lang

‎tests/neg/missing-implicit-2.scala‎

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import Predef.{byte2Byte => _, _}
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import scala.concurrent.Future
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val f = Future[Unit] { } // error
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val b: java.lang.Byte = (1: Byte) // error, but no hint

‎tests/neg/missing-implicit-3.check‎

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@@ -0,0 +1,25 @@
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-- [E007] Type Mismatch Error: tests/neg/missing-implicit-3.scala:6:44 -------------------------------------------------
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6 |val d: scala.concurrent.duration.Duration = (10, DAYS) // error
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| ^^^^^^^^^^
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| Found: (Int, java.util.concurrent.TimeUnit)
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| Required: concurrent².duration.Duration
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|
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| where: concurrent is a package in package java.util
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| concurrent² is a package in package scala
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|
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|
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| The following import might fix the problem:
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|
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| import concurrent.duration.pairIntToDuration
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|
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-- [E008] Not Found Error: tests/neg/missing-implicit-3.scala:8:48 -----------------------------------------------------
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8 |val d2: scala.concurrent.duration.Duration = 10.days // error
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| ^^^^^^^
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| value days is not a member of Int, but could be made available as an extension method.
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|
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| One of the following imports might fix the problem:
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|
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| import concurrent.duration.DurationInt
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| import concurrent.duration.DurationLong
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| import concurrent.duration.DurationDouble
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|

‎tests/neg/missing-implicit-3.scala‎

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@@ -0,0 +1,8 @@
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import Predef.{byte2Byte => _, _}
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import math.Numeric
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val DAYS = scala.concurrent.duration.DAYS
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val d: scala.concurrent.duration.Duration = (10, DAYS) // error
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val d2: scala.concurrent.duration.Duration = 10.days // error

‎tests/neg/missing-implicit.check‎

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|
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| import math.Numeric.Implicits.infixNumericOps
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|
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-- Error: tests/neg/missing-implicit.scala:10:24 -----------------------------------------------------------------------
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10 |val f = Future[Unit] { } // error
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| ^
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| Cannot find an implicit ExecutionContext. You might pass
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| an (implicit ec: ExecutionContext) parameter to your method.
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|
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| The ExecutionContext is used to configure how and on which
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| thread pools Futures will run, so the specific ExecutionContext
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| that is selected is important.
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|
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| If your application does not define an ExecutionContext elsewhere,
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| consider using Scala's global ExecutionContext by defining
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| the following:
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|
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| implicit val ec: scala.concurrent.ExecutionContext = scala.concurrent.ExecutionContext.global
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|
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| The following import might fix the problem:
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|
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| import concurrent.ExecutionContext.Implicits.global
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|
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-- [E007] Type Mismatch Error: tests/neg/missing-implicit.scala:12:25 --------------------------------------------------
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12 |val b: java.lang.Byte = (1: Byte) // error, but no hint
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| ^^^^^^^
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| Found: Byte
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| Required: Byte²
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|
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| where: Byte is a class in package scala
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| Byte² is a class in package java.lang
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-- [E007] Type Mismatch Error: tests/neg/missing-implicit.scala:16:44 --------------------------------------------------
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16 |val d: scala.concurrent.duration.Duration = (10, DAYS) // error
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| ^^^^^^^^^^
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| Found: (Int, java.util.concurrent.TimeUnit)
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| Required: concurrent².duration.Duration
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|
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| where: concurrent is a package in package java.util
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| concurrent² is a package in package scala
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|
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|
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| The following import might fix the problem:
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|
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| import concurrent.duration.pairIntToDuration
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|
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-- [E008] Not Found Error: tests/neg/missing-implicit.scala:18:48 ------------------------------------------------------
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18 |val d2: scala.concurrent.duration.Duration = 10.days // error
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| ^^^^^^^
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| value days is not a member of Int, but could be made available as an extension method.
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|
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| One of the following imports might fix the problem:
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|
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| import concurrent.duration.DurationInt
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| import concurrent.duration.DurationLong
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| import concurrent.duration.DurationDouble
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|

‎tests/neg/missing-implicit.scala‎

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@@ -4,15 +4,3 @@ import math.Numeric
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def consume[T: Numeric](xs: List[T], limit: T): List[T] = xs match
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case x :: xs1 if limit > 0 => consume(xs1, limit - x) // error // error
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case _ => xs
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import scala.concurrent.Future
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val f = Future[Unit] { } // error
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val b: java.lang.Byte = (1: Byte) // error, but no hint
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val DAYS = scala.concurrent.duration.DAYS
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val d: scala.concurrent.duration.Duration = (10, DAYS) // error
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val d2: scala.concurrent.duration.Duration = 10.days // error

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