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KordyjanKordyjan
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Merge pull request #15761 from dotty-staging/backport-15625
Backport #15625: Fix two problems related to match types as array elements
2 parents 68a70cb + 23ab800 commit d669b1e

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7 files changed

+105
-25
lines changed

7 files changed

+105
-25
lines changed

‎compiler/src/dotty/tools/dotc/core/TypeErasure.scala‎

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Original file line numberDiff line numberDiff line change
@@ -328,6 +328,9 @@ object TypeErasure {
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isGenericArrayElement(tp.alias, isScala2)
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case tp: TypeBounds =>
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!fitsInJVMArray(tp.hi)
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case tp: MatchType =>
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val alts = tp.alternatives
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alts.nonEmpty && !fitsInJVMArray(alts.reduce(OrType(_, _, soft = true)))
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case tp: TypeProxy =>
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isGenericArrayElement(tp.translucentSuperType, isScala2)
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case tp: AndType =>

‎compiler/src/dotty/tools/dotc/core/Types.scala‎

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Original file line numberDiff line numberDiff line change
@@ -428,11 +428,13 @@ object Types {
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/** Is this a match type or a higher-kinded abstraction of one?
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*/
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def isMatch(using Context): Boolean = stripped match {
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case _: MatchType => true
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case tp: HKTypeLambda => tp.resType.isMatch
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case tp: AppliedType => tp.isMatchAlias
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case _ => false
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def isMatch(using Context): Boolean = underlyingMatchType.exists
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def underlyingMatchType(using Context): Type = stripped match {
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case tp: MatchType => tp
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case tp: HKTypeLambda => tp.resType.underlyingMatchType
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case tp: AppliedType if tp.isMatchAlias => tp.superType.underlyingMatchType
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case _ => NoType
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}
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/** Is this a higher-kinded type lambda with given parameter variances? */

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

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Original file line numberDiff line numberDiff line change
@@ -28,26 +28,35 @@ class Synthesizer(typer: Typer)(using @constructorOnly c: Context):
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private type SpecialHandlers = List[(ClassSymbol, SpecialHandler)]
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val synthesizedClassTag: SpecialHandler = (formal, span) =>
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formal.argInfos match
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case arg :: Nil =>
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if isFullyDefined(arg, ForceDegree.all) then
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arg match
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case defn.ArrayOf(elemTp) =>
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val etag = typer.inferImplicitArg(defn.ClassTagClass.typeRef.appliedTo(elemTp), span)
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if etag.tpe.isError then EmptyTreeNoError else withNoErrors(etag.select(nme.wrap))
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case tp if hasStableErasure(tp) && !defn.isBottomClassAfterErasure(tp.typeSymbol) =>
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val sym = tp.typeSymbol
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val classTag = ref(defn.ClassTagModule)
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val tag =
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if defn.SpecialClassTagClasses.contains(sym) then
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classTag.select(sym.name.toTermName)
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else
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val clsOfType = escapeJavaArray(erasure(tp))
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classTag.select(nme.apply).appliedToType(tp).appliedTo(clsOf(clsOfType))
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withNoErrors(tag.withSpan(span))
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case tp => EmptyTreeNoError
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else EmptyTreeNoError
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case _ => EmptyTreeNoError
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val tag = formal.argInfos match
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case arg :: Nil if isFullyDefined(arg, ForceDegree.all) =>
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arg match
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case defn.ArrayOf(elemTp) =>
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val etag = typer.inferImplicitArg(defn.ClassTagClass.typeRef.appliedTo(elemTp), span)
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if etag.tpe.isError then EmptyTree else etag.select(nme.wrap)
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case tp if hasStableErasure(tp) && !defn.isBottomClassAfterErasure(tp.typeSymbol) =>
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val sym = tp.typeSymbol
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val classTagModul = ref(defn.ClassTagModule)
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if defn.SpecialClassTagClasses.contains(sym) then
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classTagModul.select(sym.name.toTermName).withSpan(span)
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else
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def clsOfType(tp: Type): Type = tp.dealias.underlyingMatchType match
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case matchTp: MatchType =>
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matchTp.alternatives.map(clsOfType) match
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case ct1 :: cts if cts.forall(ct1 == _) => ct1
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case _ => NoType
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case _ =>
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escapeJavaArray(erasure(tp))
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val ctype = clsOfType(tp)
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if ctype.exists then
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classTagModul.select(nme.apply)
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.appliedToType(tp)
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.appliedTo(clsOf(ctype))
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.withSpan(span)
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else EmptyTree
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case _ => EmptyTree
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case _ => EmptyTree
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(tag, Nil)
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end synthesizedClassTag
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val synthesizedTypeTest: SpecialHandler =

‎tests/neg/i15618.check‎

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@@ -0,0 +1,18 @@
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-- Error: tests/neg/i15618.scala:17:44 ---------------------------------------------------------------------------------
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17 | def toArray: Array[ScalaType[T]] = Array() // error
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| ^
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| No ClassTag available for ScalaType[T]
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|
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| where: T is a type in class Tensor with bounds <: DType
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|
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|
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| Note: a match type could not be fully reduced:
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|
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| trying to reduce ScalaType[T]
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| failed since selector T
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| does not match case Float16 => Float
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| and cannot be shown to be disjoint from it either.
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| Therefore, reduction cannot advance to the remaining cases
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|
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| case Float32 => Float
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| case Int32 => Int

‎tests/neg/i15618.scala‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
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sealed abstract class DType
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sealed class Float16 extends DType
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sealed class Float32 extends DType
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sealed class Int32 extends DType
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object Float16 extends Float16
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object Float32 extends Float32
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object Int32 extends Int32
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type ScalaType[U <: DType] <: Int | Float = U match
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case Float16 => Float
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case Float32 => Float
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case Int32 => Int
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class Tensor[T <: DType](dtype: T):
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def toSeq: Seq[ScalaType[T]] = Seq()
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def toArray: Array[ScalaType[T]] = Array() // error
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@main
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def Test =
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val t = Tensor(Float32) // Tensor[Float32]
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println(t.toSeq.headOption) // works, Seq[Float]
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println(t.toArray.headOption) // ClassCastException

‎tests/run/i15618.check‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
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Some(1)

‎tests/run/i15618.scala‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,24 @@
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sealed abstract class DType
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sealed class Float16 extends DType
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sealed class Float32 extends DType
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sealed class Int32 extends DType
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object Float16 extends Float16
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object Float32 extends Float32
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object Int32 extends Int32
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type ScalaType[U <: DType] <: Int | Float = U match
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case Float16 => Float
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case Float32 => Float
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case Int32 => Int
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abstract class Tensor[T <: DType]:
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def toArray: Array[ScalaType[T]]
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object IntTensor extends Tensor[Int32]:
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def toArray: Array[Int] = Array(1, 2, 3)
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@main
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def Test =
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val t = IntTensor: Tensor[Int32]
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println(t.toArray.headOption) // was ClassCastException

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